Eggs features and tactical variability in the reproduction of different egg-laying species of reptiles (Testudines, Ophidia) in Azerbaijan

The article discusses the features of eggs,the confinement of oviposition to certain stages of embryonic development,and its adaptive significance in some oviparous reptile species in Azerbaijan.Information is reported on the size and numbers of eggs in clutches, stages of development of embryos at the time of oviposition, as well as the timing of natural incubation of eggs in the Mediterranean tortoise (Testudo graeca ibera) and the Levantine viper (Macrovipera lebetina obtusa), including providinginformation on the size and number of eggs in clutches, as well as the relationship between the number of eggs in clutches and their size and weight. It has been experimentally proven that it is by the day of oviposition that embryos acquire the greatest resistance to temperature factors of the external environment. The embryos are most protected in eggs of a turtle with a hard shell (Testudo graeca), eggs are laid in the early stages of embryonic development(beginning and middle of gastrulation). However, in the Levantine viper (Macrovipera lebetina obtusa), the eggs are covered only with a fibrous membrane and the laying of eggs occurs at later stages of embryonic development (the stage of laying the tongue). It was also identified that in both species the ranges of morphological variability of embryos at the time of oviposition, in populations living at different heights, are the same. The tactical variability in the reproduction of oviparous reptiles is thought to be a result of their evolutionary adaptation to land reproduction.The incubation of eggs in the external environment lasted 80-85 days in the tortoise and 50-55 days in the viper. This is becausein turtles, eggs are laid earlier, and in the Levantine viper at later stages of embryo development. In the Levantine viper, a significant part of the development of the embryos (30-35 days) occurs while the eggs are in the oviducts of the female.