Rivista Italiana di Paleontologia e Stratigrafia voìume 104 numero 1 tavote l-l pagrne 131-138 Aprile 1998 NOA BREVE TUBE MORPHOLOGY AND STRUCTURE OF THE BATHYAL MEDITERRANEAN S ERPULID H Y ALO P OM ATU S V AR I O R UG OS US BEN-ELIAHU & FIEGE, 1996 (ANNELIDA, POLYCHAETA) ROSSANA SANFILIPPO* Receioed September 23, 1997; accepted February 13,1998 Key-uords: Polychaeta, Serpulidae, tube morphologn tube structure, Recent, Pleistocene, Mediterranean, deep-sea benthos. Riassunto. Il polichete serpulide Hyalopomatus oariorugosus, re- centemente descritto da Ben-Eliahu & Fiege (1996), mostra una pecu- liare rugosità sulla superficie esterna del tubo, a differenza d,elle a\tre specie cogeneriche. Tale c^ratreÍe presenta una notevole variabilità, anche lungo uno stesso tubo. Osservazioni al SEM rivelano che 1a rugosità è data dalla presenza da "scaglie", irregolari per forma e di- mensione, disposte lungo le strie di accrescimento. Viene discusso il valore sistematico di questo ed altri caratteri morfologici. Da osserva- zioni su fratture, la parete del tubo presenta cristalli di carbonato di calcio equidimensionali, ad habitus prismatico. Questi hanno una struttura omogenea microcristallina granulare e sono disposti in strati che si sovrappongono durante l'accrescimento intorno al lume del tubo secondo superfici coniche. Una pellicola discontinua di cristalli a struttura amorfa criptocristallina può ricoprire la superficie estèrna del tubo. Tubi fossili di tale specie non sembrano presentare modrfì- cazioni diagenetiche dal punto di vista strutturale. Lr specie, di minuscole dimensioni, colonizza piccoli substrati duri sparsi su fondali fangosi de1 Piano Batiale. Può anche essere gre- garia; in questo caso i tubi incrostano microcavità come l'interno dei calici di coralli. Sono, infine, riportate nuove segnalazioni di H. variorugosus in tanatocenosi profonde del Mediterraneo occidentale ^lt'. "h" i. depositi batiali pleistocenici dell'Italia meridionale. Abstract. The species studied differs from the orher Hyalopo. matus species by having a peculiar rugose sculptured outer tube surfa- ce. This character is markedly variable; it can be more or less develo- ped and may also vary along the same tube. Observed by SEM, this rugosity proves to consist of irreguÌar flaps, roughly following the groFth lìnes. SEM obsenations on transverse fractures show a homoge- neous conposition of the tube wall, consisting of calcium carbonate crystals. These crystals show a prismatic habitus and are arranged in a homogeneous granular microcrystalline structure. New records of H. variorugosus are from deep water stations in the Western Mediterranean and from Pleistocene bathyal deposits of Southern ltaly. The discussion covers aspects of tube characters of use for ta- xonomy. Introduction. Expeditions LIRANIA 92, EOCUMM 94 and EOCUMM 95 in the Southern Tyrrhenian Sea provided material of the recently described serpulid Hyalopomatws aariorugosus Ben-Eliahu Ec Fiege, 1996. The species has also been found in Pleistocene pelitic sediments from Southern kaly (Di Geronimo et a1., in press). Previously tubes of this species had been menrio- ned as "Serpulidae sp." in Barrier er al. (1939) and as Protis sp.\ in Di Geronimo et al. (1995). These records were from Mediterranean bathyal thanatocoenoses and Pleistocene deposits in Southern ltaly. Ben-Eliahu & Fiege (1996) described H. vartorugo- sus [rom the Levant Basin. In the present paper, the tube morphology and structure of H, rtariorugosus are investigated in more de- tail. The tube is characterised by a rugose microsculptu- re, which allows an easy identificarion even of empty tubes (dead or fossil specimens). Serpulid tube morphology and strucrure have ra- rely been investigated with modern techniques. Some more recent works insist on the importance of tube characters (Bubel et a1., 1983; ten FIove & Zibrowius, 1986; Zlbrowius 6c ten Hove, 1987; ten Flove & Smith, 1990; Nishi, 1993;PtIIai 6c ten Flove, 1994; Aliani et ai., 1995, Sanfiiippo, 1996). The study of H. oariorugosus provides the oppor- tunity to investigate the reliability of tube morphology and structure as diagnostic features for taxonomy. Examined material. Recent (Southern Tyrrhenian Sea) (Fig. 1): - URANIA Cruise, July 1992, "del Thoro" canyon, Stn. DG03, 38o43.78'N, 8020.59'8, I95 m: many emp- ty tubes on fossil oyster shells of Wùrmian age; a few tubes and fragments free in the mud. - EOCUMM 94 Exp., July 1994. Stn. 9, 38'34.39'N, 14"29.56'F-,359 m: a few tube fragments free in the mud. - Stn. 18, 38'31.59'N, 1,4"53.57'F.,3OO m: a few 'r Istituto Policattedra di Oceanologia e Paleoecologia, Corso Italia 55,95729 Catania. ). TYRIìHENIAN SE s N + I I 0 100 Knr . Eolian Islands Stn. 18, 300 m r Eolian Islands Stn. 27, 350 m I Eolian Islands Stn. 26, 945 m A Eolian Islands Sur. 9, 959 m o Eolian lslands Sll. 7. i197 m r Eolian Islands Stn. 328, \219 nt [ "dclTbro"ciuryon Sm. DG03, 195 m a Lazzàro, Brly to Middlc Pleistocene marls o Archi, Elrly to Middle Plcistoccne marls SICILY 14 1,32 N" R. Sanfilippo l6 tube fragmenrs. - stn. 27,38"2t.45'N, 15o46.55'E, 350 m: five tube fragments free in the mud. - EOCUMM 95 Exp., June 1995. Stn. 7, 38o34.09'N, 1.4"25.01'F-, ll97 m: one complete empty tube on a pteropod shell fragment; some broken tubes on ptero- pod shells and on pumice. - Stn. 26, 38o38.30'N, 14o57.53'E, 945 m: one broken tube on a pteropod shel1 fragment; one distal end. - Stn. 32B, 38'33.53'N, 15'05.33'E 121,9 m: two complete empty tubes on a small piece of volcanic rock; one incomplete tube on a pteropod she1l. Pleistocene (Southern Calabria) (Fig. 1): - Lazzàro, Early to Middle Pleistocene bathyal marls rich in scleractinians and isidid gorgonians, various samples: one tube on a scleractinian, some tubes inside Lophelia pertusa calices; one distal end of tube; many tube fragments. - Archi, Early to Middle Pleistocene bathyal marls, va- rious samples: many distal ends and tube fragments. Methods. The deep water material was collected by means of dredge (Stn. DG03), grab (Stn. 27) or box corer (Stn. Fig. 1 - Location of samples. 7,9, 18,26,328). The fossil material was collected by means of bulk-samples (Di Geronimo & Robba, 1976). Except for part of DGO3, in which serpulids were found encrusting oyster shells, the samples were treated as routinely done for macrofauna studies, i.e. washed and sieved. H, aariorugoszs tube fragments s/ere found in the fine fractions (500 pm and 250 pm). Some tubes were brokeú, in order to show the in- ner structures. Before coating with gold palladium, tu- bes were treated with concentrated FIzOz to eliminate organic matter from the surface. Results. Tube morphology and structure. lVhereas the original diagnosis of H. variorugosus was mainly based on the anatomy of the soft body (Ben-Eliahu & Fiege, 1,996), the present description fo- cuses on tube morphoiogy and structure. The tube is white, opaque and small-sized, up to 15 mm in length (P1. 1, fig. 1,2), often more or less coiled, folding on itself in the attached part and distally becoming straight and rising from the substrate (P1. 1, fig. 6a, b, c). PLATE 1 Hyalopomatus oariorugosus Ben-Eliahu Ec Fiege, 1996. Scaie bar : 500 pm (Figs. 1-2), 100 pm (Figs. 3-6). Fig. 1 - Tubes cryptic in a small cavity of the substratum. Lazzà,ro. Fig. 2 Tubes gregarious in inner pan of a scleractinian calìce. Lazzàro. Fig. 3 - Tube orifice with a circular smooth peristome. Eolian Islands, Stn.27. Fig. 4 - Distal ends of tubes. Lazzaro. Fig.5 - Attached pan of the tube with a smooth peristome directed towards the tube orifice. "del Thoro" canyon, Stn. DG03 Fig. 6 - Distal erecr parts of tubes, rising from the substratum, more (6a) or less (6b, 6c) rugose. Lazzà;o (6a), Archi (6b, 6c). 133Pl. 1 Tube motpbology and structure of HyaLopomatus aariorugosus t34 R. San/ìlippo The cross section is circular (P1. 1, fig. 1,2,3), the outer diameter relatively constant aiong the tube, ca. 170 ytm (Pl. 1, fig. 3), and the wall thickness reaching ca. 20 pm (Pl. 2, fig. 3, 5). Sometimes there are peristome collar rings, sli- ghtly flaring and directed distally (P1. 1, fig. 5). The tube orifice may be surrounded by a smooth peristome, slightly flaring (Pl. 1, fig. 4, 5. Pl. 2, fíg. 3a). Like in other serpulids, the early part of the tube, corresponding to the juvenile stage (Sanfilippo, 1993), is smóoth. It is separated from the adult portion by a peri- stome (Pl. 2, fìg. 1,). Being very thin and fragile, the ear- ly portion is often lost in the adult specimens and in fossil material. The outer surface of the tube is rugose. SEM exa- mination shows the rugosity to consist of transverse flaps, more or less frayed out and posteriorly directed (Pl. 1, figs. 4, 5, 6; Pl. 2, fig. 2), roughly following the growth line pattern. Sometimes these flaps are few and weakly developed (Pl. 2, fig. 3c), the tubes appearing almost "smooth" (Pl. 1, fig. 4; Pl. 2, fig. 3b). In other cases, the flaps are well-developed and numerous (Pl. 2, fig. 2), giving the tube a "scaly" appearance. Both "scaly" and "smooth" tubes may occur in the same sam- ple. The sculpture may also vary along the same tube, as already stressed by Ben-Eliahu & Fiege (1996). SEM observations on transverse fractures of Re- cent material evidence a homogeneous composition for the tube wall, consisting of calciurn carbonate crystals (Pl. 2, fig. 3, 6). In longitudinal section the crystals are arranged in layers that dip towards the opening at an angle of ca. 30" (Pl. 2, fig. 5). The layers overlay each other during growth, according to a conical plane. This type of microstructure and the layered pattern are com- mon to most of the Mediterranean serpulids (Sanfilippo, t993, t996). At higher magnification all crystals show a simiiar size Q-3 pm in length), and they have a prismatic habi- tus (Pl. 2, fig. 6). They are arranged in a criss-cross orientation, in a homogeneous granular microcrystalline structure (see Hall, 1980) (P1. 2, fig. 6). The opaque ap- pearance of the tube is due to the randomly arranged small crystals, as reported also for other serpulids (ten Hove & Zibrowius, 1986;Zrbrowius & ten Hove, 1987). Crystals and their arrangement are also visible on the outer surface of the tube. Rarely, the surface may be covered by a discontinuous film of very small crystals, organised in amorphous cryptocrystalline masses (Pl. 2, rtg. / ). The microstructure appears not to be affected by diagenetic modifications, being unchanged in fossil tu- bes. Distribution and ecology. In the Tyrrhenian stations (muddy bottoms, depth 200-2000 m) FL oariorugosus occurs rogether with other small-sized serpulids, í.e. Metaoermilia multiuista- ta (Philippi), Sernioermilia agglutinata (Marenzeller), Fl- logranula stellata (Southward) and Filogranula gracilis Langerhans. In the Early to Middle Pleistocene marls of Laz- zàro (Barrier et al., 1996), H, aariorugosus co-occurs with f, stellata, S. agglutinata and 44. mwlticristata. Boul- ders in these marls are encrusted by serpulids l(Vitreotu- bus digeronimoi Zlbrowius, Newermilia falcigera Sou- Ie), Placostegus tridentatu.s (Fabricius)1, isidid gorgonians and scleractinians. Many species of these palaeocommu- nities are no longer part of the Mediterranean fauna G.e. V digeronimoi and l/. falcigera). Both the marl and the boulder faunas indicate a depth of about 600 m. The Archi section (Di Geronimo et a1., in press), consisting of a pelitic Early to Middle Pleistocene se- quence, supplied several tubes ol H. aariorugosus. Benthic assemblages point to a depth of 500-1000 m and are marked by an Atlantic affinity. Among serpulids N. falcigera and F. stellata are common. These ne'q/ records ol H. aariorugoszzs extend its previously known geographical distribution. Ben-Eliahu tr Fiege (1996) reported living speci- mens of this species from the Levant Basin (S of Crete, S-SV of Cyprus, off Israel, off Egypt) and from the Io- nian Sea (Guif of Taranto), depths 792-2009 m, in crevi- ces of hard substrates, such as coal, slag, hardened sedi- ment crusts, and on pteropod shells. PLATE 2 Hyalopornatus aariorugosus Ben-Eliahu 6c Fiege, 1996. Scale bar : 100 pm (fig. I, 2, 4), 5 ;tm (fig. 3, 5, 6, 7). Arrows indicating direction of growth. Fig. 1 - Micromorphology of outer surface consisting of transverse flaps. Lazzàro. Fig.2 - Initial pan of the tube, smooth, no ornamentations. Eolian Islands, Stn.7. Fig. 3 - Transverse section of tube wall, Outer surface continued into flaps. Archi. Fig. 4 - Crowded high transverse flaps, frayed out and turned. Lazzàro. Fig. 5 - Longitudinal section of tube. Vall consisting of layers dipping towards tube mouth. Eolian Islands, Stn. 27. Fig. 6 - Tube microsrmcture. Criss-cross arranged crystals of prismatic habitus, with a homogeneous microcrystalline structure. Eolian Islands, Stn. 27. Fig,7 - Outer tube surface, covered by an irregular film of very small crystais forming amorphous cryptocrystalline masses. Eolian Islands, Stn. 27. Pl. 2 Tube morphology and structure of Hyalopomatus oarìorugosus 135 I )t) R. Sanfi.lippo Therefore, H. oariorwgosus can be regarded as a Mediterranean species, although a record from the Atlantic (halfway between Madeira and Gibraltar) Q" browius, pers. com.) should be noted, suggesting a possi- bly wider Atlantic distribution. The new Recent material was found on a variety of both smooth and irregular substrates, e.g. pteropod shells, oyster shells, pumice and slag. In fact, its small size particularly enables the species to colonize intersti- ces and microhabitats. The new fossil material was gene- rally cryptic, within small crevices of hard substrates or inside the calices of scleractinians. Detached and frag- mented tubes (especially disal ends), secondarily free, were found in muddy sediments. Branching tubes are interpreted as a proof of scis- siparity, as it had also been reported in other genera (Fi- logranula Langerhans, Josephella Caullery & Mesnil, Rhodopsis Bush, Spiraserpula Regenhardt, Filograna Ber' keley; ten Hove, 1979; Ben-Eliahu & ten Hove, 1989; Plllai,1993; Pillai & ten Hove, 1994). Discussion. The finding and description of H. aariorugosus were carried out relatively late, owing to its ecological, biogeographical and stratigraphical range. Its scanty oc- currence could be also due to the inadequate routine methods: the very small-sized tubes are not found until the finest granulometric fractions of sediment (250 and 500 prm) are examined. The scarcity of deep-sea benthos in the Mediterra- nean Sea (Bellan-Santini et al., 1992) ís another reason why H. oariorugosus has seldom been recorded. Records of other species of Hyalopomatus from deep Mediterranean 'waters are rare (Zibrowius, 1969; 1977) and of uncertain specific attribution (Ben-Eliahu Ec Fiege, 1996). The other nominal species of the world- wide distributed genus Hyalopornatws are morphological- ly close to each other, and also iive in bathyal and abyssal depths" H. variorwgosrzs is similar to some other Hyalopomatus species (Ben-Eliahu & Fiege, 1996). How- ever, it markedly differs from all other species in its ru- gose sculpture. In most descriptions of recent serpuiid species no attention is paid to the tube structure. Nevertheless, it may provide useful characters for identification. However, the knowledge of variability of these tube structures, for instance caused by external factors, is still insufficient for an optimum use. This might be corroborated by Bornhold & Milliman (1973) who men- tion a temperature-dependent mineralogy. In fact, the shape and size of the tube wall crystals seem not useful for generic nor for specific determination. These charac- ters are not related to the size or to phylogenetic posi- tion of the worms; they seem to have evolved inde- pendently (Nishi, 1993). A few occasional studies, especially when using SEM techniques, have shown a considerable diversity in the tube wall structure, such as homogeneously opaque oneJayered tubes (e.g. Vermiliopsis Saint-Joseph, Meta- vermilia Bush, Filogranula Langerhans, Filograna Berke- ley, Protula Risso) and twoJayered tubes, the outer layer of which is transparent (Ditrupa Berkeley, Laminatubus, Regenhardt, Galeolaria Lamarck, Neoaermilia Day, Pseu- dochitinopoma Zibrowius). Some other genera (Placoste- gzs Philippi, Vitreotwbus Zibrowius) are characterised by an entirely transparent tube. Small serpulids such as Fi- logranula, Filograna, Protis and Josepbella possess tubes with thin and entirely opaque walls, as shown in this paper for H. aariorugosus. In other genera tube charac- ters may not be constant within the genus. Thus, shape and other morphological features are available for determination at specific level but, till noq it has not been possible to find tube attributes charac- terising the various genera. The same problem exists in Hyalopornatus. Although the tube of H. variorugosus has a morphologi- cal character distinctive at specific level, it is hardly pos- sible to refer the tube to the genus Hyalopomatus without characters of the worms themselves. A morpho- logical tube feature, diagnostic at a generic level, appa- rently has not yet been found for the genus Hyalopoma' tws. Thus, tubes lacking the specific rugosity, could be misidentified {or Protis or Filograna species, wich have similar generic tube characters. In the eyes of a paleontologist, this may be caused by the strong systematic weight given to characters of the worm by neontologists. The paleontological ap- proach is clearly based on different morphological featu- res which may lead to different systematic views. The calcareous tubes are the fossilizable remains palaeontologists have access to whereas the classical ta- xonomy of serpulids by biologists is widely based on morphological features of the soft-bodied worm. In view of a better coordination between the classi- cal "soft-body" taxonomy and the palaeontological ap- proach, it is necessary to carefully study the macro- and microstructures of the tubes of all Recent serpulid species. In summary despite the recent interest in tube ta- xonomy, with promising results, further studies in this field are needed. AclenouLedgements. I am grateful to H. Zibrowius (Stat. Mar. Endoume, Marseille) and H.A. ten F{ove (Instituut voor Taxonomische Zoòlogie, Amsterdam) for their critical review of the manuscript; to S. Di Geronimo (Istituto Policattedra di Oceanologia e Paleoecologia, Catania), P and E.S(/ Knight-Jones (Department of Zoology, Swansea) for useful suggestions; to C. Corselli (Dipanimento di Scienze della Terra, Milano) for loaning some material; O. Torrisi (C.N.R., Catania) and M. Canzanella (Dipanimento di Scienze della Terra, Napoli) kindly supplied assistance in SEM obserwetions. This paper is financially supponed by 40o/' (Rosso) and 600/o (Di Geronimo) M.U.R.S.T. grants. Tube rnorphology and structure of Hyalopomatus ztariorugosus REFERENCES r37 Aliani S., Bianchi C.N., De Asmundis C., Meloni R. (1995) - Scanning electron microscope observations on the tube of the reef-forming serpulìd Ficopornatus enigmaticus (Fauvel) (Annelida, Polychaeta). Boll. Zool., v. 62, pp. 363-367, Padova. 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