Observation on embryonic development of Gymnodiptychus dybowskii (Kessler, 1874) in Manas River, Xinjiang, China

Abstract

To protect the germplasm resources of Gymnodiptychus dybowskii (Kessler, 1874), a species endemic to Xinjiang, the key stages of embryonic development of G. dybowskii were studied. From May to July 2021, the artificial breeding of G. dybowskii was carried out at the fish breeding station of the Kenswart Water Conservancy Project. The embryos and early larvae were obtained using temperature promotion, water stimulation, hormone induction, and dry insemination techniques. their development process was observed, and morphological characteristics of each developmental stage were recorded. The results showed that the mature oocyte was round, heavy, and light yellow, with an egg diameter of (2.32 ± 0.21) mm. The fertilized egg was slightly viscous, and the viscosity disappeared after water absorption. Under the temperature of 15.6-17.7 ℃ (16.23 ± 0.52) ℃, the embryonic development of G. dybowskii lasted for 142 h and 33 min and went through 7 stages of fertilization, cleavage, blastula, gastrula, neurula embryo, organ formation, and membrane hatching, with a total of 26 periods. The membrane broke after 2376.724 ℃·h. The embryonic development of G. dybowskii follows the rule of freshwater bony fish, but it differs from other Schizothorax species in the muscular effect period and membrane emergence mode. In addition, differences in hatching water temperature among different geographic populations lead to differences in embryo development duration and accumulated temperature, which further proves that G. dybowskii is highly adaptive to the ecological environment of its habitat water, and these characteristics together constitute its survival and reproduction strategy in the natural environment. In this study, through the artificial breeding experiment of G. dybowskii, the characteristics of its embryonic development were explored, which laid the foundation for the cultivation of unique fish seedlings, enriched the early life history data of G. dybowskii, and further provided basic data for its resource protection.