Background. The questions of amphibians adaptation to the different environmental conditions are very actual. Of particular interest are the studies of early ontogenesis, as the most significant critical period of development, which determines the life strategy of the species as a whole. The aim of the work was to study the embryogenesis and larval development of the Caucasian brown frog, Rana macrocnemis from Dagestan high-mountain populations of at different temperatures in captivity. The morphological features of eggs, the duration of the stage of embryogenesis and larval development of R. macrocnemis were studied.
Materials and methods. Experimental works was carried out in 2017–2018. The object of study was the posterity of the Caucasian brown frog in captivity. The adults of R. macrocnemis were caught in the first decade of May in the highmountain of Dagestan: in the vicinities of Kaya village (1600 m above sea level) – 5 coupler of frog, and in the vicinities of Burshi village (2250 m above sea level) – 3 coupler. The incubation of eggs, the keeping of pre-larvae and growing of larvae was carried out at two temperature regimes – 22–24 and 5 °C. The density of planting was 5 individuals per 1 liter of water. The morphological characteristic of eggs, pre-larvae, larvae, duration of an embryogenesis and its separate periods, survival of embryos and larvae, occurrence of morphological anomalies duration of larval development were taken into account. In total, 7000 eggs, 840 embryos, and 140 larvae were studied.
Results. Females of R. macrocnemis from Kaya (n = 4) oviposited 1710,0 ± 282,56 eggs weighing 234,6 ± 2,51 g, and from Burshi (n = 3) – 2336,3 ± 523,26 eggs weighing 243,2 ± 13,89 g. The duration of embryogenesis from egg laying to hatching at the water temperature of 22–24 °C was 4–6 days, and at the temperature of 5 °C – 22–25 days. The average survival of embryos to emergence from the egg at the water temperature of 22–24 °C (53,9 %) was similar with the other group (51,0 %). The survival of larvae (%) until metamorphosis at 5 °C (24,3 ± 3,74) was on average higher, than at 22–24 °C (18,6 ± 3,40). The duration of larval development in laboratory conditions at the temperature of 22–24 °C was shorter by 25,8 % compared of 5 °C. High temperature hadn’t effect on the size of pre-larvae at the time of hatching and young frogs at exit to the land.
Conclusions. Thus, the embryos and larvae of the Caucasian brown frog are capable to develop in the wide temperature range, differing by 4–5 times. It should be assumed, that this adaptation allows them to occupy the wide range of heights from sea level to the Alpine belt.
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