ULTRASTRUCTURAL STUDY OF SPERMATOGENESIS IN SILVERSIDES ONCORHYNCHUS KISUTCH
AND CHERRY SALMON O. MASOU (SALMONIDAE, TELEOSTEI)
S. Y. Neznanova, A. A. Reunov
A. V. Zhirmunsky Institute of Marine Biology FEB RAS;
e-mail: masou@yandex.ru
Spermatogenesis in the silversides Oncorhynchus kisutch and cherry salmon O. masou, was investigated by transmission electron microscopy.
It has been shown that male germ cells of both species had no difference in dimensional and ultrastructural parameters. The characteristic feature of spermatogonia
was the presence of germ determinant substance, a cytoplasmic barker of sex line cells. Primary and secondary spermatocytes, as well as early spermatids were
arranged in clusters consisted of synchronously developing cells. The spermiogenesis was peculiar in arising of electron-lucent vesicle which formed a structural complex
with apical dense part of nuclear envelope. This complex has clear similarity with unformed spermatid acrosomes in many Metazoa and has been termed by the authors
as an acrosome-like structure (AS). Disappearance of AS occurring at the final stage of the spermiogenesis allows considering AS as a temporary existing structure
recapitulating the ancestral morphotype of salmonid sperm. Spermatozoa of both species are typical acrosome lacking cells which are characteristic of many representatives
of Teleostei having external fertilization.
Key words: spermatogenesis, ultrastructure, Oncorhynchus kisutch, O. masou
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