年間 6 号発行
ISSN 印刷: 0018-8166
ISSN オンライン: 1943-5991
Indexed in
Comparative Morphology of Early Oogenesis Stages in Two Forms of Baikal Grayling Thymallus baicalensis (Thymallidae)
要約
The comparative histological study was performed on gonads at the early stages of ontogenesis of two forms of grayling Thymallus baicalensis grown in aquaculture. It was established that cytological features of ovaries are formed earlier than anatomical. Over gonads' forming germ cells in black and white grayling undergo identical phases of development at the same age. Diameter of oocytes (and their nuclei) was similar at the beginning of previtellogenesis. Both forms of grayling of the same age differ by the ratio of the number of germ cells of different development phases. The number of maturing oocytes at the pachytene stage and at the beginning of previtellogenesis does not increase in the black grayling at the age of 733 and 1102 degree-days, whereas in the white grayling at the age of 1102 degree-days the ratio of germ cells varies at all stages of development. Moreover, the number of maturing oocytes at the pachytene stage and at the beginning of previtellogenesis is 2 and 3 times higher than in the black grayling. Dynamics of germ cell ratios may indicate the completion of the reserve of maturing oocytes forming in the black grayling and the continuation of this process in the white one. Further investigations are required for studying differences in the rates of reproduction of gonium and primordial germ cells and nature of the replenishment of oocyte reserves.