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Provided by CMFRI Digital Repository Indian Journal ofFislieries 38 (1): 30-34, March 1991 Oral incubation in marine of the family Tachysuridae

N GOPINATHA MENON'

Central Marine Fisheries Research Institute, Cochin, Kerala 682 031

Received: 7 December 1990

ABSTOACT

Mouth breeding in several of tachysurid catfishes was observed during 1970-76. In all tachysurids male is the brood-carrier. Large, yolked and ripe functiraial ova as well as small and non-yolked, non-functional ova were extruded at the time of spawning. After retaining the large functional ova in the mouth, the non-functional ova were probably eaten by the male parent. Efficiency in fertilization and transfer of eggs was brought about by enlarged pelvic fins of female. The oral cavity of the incubating male got enlarged to receive large number of eggs and the oral epithelium secreted large quantity of mucus for the safe carrying of eggs or embryos in the mouth. The incubating parent usually went without food, although the fry fed in the parent's mouth. Incubation in Tachyswus thalassinus lasted for 28-30 days.

Most members of family Tachysuridae thalassinus at all stages of maturity was re­ which inhabit the seas and estuaries exhibit corded. A few feriiUzed eggs of T. thalassinus mouth breeding. Those observed during this were collected from the mouth of incubating study were: Tachysurus thalassinus, T. serra-parent and reared in the laboratory or aquar­ tus, T. dussumieri, T. tenuispinis, T. caelatus,ium. T. sona, T. maculatus, T. subrostratus, T. platystomus and Osteogeneiosus militaris. RESULTS AND DISCUSSION Most of the members of Tachysuridae MATERIAl^ AND METHODS usually inhabit the shallow waters, where the The fish samples for investigation were bottom is muddy. Muddy bottom is not the collected from the trawl and drift net catches at successful spawning ground for these fishes Mandapam, Pamban, Rameswaram and because thfc eggs, being large and heavy, are Azhikodc during 1969-76. Ovaries at various likely to sink to the muddy bottom and face stages of maturity from different species of many natural hazards. Oral incubation appears tachysurid catfishes were collected and pre­ to be a well-developed and effective way of served in 5% formalin. The sex of the incubat­ protection of the young ones to ensure the ing parent was noted and the eggs, embryos or survival of the species, as has been made out yolked-young ones were collected from the iQx Felichlhys felis by Gudger (1918). mouth and preserved for further study. The In the ovary of T. thalassinus, Menon stomach contents of yolked young ones and (1979) observed 3 different groups of ova, a, b incubating parents were analysed. The length and c, of which the former 2 groups were of the pelvic fin of male and female T. reproductively non-functional. During obser­ vation on the ripe and oozing females of sev­ Present address; 'Scientist Selection Grade. eral species of tachysurids mentioned earlier.

30 Much 1991] ORAL INCUBATION IN CATFISHES

itwasfoundthatthenon-functional ova occupy Tachysurua thalasslnus the posterior region of the ovary. After getting liberated finm the follicles they formed bunches attaching to a few posteiorly located ripe and liberated functional group c ova. While the ;m c ova were heavily yolked, opaque and largMi^groups a and b ova were small, non- yolked w^LtransIucent (Menon 1979), On sevmil occasuM}s, incubating males of various Tachysurus dussumlert species were foun^f-^ith all the 3 groups of ova in their mouth. MoreoVigr. the spent ovaries of these mouthbreeding camsljes contained the ripe group c ova as well as a fe^^sremaining lib­ erated a and b groups of ova. ThuMlwas clear that the reproductively functional groil^ic ova were liberated along with bunches of a a^idb groups of ova at the time of spawning in all the tachysurid catfishes studied- Further, the ex­ ^Fig. 1. Progressive modification of the inner ray of the amination of the stomach contents of incubat­ N^ pelvic fin of T. Ihalassinus and T. dussumieri ing males showed the remains of partly di­ ^f^males al maturity stages E-VI. gested a and b groups of ova. of the pelvic^n got thickened and enlarged. Gunter (1947) made a similar observation As the ovaries matured to stages V and VI, the on the ovary of felis. He found anterior dorsal inner margin of each pelvic fin yellow ripe eggs and whitish or opaque smaller developed^ thick muscular fold-like struc­ eggs of around 3 mm in tKfe ovary. It indicated ture. In ripe females of T. ihalassinus, T. ser- that the smaller non-functional eggs, instead ralus, T. sona and T. maculaius this proU"uber- of developing further, lose their colour and ence acquired a triangiriar shape and in 7'. whatever internal differentiation they have, dussumieri, T. tenuispinis, T. caelaius, T. and become merely sacs of clear material as platystomus T. subrostratus and 0. miliiaris it spawning approaches. The exact function of was cylindrical in shape (Figs 1, 2). This the ova of groups a and b is not clearly known. modification of pelvic fin did not involve any However, Gunter (1947) suggested that these additional bony or cartilagenous structure. eggs were reproductively non-functional, and After spawning the finacquire d its natural size were eaten by the male as additional food and shape except for a white thickening on the before the long fast ahead. He also suggested inner margin. Hardenberg (1935) and Lee that there might be a strong selection for (1937) noticed similar type of sexual dimor­ females that spawn in this manner. phism in Arius maculatus and Galeichthys felis respectively. Al-Hassan et al. (1988) MocUficalion of pelvic fins of females duringobserve d that the pelvic fins were reliable breeding time indicators of sex. When fully extended the en­ As the gonadal maturation progressed, tire female pelvic fins were cupped. In con- the pelvic fins of all Uichysurid female cat- u-ast, the male pelvic fins were su-aighi edged, fishes showed some peculiar modifications. nearly triangular in shape and planar when At maturity stage IV, the tissues in the first ray extended. But this statement did not seem to be

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mouth at this Stage. Gudger (1918) and Gunter Academy of Sciences 14(B) : 502-08. (1945) found the incubation period in G.felis Dmitrenko Ye. 1970. Reproduction of the (Arius thalassinus) in the Arabian Sea. Journal of as 60-70 days. Chidambaram (1942) found Iclhyology 10: 634-40. the period of incubation in Arius jella as 2 Gudger E W. 1918. Oral incubation in the gaff-topsail months. ca\iishFelichlhysfelis. pap. Depl. Mar. Biol. Carn In all the mouth-breeding tachysurids Inst Wash 12 (252): 25-52. studied, male was thebroodingparent.Harden- Gunter G. 1945. Studies on Marine Fishes of Taxas. PubUcatirai 1, pp. 1-190. Institute of Marine Sci­ berg(1935),Lee(1937),Chidambaram(1942) ences. and Ward (1957) noticed the same phenome­ Gunter G. 1947. Observations on breeding of the non in various tachysurid catfishes from u-opi- marine catfish, Galeichthys felis (L). Copeia 4 : cal as well as temperate waters. 217-23. Hardenberg J D F. 1935. Miscellaneous notes on Indian ACKNOWLEDGEMENT fishes. IV. On the propagation of Arius maculatus (Thunb) Naiurk Tijdselt Nedal Ind. 25 : 54-57. I thank Dr P S B R James, Director, Ixe G. 1937. Oral incubation in the marine catl'ish, Central Marine Fisheries Research Institute Galeichthys felis. Copeia I : 49-56. Cochin, for his constant encouragement. I.iebnian E. 1933. Some observations on the breeding habits of Palestine Cichlidae. Proceedings of Zoo­ REFERE.NCES logical Society, London 3 : 85-87. Mcnon .N G. 1979. 'Studies on the biology and fisher)' of Al-Hassaii J M, Clayton D A, Thomson M and Criddle R the giant marine catl'ish, Tachysurus thalassinus S. 1988. and distribution of arid cal- (Ruppell)'. Ph. D. thesis, University of Cochin, fishes from the Arabian Gulf. Journal of Natural Cochin. History 22: 473-87. Balon E K. 1975. Reproductive guilds of fishes. A Oppenheimer J R. 1970. Mouthbreeding in fishes. Ani­ proposal and definitions. Jourital of Fisheries mal Behaviour IS : 493-5ai. Research Board, Canada 32(6): 821-64. '' Ward J W. 1957. Reproduction and early development of the sea catfish, Galeichthys felis in the Biloxi (Mis­ Chidambaram K. 1942. Observations on llie develop­ sissippi) Bay. Copeia 4 : 205-98. ment oi Arius jella (Day). Proceedings of Indian

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