Seasonal dynamics of male and female reproductive systems in the Siberian salamander, Salamandrella keyserlingii (Caudata, Hynobiidae)

It is not well known how low temperatures, like a subarctic steppe–tundra climate, influence reproductive traits of ectothermic vertebrates. To begin answering this question, we studied male and female reproductive systems of Salamandrella keyserlingii inhabiting a Tomsk population (southeast of Western Siberia), Russia, in ecological and physiological terms. In males, before spermiation, the testicular size and weight in late April–early May were greatest of all. Spermiation occurred during breeding immigration in spring when mean air temperature was above 10°С, and at the same time rain fell. After spermiation, the testicular size and weight decreased sharply, and the diameter of the vasa deferentia increased. “Spawning” (i.e., simultaneous extrusion of sperm and oviposition) occurred from late April to late May, and this duration fluctuated in temperature and humidity. The testicular size and weight increased in summer. Sperm mass was detected in the testes by the smear method in April–September, except in June when single fragmented unrealized sperm was detected and in July when spermatids were detected. In females, ovarian weight was greatest in spring before ovulation. From late June, vitellogenesis began in ovarian follicles, in which mint green yolks accumulated. Melanin deposited in the surface of the ovary from July when oviducts were hypertrophying. In contrast, some large-sized females did not show any sexual maturity shortly before hibernation (although these females may be subadults). These results suggest that low temperatures in Siberia induce early timing of gamete maturation in females, but the females’ reproductive cycle might also be biennial. A reproductive cycle in males was annual with the completion of the gamete maturation process in August