Life history of the Anji salamander (Chordata, Amphibia, Caudata, Hynobiidae) from fertilized eggs to subadults

Anji salamander (Hynobius amjiensis) is a rare species endemic to China, living in peat moss swamp at an altitude of 1,300 meters on Longwang Mountain in Anji County, Zhejiang Province. Anji salamander larvae live in natural puddles in the swamp, and the adults spend most of their time in the humus under the peat moss, only briefly visiting the puddles during the breeding period to spawn and then disappear back into the swamp. Therefore, the life history of Anji salamander is poorly understood. In this study, we analyzed the developmental characteristics, behaviors and life habits of Anji salamander embryos from fertilized eggs to subadults. Following previous studies on the development of small salamanders and amphibians, we divided Anji salamander development into six stages, including embryonic development, balance bar, limb development, pre-metamorphosis, metamorphosis, and subadult development, with 34 developmental nodes. The period before the shedding of the balance bar was a relatively sensitive period. The metamorphosis period, especially the late metamorphosis period, was the most sensitive period from larvae to subadults, during which the small salamanders undergo complex physiological and biochemical changes such as relatively long fasting time, respiratory changes, and transition from aquatic to terrestrial life. These data fill in some of the gaps in the life history of Anji salamander from fertilized eggs to subadults, and are valuable for its conservation and future endeavor on artificial breeding.