) TAXONOMIC COMPOSITION AND DISTRIBUTION OF BRACHIONUS (ROTATORIA: MONOGONONTA) POPULATIONS IN PONDS1 R. Sampathkumar2 (With twelve text-figures The different species and varieties constituting the Brachionus population of four freshwater fish-ponds at Tuticorin, south India, were identified and their numerical abundance and frequency of occurrence studied over a period of 19 weeks. Ninevarieties belonging to seven species ofBrachionus were identified. The identifiedtaxa were compared and contrasted with those reported from otherparts ofIndia. B. calyciflorus var. anuaeriformis,B.plicatilis and B. angularis var. angularis dominated the populations during mostofthe investigation period. The other species and varieties occurred occasionally orrarely. Introduction ResultsandDiscussion Rotifers in general, and Brachionus in par- During the study, a total of ten taxa (nine ticular, form an important constituent of varieties belonging toseven species) wereidentified zooplanktonbiomass offreshwaterfishponds.Then- from the four ponds. The species are discussed in importance as food or in the food chain of fish is order of decreasing abundance. Table 1 gives the often emphasised (Jyoti and Sehgal 1979). measurements of the taxa. The weekly variations in However, studies on this group in fish ponds the numerical abundances of the taxa are presented are limited, although several works have been car- in Fig. 12. riedoutin natural waters ofthenorthernpartofIndia 1. Brachionus calyciflorus (George 1961, Jyoti and Sehgal 1979, Nasar 1973, Pasha 1961, Sharma 1976, 1979, 1980, 1981, 1983) This species was represented by three and some in the southern part of India (Dhanapathi varieties. Sharma (1979), however, preferred to 1974, Naidu 1967, Nayar and Nair 1969, Pasha place the three as ‘formae’ and refrained from call- 1961). Such studies in south Tamil Nadu are almost ing them ‘varieties’. absent. In the present study the species and varietal (i) B. calyciflorus v. anuaeriformis Brehm, composition of the genus Brachionus of fish ponds 1909: Antero-dorsal (occipital) margin of lorica and their weekly distribution are dealt with. with four long and equal spines. Postero-lateral spines long, slender and diverging. Two caudal Materialand Methods spines shorter (Fig. 1). The form is identical with Four freshwater fish culture ponds located in that reported from Punjab (Vasisht and Battish the premises of Fisheries College, Tuticorin (Tamil 1971). Nadu) were selected forthepresent study. The man- This variety was one of the two taxa occurring made earthern ponds were under semi-intensive throughout the period ofstudy except in the sample carp culture. Weekly plankton samples were col- of 8 November 1986. Swarming of the variety was lected using a plankton netof60 pm mesh size over noticedwheneverthedissolvedoxygen in water was a period of 19 weeks from 8 November 1986 to 13 high (above 5.0 ppm). March 1987. The samples were preserved in 5% (ii) B. calyciflorus v. dorcas Gosse, 1851: formalin prior to microscopic identification, Lorica rounded and highly stippled. Occipital mar- measurement and enumeration. gin with fourspinesofwhich medians twiceas long. Base of medians wide (Fig. 2). This variety occurred less frequently and less Accepted April 1989. abundantly than B. calyciflorus anuaeriformis. fisheriesCollege,Tuticorin628008,TamilNadu,India.Present address: Dept, of Zoology, National University of Singapore, (iii) B. calyciflorus v. hymani Dhanapathi, Lower Kent Ridge Road, Singapore 0511. 1974: Occipital margin ofthe lorica with four wide- , 68 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. 88 Figs. 1-6. Brachionus spp. 1. Brachionus calyciflorus v. anuaeriformis 2. B. calyciflorus v. dorcas\ 3. B. calyciflorus v. hymani, 4. B. plicatilis, 5. B. angularis v. angularis, 6. B. angularis v. bidens. TAXONOMIC COMPOSITION AND DISTRIBUTION OF BRACHIONUS POPULATIONS 69 based spines of which the laterals slightly shorter. this variety was high, being next to that of B. Outer base of the medians bearing a tooth-like calyciflorus anuaeriformis andif plicatilis. In most projection. Antero-ventral spines flanking the instances it co-occurred with B. plicatilis except median sinus and less prominent in contrast to the during mid-December to mid-March when this form reported from West Bengal (Sharma 1979) variety showed a rare occurrence. (Fig. 3). Sharma. (1979) identified this taxon as B. (ii) Brachionus angularis v.bidens Plate, calyciflorus f. borgeti. 1886: Occipital margins ofthe lorica flattened. This This variety occurred rarely. variety differs from B. angularis angularis in having smaller median spines, V-shaped sinus and 2. Brachionus plicatilis Muller, 1786: ventral margin being moreparallel to thedorsal mar- Posterior of lorica broad. Occipital spines six gin and not wavy. Caudal end of lorica somewhat which are short, stumpy and broad- based. Separa- tapering (Fig. 6). tions between medians and intermediates less dis- This variety occurred less frequently and less tinct. Median sinus verydeepandU-shaped. Antero- abundantly than B. angularis angularis. ventral margin wavy. Footopeningdeepand flanked 4. Brachionus urceolaris v. urwaensis by tooth-like projections (Fig. 4). Sudzuki, 1964 This species also occurred throughout the study period (except in the sample of 19 December Lorica broad and bulged at middle. Dorsal and 1986) as B. calyciflorus anuaeriformis. Also, this ventral plates separated. Occipital spines six. species was the most abundant of all taxa. Swarm- Medians slender, pointed and Banking the deep ing of the species was noticed at ponds at times of median sinus. Laterals also slender but slightly low dissolved oxygen. shorter and less pointed than other spines. Inter- mediates very broad with pointed ends. Caudal 3. Brachionus angularis opening wide and flanked by two spine-like projec- (i) B. angularis v. angularis Gosse, 1851: tions (Fig. 7). Anterior margin of the lorica characteristically This species was rare during the study. rounded and slightly narrower than the posterior. 5. Brachionus caudatus v. aculeatus Occipital spines two, short, slightly pointed and Hauer 1937 flanking the deep U-shaped median sinus. Antero- ventral margin more or less parallel to the dorsal Occipital margin somewhat flat with two margin, showing a shallow depression at median medians and two laterals, all short and pointed at and curved anteriorly at corners. Fool opening ends. Intermediates absent. Two long caudal spines flanked by two shortand rounded caudal spines bent with blunt ends and curved inwards (Fig. 8). This inwards (Fig. 5). form was identical with that reported from Andhra The frequency ofoccurrence and abundance of Pradesh (Dhanapathi 1974). Another form identical Table 1 MEASUREMENTS OFTAXA OFBrachionus FROMFISHPONDS AT TUTICORIN Taxon ofBrachionus Total length Maximum width (gnt) (gm) B. calyciflorus anuaeriformis 243 138 B. calyciflorus hymani 280 170 B. calyciflorus dorcas 217 152 B. angularis angularis 117 88 B. angularis bidens 105 80 B. plicatilis 260 220 B. urceolaris urwaensis 184 164 B. caudatus aculeatus (Fig. 8) 136 101 B. caudatus aculeatus (Fig. 9) 162 104 B falcatus lyratus 450 170 . B. quadridenlalus rhenanus 180 160 70 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. 88 Figs. 7-11. Brachionus spp. & 7. B. urceolaris v. urwaensis, 8. 9. B. caudatus v. aculeatus, 10. B.falcatus v. lyralus, 11. B. quadridentatus v. rhenanus. . TAXONOMICCOMPOSITION AND DISTRIBUTION OF BRACHIONUS POPULATIONS 71 o o ¥ o o + 8 IS 22 29 6 13 19 27 23 30 13 20 27 21 27 NOV. | DEC JAN. | FEB. | MAR. 19 8 6 19 8 7 d© Brachionus calyciflorus v. anuaeriforrnis O9ft. B. calyciflorus v. dorcas. A7 B. calyciflorus v. hymani: ft.plicalilis. B. angularis v. angularis. B. angularis v. bidens. f B.urceolaris v. urwaensis. t&i B. caudalus v. aculeatus. €' B.falcalus v. lyratus. /X B. quadrideniatus v. rhenanus. Fig. 12. Weekly variations in the numerical abundance oftaxa ofBrachionus (The values are averages ofthe fourponds) with the one reported from Orissa (Sharma 1980) tremely long, curved inwards but ends bent out- was also found to occur. The latter had straight wards. Except the relatively greater curvature of the posterior spines with a sharp hook-like projection at intermediates, the form is identical with the one the base, abulgeat the middle andpointed ends (Fig. reported from Bihar (Nasar 1973) (Fig. 10). 9). This species was found to occur only twice Both the forms of this variety occurred only during the study ( 22 and 29 November 1986). twice in the study (15 and 21 November 1986). 7. Brachionus quadridentatus v. rhenanus 6. Brachionus falcatus v. lyratus Lauterbom 1893 Lemmerman, 1908 Posterior half of lorica laterally bulged. Oc- Lorica with six Occipital spines, all blunt. cipital spines six. Medians Hanking deep V-shaped Medians straight and marginally longer than the median sinus and bent gently outwards. Inter- laterals. Laterals slightly curved and pointed out- mediates less distinct, short, broad and pointed. wards. Intermediates seven times as long as the Laterals longer than intermediates and shorter than medians and bent outwards. Two posteriors ex- medians. Antero-ventral margin with two spine-like 72 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. 88 median projections flanking a shallow sinus. ma 1981). Posterior margin slightly flattened bearing two short This taxon ofBrachionus occurred only once nipple-like spines at ends (Fig. 11). This form was during the study (21 March 1987). identical with the one reported from Punjab (Shar- Acknowledgements I thank Dr N. Sukumaran, Fisheries College, Tuticorin, for correcting the manuscript critically. References Dhanap—athi.M.V.S. (1974): RotifersfromAndhraPradesh,India Pasha,S.M.K. (1961): Onacollectionoffreshwaterrotiferafrom I. Hydrobiologia 45 (4): 357-372. Madras. J. Zool. Soc. India 13 (1): 50-55. George,M.G. (1961): Observations on the rotifers from shallow Sharma, B.K. (1976): Rotifers collectedfrom North-WestIndia. ponds in Delhi. Curr. Sci. 30: 247-250. Newsl. Zool. Surv. India 2 (6): 255-258. & JYOTI, M.K. Sehgal, H. (1979): Ecology ofRotifers ofSurin- Sharma, B.K. (1979): Rotifers from West Bengal. 3. Further sar, a subtropicalfreshwaterlake in Jammu (J & K), India. studies on the Eurotatoria.Hydrobiologia 64 (3): 239-250. Hydrobiologia 65: 23-32. Siiarma, B.K. (1980): Contributions to the rotiferfauna of Oris- Michael, R.G. (1973): A Guide to the study of freshwater or- sa, Lidia, ibid. 70: 225-233. ganisms: Rotatoria. ./. Madurai Univ. Suppl. 1: 23-36. Sharma, B.K. (1981): Contributions to the ralifer fauna of Pun- Naidu, K.V. (1967): A contribution to the Rotatonan fauna of jabState,India. I. Family Brachionidae. ibid. 76: 249-253. South India/. J. Bombay nal. Hist. Soc. 64: 384-388. Sharma, B.K. (1983): The Indian species of the genus Nayar, C.K.G. & Nair, K.K.N. (1969): A collection of Brachionus (Eurotatoria: Monogononta: Brachionidae). Brachionid rotifers from Kerala. Proc. Indian Acad. Sci. ibid. 104: 31-39. & 69: 223-233. Vasisht, H.S. Battish,S.K. (1971): The rotiferfaunaofNorth Nasar, S.A.K. (1973): The zooplankton fauna of Bhagalpur: India:Brachionus.Res. Bull, (n.s.) Punjab Univ. 22 (1/2): Rotifera. J. Bhagalpur Univ. 6 (1): 55-62. 179-188.