82175 UF MNH txt.pmd, page 10 @ Preflight BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 109 1Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH 44115; 2Department of Biology, John Carroll University, University Heights, OH 44118; Borden, W.C. and M.M. Coburn. 2008. Striated muscles of the black basses (Micropterus, Centrarchidae): Myological stasis in a generalized group of percomorph fishes. Florida Museum. Nat. Hist. Bull. 47(4):109-136. [End of volume] STRIATED MUSCLES OF THE BLACK BASSES (MICROPTERUS, CENTRARCHIDAE): MYOLOGICAL STASIS IN A GENERALIZED GROUP OF PERCOMORPH FISHES W. Calvin Borden1 and Miles M. Coburn2 ABSTRACT Striated muscles of a generalized genus of percomorph fishes (Micropterus, Centrarchidae, Percomorpha) were described. Overall, myological variation was sparse among species of black bass. Variation took the form of minor variants in the size or shape of a muscle or of singular or incongruous variants characterized by abnormalities in a single specimen. The remaining myological variation occurred as mimicking variants and was shared irregularly among taxa. The lack of myological variation among black bass may well be correlated with the low degree of diversity exhibited in their ecology, life history, and external anatomy. However, the value of Micropterus in systematic and evolutionary studies is not compromised by morphological stasis. Instead, because Micropterus and other conserved lineages have been minimally responsive to ecological factors, they are valuable as outgroups to polarize character states, as identifiers of vicariant events leading to allopatric speciation, and as exemplars for studying the evolutionary mechanism of stabilizing selection. In addition, the description and assessment of myological variation in this generalized percomorph will be useful in future studies of comparative anatomy, functional morphology, and higher level systematics. Key Words: Black bass, Centrarchidae, Micropterus, Myology, Stasis. TABLE OF CONTENTS Introduction .........................................................................................................110 Methods...............................................................................................................110 Material Examined................................................................................................112 Results and Myological Descriptions..................................................................112 Muscles of the Cheek....................................................................................112 Muscles of the Ventral Surface of the Head.................................................. 116 Muscles Serving the Dorsal Elements of the Branchial Arches.....................117 Muscles Serving the Ventral Elements of the Branchial Arches.................... 118 Muscles Between the Pectoral Girdle and the Skull, Hyoid, and Branchial Arches............................................................................................................120 Muscles of the Pectoral Fin...........................................................................121 Muscles of the Pelvic Fin..............................................................................122 Muscles of the Caudal Fin.............................................................................126 Notes on Other Features of the Soft Anatomy in Micropterus species........128 Discussion............................................................................................................129 Myological Notes..........................................................................................129 Myological Variation..................................................................................... 129 Macroevolutionary Patterns..........................................................................130 Phylogenetic Utility.......................................................................................131 Acknowledgements.............................................................................................. 132 Literature Cited.................................................................................................... 132 110 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) M. dolomieu comprising a second lineage (Fig. 1C). These morphological hypotheses were followed by a series of molecular analyses using phylogenetic meth- ods (Fig 1D, Johnson et al. 2001; Fig. 1E, Kassler et al. 2002; Fig. 1F, Near et al. 2003, 2005). While the results of the Johnson et al. (2001) study resembled those mor- phological hypotheses with M. salmoides as the basal clade, the remaining molecular studies suggested new phylogenetic relationships. Kassler et al. (2002), em- ploying meristic and molecular characters, recovered M. salmoides deeply nested in the tree and a non-sister group relationship between M. punctulatus henshalli and M. punctulatus punctulatus (Fig. 1E). Most re- cently, Near et al. (2003, 2005) recovered a fully re- solved tree supporting a M. dolomieu-M. punctulatus clade as the sister group to the remaining black bass (Fig. 1F). Black bass are high trophic level predators prima- rily of fishes and crayfishes (Scott & Crossman 1973; Koppelman & Garrett 2002) and well known as sport fishes. As a consequence, numerous studies have in- vestigated facets of their ecology, reproduction, life his- tory, and behavior (see Philipp & Ridgway 2002 as a starting point). In addition, various anatomical compo- nents have been described as exemplars in the context of functional morphology (Wainwright & Lauder 1992; Higham 2007), kinematics (Lauder 1982), ecomorphology (Norton & Brainerd 1993; Wintzer & Motta 2005), de- scriptive osteology (Shufeldt 1900; Blair & Brown 1961; Mabee 1988), ontogeny (Mabee 1993), and pigment patterns (Mabee 1995). A complete morphological ap- praisal of a relatively conservative anatomical system (i.e. myology) promotes a fuller understanding of the comparative anatomy, functional morphology, and sys- tematics of these fishes. METHODS Sample size can adversely affect phylogenetic results particularly if character state variation within the taxo- nomic unit is not identified. A protocol for detecting myological variants was put forth by Raikow et al. (1990) and subsequently modified by Kesner (1994). Their models suggested that at least 10 specimens of a refer- ence species should be bilaterally dissected in a search for variable character states. Variants were catego- rized as “incongruous” (abnormal and nonfunctional variation due to a malformation), “mimicking” (an atypi- cal condition in one species that is typical for a different species), “minor” (slight variation in size, shape, position and perhaps resulting from nonbiological causes), and “singular” (atypical but not nonfunctional, and not present in other taxa) (Raikow et al. 1990). Incongruous, minor, INTRODUCTION The myology of fishes is an under-described morpho- logical system relative to osteology. This is unfortunate because it has been shown to be relevant in determining phylogenetic relationships across a variety of diverse fish groups and taxonomic levels (e.g. tetradontiforms - Winterbottom 1974b; acanthurids – Winterbottom 1993; teleosts - Greenwood & Lauder 1981; cottoids - Yabe 1985; cirrhitoids – Greenwood 1995; acanthomorphs - Mooi & Gill 1995; nasines - Borden 1999; siluriform fami- lies - Diogo 2005; notothenioids - Iwami 2004; actinopterygians - Springer & Johnson 2004; basal acanthomorphs - Wu & Shen 2004; bony fish and tetra- pods – Diogo & Abdala 2007). We initiated the current study to (1) describe a relatively unknown character system, striated muscles, in a generalized percomorph genus, (2) evaluate the utility of myology in resolving species level relationships among the black bass (Micropterus, Centrarchidae), and (3) contribute to the development of a myological data base suitable for higher level systematic studies among percomorphs. The phylogenetic affinities of Centrarchidae within Percomorpha are unknown although centrarchids are considered basal members of the order. The family is monophyletic and consists of eight genera with 31 spe- cies inhabiting freshwaters, mostly in eastern North America, and known commonly as black bass, sunfish, rock bass, and crappies (Nelson 2006). The genus Micropterus Lacépède (1802) is monophyletic and is comprised of seven species, the redeye bass (M. coosae), the shoal bass (M. cataractae), the Suwannee bass (M. notius), the Guadalupe (M. treculii), and three species which have recognizable subspecies: the small- mouth bass (M. dolomieu: dolomieu and velox), the spotted bass (M. punctulatus: henshalli and punctulatus), and the largemouth bass (M. salmoides: floridanus and salmoides). Black bass have been iden- tified as the basal clade of centrarchids (Ramsey 1975; Wainwright & Lauder 1992; Mabee 1993) or a derived clade either as the sister group to Lepomis (Branson & Moore 1962; Avise et al. 1977; Near et al. 2005), or with unresolved affinities (Roe et al. 2002). The interspecific relationships of Micropterus spe- cies have also varied considerably. Bailey (1938) and Hubbs and Bailey (1940) envisioned two lineages of black bass, one consisting solely of M. salmoides placed in the genus Huro (Fig. 1A). Branson and Moore (1962) recognized six species and identified M. salmoides as the basal lineage based on a detailed analysis of the acustico-lateralis system (Fig. 1B). Ramsey (1975) grouped seven species into three lineages with M. salmoides comprising one lineage, and M. coosae and BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 111 and singular variants are phylogenetically uninformative; mimicking variants create homoplasies in the form of convergences or parallelisms. Raikow et al. (1990) rec- ommended initial dissections of a reference species to identify and eliminate minor and incongruous variants. Single bilateral dissection and at least two unilateral dis- sections should be undertaken in the remaining species to resolve mimicking and singular variants. Alternatively, in the absence of 10 specimens for a given species, four to five specimens of several species should be dissected (Kesner 1994). Lacking a series of 10 specimens, M. coosae, M. d. dolomieu, and M. s. salmoides were dissected for seven, five, and eight specimens respectively of which Figure 1. Proposed phylogenetic relationships among the black bass. Each hypothesis is based on a different data set and tree building criterion, if any. A. Hubbs and Bailey (1940, Fig. 1). “dolomieu” and “velox” are subspecies of M. dolomieu. “henshalli”, “punctulatus”, and “wichitae” are subspecies of M. punctulatus. B. Branson and Moore (1962, Fig. 15). C. Ramsey (1975) included 2 subspecies in M. salmoides and M. dolomieu each and 3 subspecies in M. punctulatus. D. Johnson et al. (2001, Fig. 2). E. Kassler et al. (2002, Fig. 6). F. Near et al. (2005, Fig. 7). Near et al (2003) switched the position of “cataractae” and “coosae”. The numbers located at each node are age esti- mates in “millions of years ago” using a fossil cross-validation methodology (Near et al. 2005). 112 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) subspecies following the recommendation of Nelson et al. (2004) for additional analysis. MATERIAL EXAMINED Institutional abbreviations follow Leviton et al. (1985). The number of specimens dissected and their standard length(s) in millimeters follows the catalog number. Micropterus. — (1): M. cataractae Williams & Burgess 1999, ROM 82445, 1 (216.2 mm SL); UMMZ 168752, 1 (102.8 mm SL). (2): M. coosae Hubbs & Bailey 1940, OSUM 105229, 1 (104.3 mm SL); ROM 82449, 1 (116.0 mm SL); ROM 82450, 1 (126.1 mm SL); UF 86268, 1 (131.8 mm SL); UF 86313, 1 (122.2 mm SL); UF 89989, 1 (154.7 mm SL); USNM 168075, 1 (98.7 mm SL). (3): M. d. dolomieu Lacépède 1802, CAS 13020 C&S, 1 (77.2 mm SL); OSUM 102599, 1 (173.2 mm SL); OSUM 102600, 1 (155.2 mm SL); ROM 1783CS, 1 (178.3 mm SL); ROM 82436, 1 (248.8 mm SL); ROM 82437, 1 (133.2 mm SL). (4): M. d. velox Hubbs & Bailey 1940, UMMZ 116802, 1 (121.6 mm SL); UMMZ 128680, 1 (120.7 mm SL). (5): M. notius Bailey & Hubbs 1949, UF 57323, 1 (187.6 mm SL); UF 58761, 2 (131.8 – 145.2 mm SL, fish labeled “4” and “5” respectively by UF); TU 9775, 2 (107.4 – 152.3 mm SL). (6): M. p. henshalli Hubbs & Bailey 1940, UAIC 10587.15, 1 (154.3 mm SL); UAIC 12652.19, 1 (132.8 mm SL). (7): M. p. punctulatus (Rafinesque 1819), OSUM 102597, 1 (153.4 mm SL); OSUM 102598, 1 (144.7 mm SL); USNM 251991, 2 (88.0 - 95.4 mm SL). (8): M. s. floridanus (Lesueur 1822), UMMZ 158634, 1 (128.8 mm SL); UMMZ 163350, 1 (125.6 mm SL). (9): M. s. salmoides (Lacépède 1802), CAS 19030 C&S, 1 (60.6 mm SL); ROM 1780CS, 1 (170. mm SL); ROM 1781CS, 1 (159.1 mm SL); ROM 1782CS, 1 (138.2 mm SL); ROM 82435, 1 (176.5 mm SL); ROM 82446, 4 (153.2 – 219.4 mm SL). (10): M. treculii (Vaillant & Bocourt 1874), OSUM 105227, 1 (254.0 mm SL); ROM 1784CS, 1 (253.0 mm SL); UMMZ 136849, 1 (112.8 mm SL); UMMZ 220247, 1 (137.2 mm SL). Centrarchids. — (1): Ambloplites ariommus Viosca 1936, ROM 82444, 1 (105.2 mm SL). (2): Centrarchus macropterus (Lacépède 1801), UMMZ 164961, 1 (124.8 mm SL). (3): Lepomis cyanellus Rafinesque 1819, ROM 82438, 1 (81.1 mm SL). (4): Lepomis gibbosus (Linnaeus 1758), ROM 82439, 1 (113.6 mm SL). (5): Pomoxis nigromaculatus (Lesueur 1829), ROM 82440, 1 (152.3 mm SL). RESULTS AND MYOLOGICAL DESCRIPTIONS I. MUSCLES OF THE CHEEK The ligamentum primordium attaches tendinously four, four, and six specimens were bilaterally dissected. In all specimens examined, muscles of the branchial and hyoid arches, pectoral, pelvic, and caudal fins were bi- laterally dissected. Muscles of head, cheek, jaws, sus- pensorium, and those connecting any two components of the head, suspensorium, and fins were dissected bi- laterally in at least one specimen. Specimens were dis- sected sequentially and in random order excepting most specimens of M. d. dolomieu and M. s. salmoides, which were dissected at the beginning of the study to assess the prevalence of the four variant classes. Striated muscle terminology follows Winterbottom (1974a); nerves follow Freihofer (1963). Muscle de- scriptions represent a consensus or generalized form of each species, thus averaging out the effects of minor variation such as muscle proportions or muscle origins on bones with fimbricate sutures (e.g. prootic and pterotic suture). Swimbladder and subcutaneous muscles were not observed, median fin and eye muscles were not ex- amined, and body and carinal muscles were not described in detail except as relevant to muscles described below. Roman numerals were used to denote muscles; Arabic numbers were used to denote bones. Singular and in- congruous variants were noted under the appropriate muscle and checked against antimeres and other speci- mens. Intraspecific and mimicking variation is listed in Table 1. Soft anatomical features such as the number and structure of pyloric caecae and the nasal rosette were also described. Morphological conditions in outgroup species were described for characters vari- able only among Micropterus species or for incongru- ous and singular variants. Fish were fixed in 10% formalin and stored in 70- 75% ethyl alcohol. Specimens were dissected using a Nikon SMZ-U microscope and drawn using a camera lucida attachment on a Leica MZ125 microscope. Small and questionable muscle fibers were stained with a modi- fied iodine solution (Bock & Shear 1972) to highlight them against non-muscle tissue. Following dissection, some specimens were cleared and double stained for bone (alizarin red-S) and cartilage (Alcian blue) using modified protocols of Potthoff (1984) and Taylor and Van Dyke (1985). Scientific names follow Nelson et al. (2004) with the following additions that recognized subspecific sta- tus in M. dolomieu [dolomieu and velox], M. punctulatus [henshalli and punctulatus] (following Hubbs & Bailey 1940), and M. salmoides [floridanus and salmoides] (following Bailey & Hubbs 1949). Al- though Kassler et al. (2002) argued for the promotion of M. s. floridanus and M. s. salmoides to specific status based on meristic and molecular data, we retain them as BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 113 on the dorsolateral surface of the maxilla and arcs pos- teriorly and ventrally to attach on the lateral surface of the angular (angulo-articular) anterior of the quadrate- angular articulation. Adductor mandibulae (A1, A2, A3, Aù , Figs. 2-5, 8). All sections of the adductor mandibulae are graded to varying degrees, and the extensive grading complicates assignment of fibers to a specific section. After removal of the skin and infraorbitals, the adductor mandibulae occupies the lateral side of the suspenso- rium in the space bounded by the orbit, preopercle, and jaws. The lateralmost section of the adductor mandibulae is A1. Section A1 is described as two bundles of un- equal size. The dorsalmost of the two sections origi- nates on the preopercle, anterodorsal face of the hyomandibula, and base of the levator arcus palatini. The ventral border is separable from the ventral and main mass of A1 only laterally as fibers are graded me- dially. As the dorsal section passes anteriorly, it rolls medially over the main mass of A1 and grades into a medial aponeurosis shared by several sections of the adductor mandibulae. Fibers of the main bundle of A1 originate primarily on the preopercle but also include the hyomandibula. Insertion includes the ligamentum pri- mordium particularly at the anterodorsal corner of the muscle and the aforementioned medial aponeurosis. In addition, a well-developed tendon arises from the anteromedial corner of the muscle mass, runs parallel to the ligamentum primordium, and inserts on the medial surface of the maxilla at the level of the ligamentum primordium. Insertion on the medial surface of the max- illa suggests that it is A1â; however, the lack of a dis- tinct origin from the palatal arch or suspensorium and its dorsolateral position relative to A2 preclude its identifi- cation as A1â. A2 originates on the preopercle and hyomandibula and is inseparable from A1 due to extensive grading. Minor grooves and lateral separations were occasion- ally present in the fused A1- A2á bundle, but disappeared medially due to extensive grading and, therefore, were not given subsection status. Anterior and more dorsal fibers of A2 grade into the medial aponeurosis shared by the bundles of A1 while more ventral fibers grade into Aù via a myocommatum. A tendon arises from the anteroventral corner of the A1- A2 muscle mass and inserts on the medial side of the angular in the Meckelian fossa ventral to the cartilage. Ramus mandibularis V of the 5th cranial nerve (trigeminal nerve) is medial to A1- A2 and lateral to a single section of muscle identified as A3. A3 originates on the quadrate, symplectic, hyomandibula, preopercle, metapterygoid, and base of the levator arcus palatini at the metapterygoid. The posterior border of A3 is notched weakly giving it a chevron shape. Dorsal fibers of A3 attach to the tendon of A1-A2, the shared medial apo- neurosis, and Aù . More ventral fibers of A3, originat- ing on the quadrate and symplectic, run near horizontal and give rise to a tendon that inserts on the medial side of the angular in the Meckelian fossa dorsal to the car- tilage and near its posterior end. This tendon is lateral to the tendon from A1-A2. Aù attaches on the medial side of the lower jaw from the intermandibularis at its anterior end and ex- tends posteriorly via a strong tendon to originate on the quadrate, preopercle, and symplectic. The tendon of Aù is medial to the tendons from sections A1-A2 and A3; however, fibers of Aù are heavily graded with both tendons and determining which fiber belongs to which section is both frustrating and fruitless as this pattern is consistent among Micropterus species. Levator arcus palatini (LAP, Figs. 2, 3, 7). This muscle is a large bundle forming the posterior wall of the orbit. It originates on the sphenotic and fans out onto the metapterygoid and hyomandibula with a few fibers extending to the adductor arcus palatini. The ori- gin does not appear to include the frontal dorsally or prootic medially. The posterior border passes medial to the anterior border of the dilatator operculi, but the two muscles have only a few, if any, graded fibers. Figure 2. Left, lateral view of the superficial cheek musclulature of M. p. henshalli (UAIC 12652.19, 132.8 mm SL). Anterior is to the left. Scale bar = 5 mm. Abbreviations: A1, A2, A3 – sections of the adductor mandibulae; AAP – adductor arcus palatine; DOp – di- latator operculi; LAP – levator arcus palatini; LOp – levator operculi; lp – ligamentum primordium; LPect – levator pectoralis; RMV – ramus mandibularis V. 114 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) Figure 3. Left, lateral view of the superficial cheek musculature of M. cataractae (UMMZ 168752, 102.8 mm SL). Anterior is to the left. A. as above. Scale bar = 5 mm. B. Detailed view of the tendons inserting on the medial side of the maxilla and fibers passing to the medial side of the lower jaw. Scale bar = 1 mm. Abbreviations as in Figure 2. Figure 4. Medial view of the cheek musculature of M. p. henshalli (UAIC 12652.19, 132.8 mm SL). Anterior is to the right. Scale bar = 5 mm. A. The lower jaw has been removed, and the tendon of Aù to the suspensorium and preopercle has been cut. B. As above with Aù removed and most of A3 cut and removed. Abbreviations: Aù – medial section of the adductor mandibulae; as in Figure 2. BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 115 Dilatator operculi (DOp, Figs. 2, 3, 6, 7). This muscle has the shape of an inverted triangle with a broad origin on the sphenotic, pterotic, and hyomandibula. It tapers ventrally and inserts on the dilatator process of the opercle. Fibers pass medial to the dorsal tip of the preopercle. The posterior border is medial to the leva- tor operculi; fibers of the two muscles are not graded. Levator operculi (LOp, Figs. 2, 5-7). The origin is confined to the pterotic but the muscle quickly fans out onto the medial, dorsal surface of the opercle. A small, autonomous section of fibers originates from the posttemporal and inserts on the medial, dorsal surface of the opercle posterior to the main mass. This poste- rior section is weakly developed and lies within connec- tive tissue running from the skull to the opercle. This posterior section was the most diffuse and smallest in both specimens of M. cataractae, and absent in Lepomis cyanellus (ROM 82438). Adductor arcus palatini (AAP, Figs. 2, 3, 5). This muscle forms the posterior half of the orbit floor. It originates on the prootic and parasphenoid and inserts on the metapterygoid and mesopterygoid. Posteriorly it is continuous and graded heavily with the adductor hyomandibulae. Adductor hyomandibulae (AddHy, Figs. 5, 7). This muscle is continuous with the posterior border of the adductor arcus palatini. It inserts solely on the me- dial side of the hyomandibula. The origin includes the prootic, pterotic, and anteriodorsal corner of the intercalar. Figure 5. Medial view of the muscles connecting the cranium to the right suspensorium and opercular series of M. s. floridanus (UMMZ 163350, 125.6 mm SL). Anterior is to the left. Scale bar = 5 mm. Abbreviations: AddHy – adductor hyomandibulae; AddOp – adductor operculi; HyoAdd – hyohyoides adductores; i – site of interhyal articulation; as in Figures 2 and 4. Figure 6. Left, lateral view of the posterior muscles con- necting the cranium and opercular series of M. p. punctulatus (OSUM 102598, 144.7 mm SL). Anterior is to the left. Scale bar = 5 mm. Abbreviations as in Figure 2. Figure 7. Left, lateral view of muscles connecting the cranium to the suspensorium and pectoral girdle and the dorsal muscles of the branchial gill arches of M. p. punctulatus (OSUM 102598, 144.7 mm SL). Anterior is to the left. Scale bar = 5 mm. Abbreviations: Epx – epaxialis; h – site of hyomandibular articulation; LE – levator externus; LI – levator internus; LPost – levator posterior; OD – obliquus dorsalis; PrPect – protractor pectoralis; TD – transverses dorsalis; as in Figures 2 and 5. 116 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) The origin is linear on the neurocranium (sphenotic- pterotic) along the medial side of the hyomandibula’s articulation with the skull. The muscle is bulkier on ei- ther side of this articulation. Adductor operculi (AddOp, Figs. 5, 7). The ad- ductor operculi originates on the intercalar and extends ventrally to the suture with the exoccipital but not onto the exoccipital. The origin lies posterior to the adductor hyomandibulae and anterior to the levator posterior. The adductor operculi is separable from the latter but may grade with the adductor hyomandibulae. Insertion is on the medial side of the opercle dorsal to a horizontal bony ridge, and posterior to the opercle-hyomandibula articu- lation and levator operculi. II. MUSCLES OF THE VENTRAL SURFACE OF THE HEAD Intermandibularis (IntM, Fig. 8). The intermandibularis originates on the medial surface of the dentary, on either side of the symphysis, and meets its antimere at the ventral midline in the absence of a raphé. The muscle is a flattened sheet lying in a frontal plane. Protractor hyoidei (PrHy, Fig. 8). The anterior border of this muscle is bifurcated to accommodate its origin on the medial surface of the dentary above and below the intermandibularis. Anteriorly the antimeres are held together along the ventral midline via a septum but diverge posteriorly. Two myocommata are present posteriorly. Insertion is on the lateral side of the anterior ceratohyal with the posteroventral fibers passing later- ally to branchiostegal rays 1 and 2, but medially to ray 3. An exception to this pattern was M. coosae (UF 86313), in which the right antimere passes lateral to branchiostegal rays 1-3 and medial to ray 4; however, the left antimere follows the “normal” pattern. It may be more accurate to note that the protractor hyoidei passes medial to the first branchiostegal ray having a well-developed head (usually the third ray) that also ar- ticulates on the lateral side of the anterior ceratohyal. Branchiostegal rays anterior to this ray lack such well- developed heads and abut the ventral edge of the ante- rior ceratohyal, not its lateral surface. Hyohyoides inferioris. This muscle running from the urohyal to the hyoid arch is absent. Hyohyoidei adductores (HyoAdd, Fig. 9). The adductor bundles originate primarily on the medial side of the opercle and insert on the dorsoposterior surfaces of the posteriormost branchiostegal rays. Additional bundles are isolated distally between branchiostegal rays. In general, adductor fibers parallel the ventral borders of the anterior and posterior ceratohyals. Hyohyoidei abductores (HyoAbd, Fig. 9). The abductors are composed of many isolated bundles. The largest bundle originates tendinously on the dorsal and ventral hypohyals. This bundle crosses the midventral line and attaches to the medial surfaces of branchiostegal rays 1 and 2. Antimeres overlap at the origin with the left antimere (left side of hypohyals to right branchiostegal rays) ventral to the right antimere. Addi- tional bundles originate muscularly on the ventral side of the anterior ceratohyal and insert on the medial, proxi- mal surfaces of adjacent branchiostegal rays. In gen- eral, abductor bundles are orientated obliquely relative to the ventral borders of the anterior and posterior ceratohyals. Figure 8. A. Dorsal and B. ventral view of the lower jaws and of M. coosae (ROM 82449, 116.0 mm SL). Anterior is to the left. Unfilled area of A is toothed. Scale bar = 5 mm. Abbreviations: IntM – intermandibularis; PrHy – protractor hyoidei; as in Figure 4. Figure 9. Right, lateral view of the hyoid arch minus the urohyal of M. d. dolomieu (OSUM 102600, 155.2 mm SL). Anterior is to the right. Scale bar = 5mm. The branchiostegals have been spread and not all fibers of the hyohyoidei abductores were drawn including the antimere originating from the hypohyals. Abbreviations: HyoAbd – hyohyoideus abductores; as in Figure 5. BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 117 III. MUSCLES SERVING THE DORSAL ELE- MENTS OF THE BRANCHIAL ARCHES Levatores externi (LE I-IV, Figs. 7, 10, 11). Four muscles, each a levator externus, constitute the leva- tores externi with each bundle serving the dorsal ele- ments of one of the first four gill arches. Levatores externi I and II originate primarily on the prootic while III and IV originate primarily on the pterotic although all four muscles probably share both the prootic and pterotic. Levator externus I is nearly vertical but the remaining externi muscles are orientated obliquely. Levatores externi III and IV are closely appressed but not graded. Levator externus I inserts on epibranchial 1 anterolat- eral to its articulation with the interarcual cartilage. Levator externus II inserts on a raised dorsoposterior ridge of epibranchial 2; levator externus III inserts on a well developed uncinate process of epibranchial 3, and levator externus IV inserts on a raised ridge of epibranchial 4 that is lateral to the uncinate process but medial to a very small levator process. Insertion sites move distally from levator externus I to IV. Levatores interni (LI II-III, Figs. 7, 10). Two muscles, each a levator internus, serve the dorsal ele- ments of either the second or third gill arch. They origi- nate on the prootic and pterotic medial to the levatores externi. Levator internus II is medial to III, and they form an “X” in lateral view. Levator internus II inserts on the dorsal surface of pharyngobranchial 2 adjacent to its articulation with the interarcual cartilage. Levator internus II inserts on the dorsal surface of pharyngobranchial 3 adjacent to its articulation with epibranchial 3. In M. treculii (UMMZ 136849), fibers of levator internus III also insert on the cartilaginous end of epibranchial 3 at its articulation with pharyngobranchial 3. Levator posterior (LPost, Figs. 7, 10). The leva- tor posterior is well developed and separated from the externi and interni muscles. It originates on the intercalar, posterior of the adductor operculi, at the base of the ‘stump’ that articulates with the posttemporal. It inserts Figure 10. Dorsal view of the branchial gill arch muscles of M. p. henshalli (UAIC 12652.19, 132.8 mm SL). Anterior is to the left. Scale bar = 5 mm. The left epibranchial 1 has been removed as has the right pharyngobranchial 1. The right antimere of the retrac- tor dorsalis, obliquus dorsalis III/IV, and transversus dor- salis IV have been removed. Abbreviations: Add – ad- ductor; OP – obliquus posterior; RD – retractor dorsa- lis; SphOes – sphincter oesophagi; as in Figure 7. Figure 11. Posterior view of the left fourth and fifth bran- chial gill arches and muscles of M. d. velox (UMMZ 128680, 120.7 mm SL). The esophagus is to the right. Scale bar = 1 mm. The sphincter oesophagi grades into the obliquus posterior medially. The protractor pectora- lis has been removed. Muscle fibers extend ventrally to the level of the epibranchial-ceratobranchial articulation before grading into the branchial wall. The latter is at- tached to the posterior surfaces of epibranchial 4 and ceratobranchials 4 and 5. Abbreviations: cb 4 – ceratobranchial 4; cb 5 – ceratobranchial 5; eb 4 – epibranchial 4; as in Figures 7 and 10. 118 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) on the dorsal, distal surface of epibranchial 4 anterior to levator externus IV. Obliquus dorsalis (OD III/IV, Figs. 7, 10). A single bundle originates from the dorsal surfaces of epibranchials 3 and 4 and extends medially to insert on the dorsal surface of pharyngobranchial 3. Fibers along the epibranchials are heavily graded. Transversi dorsales (TD II, III/IV, Figs. 7, 10). Transversus dorsalis II consists of two graded bundles. An anterior circular bundle arises from the dorsolateral surface of pharyngobranchial 2 and passes medially where it attaches to its antimere via a raphé. A more posterior bundle arises along the dorsal surface of epibranchial 2 and passes to the dorsal midline where it attaches to its antimere via a raphé. The posterior bor- der of the circular section is dorsal to the more posterior section but the two sections are heavily graded. Ven- trally the bundles adhere to the dorsal side of the skin lining the buccal cavity along the dorsal midline. Dor- sally, the muscle abuts the parasphenoid. Springer and Johnson (2004) noted a small accessory cartilage on the anterodorsal tip of pb2 as part of the origin of TD II in cleared and stained material of M. dolomieu. In es- sence, this cartilage lies on the “free” and cartilaginous end of pb2 adjacent to the interarcual cartilage. Such a cartilage was not observed during the dissection of the dorsal gill arches prior to double-staining. Eight speci- mens were cleared and stained (one each of M. coosae, M. d. dolomieu, M. notius, M. p. punctulatus, M. treculii, and three M. s. salmoides) following dissec- tion. The first author noticed what he would call a car- tilaginous bud on one specimen of M. d. dolomieu and M. s. salmoides. However, confidence in this interpre- tation is not high since the TD II and/or pb’s were re- moved in many dissections and consequently could have removed any autogenous or bud-like cartilages. A transversus dorsalis III/IV bundle originates on the dorsal surfaces of epibranchial 3 and pharyngobranchial 3 and often includes the medial carti- laginous end of epibranchial 4 and dorsal surface of pharyngobranchial 4. Fibers extend medially to join its antimere in the absence of a raphé. The posterior bor- der of the bundle is usually separable from fibers of the sphincter oesophagi. Obliquus posterior (OP, Figs. 10-11). This is a well-developed muscle posterior to both of the adductor muscles. It is attached to the posterior side of ceratobranchial 5 and runs dorsally to insert on the pos- terior surface of epibranchial 4, medial to levator externus IV. The obliquus posterior grades into the sphincter oe- sophagi medially. Adductores (Add IV-V, Figs. 10, 11). Adductor IV connects ceratobranchial 4 and epibranchial 4. The insertion on epibranchial 4 is lateral to the obliquus pos- terior. Adductor V connects ceratobranchials 4 and 5; however, fibers may extend onto the cartilaginous end of epibranchial 4 at its articulation with ceratobranchial 4. Adductor V is posterior to adductor IV. Retractor dorsalis (RD, Fig. 10). The retractor dorsalis is a large muscle originating on the ventral sur- faces of vertebral centra 2 and 3, with some fibers on the posterior half of vertebral centrum 1. The left and right muscles pass anteroventrally to insert on the dorsal surfaces of pharyngobranchials 3 and 4. Interbranchiales abductors. The abductors con- nect the proximal, lateral bases of the filaments to the bony arches. Interbranchiales adductores (IntBAdd, Fig. 12). These bundles originate on the base of the gill fila- ment of one hemibranch and attach distally to the gill filament of the opposite hemibranch. Thus, this is a Type I adductor as defined by Pasztor and Kleerekoper (1962). IV. MUSCLES SERVING THE VENTRAL ELE- MENTS OF THE BRANCHIAL ARCHES The ventral side of the branchial arches is charac- terized by a distinct pattern of ligaments connecting the bony elements. From the ventral surface of basibranchial 3 a cupula (cartilaginous pedicle) arises and is positioned between the fourth ceratobranchials. An U-shape liga- ment connects the cupula posteriorly to each of the pro- cesses on the ventral surfaces of the third hypobranchials. This semi-circular ligament was originally considered to be characteristic of acanthopterygians (Dietz 1914, as cited by Winterbottom 1974a; Stiassny 1992), but has been identified in several non-acanthopterygians (Springer & Johnson 2004). Additional ligaments connect hypobranchials 2 and 3. The ventral aorta ascends and passes just anterior to the cartilaginous pedicle. Sphincter oesophagi (SphOes, Figs. 10-11, 13). This muscle is comprised of many autonomous bundles and fibers. Perhaps the most obvious bundles circum- scribe the esophagus. In doing so, they may grade with the obliquus posterior. Fibers also parallel the posterior borders of transversus dorsalis III/IV and transversus ventralis V and may grade with either muscle. One sphincter bundle holds the retractor dorsalis against the esophagus acting as a ‘belt’. Additional sphincter bundles lie medially and laterally to the retractor dorsalis as the fibers run from the esophagus to the dorsal side of pharyngobranchial 3. Obliqui ventrales (OV I-III, Fig. 13). Three obliquus ventralis muscles connect the ceratobranchials with their respective hypobranchials across their ventral BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 119 surfaces. The majority of each muscle lies on the hypobranchials while the ceratobranchials contain strong tendinous attachments. Some fibers of obliquus ventra- lis III also attach to the U-ligament. By definition, these latter fibers comprise rectus ventralis III, and the result- ing bundle is a graded obliquus ventralis III and rectus ventralis III. Recti ventrales (RV IV, Fig. 13). A single rectus ventralis IV connects the ventral side of ceratobranchial 4 to the U-ligament. Antimeres converge slightly to- ward the ligament. A fascia extends dorsally along the margins of rectus ventralis IV and the rectus communis forming a longitudinal branchial wall. This fascia ex- tends posteriorly and attaches to ceratobranchial 5 im- mediately posterior to transversus ventralis IV. M. treculii (ROM 1784CS) possesses an extra bundle of rectus ventralis IV originating on the left ceratobranchial 4 and inserting on the U-ligament. Centrarchus macropterus (UMMZ 164961) also has an additional rectus bundle originating on ceratobranchial 4, passes ventral to transversus ventralis IV, and inserts tendinously on the posterior side of the cupula at its base. Transversi ventrales (TV IV-V, Fig. 13). Trans- versus ventralis IV connects the medial surfaces of ceratobranchials 4 across the midline in the absence of a raphé. The posterior border is ventral to the anterior border of transversus ventralis V. Transversus ventralis V connects the fifth ceratobranchials in a similar man- ner. The posterior border of transversus ventralis V is continuous with sphincter oesophagi with some fibers appearing to grade with it. Dorsally, the transversi ventrales attach to skin between the ceratobranchials. Rectus communis (RComm, Fig. 13). Antimeres insert on the lateral surfaces of the urohyal and are graded above its dorsal edge. Antimeres diverge posteriorly and pass medially to ligaments connecting the urohyal and hypobranchials 2 and 3. They insert tendinously on the ventrolateral edges of the fifth ceratobranchials, lat- Figure 12. Dorsal view of a gill filament from the trans- verse section of the left, ceratobranchial 3 of M. p. punctulatus (OSUM 102598, 144.7 mm SL). Anterior is to the left. Scale bar = 1 mm. The interbranchiales abductores were not included but would connect either side of the ceratobranchial to the bases of the gill fila- ments. Abbreviations: IntBAdd – interbranchialis ad- ductor; as in Figure 11. Figure 13. Ventral view of the branchial gill arch muscu- lature of M. d. dolomieu (OSUM 102600, 155.2 mm SL). Anterior is to the left. Scale bar = 5 mm. The hyoid arch has been removed and the rectus communis cut away from the urohyal. The right antimere of the rec- tus communis has been cut near its insertion. Abbrevia- tions: hb – hypobranchial; OV – obliquus ventralis; PCE – pharyngoclavicularis externus; PCI – pharyngoclavicularis internus; RComm – rectus com- munis; RV – rectus ventralis; TV – transverses ventra- lis. 120 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) eral to the insertions of pharyngoclavicularis externus and internus. The rectus communis may become tendi- nous as it passes lateral to the ventral aorta. V. MUSCLES BETWEEN THE PECTORAL GIRDLE AND THE SKULL, HYOID, AND BRAN- CHIAL ARCHES Sternohyoideus (StHyo, Figs. 8, 14-15). The sternohyoideus originates on the dorsal surface of the ventral arm of the cleithrum, lateral and anterior to the origin of pharyngoclavicularis externus. Antimeres are heavily graded and contain three myocommata. The bundles pass anteriorly and insert on the lateral sides of the urohyal. Connective tissue from the sternohyoideus extends dorsally and attaches to the ventral processes of hypobranchials 2 and 3. The sternobranchialis, which is derived from the sternohyoideus and attaches to the third hypobranchial, is absent. Pharyngoclavicularis externus (PCE, Figs. 13- 15). This muscle originates on the dorsal surface of the ventral arm of the cleithrum. It passes vertically to in- sert tendinously on the ventral side of ceratobranchial 5. Length of its insertion is almost that of transversus ven- tralis V. Pharyngoclavicularis internus (PCI, Figs. 13- 15). This muscle originates on the medial surface of the cleithrum near the ‘bend’ at the juncture of the dorsal and ventral arms. The bundle passes horizontally to in- sert tendinously on the ventral side of ceratobranchial 5, medial to the pharyngoclavicularis externus. The inser- tion occupies a small area near the posterior border of transversus ventralis V. Pomoxis nigromaculatus (ROM 82440) is unique in that the anterior portions of both antimeres continue anteriorly and insert tendinously on the tips of ceratobranchial 5. In doing so, this ante- rior extension passes dorsal to transversus ventralis IV. Protractor pectoralis (PrPect, Fig. 7). This is a well-developed muscle posterior to the muscles serving the dorsal elements of the branchial arches. It origi- nates tendinously on the wing of the pterotic and passes ventrally where it grades into the branchial wall. At the point where muscle fibers disappear, the branchial wall attaches strongly to the cleithrum, dorsal to pharyngoclavicularis internus and ceratobranchial 4. Figure 14. Left, lateral view of the pectoral fin (15 rays) and girdle of M. treculii (UMMZ 220247, 137.2 mm SL). Anterior is to the left. Scale bar = 5 mm. A. Super- ficial abductor muscles and those attaching to the cleithrum from the branchial and hyoid arches. B. Me- dial abductor muscles. Abbreviations: AbdP – abductor profundus; AbdS – abductor superficialis; ArrV – ar- rector ventralis; cl – cleithrum; StHyo - sternohyoideus; as in Figure 13. Figure 15. Left, medial view of the pectoral fin (15 rays) and girdle of M. treculii (UMMZ 220247, 137.2 mm SL). Anterior is to the right. Scale bar = 5 mm. A. As above. B. After removal of the adductor superficialis bundles. The adductor radialis is outlined by the dashed line. Abbreviations: AddM – adductor medialis; AddP – adductor profundus; AddRad – adductor radialis; AddS – adductor superficialis; ArrD – arrector dorsalis; cr - coracoid; as in Figures 13 - 15. BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 121 Levator pectoralis (LPect, Figs. 2, 6, 7). The most obvious fibers of this muscle originate on the pterotic and intercalar and insert on the cleithrum and posttemporal. Perfunctory attention was paid to this muscle so additional attachment sites are not described. Baudelot’s ligament. Although possessing no muscle fibers, this ligament passes from the exoccipital to a vertical ridge on the medial side of the supracleithrum. VI. MUSCLES OF THE PECTORAL FIN The pectoral girdle consists of the cleithrum, coracoid, scapula, and four radials with which the rays articulate. An interosseus septum occurs between the coracoid and cleithrum. The number of fin rays varies from 14 to 17 in Micropterus, and spines are absent in all species. The first ray is the most robust and referred to as the marginal or leading ray. The interradialis pec- toralis is absent in all specimens dissected. Abductor superficialis (AbdS, Fig. 14). This muscle originates on the posterior side of the lateral flange of the cleithrum. The individual tendons form a continuous aponeurotic sheet and insert on the anterior surfaces of the fin ray bases of all but the marginal or leading ray. Abductor profundus (AbdP, Figs. 14, 16). This muscle is medial to the abductor superficialis and origi- nates primarily on the lateral surface of the coracoid but also includes the cleithrum near its ventral tip and the interosseus septum between these two bones. The lat- eral surface of the muscle often has a vertical ridge that coincides with the ventral border of the abductor superficialis. The development of this ridge is variable across specimens. The insertion site is the ventral sur- face of the posteriorly directed flange at the base of the fin ray. Insertion is tendinous on all rays. The tendon serving the leading ray arises from fibers only partially separated from the main abductor mass. The size of the ray and the tendon serving it decrease at the trailing end of the fin. Arrector ventralis (ArrV, Fig. 14). The arrector ventralis lies anterior to the abductor profundus and medial to the abductor superficialis. It originates primarily on the cleithrum but also includes the anterodorsal corner of the coracoid and the interosseus septum. Insertion is on the anteromedial surface of the leading ray via a well- developed tendon. Adductor superficialis (AddS §1-3 and AddM, Fig. 15). Three bundles comprise the adductor superficialis. The distinct middle bundle is given the name of adductor superficialis medialis. Bundle one (§1) is the most medial section and originates on the dorsal arm of the cleithrum. It is vertically orientated and inserts on Figure 16. Different patterns of the origin and insertion of the adductor radialis of the pectoral fin. Pectoral rays served have been numbered with the leading ray as ray 1. Scale bar = 1 mm. A. Medial view of the left pectoral fin (16 rays) of M. notius (TU 9775, 107.4 mm SL) after removal of the adductor muscles. Anterior is to the right. B. Medial view of the left pectoral fin (17 rays) of M. notius (UF 57323, 187.6 mm SL) after re- moval of the adductor muscles. Anterior is to the right. C. Medial view of the right pectoral fin (17 rays) of M. notius (UF 57323, 187.6 mm SL) after removal of the adductor muscles. Anterior is to the left. Abbreviations: r – ray number; as in Figures 14-15. 122 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) the more ventral fin rays. The adductor superficialis medialis (§2 - AddM) is oblique to §1 and originates on the cleithrum along the bend where the dorsal and ven- tral arms converge. Section 2 serves the middle fin rays. The third section originates on the cleithrum, dorsal cor- ner of the coracoid, and usually the ventral border of the scapula and the interosseus septum. Section 3 is twisted such that tendons from the ventral border of the bundle serve the dorsalmost fin rays. Tendons insert on the anterodistal surfaces of the base of all but the leading fin rays. Tendon length is greatest near ray 8. Adductor profundus (AddP, Fig. 15). The pro- fundus muscle is lateral and ventral to the adductor superficialis. Origin includes the cleithrum, coracoid, and interosseus septum. Insertion is tendinous on the ventral surface of a posteriorly directed flange of the fin ray. It is noteworthy that tendons serving the ventralmost three rays are greatly reduced in size, and tendons serv- ing the last two fin rays are closely bound to the ante- penultimate tendon. Their small size and hidden appear- ance in combination with neighboring connective tissue create uncertainty in determining the number of ventralmost rays served. In the majority of specimens, all rays except the leading ray are served. Thorsen and Westneat (2005) report variable insertion patterns, such as those noted above, in labroids and five additional percomorph families. Arrector dorsalis (ArrD, Fig. 15). It originates on the cleithrum, coracoid, and interosseus space be- tween cleithrum and coracoid and inserts on the leading ray. This muscle is graded with the adductor profundus. Adductor radialis (AddRad, Figs. 15-16. Table 1). This muscle is small and lateral to the adductor pro- fundus. It originates on the medial sides of radials 2-4. Anteriorly fibers may also originate on a fine ridge of the scapula. Insertion is tendinous on the ventralmost fin rays, the number of which is variable both within species and individuals (Table 1). In many instances when the specimen is asymmetrical with respect to the number of fin rays, the fin with the additional ray usually has an additional tendon of the adductor radialis although this pattern is not constant. Given the small size of the tendons, it is possible that some inconsistencies may be the result of observation error, although Thorsen and Westneat (2005) also find interspecific variation of the adductor radialis among labroids and five additional fami- lies of coral reef fishes. Sometimes muscle fibers of the adductor radialis are found that originate separately on the ventromedial face of radial 4 [M. coosae, OSUM 105299 (Right side); M. notius, UF 57323 (R), UF 58761 (L); M. p. punctulatus USNM 251991 (88.0 mm SL) (R); P. nigromaculatus, ROM 82440 (L, R)] or the coracoid at its deepest indentation [M. coosae, OSUM 105299 (L), ROM 82449 (R); M. notius, UF 57323 (L); M. p. punctulatus, OSUM 102597 (L); M. s. salmoides, ROM 1782CS; M. treculii, UMMZ 136849 (L); L. gibbosus, ROM 82439 (L, R)]. A single specimen may have mul- tiple conditions. These fibers comprise a small slip of the adductor radialis that is lateral to the adductor profundus and clearly separable from the more lateral abductor profundus which is exposed in medial view between the coracoid and fourth radial. This slip is separable from the adductor radialis at its origin but then grades to varying degrees with the main adductor mass. A tendon of the slip in- serts on the last fin ray and is generally either posteri- orly (if from radial 4) or laterally (if from the coracoid) displaced relative to tendons from the adductor radialis although it passes into the main mass prior to insertion in L. gibbosus (ROM 82439). Coracoradialis. Fibers originate from the cora- coid near its deepest indentation and attach tendinously to a process on the ventromedial face of radial 4 in M. treculii (OSUM 105227, ROM 1784CS). This process occurs distally at approximately one-third the length of radial 4 and is not observed in other dissected centrarchids. The muscle is lateral to the adductor profundus and medial to a translucent connective sheet between radial 4 and the coracoid. These two speci- mens of M. treculii are the largest black bass (> 250 mm SL) dissected and originate from hatchery ponds (G. Garrett, pers. comm.). Fibers in this same orienta- tion are present in M. d. dolomieu [OSUM 102599 (L), 173.2 mm SL; ROM 82437 (R), 133.2 mm SL] but at- tach proximally on the ventromedial surface of the fourth radial in the absence of a process. VII. MUSCLES OF THE PELVIC FIN The pelvic fin contains one spine and five rays. The rays are numbered from 1-5 with ray 1 adjacent to the spine and ray 5 being the most medial. Only M. s. salmoides (ROM 1780CS) deviated from this pattern with a pelvic fin of I4 (bilaterally). Abductor superficialis pelvicus (AbdSP, Fig. 17). The abductor superficialis pelvicus originates on the abductor profundus pelvicus, posterior end of the basipterygium, and a mid-ventral septum where it joins its antimere. It grades to varying degrees with the ab- ductor profundus pelvicus, but the two muscles are most easily separable posteriorly. The muscle extends ~50- 60% of the pelvic length and inserts via an undifferenti- BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 123 Ta bl e 1. V ar ia tio n in th e in se rti on si te s o f t hr ee st ria te d m us cl es : a dd uc to r r ad ia lis (p ec to ra l f in ), hy po ch or da l l on gi tu di na lis a nd fl ex or v en tra lis e xt er nu s ( ca ud al fi n) ; n um be r of ca ec ae ; a nd n as al ro se tte in M ic ro pt er us an d ce nt ra rc hi d sp ec ie s. St an da rd le ng th (m m ) f ol lo w s t he ca ta lo gu e n um be r f or sp ec im en s f ro m th e s am e l ot . “ L” an d “R ” r ef er to th e l ef t a nd ri gh t s id es o f t he sp ec im en re sp ec tiv el y. “N /A ” i nd ic at es d am ag e t o th e m us cu la tu re o r c le ar in g an d st ai ni ng p rio r t o di ss ec tio n. A dd uc to r r ad ia lis : A d as h se pa ra te s th e n um be r o f p ec to ra l f in ra ys fr om th e n um be r o f f in ra ys se rv ed . A n as te ris k fo llo w in g th e n um be r o f p ec to ra l f in ra ys in di ca te s t ha t t he la st fi n ra y is a ru di m en t. H yp oc ho rd al lo ng itu di na lis , f le xo r v en tra lis e xt er nu s: “ D ” or “ V ” re fe rs to c au da l f in ra ys d or sa l o r v en tra l t o th e la te ra l m id lin e re sp ec tiv el y; fi n ra ys a re n um be re d se qu en tia lly in e ith er di re ct io n fro m th e m id lin e. R os et te : R os et te n ot at io n de sc rib es th e n um be r o f f ol ds (m ov ab le fl ap s o f e pi th el iu m ) a nd ri dg es (i m m ob ile fl ap s) d or sa l a nd v en tra l o f a lo ng itu di na l ax is . A t t he p os te rio r e nd o f t he lo ng itu di na l a xi s, a si ng le fo ld is a lw ay s p re se nt a nd is d en ot ed “ /1 /” . T he n um be r o f f ol ds is se pa ra te d fr om th e nu m be r o f r id ge s b y a co lo n. El em en ts do rs al o f t he lo ng itu di na l a xi s a re le ft of “/ 1/ ” w hi le el em en ts ve nt ra l o f t he ax is ar e r ig ht o f “ /1 /” . F or ex am pl e, “4 :2 /1 /4 :1 ” i nd ic at es 1 2 ro se tte el em en ts. F ou r f ol ds an d tw o rid ge s a re p re se nt d or sa l t o th e lo ng itu di na l a xi s, fo llo w ed b y a si ng le fo ld a t t he p os te rio r e nd o f t he a xi s, an d fo ur fo ld s a nd o ne ri dg e ve nt ra l t o th e ax is . R id ge s a lw ay s oc cu rr ed a nt er io r t o fo ld s. Sp ec ie s a nd A dd uc to r H yp oc ho rd al Fl ex or V en tra lis N o. o f R os et te N o. o f R os et te C at al og ue N um be r Ra di al is L on gi tu di na lis E xt er nu s Ca ec ae Fo rm ul a El em en ts L R L R L R L R L R M . c at ar ac ta e R O M 8 24 45 16 - 4 16 - 4 D 5 -9 D 4 -9 V 1 -2 V 1 -2 10 5: 1/ 1/ 5: 1 4: 2/ 1/ 4: 1 13 12 U M M Z 16 87 52 16 - 4 16 - 3 D 5 -9 D 5 -9 V 1 -2 V 1 -2 12 3: 0/ 1/ 2: 0 N /A 6 N /A M . c oo sa e O SU M 1 05 22 9 16 - 4 16 - 4 D 4 -9 D 5 -9 V 1 -2 V 1 -2 10 3: 0/ 1/ 3: 0 2: 1/ 1/ 2: 1 7 7 R O M 8 24 49 15 - 3 15 - 3 D 5 -9 D 5 -9 V 1 -2 V 1 -2 10 3: 0/ 1/ 3: 0 3: 0/ 1/ 3: 0 7 7 R O M 8 24 50 15 - 3 15 - 3 D 6 -9 D 4 -9 V 1 -2 V 1 -2 9 3: 0/ 1/ 2: 1 3: 0/ 1/ 3: 0 7 7 U F 86 26 8 15 - 4 15 - 4 D 3 -8 D 3 -8 ab se nt ab se nt 10 4: 0/ 1/ 3: 0 4: 0/ 1/ 3: 0 8 8 U F 86 31 3 16 - 4 16 - 3 D 5 -9 D 5 -9 V 1 -2 V 1 -2 8 4: 0/ 1/ 3: 1 4: 0/ 1/ 3: 1 9 9 U F 89 98 9 N /A - 5 N /A - 4 D 5 -9 N /A V 1 V 1 -2 13 N /A N /A N /A N /A U SN M 1 68 07 5 14 * - 3 16 - 4 D 5 -9 D 3 -9 V 1 -3 V 1 -2 11 3: 1/ 1/ 3: 1 3: 1/ 1/ 3: 1 9 9 M . d . d ol om ie u R O M 1 78 3C S 16 - 4 16 – 4 D 6 -9 D 5 -9 V 1 -2 V 1 -2 16 N /A N /A N /A N /A R O M 8 24 36 16 - 4 16 – 3 D 4 -9 D 4 -9 V 1 -2 V 1 -2 14 6: 0/ 1/ 5: 0 6: 0/ 1/ 5: 0 12 12 R O M 8 24 37 16 - 4 17 – 5 D 6 -9 D 5 -9 V 1 -2 V 1 -2 12 4: 0/ 1/ 4: 0 3: 1/ 1/ 3: 1 9 9 O SU M 1 02 59 9 16 - 4 16 - 4 D 4 -9 D 4 -9 V 1 -2 V 1 -2 12 5: 0/ 1/ 5: 0 4: 1/ 1/ 2: 0 11 8 O SU M 1 02 60 0 16 - 4 16 - 4 D 5 -9 D 5 -9 V 1 -2 V 1 -2 14 4: 0/ 1/ 4: 1 4: 1/ 1/ 3: 2 10 11 M . d . v el ox U SN M 1 16 80 2 17 - 4 17 - 4 D 3 -9 D 4 -9 V 1 -2 V 1 -2 10 3: 0/ 1/ 2: 1 3: 1/ 1/ 2: 1 7 8 U SN M 1 28 68 0 16 - 4 16 – 4 D 5 -9 D 5 -9 V 1 -2 V 1 -2 12 3: 1/ 1/ 3: 0 3: 0/ 1/ 3: 0 8 7 M . n ot iu s U F 57 32 3 17 - 5 17 - 6 D 5 -9 D 5 -9 V 1 -2 V 1 -2 11 2: 0/ 1/ 2: 0 2: 0/ 1/ 1: 1 5 5 U F 58 76 1 (1 31 .8 ) 17 - 4 17 - 4 D 5 -9 D 5 -9 V 1 -2 V 1 -2 12 4: 0/ 1/ 4: 0 5: 0/ 1/ 4: 1 9 11 U F 58 76 1 (1 45 .2 ) 16 - 5 16 - 5 D 5 -9 D 5 -9 V 1 -2 V 1 -2 11 4: 1/ 1/ 4: 0 4: 1/ 1/ 4: 1 10 11 TU 9 77 5 (1 07 .4 ) 16 - 5 16 - 5 D 5 -9 D 6 -9 V 1 -2 V 1 -2 12 1: 0/ 1/ 1: 0 1: 0/ 1/ 1: 0 3 3 TU 9 77 5 (1 52 .3 ) 16 - 5 16 - 4 D 6 -9 D 5 -9 V 1 -2 V 1 -2 12 1: 0/ 1/ 1: 0 N /A 3 N /A 124 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) Ta bl e 1 . C on t. M . p . p un ct ul at us O SU M 1 02 59 7 15 - 4 15 - 3 D 5 -9 D 5 -9 V 1 -2 se e te xt 11 4: 0/ 1/ 4: 0 4: 0/ 1/ 3: 1 9 9 O SU M 1 02 59 8 15 - 3 15 - 4 D 3 -9 D 3 -9 V 1 -2 V 1 -2 11 5: 0/ 1/ 4: 1 6: 0/ 1/ 5: 0 11 12 U SN M 2 51 99 1 (9 5. 4) 14 - 2 15 - 3 D 5 -9 D 5 -9 V 1 -2 N /A 11 N /A N /A N /A N /A U SN M 2 51 99 1 (8 8. 0) 15 - 4 14 - 3 D 5 -9 D 5 -9 V 1 -2 V 1 -2 10 3: 0/ 1/ 3: 0 3: 0/ 1/ 3: 0 7 7 M . p . h en sh al li U A IC 1 05 87 .1 5 16 - 4 16 - 4 D 5 -9 D 5 -9 V 1 -2 V 1 -2 10 6: 0/ 1/ 5: 0 5: 0/ 1/ 5: 0 12 11 U A IC 1 26 52 .1 9 16 - 5 16 – 4 D 6 -9 D 5 -9 V 1 -2 V 1 10 5: 1/ 1/ 4: 1 4: 1/ 1/ 4: 1 12 11 M . s . f lo rid an us U M M Z 15 86 34 15 - 4 15 - 4 D 6 -9 D 5 -8 V 1 -2 V 1 -2 37 2: 1/ 1/ 2: 1 2: 0/ 1/ 2: 1 7 6 U M M Z 16 33 50 15 - 4 15 - 4 D 6 -9 D 5 -9 V 1 -2 V 1 -2 40 3: 1/ 1/ 4: 0 4: 0/ 1/ 4: 0 9 9 M . s . s al m oi de s R O M 1 78 0C S 14 - 3 15 - 4 D 6 -9 N /A V 1 -2 V 1 -2 26 N /A N /A N /A N /A R O M 1 78 1C S 15 - 4 15 - N /A D 6 -9 N /A V 1 -2 N /A 29 N /A N /A N /A N /A R O M 1 78 2C S 14 - N /A 14 - 3 D 6 -9 D 6 -9 V 1 -2 N /A 23 N /A N /A N /A N /A R O M 8 24 35 15 - 4 15 - 4 D 6 -9 D 5 -9 V 1 V 1 33 4: 0/ 1/ 4: 0 4: 0/ 1/ 3: 0 9 8 R O M 8 24 46 ( 15 3. 2) 15 - 3 14 - 2 D 6 -9 D 6 -9 V 1 -2 V 1 30 N /A 3: 1/ 1/ 3: 1 N /A 9 R O M 8 24 46 ( 17 3. 0) 14 - 3 15 - 4 D 6 -9 D 6 -9 V 1 V 1 31 4: 0/ 1/ 3: 1 N /A 9 N /A R O M 8 24 46 ( 21 4. 4) 15 - 3 16 - 4 D 6 -9 D 6 -9 V 1 V 1 -2 24 4: 1/ 1/ 3: 1 3: 0/ 1/ 4: 0 10 8 R O M 8 24 46 ( 21 9. 4) 14 * - 3 14 - 4 D 6 -9 D 6 -9 N /A N /A 27 4: 1/ 1/ 3: 1 3: 1/ 1/ 3: 1 10 9 M . t re cu lii O SU M 1 05 22 7 14 - 4 15 – 5 D 4 -9 D 5 -9 N /A N /A N /A 4: 0/ 1/ 4: 0 N /A 9 N /A R O M 1 78 4C S 15 - 4 15 - 4 D 4 -9 D 4 -9 N /A V 1 -2 N /A N /A 5: 0/ 1/ 5: 0 N /A 11 U M M Z 13 68 49 16 – 4 16 – 5 D 3 -9 D 3 -9 V 1 -3 V 1 -3 9 N /A 3: 0/ 1/ 2: 1 N /A 7 U M M Z 22 02 47 15 - 3 15 – 4 D 5 -9 D 3 -9 V 1 -2 V 1 -2 N /A 3: 0/ 1/ 3: 0 3: 0/ 1/ 2: 1 7 7 A. a rio m m us R O M 8 24 44 14 - 4 15 - 4 D 4 -9 D 5- 9 V 1 -2 V 1 -3 7 2: 1/ 1/ 2: 1 3: 0/ 1/ 2: 1 7 7 C. m ac ro pt er us U M M Z 16 49 61 13 – 3 13 - 3 D 5 -9 D 5 -9 V 1 V 1 -2 8 4: 1/ 1/ 4: 1 6: 0/ 1/ 5: 0 11 12 L. cy an el lu s R O M 8 24 38 13 – 3 13 - 3 D 5 -9 D 5 -9 V 1 -2 V 1 -2 4 3: 0/ 1/ 2: 1 2: 2/ 1/ 2: 1 7 8 L. g ib bo su s R O M 8 24 39 13 – 2 13 - 3 D 5 -9 D 5 -9 V 1 -3 V 1 -3 7 2: 2/ 1/ 3: 1 4: 0/ 1/ 2: 1 9 8 P. n ig ro m ac ul at us R O M 8 24 40 14 – 3 14 - 4 D 7 -9 D 6 -9 V 1 V 1 8 4: 1/ 1/ 4: 0 4: 1/ 1/ 4: 1 10 11 Sp ec ie s a nd A dd uc to r H yp oc ho rd al Fl ex or V en tra lis N o. o f R os et te N o. o f R os et te C at al og ue N um be r Ra di al is L on gi tu di na lis E xt er nu s Ca ec ae Fo rm ul a El em en ts L R L R L R L R L R BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 125 ated tendinous sheet to the spine and all rays on the anterior surface of their medially directed, basal flanges. Hypaxial fibers attach to this muscle via myocommata and complete separation of the two muscles is very dif- ficult. Abductor profundus pelvicus (AbdPP, Fig. 17). This long muscle originates on the basipterygium and mid-ventral septum and extends ~80% of the pelvic length. The insertion is tendinous on the dorsal surfaces of the five rays but not the spine. Arrector ventralis pelvicus (ArrVP, Fig. 17). This muscle originates on the ventral side of the pelvis, lat- eral to the abductor profundus pelvicus, although some fibers may extend medially onto it. The arrector ventral pelvicus extends to the anterior end of the pelvis but not beyond it. Insertion is tendinous on the proximal, ventral surface of the spine. Adductor superficialis pelvicus (AddSP, Fig. 17). This muscle originates on the dorsal side of the adductor profundus pelvicus and basipterygium near the posterior pelvic process. Antimeres converge at the midline but are not in contact; the muscle extends ~75% of the pelvic length. Tendons insert on the anterior faces of the medially directed flanges of the spine and first four rays. The fifth ray does not possess a medially directed flange and consequently is not served by the adductor superficialis pelvicus. Adductor profundus pelvicus (AddPP, Fig. 17). This long muscle originates on the basipterygium and extends to the anterior tip of the pelvis but not beyond it. The tendons form a continuous sheet that attaches to the anterior surfaces of the five rays. This attachment site is ventral to that of the adductor superficialis pelvicus. Arrector dorsalis pelvicus (ArrDP, Fig. 17). The arrector dorsalis pelvicus originates on the lateral side of the basipterygium. Posteriorly the bundle sits in a well- defined bony groove of the basipterygium. Fibers may extend ventrally onto the arrector ventralis pelvicus. It extends anteriorly ~75% of the pelvic length. A large tendon inserts on the proximal, lateral surface of the spine. Extensor proprius (ExtP, Fig. 17). This small, but well-developed muscle originates on the adductor superficialis and profundus pelvicus with fascia extend- ing laterally to the basipterygium. Insertion is on the dorsal, distal surface of ray 5, where a small tuberosity is present. Micropterus coosae (OSUM 105229) and M. treculii (ROM 1784CS) each possess one bundle that attaches to rays 4 and 5, while its antimere attaches to ray 5. The extensor proprius inserts on ray 4 bilater- ally in M. s. salmoides (ROM 1780CS), which has only four fin rays. Figure 17. Pelvic fin musculature of M. s salmoides (ROM 82446, 153.2 mm SL). Anterior is to the left. Scale bar = 5 mm. A. Dorsal view of the pelvis. The left antimeres of the extensor proprius and adductor superficialis pelvicus have been removed. B. Ventral view of the pelvis. The left abductor superficialis pelvicus antimere has been removed. C. Left, lateral view of the pelvis including the ventral tip of the left cleithrum. Ab- breviations: AbdPP – abductor profundus pelvicus; AbdSP – abductor superficialis pelvicus; AddPP – ad- ductor profundus pelvicus; AddSP – adductor superficialis pelvicus; ArrDP – arrector dorsalis pelvicus; ArrVP – arrector ventralis pelvicus; ExtP – extensor proprius; Hyp – hypaxialis; ICA – infracarinalis ante- rior; ICM – infracarinalis medialis; spine – pelvic spine; as in Figures 14 and 16. 126 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) VIII. MUSCLES OF THE CAUDAL FIN There are 17 principal caudal rays in black bass; nine dorsal and eight ventral to the midline. The outer- most principal caudal rays are segmented and un- branched (Schultze & Arratia 1989). These rays are numbered sequentially beginning at the midline, with those dorsal and ventral to the midline denoted “D” and “V” respectively. Thus, “V6” is the sixth principal caudal ray ventral to the midline. Along the dorsal and ventral margins of the caudal fin are a variable number of procurrent rays which may be segmented but are un- branched (Schultze & Arratia 1989). The caudal fin of Micropterus species is typically composed of three epurals, two uroneurals, and five autogenous hypurals. The ural complex (pU1 and caudal centra) is ossified and fused as a single entity. Vertebrae anterior to the ural complex are denoted “pU#” starting with pU2 and sequentially numbered anteriorly. The neural spine of pU2 is short. Cartilaginous distal radials lie distal to the neural and hemal spines of pU3-pU4 or pU4-pU5 and anterior to the procurrent caudal rays. The adductor dorsalis is absent in all species observed. Interradialis (IntRad, Fig. 18). The interradialis originates and inserts on caudal rays and usually over- laps several fin rays. These bundles span from V8 to D8 or D9. In addition, separate bundles occur between D9-10 and D8-10. At the middle of the fin, fibers origi- nate from a single attachment site on V1 proximally and insert broadly along the ventral side of D1. Medially this arrangement is reversed with fibers originating on D1 and fanning onto V1. Hypochordal longitudinalis (HL, Fig. 18. Table 1). This muscle is asymmetrical and originates on the ural complex, hypurapophysis, head of the hypural, hypural plates 1-3, and in some specimens on the cen- trum of pU2. Insertion is tendinous on a variable num- ber of fin rays (Table 1). With two exceptions (M. coosae, UF 86268; M. s. floridanus UMMZ 158634), the dorsalmost fin element is D9. The tendon serving D9 is the largest. The site of attachment is the anteroventral corner of the ventralmost fin ray, but the site moves distally on more dorsal fin rays. Often the tendon serving the ventralmost ray ‘hides’ against the posteromedial surface of the preceding tendon thus lead- ing to erroneous observations. Removal of singular and minor variants reveals D5-9 as the generalized condi- tion with M. s. floridanus and M. s. salmoides charac- terized by D6-9. Flexor dorsalis (FD, Fig. 18). The flexor dorsa- lis originates on the centra and neural spines of pU2-5, ural complex, epurals, uroneurals, hypural plates 4-5 and variably on hypural plate 3. Insertion is tendinous on the Figure 18. Left, lateral views of the caudal fin muscula- ture. Anterior is to the left. Scale bar = 5 mm. A. M. coosae (UF 86268, 131.8 mm SL) after removal of the epaxialis and hypaxialis. Note that the flexor ventralis externus is missing and the dorsalmost insertion of the hypochordal longitudinalis is to the eighth ray dorsal of the lateral midline. B. M. p. punctulatus (OSUM 102598, 144.7 mm SL) after removal of the epaxialis and hypaxialis. The solid black line is a nerve. Abbrevia- tions: D – dorsalmost caudal ray served by the hypo- chordal longitudinalis; FD – flexor dorsalis; FDS – flexor dorsalis superior; FV – flexor ventralis; FVE – flexor ventralis externus; FVI – flexor ventralis internus; HL – hypochordal longitudinalis; ICP – infracarinalis poste- rior; IntRad – interradialis; SCP – supracarinalis poste- rior; V – ventral caudal rays served by flexor ventralis externus. BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 127 anterior ends of D1-8 with the insertion moving to the lateral surface at D8. Tendons serving D7 and D8 become ‘stringy’, meaning that they appear to be comprised of multiple strands and therefore multiple insertion sites. On many specimens, two tendons appear to insert on D8. One tendon inserts medially in an orientation consistent with tendons of the flexor dorsalis, while a more distal and lateral insertional site is consistent with the flexor dorsa- lis superior. Under this interpretation, both the flexor dorsalis and flexor dorsalis superior insert on D8 in a majority of specimens. At times, a similar orientation is observed on D7. Flexor dorsalis superior (FDS, Fig. 18). The flexor dorsalis superior originates muscularly on the epurals, distal tip of neural spine pU3, and tendinously on distal radial at the tips of neural spines pU4 or pU5. This distal radial is serves as an attachment site for the supracarinalis posterior, but the two muscles are not continuous as the flexor dorsalis superior is removable largely without affecting the supracarinalis posterior. The flexor dorsalis and flexor dorsalis superior are graded. The most common insertion is on the dorsal, distal sur- faces of D8-D12 but may vary to either D8-D11 or D8- D13. Flexor ventralis (FV, Fig. 18). The flexor ven- tralis originates on the parhypural, hypurapophysis, ural complex, hypural plate 1, centra pU2-5, and hemal spines pU2-3. The centrum of pU5 and hemal spine of pU4 may variably be included. Insertion is on the anterior faces of V1-8 with the site moving anterodorsally from V1 to V8. Flexor ventralis inferior (FVI, Fig. 18). This muscle is chevron shaped and separable from the flexor ventralis. Origin of the dorsal arm includes hemal spines pU2-3 while the ventral arm originates on the distal tip of hemal spine pU4 and distal radials between hemal spines pU3-pU4 or pU4-pU5. The infracarinalis poste- rior also attaches to this distal radial where some fibers may grade with the flexor ventralis inferior. The most common insertion is on the ventrodistal surfaces of V9- 11 but may vary to either V9-V10 or V9-V12. Flexor ventralis externus (FVE, Fig. 18. Table 1). This small slip of a muscle originates on a combina- tion of centra pU3-5 and hemal spines of pU2-3. Poste- riorly, fibers disappear into an aponeurosis which yields long and slender tendons that insert on a variable num- ber of caudal fin rays (Table 1). Often a single tendon will extend to a point between two adjacent fin rays thus appearing to insert on both rays. This pattern was inter- preted as a single tendon which should serve a single ray, the dorsalmost of the two rays. The flexor ventralis Figure 19. Branching patterns of the pyloric caecae. Scale bar = 5 mm. A. and B. Two observed patterns of branching in M. s. floridanus (UMMZ 158634, 128.8 mm SL). C. M. cataractae (UMMZ 168752, 102.8 mm SL) has 12 single caecae surrounding the stomach. The intestine has not been included. Figure 20. Left, lateral view of the nasal rosette. Dotted line indicates the extent of the nasal capsule. Scale bar = 1 mm. A. M. coosae (UF 86268, 131.8 mm SL). Pattern notation is 4:0/1/3:0 as described in Table 1. B. M. notius (UF 58761, 131.8 mm SL). Pattern notation is 4:0/1/4:0. 128 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) externus grades with the hypaxialis in M. p. punctulatus (OSUM 102599) and the flexor ventralis in M. s. salmoides (ROM 82446, 219.4 mm). In both instances, their respective insertions remain distinct. Micropterus coosae (UF 86268) is unique in lacking a flexor ventra- lis externus. IX. NOTES ON OTHER FEATURES OF THE SOFT ANATOMY IN MICROPTERUS SPECIES Pyloric Caecae (Fig. 19). Pyloric caecae are blind sacs that circle the intestine immediately below the stom- ach. They are assumed to increase retention time of food and therefore serve to facilitate protein digestion and fat or carbohydrate absorption (Barrington 1957). The structure and numbers of caecae are variable among species and absent in other species (e.g. Cyprinidae). The number of caecae and the presence of branched caecae are not independent characters although they are described separately. Micropterus s. floridanus and M. s. salmoides have predominantly branched caecae that occur vari- ably along the length of the caecum. Frequently a cae- cum has multiple branches resulting in a single base hav- ing three, four, and in one instance, seven tips (M. s. salmoides, ROM 82446, 153.2 mm). The remaining species of Micropterus and other centrarchids have predominantly unbranched caecae. In the majority of these latter exceptions, adjacent branches share part of their walls and thus are caecae not completely sepa- rated from each other (M. coosae UF 89989, USNM 168075; M. d. dolomieu OSUM 102600, ROM 82436; M. p. punctulatus OSUM 102597). M. s. floridanus and M. s. salmoides have the most caecae averaging 38.5 and 27.9 respectively. The remaining species of Micropterus average 9.0 (treculii), 10.0 – 10.8 (coosae, henshalli, punctulatus), 11.0 – 11.6 (cataractae, notius, velox), and 13.6 (dolomieu) caecae. The single specimen of each outgroup species has eight (Pomoxis, Centrarchus), seven (Ambloplites, Lepomis gibbosus), or four (Lepomis cyanellus) caecae (Table 1). If branches are ignored, M. s. floridanus and M. s. salmoides average 14.0 and 10.0 bases respectively and fall within the range of other Micropterus species. Nasal rosette (Figs. 20, 21. Table 1). The nasal rosette consists of a number of folds in the nasal epithe- lium arranged above and below the longitudinal axis of the nasal cavity, with a single fold at the posterior end of this axis. This arrangement results in an odd number of folds with an equal number of folds above and below the longitudinal axis. ‘Folds’ and ‘ridges’ were differen- tiated based on their flexibility. A fold is defined as flex- Figure 21. A. Scatterplot of the average number of rosette structures (folds and ridges) per specimen against stan- dard length for Micropterus species (filled circles, solid line) and outgroups (open circles, dashed line). B. Scatterplot of the average number of rosette structures per specimen against standard length for each Micropterus and outgroup species. Subspecies have not been differentiated. Lines of best fit were forced through the origin. Abbreviations: C – M. cataractae; D – M. dolomieu; N – M. notius; O – M. coosae; P – M. punctulatus; S – M. salmoides; T – M. treculiis. BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 129 ible piece of tissue that ‘flops’ when pushed with a probe, whereas a ridge is immobile resembling a speed bump. Folds are always posterior to ridges. The fold is simple, not crenulated, such that a cross-section resembled a keyhole. In the notation below, the number of folds pre- cedes the number of ridges and is separated by a colon. A backslash on either side of “1” represents the single fold along the horizontal axis. The number of folds and ridges ventral of the axis follows in a format consistent with the number of dorsal structures (Table 1). For ex- ample, the rosette pattern “4:1/1/3:2” has 11 structures in total. Dorsal to the axis are four folds and a single ridge, followed by a single fold parallel to the longitudi- nal axis. Three folds and two ridges are ventral to the axis. Rosette size and the number of elements within the rosette increase with standard length. Variation in standard length explained 47% and 20% of the variation in the number of rosette elements for outgroup and ingroup species respectively (Fig. 21A). Analysis by ingroup species resulted in five clusters of species (Fig. 21B). The positive relationship between standard length and the number of rosette elements is supported by ob- servations that smaller (ridges) and ‘missing’ elements (denoted by appropriate spaces) are found at the ante- rior end of the rosette. Posterior elements (folds) are always larger and thus presumably older than more an- terior elements (ridges). In instances of asymmetry above and below the longitudinal axis, elements on the dorsal side of the longitudinal axis are either more nu- merous or more developed than elements below the lon- gitudinal axis. DISCUSSION MYOLOGICAL NOTES Myological descriptions of Micropterus are consistent with the conditions of other teleosts (Winterbottom 1974a) and specific observations of the dorsal branchial arch muscles in M. dolomieu (Springer & Johnson 2004). A “universal division” (Wu & Shen 2004) of the adductor mandibulae originates from the hyomandibula and palatal arch and passes lateral to ra- mus mandibularis V (RMV) to insert on the Meckelian fossa and a shared myocommatum with Aù . Wu & Shen (2004) identify this section as A2â and synony- mize it with A2â of Winterbottom (1974a) and A2-A3 of Gosline (1989). The A3 division described herein is the universal division, and the graded A1–A2 section is the A1-A2á bundle sensu Wu and Shen (2004). The pres- ence of an A1-A2á bundle with autonomous divisions of A2â and Aù in the absence of A3 appears to be a gen- eral characteristic of Perciformes (Wu & Shen 2004). Divisions of the adductor mandibulae have come under recent scrutiny in an effort to determine the reli- ability of the course of RMV. One school notes that the path of RMV through divisions of the adductor mandibulae is variable and phylogenetically uninforma- tive (Edgeworth 1935; Winterbottom 1974a; Gill & Mooi 1993). An opposing view suggests that the path of RMV may be phylogenetically informative (Gosline 1989; Diogo & Chardon 2000; Nakae & Sasaki 2004; Wu & Shen 2004), with the primary obstacle to robust interpreta- tions being comparisons among non-homologous divi- sions of the adductor mandibulae. This latter opinion implies that if the problem of non-homology among divi- sions of the adductor mandibulae is resolved, the path of the RMV would likely contain a recoverable phyloge- netic signal (Gosline 1989). Evolutionary models ex- plaining the origin and pattern of division of the adductor mandibulae were then developed (Gosline 1986, 1989; Diogo & Chardon 2000; Wu & Shen 2004). However, such explanations are based on the a priori premise that the course of the RMV is a valid taxonomic char- acter. While it is highly probable that nerves, and their paths, retain a phylogenetic signal, we seek to avoid the circularity of employing the path of RMV to identify divisions of the adductor mandibulae. An ontogenetic analysis of the adductor mandibulae may resolve this dilemma and inform the larger issue of using nerves to identify muscles. MYOLOGICAL VARIATION Black bass display all four classes of myological variation: minor, incongruous, singular, and mimicking. Minor variants are slight differences in the size, shape, or position of the muscle arising from a variety of fac- tors including biological (specimen health, age, sex, etc.) and non-biological (storage, preservation) effects. Ex- amples include variable lengths of the pelvic adductors and abductors and the variable origin of the adductor hyomandibulae on the prootic, the pterotic, or both bones due to the fimbricate suture between them. By describ- ing the generalized condition of a species, minor vari- ants are necessarily excluded. Incongruous variants result in nonfunctional muscles and include cases of absent muscles normally present or shifted insertions, which have negated the original function of the muscle. The sole example of a muscle absent in a specimen was the flexor ventralis externus (caudal fin, M. coosae, UF 86268). Singular variants are atypical and unique to a given specimen. Examples from centrarchids include three bundles of rectus ventralis IV (ventral branchial arches) either all serving the U-shaped ligament (M. treculii, 130 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) ROM 1784CS) or the U-shaped ligament and cupula (Centrarchus macropterus, UMMZ 164961) and the shared origin of the flexor ventralis externus (caudal fin) with either the flexor ventralis (M. s. salmoides, ROM 82446, 219.4 mm SL) or the hypaxialis (M. p. punctulatus, OSUM 102597). Presumably these muscles retain their original functions despite an altered insertion or origin. Polymorphic states of the adductor radialis (pec- toral fin), hypochordal longitudinalis (caudal fin), and flexor ventralis externus (caudal fin) are a result of mim- icking variants which atypically resemble the usual con- dition of another species. Identifying the cause of this variation is problematic but it could result in part from fluctuating developmental conditions or phenotypic plas- ticity induced by locomotory differences between indi- viduals. While some variation may be the result of dis- section errors, safeguards against observer bias were employed. A random dissection order and independent dissections of the bilateral elements in the same indi- vidual suggest that intra-individual, intraspecific, and in- terspecific variation is considerable in black bass. A fifth, and rare, trait-category characterized by a high frequency of diverse morphologies is “explosive” variation (Raikow et al. 1990). The breadth of variation in the adductor radialis (pectoral fin) might be consid- ered explosive and likely results from a combination of mimicking and singular variants. In addition, an unex- plained compensatory mechanism exists whereby the number of pectoral rays served by the muscle co-varies with the number of fin rays present, even within the same specimen. If meristic variation such as the num- ber of fin rays can influence the number of insertion sites, a similar pattern between muscles and other serial bony elements might be expected. The extensor pro- prius (pelvic fin) inserts on the medialmost ray, which is usually the fifth ray in black bass; however, it can insert on the fourth ray in the absence of the fifth ray (M. s. salmoides, ROM 1780CS). Finally, specimens possessing one incongruous or singular variant often possessed a second or third vari- ant. Why variants accumulate in some individuals is not clear, but a variety of intrinsic (genetics, life history, body size – Billerbeck et al. 1997, McDowall 2003) and ex- trinsic (fluctuating environmental conditions – e.g., Gabriel 1944, Hubbs 1959) factors experienced during development are long known to affect the meristics of serial bony elements. For instance, an increase in ver- tebrae but a decrease in anal fin rays is attributed to colder water temperatures experienced by larval M. p. punctulatus at two of nine locations in the Ohio River (Bryan 1969). Observations from the present study sug- gest that co-variation in the number of fin rays and the number of insertion sites occurs in the adductor radialis (pectoral fin) and the extensor proprius (pelvic fin). For example, bilateral differences in the number of pectoral fin rays occurred in seven specimens, and in six of those the number of rays served by the adductor radialis in- creased as the number of fin rays increased. If envi- ronmental conditions affect meristic variation and myo- logical variation is tied to the meristic counts of fins and vertebrae, for instance, then fluctuating environments may also contribute to myological variation. This line of reasoning is in contrast to Raikow et al. (1990, p. 367), who asserted “that neither sexual difference nor indi- vidual developmental instability contributes substantially to intraspecific myological variation” in passerine birds (emphasis added). How much variation constitutes “sub- stantial” variation is not clear. MACROEVOLUTIONARY PATTERNS Micropterus species share a remarkably uniform external morphology characterized by a fusiform body, large mouth, and posterior extension of the median fins. Myologically they display minor variation of the cheek, jaws, branchial and hyoid complexes and slightly more variation in the pectoral and caudal fin complexes. Ad- ditionally, Jayne and Lauder (1994) found M. salmoides had the least variation in the linear dimensions of the myoseptal system relative to one species each of Lepomis, Pomoxis, and Ambloplites. Ecologically, black bass are ram feeders of elusive prey such as fishes and crayfishes. Biogeographically, black bass and their sis- ter group Lepomis (Near et al. 2005) occupy most of the same drainages, but Lepomis is more diverse in the Mississippi basin whereas Micropterus is more diverse along the Gulf Coast and southeastern Atlantic drain- ages where M. cataractae, M. coosae, M. notius, M. p. henshalli, and M. s. floridanus are restricted (Lee et al. 1980). Geographical outliers include M. treculii of the Guadalupe River basin in Texas and M. d. velox of the Neosho River and tributaries of the Arkansas River on the western slope of the Ozark Plateau (Koppelman & Garrett 2002). The remaining species of black bass are distributed from the southern USA, northward into the Ohio River basin (M. p. punctulatus) and Great Lakes including Ontario and Quebec (M. d. dolomieu, M. s. salmoides) (Scott & Crossman 1973; Lee et al. 1980; Trautman 1981). Studies of ecological morphology have concluded that a strong relationship exists between feeding anatomy and diet among fish guilds (e.g., Wainwright & Lauder 1992; Wainwright & Richard 1995), although the ab- sence of a direct one-to-one correlation between mor- BORDEN and COBURN: Striated Muscles of the Black Basses (Micropterus, Centrarchidae) 131 phology and function has been noted (Norton 1995; Wainwright et al. 2005; Collar & Wainwright 2006; Dean et al. 2007). A fuller appreciation of the evolution of the family Centrarchidae requires a consideration of the sta- sis exhibited by one major lineage, Micropterus, in com- parison to the ecological and morphological variation exhibited by its sister lineage, Lepomis, which likely di- verged from each other about 25 mya (Near et al. 2005). The conservatism in Micropterus stands in con- trast to the morphological diversity of the 12 species of Lepomis, which are primarily suction feeders on a range of sedentary to elusive and soft-bodied to hard-bodied prey (Collar et al. 2005). Comparison of the relation- ship between diet and morphological diversity in Micropterus and Lepomis supports the assertion that highly diverse diets across Lepomis spp. are correlated to changes in those elements of the skull, jaws, and sus- pensorium related to food acquisition (Lauder 1983; Wainwright & Lauder 1992; Wainwright & Shaw 1999; Collar et al. 2005). The higher rate of evolution in Lepomis (Collar et al. 2005) is driven in part by diet or habitat specialization resulting in differential biomechani- cal efficiencies and is evidence of natural selection act- ing in a directional manner (Ehlinger 1990; Cutwa & Turingan 2000 and references therein; Thorsen & Westneat 2005; Wintzer & Motta 2005 and references therein; Higham 2007). The high degree of myological and overall mor- phological stasis among Micropterus species indicates natural selection has been stabilizing, not directional, and suggests that speciation in this lineage is driven not by ecological specialization but more probably by vicariant events, a conclusion also arrived at by Near et al. (2003). At least in this taxonomic example, speciation events in a static lineage may retain a clearer signal of vicariant geological events when compared to a more speciose lineage whose cladogenesis results from a mixture of ecological, behavioral, and life history specialization as well as vicariance. The majority of speciation events in Micropterus occur during great topographic and climatic change dur- ing the Cenozoic of North America (Near et al. 2003, 2005). Warm, tropical temperatures with minimal latitu- dinal variation in the Eocene gave way to more modern conditions of cooler temperatures (drop of mean annual temperature 8.2 ± 3.1 °C, Zanazzi et al. 2007), and sea- sonal and latitudinal variation in the Oligocene across central North America (Prothero et al. 2003). The early Miocene (23-17 mya) witnessed large-scale changes in the size of the Antarctic ice sheet (Pekar & DeConto 2006). The cooling phase was marked by Antarctic ice sheet expansion during the middle Miocene (~14 mya, Holbourn et al. 2005) and subsequent sea level fluctua- tions as the Antarctic ice sheet waxed and waned. The timing of late Miocene-early Pliocene sea fluctuations is consistent with the majority of speciation events in Micropterus which are dated to this period (Near et al. 2003, 2005). Fluctuating sea levels may have produced vicariant isolation events at watershed levels. Stabiliz- ing selection resulting in conservative black bass mor- phology and ecology is reflective of a stable river habi- tat during the late Miocene and early Pliocene. Other morphologically static perciform groups such as moronids and non-darter percids may also be reliable identifiers of historical geological events that resulted in allopatric speciation during this time. An alternative hypothesis leading to an increased rate of speciation in Micropterus, and consequently other lineages of North American freshwater fishes, is sec- ondary effects of the tremendous uplift of the Colorado Plateau in Western North America. During the Miocene, Colorado Plateau uplift began about 20 mya and formed the Colorado River less than 6 mya (Dorsey et al. 2007). The large western uplift of the Colorado Plateau may have resulted in a much lesser but still significant uplift in eastern North America (i.e., exhumation of the Appa- lachians during the Miocene-Pliocene), with the effect of entrenching some established eastern river systems (eg., the Susquehenna, New River, Green and Cumberland systems), and isolating other drainages along the Gulf Coast and Atlantic. An explanation of eastern North American uplift in the Mio-Pliocene, although speculative, is consistent with the phylogenies of Catostomidae, Ictaluridae, and Percidae where mem- bers of basal lineages (Carpiodes, Ictiobus in Catostomidae, Harris & Mayden 2001; Ictalurus and Pylodictis in Ictaluridae, Sullivan et al. 2006; Perca in Percidae, Wiley 1992) are lower gradient, large river or more lacustrine than derived lineages which occupy higher gradient habitats. The current habitats occupied by Micropterus, moderate-sized rivers of moderate to higher gradient, suggest it would be subject to the selec- tive pressure generated by uplift. PHYLOGENETIC UTILITY Within the context of this study, muscle complexes in the caudal and pectoral fins exhibit the greatest varia- tion while complexes of the branchial gill arches, cheeks, and pelvic fin are static. The high frequency of mimick- ing variants in the caudal and pectoral fins necessitates the use of alternative coding methods to incorporate intraspecifically polymorphic characters into phylogenetic analyses (e.g., Wiens & Servedio 1997; Wiens 1999, 2001). Overall, the paucity of myological characters 132 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 48(1) suitable for phylogenetic analysis at low taxonomic lev- els, including Micropterus, and their relative rarity com- pared to osteological characters at these same taxonomic levels is a generally supported tenet (Kesner 1994 and references therein; Borden 1998; Diogo 2004). How- ever, across higher taxonomic levels, these five muscle systems (cheek, branchial gill arches, paired fins, caudal fin) are evolutionarily stable complexes that provide nu- merous myological characters suitable for comparative and systematic analyses of teleosts and perciforms. Higher taxonomic levels usually circumscribe greater ecological diversity, which may yield greater anatomical diversity. Rightly or wrongly, static lineages are often con- sidered to be generalized starting points when examin- ing ecological, trophic, or morphological diversity within a larger clade. This perception explains in part why generalized species (i.e., members of static lineages) are often selected as outgroups to polarize character transformation series in phylogenetic analyses. Certainly, the interest and attention of many investigators are drawn to diverse and speciose groups where hypotheses of ecologically-driven divergence mechanisms are possible to test, but static lineages resulting from stabilizing se- lection give a different but equally valuable perspective into the study of evolutionary mechanisms. Because static lineages are difficult to resolve phy- logenetically at low taxonomic levels using morphology, their most efficient application in systematics may be at unraveling higher-level relationships. Conversely, diverse lineages may have higher resolution at lower taxonomic levels but the use of species with specialized morpholo- gies to serve as outgroups or exemplars of clades in higher-level systematics may introduce unintended bi- ases into analyses. Systematists wishing to incorporate myology, and morphology more generally, into macro- evolutionary studies at low taxonomic levels might esti- mate the relative cost in time and effort of muscle dis- sections by assessing the ecological diversity of the ingroup. A cost-benefit assessment a priori may yield more efficient systematic research, although ultimately it is the distribution of character states that is more rel- evant than the number of characters (Kesner 1994). ACKNOWLEDGEMENTS We thank a number of people for the loans and gifts of material including R. Robins, T. Vigliotti, L. Page, and J. Albert (FLMNH), R. Winterbottom (ROM), B. Kuhajda (UAIC), J. Williams, S. Smith, and S. Jewett (USNM), N. Rios and H. Bart, Jr. (TU), D. Catania (CAS), T. Cavender and M. Kibbey (OSUM), D. Nelson (UMMZ), G. Steinhart and R. Stein (OSU), B. Shaner, P. Landford, and J. Biagi (GADNR), G. Garrett (TXDP&W), and J. Williams (USGS-FL). C. Sheil (JCU) kindly made space and time for use of a camera lucida and critiques of the illustrations, and P. Doerder (CSU) patiently endured his ciliate lab smelling of preserved fish. R. Krebs (CSU), D. Franz (FLMNH), and one anonymous reviewer pro- vided valuable critiques of the manuscript. In particular, we thank E. Hilton (FMNH) for a careful review of the manuscript and his many valuable suggestions. The Department of Biological, Geological, and Environmen- tal Sciences (CSU) provided support to WCB. 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