Features of gametogenesis and sexual cycles of six notothenioid fishes from East Antarctica

Abstract

Some features of gametogenesis and sexual cycles of three species of the genus Trematomus (fam. Nototheniidae)-Trematomus centronotus Regan, T. eulepidotus Regan and T. scotti (Boulenger) and three species of icefishes (fam. Channichthyidae)-Chionodraco hamatus (Lonnberg), Ch. myersi Tyler and Neopagetopsis ionah Nybelin-were studied at Davis and Mawson Seas during austral autumn (March–April), 1983. Two peculiarities of the sexual cycles of Trematomus species may be noted: the uniform state of gonads of mature specimens of each species, and differences in time of spawning (austral summer and autumn for T. centronotus and T. eulepidotus, and, evidently, beginning of spring or the end of winter for T. scotti). Among the features of gametogenesis of icefishes are the early accumulation of yolk in oocytes, and the beginning of polarization and homogenization of yolk in oocytes, which are far from definitive sizes. Some differences in spawning time were registered in first maturing and repeatedly maturing specimens of Ch. hamatus. Repeatedly maturing specimens probably begin to spawn in December–January; those maturing for the first time evidently still spawn in March–April. Ch. myersi and N. ionah, judging by singular mature specimens, supposedly spawn during austral autumn.