Особенности размножения живородящей ящерицы Zootoca vivipara (Lichtenstein, 1823) (Sauria, Lacertidae) различных высотных поясов Кузнецкого Алатау

Abstract

In order to identify the specific features of mountain populations of the wide-range species of reptiles Zootoca vivipara, we analyzed various aspects of reproduction. This is the key process that ensures the existence of the species in extreme mountain conditions. From spring to autumn 2012-2016, we studied of Z. vivipara populations in the subalpine and mountain forest belts on the western slope in the central part of the Kuznetsk Alatau ridge (54-55° N, 87-88° E, southeast of Western Siberia). We studied the phenology of the active period of Z. vivipara (dates of the first and last encounters, copulation, birth of yearlings and duration of the active period). The age of animals was determined by the method of skeletochronology. As a result, life expectancy, growth rates of different sexes, gender and age structure during the activity season were estimated. The state of the reproductive system of males (n=61) and females (n=114) during the activity season was studied (See Table 1). The scientific and technical council of the Nature Reserve “Kuznetsk Alatau” approved the research program (Protocol No. 2 as of April 6, 2012). The procedures for trapping and collecting animals comply with international and national requirements for the humane treatment of animals. We detected that the duration of the active period in the studied populations varied from 85 to 152 days. It depended on the height of the territory above sea level and weather conditions in the observed year. The phenological phases of the reproductive period and the sexual cycles of males and females differed depending on the environmental conditions of a particular altitudinal zone: in the mountains, the season of Z. vivipara activity was reduced, which led to a decrease in the growth rate and an increase in the age of puberty of males (2-3 years) and females (3-4 years). As a result, the linear sizes and life expectancy of Z. vivipara individuals were greater in mountain populations than in plain populations. We found that the reproductive core of the low and mid-mountain populations were three-year-old females, and the high-mountain populations were four to five-year-old females. The reproductive core of the high-mountain and mid-mountain populations were two-year-old males, and the low-mountain ones were two- or three-year-old males. The maximum age of breeding males and females in the highlands reaches 8 years (See Fig. 1). The reproductive cycles of males and females of the populations of Z. vivipara of the Kuznetsk Alatau and other populations of the species are similar, but slightly differ in temporal characteristics. It depends on environmental conditions. The cold mountain climate of the Kuznetsk Alatau leads to the fact that spring spermiogenesis, spermation, and mating in the reproductive cycle of males occur a short time before the onset of the warmest period. It is necessary so that the gestation of the offspring by females occurs in optimal thermal conditions. There were no differences in the seasonal dynamics of the relative volume of the testes: the highest values of this parameter were in the beginning and at the end of the active period, as well as during reproduction (See Fig. 2). The sizes of the testes correlated with the length of the males’ body (p<0.01). The relationship of the females’ length and weight with the brood size was revealed (n=80; p<0.01) (See Fig. 3). In the reproductive cycle of females, vitellogenesis occurs in a short time, and the period of embryonic development can be different in time as it largely depends on the temperature conditions of the environment. In some years, the embryo development may be delayed until wintering begins. In the females, vitellogenesis took place after wintering; ovulation and fertilization were in May – early June, and pregnancy and childbirth took place in the third decade of July-August (See Fig. 4). In the midmountain population of Z. vivipara, the body length of newborns is longer compared to the high-mountain population (U=235; Z=4.6; p<0.001) (See Table 3). For mountain populations, a wider range of values was shown; a higher fecundity of females was in low and middle mountains, then in high mountains. In all altitudinal zones, the average long-term population fecundity of females, equal to 7.3 (from 7.1 to 7.6; p<0.001), was 1.2 times higher than in the plain populations in the southeast of Western Siberia and throughout the range (See Table 4). The range of intra-population variability of fertility in the mountains (3-11) was lower than on the plain (2-12). The relationship of the length and weight of females with the brood size was revealed (n = 80; p<0.01). The paper contains 4 Figures, 4 Tables and 30 References.