REPRODUCTIVE POTENTIAL OF THE KARELIN’S NEWT, TRITURUS KARELINII (AMPHIBIA, CAUDATA, SALAMANDRIDAE) FROM DAGESTAN POPULATION IN LABORATORY CONDITIONS

Abstract

Background. The Karelin’s newt, Triturus karelinii (Strauch, 1870) – a declining species listed in the Red Data Book of Russian Federation. The North-Eastern periphery of the area is located in Dagestan. Currently, methods are being developed for captive breeding of the Karelin’s newt from the Dagestan population. The purpose of the work: to characterize the reproductive potential of the Karelin’s newt from Dagestan population, including numbers of eggs, pre-larvae and larvae obtained from each female. Materials and methods. In 2017, 10 pairs of the Karelin’s newt were captured in the Tabasaran district of Dagestan, from which the first offspring were obtained in 2018 using hormonal stimulation. In 2019, hormone injections were not used, and offspring from newts were obtained with natural spawning. The resulting eggs and pre-larvae were kept separately in glass containers with 100 ml of water. Larvae after the start of exogenous feeding were grown in containers with 40 liters of water at an initial density of 1 individual per liter. Eggs after laying, pre-larvae, larvae and metamorphs were measured using standard methods. The duration of incubation and larval stage, as well as the survival rate were revealed. Results. Out of ten pairs of newts, eggs were obtained from nine pairs. The first eggs were found in different females between February 28 and March 28. Females oviposited for 14–108 days. The fertility of females for the entire season was 7–615 eggs. The last cases of egg laying in different females were recorded from May 11 to June 16. The length of the eggs was 3,6–6,1 mm, and the width was 2,0–5,1 mm. From the nine breeding females, only in offspring of seven females developed embryos were observed. From egg laying to the exit of pre-larvae, 7–17 days passed, from the exit to the beginning of exogenous feeding – 2–8 days. The total duration of embryogenesis was 11–23 days. From each female, 1–97 pre-larvae and 1–93 larvae were obtained. The percentage of exited pre-larvae from eggs in different offspring was 5,0–18,8 %. 66,7–100,0 % survived from hatching to the beginning of exogenous feeding. The total length (TL) of the pre-larvae at the exit from the egg was 7,4–13,0 mm, and the larvae at the beginning of exogenous feeding was 7,6–15,7 mm. The duration of development to metamorphosis from the beginning of exogenous feeding was 98–175 days, from hatching – 100–180 days, from egg laying – 116–195 days. 224 young newts from the offspring of seven pairs the metamorphosis were passed. The survival rate to metamorphosis in young newts from all eggs laid by seven females was 12,2 %, from exit of pre-larvae from eggs – 79,7 %, from the beginning of exogenous feeding – 85,2 %. Young newts after metamorphosis had a body length (L) of 39,6–56,5 mm, a tail length of 21,1–33,4 mm, and a mass of 0,46–1,29 g. Conclusions. Not all female of the Karelin’s newt reproduce in the laboratory every year. Eggs clutches of some females did not develop. In captivity there is an increase in female fertility and longevity of reproductive season. Due to the high embryonic mortality rate, only 1 to 97 pre-larvae were obtained from a single female. From the moment of exit the egg to metamorphosis, young newts have a very high survival rate. The main cause of death in larvae is cannibalism.

Keywords

• the karelin’s newt
• triturus karelinii
• captive breeding
• reproductive biology
• survival
• daghestan
• zooculture