مطالعه و بررسي مراحل جنيني و دگرديسي در قورباغة جنگلي (Rana macrocnemis pesudodalmatina) در استان گلستان (مينودشت)

A study of embryonic stages and metamorphosis in the jungle frog (Rana macrocnemis pseudodalmatina) in Golestan province (Minudasht city)

Regarding the importance of Amphibian in biological studies, in this article we studied embryonic stages of Rana macrocnemis psudodamatina from fertilized egg to the end of larval metamorphosis in aquarium conditions. In order to do this task, the ferti1ized eggs were collected from their natural habitat and transferred to an aquarium in the laboratory. Afterwards, every few hours some samples were taken from the aquarium and fixed for morphological characteristics to identify their developmental stage by the aid of a stereomicroscope. In brief, three hours after transferring, the embryos were at two-cell stage. After four hours, this samples were observed as four-cell embryos. Five hours later, the embryos were at the stage of gastrulation and six hours after the beginning of gastrulation, the embryos were at the early neurolation. Eight hours .after that, neural folds were closed and embryos started to elongate. Nine hours after the beginning of appearance of the tail bud, olfactory pits in the region tadpoleʹs head were distinguishable. On the fourth day, tail erected and started to take a position alongside the body length which continued during the fifth day as well. External gills could be seen on day six. Samplings which were taken at 10:30 of the eighth day, showed that the external gills have been degenerated. During the period of nine to 16th days, tadpoles were just growing and their body size increased without any discernible morphological changes. At late 16th day, two hind limb buds began to appear which completed their development until 22nd day of study. Formation of forelimb began on 25th day and completed its growth on 35th day. Simultaneous degeneration of tail became clearer on the 73rd day. Up to this stage the samples appeared as juvenile frogs without any tail. In general, these stages lasted almost 73days.