Microsoft Word - S-1. Tax-1 Lyngbya_FINAL_12Jun15.doc Bangladesh J. Plant Taxon. 22(1): 59–61, 2015 (June) - Short communication © 2015 Bangladesh Association of Plant Taxonomists POLYMORPHISM IN LYNGBYA NOTARISII (MENEGHINI) WILLE IN CULTURE ABDUL AZIZ1 Department of Botany, University of Dhaka, Dhaka 1000, Bangladesh Keywords: Lyngbya notarisii; Plectonema; Polymorphism; Porphyrosiphon; Synonyms. Morphology of blue-green algae or cyanobacteria may be influenced by environmental factors making identification very difficult. Drouet and Daily (1956) recognized only six genera of coccoid blue-green algae from about four and one-half of a dozen of genera. Drouet (1981), after examining a large number of herbarium specimens including the types of many taxa of Stigonemataceae, considered all the genera as synonyms of Stigonema. Aziz (1989) documented Hapalosiphon, Fischerella and Stigonema-like habits of a non-thermophilic blue-green algal strain D612 in axenic culture and considered all these forms/habits of organisms as Stigonema. Based on culture studies of strains designated as Hapalosiphon, Mastigocladus, Westiellopsis, Fischerella and Stigonema, Begum et al. (1994) suggested to consider these truly branched forms as Stigonema-complex. On 26 November 1995, a brownish-pink filamentous algal sample was collected along with dry coconut palm-bark from Panchagar district, Bangladesh. It was found to contain brownish- pink filaments with thick sheath that is frayed at the tips and was identified as Porphyrosiphon notarisii (Menegh.) Kütz. 1850 (Fig. 1) (Desikachary 1959, 248, Pl. 47, Fig. 9; Starmach 1966, 425, Fig. 630). The genus Porphyrosiphon Kütz. 1849 is separated from Lyngbya Ag. 1824 by having a multilayered sheath with a red or brown pigment (Bourrelly, 1985). Lyngbya aestuarii Liebn. ex Gomt., L. maior Menegh. ex Gomt. 1892 and L. majuscula Harv. ex Gomt. 1892 produce multilayered sheath (Starmach, 1966, Figs 338, 343 and 345, respectively). The coloured filament is due to the production of scytonemin pigment to protect the cyanobacterium from near UV radiation (Muehlstein and Castenholz, 1983). Many of the features mentioned in the literature of Porphyrosiphon have been highly variable and resemble Lyngbya majuscula (Desikachary 1959). In L. ceylanica Wille, Aziz and Tanbir (1999) observed variation in colour, being reddish-brownish in upper filaments that received more light when grew on moist rice-field soil (Fig. 2), with dimensions very similar to Porphyrosiphon. Drouet (1937) included Lyngbya arboricola Bruhl et Biswas and L. dendrobia Bruhl et Biswas under Porphyrosiphon notarisii. To ascertain the identity and also the variability in regards to nature of filaments, a portion of the bark sample with brownish-pink layer was placed in a Petri dish containing Chu 10D medium, incubated at a continuous light quantity of about 50 µE m-2 s-1 and a temperature of about 25º C. Many hormogonia of 4 to 9 (−20) cells were found to be released, develop into blue-green filaments. After about 15 days, many filaments attaining about 3 cm long developed centering the bark (Fig. 3). Initially filaments were blue-green with relatively thin non-stratified sheath like Lyngbya (Fig. 4). But later on some filaments produced false-branches like Plectonema Thur. (Fig. 5), while many filaments became purplish to reddish-brown with 10−12-layered sheath like Porphyrosiphon (Figs 6, 7), even more than that found in nature (Fig. 1). Further growth resulted much wider filaments with 2 or 3 trichomes within highly thickened rigid sheath (Figs 8, 9) that 1Email: dr.aziz.botany@gmail.com 60 AZIZ did not gelatinize like Microcoleus. When a reddish-brown filament was placed on a glass slide with water and exposed to sunlight for two days, huge quantity of reddish-brown water-soluble pigment scytonemin was formed, some amount came out of the filament through open end of the sheath (Fig. 10). The released scytonemin after drying formed dark coloured crystals posteriorly. However, the scytonemin produced by cells was diffused into a few innermost sheath layers but not the outermost one(s) (Figs 8, 9). Figs 1−10. Lyngbya notarisii (Menegh.) Wille 1914: 1. Porphyrosiphon-like filament with frayed sheath and very identical cell dimensions in Figs 1 & 7. 2. Filaments of Lyngbya ceylanica from rice-filed soil differing in colour but with similar thickness of sheath. 3. A bark sample in liquid Chu 10D culture medium producing many filaments. 4. Lyngbya-like filament from the culture. 5. A false-branched filament like Plectonema. 6. Porphyrosiphon-like filament with multilaminated red-brown sheath from the culture. 7. An enlarged terminal part of the Porphyrosiphon-like filament from the culture; note variation in sheath colour. 8. A Microcoleus-like filament with three trichomes inside the parent sheath. 9. An enlarged part of the filament with two trichomes showing details; note the absence of gelatinous sheath. 10. Formation and release of huge scytonemin on a glass slide after exposure to sunlight of a cultured red-brown filament in water; note the trapped scytonemin within the filament and release through open end. Bars = 25 µm: Bar A is for Figs 4−6, 8, 10; Bar B is for Figs 1, 2, 7, 9. Fig. 3 = scale is in millimeter. POLYMORPHISM IN LYNGBYA NOTARISII 61 In the culture, the developed false-branched filaments (Fig. 3) resembled the genus Plectonema (Desikachary 1959, 434, 438, Pl. 83, Figs 1, 8). The false branches were produced in young filaments due to rapid growth of intercalary hormogonia that created pressure on relatively thin sheath and came out by rupturing it like that of Scytonema with heterocysts. At lamellated thick-sheath stage, the new trichomes, grew side by side (Figs 8, 9), a feature of Microcoleus Desmaz. 1823, but here the gelatinous sheath was absent. Castenholz (1989) noted that the genus Porphyrosiphon is known primarily for a single trichome within a red to red-brown laminated sheath, although occasionally it is with more than one trichome per sheath, the feature reflecting polymorphic nature as is found in the present study. Because of similarities, Lyngbya, Phormidium Kütz. 1843 (narrow sheathed Lyngbya-like filaments forming an irregular mucilaginous mat) and Plectonema are considered as LPP group (Rippka et al., 1979). The sheath thickness and colour development in filaments appeared to be due to age and light effects, respectively. Lyngbya notarisii (Menegh.) Wille is polymorphic where the growth forms like the genera Plectonema and Porphyrosiphon were found. Considering these facts, the genera Plectonema Thuret 1875 and Porphyrosiphon Kütz. 1850 (P. notarisii (Menegh.) Kütz., monotypic) are considered as the synonyms of the genus Lyngbya Ag. 1824. References Aziz, A. 1989. Polymorphism in Stigonema (Cyanophyta) in culture and its implication on generic delimitation in Stigonematales. Nova Hedwigia 49(3 & 4): 447−454. Aziz, A. and Tanbir, M. 1999. Newly recorded algal taxa from northern districts of Bangladesh. I. Blue-greens. Bangladesh J. Bot. 28(1): 61−68. Begum, Z.T., Akhter, R., Islam, A.K.M. Nurul and Aziz, A. 1994. Taxonomy of the Stigonematalean algae in culture. In: Phamg, S.M., Kum, L.Y., Borowitzka, M.A. and Whitton, B.A. (Eds), Algal Biotechnology in the Asia-Pacific Region, Univ. Malaya, pp. 257−262. Bourrelly, P. 1985. Les Algues d’Eau Douce. Vol. III. Les Algues Blues et Rouges. Réimpression revue et augmentée. Boubée, Paris, pp. 1−512. Castenholz, R.W. 1989. Subsection III. Order Oscillatoriales. In: Staley, J.T. (Ed.), Bergey’s Manual of Systematic Bacteriology 3: 1771−1780. Desikachary, T.V. 1959. Cyanophyta. ICAR, New Delhi, pp. 1−686. Drouet, F. 1937. Brazilian Myxophyceae. I. Amer. J. Bot. 24: 602. Drouet, F. 1981. Revision of the Stigonemataceae: with summary of the classification of the blue-green algae. Beih. Z. Nova Hedwigia 66: 1−221. Drouet, F. and Daily, W. 1956. Revision of the coccoid Myxophyceae. Butler Univ. Bot. Studies 12: 1−218. Muehlstein, L. and Castenholz, R.W. 1983. Sheath pigment formation in blue-green alga, Lyngbya aestyarii, as an adaptation to high light. Biol. Bull. 165: 521−522. Rippka, R., Deruelles, J., Waterbury, J.B., Herdman, M. and Stanier, R.Y. 1979. Generic assignments, strain histories and properties of pure culture of cyanobacteria. J. Gen. Microbiol. 111:1−61. Starmach, K. 1966. Cyanophyta-Sinice Glaucophyta-Glaucophyty. Flora Słodkowodna Polski. Vol. 2. Polska Akademia Nauk, Instytut Botaniki, Warszawa, pp. 1−807. (Manuscript received on 14 September 2014; revised on 29 January 2015)