[Ultrastructural study of spermatogenesis in silversides Oncorhynchus kisutch and cherry salmon O. masou (Salmonidae, Teleostei)].

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.

[Comparative studies of follicle cells in testes of Glyptocephalus stelleri and Pleuronectes pinnifasciatus (Teleostei, Pleuronectidae)].

Accessory cells were studied in early spermatogenesis of flatfishes Glyptocephalus stelleri and Pleuronectes pinnifasciatus using transmission electron microscopy. The morphological organization of accessory cells in G. stelleri was similar to that of Sertoli cells. In P. pinnifasciatus, these cells had morphological organization, which had not been previously described.

[A comparative study of sperm postspawning destruction in flatfishes Hippoglossoides (Cleisthenes) herzensteini and Hippoglossoides dubius (Teleostei, Pleuronectidae)]. / Sravnitel'noe issledovanie postnerestovoi destruktsii spermatozoidov u kambalovykh ryb Hippoglossoides (Cleisthenes) herzensteini i Hoppoglossoides debius (Teleostei, Pleuronectidae).

Ultrastructural aspects of sperm destruction patterns were offered as additional cytological parameters for evaluation of the genus affinity of flatfishes Hippoglossoides dubius and Cleisthenes herzensteini. At the beginning of spermatozoan destruction, cell membrane in both species was found swollen, besides, discontinuity of membranes was observed, and membraneous parts were seen separating from sparmatozoa. We observed the ability of separated membraneous parts to aggregate to twisting conglomerates that wind round the objects of destruction. In H. dubius the membraneous conglomerates wound round spermatozoa, and after that such spermatozoa were phagocyted by follicular cells. In C. herzensteini, the membraneous conglomerates grasped the particles of destructed spermatozoa: the formed residual bodies were collected in the gonad lumen but not phagocyted by follicular cells. The expressiveness of the differences found in the pattern of sperm destruction is so considerable that, in the authors' opinion, these data are to supplement a list of criteria making reasonable reconsideration of the taxonomic status of C. herzensteini: its belonging to the genus Hippoglossoides, and establishing of the genus Cleisthenes as an independent rank.