Reproductive Cycle of Females and Reproduction of the Siberian Salamander (Salamandrella keyserlingii, Caudata, Hynobiidae) on the Coast of the Sea of Okhotsk

The sexual cycle of Siberian salamander females (Salamandrella keyserlingii Dybowski 1870) has been studied in the tundra of the northern coast of the Sea of Okhotsk. Spawning starts soon after the end of wintering (in the second half of May) and ends up in the first half of June. At the end of June, the ovaries show obvious features of a new ovogenic cycle; i.e., pigment starts accumulating in large vitellogenic oocytes. By the end of July, the ovaries in most individuals are already filled with pigmented follicles and the oviduct epithelium is restored. The time from spawning to the appearance of a new generation of mature oocytes lasts a little more than two months (i.e., half of the whole activity season). In the second half of August, the state of the genital system is identical to that in spring before spawning, this proving their annual reproduction. The average fecundity in the studied water bodies varies from 102 to 123 eggs and is comparable to that in other parts of the distribution range. Oogenesis both in the vast majority of females that reach pubescence (subadultus) and in those that spawn in spring occurs simultaneously, but in some subadults it is completed almost a month or a month and a half earlier. By this phenological feature, the female subadults differ considerably from the male subadults, in which completion of spermatogenesis extends much more strongly into the season. A study of the ecology of the Siberian salamander in the conditions of a short season of activity with low temperatures allows for the coast of the Sea of Okhotsk to be considered not as extreme, but, in contrast, rather favorable for its habitation. Many population characteristics in this area are typical for the species in general. The main features of the male and female sexual cycles appear to be similar to those observed in species of the same family that live in the south of the region. The short period of germinal cell development, coupled with the outstanding winter cold hardiness of the species, partially accounts for its unique adaptive potential, which allows it to colonize vast territories of northern Eurasia and successfully thrive in the territories with short and cold summer period.