COMPARATIVE-STUDY OF VITELLOGENESIS OF 2 AFRICAN CATFISH SPECIES CHRYSICHTHYS-NIGRODIGITATUS (CLAROTEIDAE) AND HETEROBRANCHUS-LONGIFILIS (CLARIIDAE)

Chrysichthys nigrodigitatus and Heterobranachus longifilis are two com mercially important African catfish species that have been studied for their reproduction and breeding possibilities in the lagoon waters of Ivory Coast. C. nigrodigitatus is characterized by an annual reproduc tive cycle with a vitellogenesis period from March to June. The reprod uctive season coincides with the short rainy season which is character ized by lower water temperature and salinity at the beginning (Septemb er) and by a progressive rise of these parameters at the end of the se ason (November). The previtellogenic oocytes enter vitellogenesis at a n average diameter of 320 mu m. This initial oocyte stock is reconstit uted progressively as soon as the spawning is achieved and lasts for a period of approximately 3 months. Fully vitellogenic oocytes reach an average diameter of 2.4-2.8 mm by the end of June. The maturation is possible only if a male and a female are confined in artificial spawni ng receptacles. Maturation and spawning generally occur within the fol lowing 3 to 5 weeks for 30 to 80% of the females. When the non-spawnin g females are kept in the nests they maintain fully vitellogenic oocyt es for 3 months with a continuous atresia of the larger oocytes, while the ovaries of the non- spawning females, placed out of the receptacl es, exhibit a complete atresia of all the vitellogenic oocytes. After an HCG-induced ovulation, a new reproductive cycle of H. longifilis -c an be achieved in less than a month. The previtellogenic oocytes enter vitellogenesis at an oocyte diameter of about 380 mu m and become ful ly vitellogenic after 15 days (1.2-1.6 mm in diameter). If maturation is not artificially stimulated the females remain at the same stage of vitellogenesis while larger oocytes undergo atresia and are continuou sly replaced by growing vitellogenic oocytes.