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

Spermatogenesis in the Siberian salamander, Salamandrella keyserlingii (Caudata: Hynobiidae)

Spermatogenic cycles of hynobiid salamanders are interesting for the study of male reproductive adaptations in amphibians living under different environmental conditions. In order to detect the main differences between spermatogenic cycles of hynobiids, we studied the spermatogenic cycle of Salamandrella keyserlingii from the suburbs of Tomsk (southeastern Western Siberia) and compared it with those in the literature of hynobiids from different regions of Asia. We histologically and histochemically examined the testes of males captured from April to September. In April, the testes of males entering breeding sites contained bundles of spermatozoa (Sz) and primary (Sg I) and secondary spermatogonia (Sg II). After spermiation and breeding, Sg II began to proliferate. Meiosis of spermatocytes occurred in late June through July. The spermiogenesis began in late July; spermatids and Sz appeared in August. In September, Sz, Sg I, and Sg II were found in testes, which was also when Sg II proliferated. There are two types of spermatogenic cycles in the studied salamanders. The first one includes one period of spermatogonial proliferation (SP) in the first half of the active season. The second type consists of two periods of SP, with one occurring at the beginning and the other at the end of the active season. To identify possible differences in hynobiid spermatogenic cycles, we tested the relation of the duration of active season (DAS), the duration of SP period in the first half of cycle (DSPP), and the number of SP periods per year (NSPPs), considering environmental (air) temperatures in these species’ habitats. We could not find a direct relationship between NSPPs and air temperatures, but DAS and DSPP were correlated with temperature. We assume that two periods of SP can play the most apparent adaptive role in S. keyserlingii in a subarctic climate and in Batrachuperus tibetanus under mountain conditions

Oviduct, egg, and egg sac structures in the Siberian salamander, Salamandrella keyserlingii (Caudata, Hynobiidae): a histological and histochemical study

Unraveling morphological and chemical features of the eggs’ jelly layers and other clutch elements, formed by the oviduct of a female, is necessary for the understanding of reproductive adaptation in amphibians. Our study is the first microstructural and histochemical descriptions about the complexity of oviduct, ovisac, jelly layer of the ovum, and egg sac in hynobiid salamanders. We examined female Salamandrella keyserlingii in preovulatory (gravid) and ovulatory (spent) conditions using anatomical, histological, and histochemical methods. Each ovum was covered with two jelly layers. All ova from one oviduct fell into one egg sac. Inner space of the oviduct, in which ova were passed through, was filled with jelly-like substances designated as «intermediate fluids». We named the membrane-like outer layer of the egg sac as «theca». Jelly layers surrounding the ovum were formed by the oviducal tubular glands of the pars recta and pars convoluta of the oviduct, consisting of acidic and neutral glycoproteins. In the ovisac (i.e., homologous uterus), there were three glandular regions and one aglandular dilatable ovisac. Of the ovisac, glands A, B, and C secreted acidic and neutral glycoproteins for the intermediate fluids, neutral glycoproteins for the theca, and mucus-like materials with a neutral glycoprotein nature, respectively. We suggest that these mucus-like materials are essential to attaching the adhesive tips of the egg sacs to some substrates during oviposition

Database of Amphibia distribution in West Siberia (Russia)

West Siberia is a large region in North Eurasia, which harbours multiple climatic zones, landscape types and biomes. Its amphibian fauna is characterised by a combination of European and Asian species. For many species, this region is the place where the limits of their global ranges are located (Rana temporaria, R. amurensis, Bufotes sitibundus). West Siberia also has at least two non-native amphibian species (Pelophylax ridibundus, Bufotes viridis). The exact ranges and patterns of distribution of the West Siberian amphibian species are poorly studied. The mapping of species ranges is important for the development of conservation measures and monitoring of invasive species is required to investigate their impacts on the natural ecosystems

Geographic variation of life-history traits in the sand lizard, Lacerta agilis: testing Darwin's facundity-advantage hypothesis

The fecundity-advantage-hypothesis (FAH) explains larger female size relative to male size as a correlated response to fecundity selection. We explored FAH by investigating geographic variation in female reproductive output and its relation to sexual size dimorphism (SSD) in Lacerta agilis, an oviparous lizard occupying a major part of temperate Eurasia. We analysed how sex-specific body size and SSD are associated with two putative indicators of fecundity selection intensity (clutch size and the slope of the clutch size-female size relationship), and with two climatic variables throughout the species range and across two widespread evolutionary lineages. Variation within the lineages provides no support for FAH. In contrast, the divergence between the lineages is in line with FAH: the lineage with consistently female-biased SSD (L. a. agilis) exhibits higher clutch size and steeper fecundity slope than the lineage with an inconsistent and variable SSD (L. a. exigua). L. a. agilis shows lower offspring size (egg mass, hatchling mass) and higher clutch mass relative to female mass than L. a. exigua, i.e. both possible ways to enhance offspring number are exerted. As the SSD difference is due to male size (smaller males in L. a. agilis), fecundity selection favouring larger females, together with viability selection for smaller size in both sexes, would explain the female-biased SSD and reproductive characteristics of L. a. agilis. The pattern of intraspecific life-history divergence in L.agilis is strikingly similar to that between oviparous and viviparous populations of a related species Zootoca vivipara. Evolutionary implications of this parallelism are discussed

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

The study of terrestrial vertebrates of the Ob River basin

The paper describes the 300-year history of studying the terrestrial vertebrates in the Ob basin and the current state of researches into amphibians, reptiles, birds and mammals. We examine the role of the research centres in Western Siberia in studying the terrestrial vertebrates in the Ob basin, from the steppe in the south to the tundra in the north and the uplands of the Altai, Kuznetsky Alatau and Salair. We describe the degree of exploration of the terrestrial vertebrates in 11 Russian regions located in the area. The paper includes discussions of rare species, population, spatial distribution and man’s impact on the animals. We also indicate areas where there is insufficient study

The study of terrestrial vertebrates of the Ob River basin

The paper describes the 300-year history of studying the terrestrial vertebrates in the Ob basin and the current state of researches into amphibians, reptiles, birds and mammals. We examine the role of the research centres in Western Siberia in studying the terrestrial vertebrates in the Ob basin, from the steppe in the south to the tundra in the north and the uplands of the Altai, Kuznetsky Alatau and Salair. We describe the degree of exploration of the terrestrial vertebrates in 11 Russian regions located in the area. The paper includes discussions of rare species, population, spatial distribution and man’s impact on the animals. We also indicate areas where there is insufficient study