Question: What is their hypothesis to the main question? Introduction The Chinese giant salamander (Andrias davidianus) belongs to the family Cryptobanchidae and is the world's largest amphibian only found in China (National environmental protection agency and Endangered species scientific commission. P. R. C., 1998). As a living fossil with over 350 million years of existence, the evolutionary history of this species involves adaptations from aquatic to terrestrial environments (Gao & Shubin, 2003; Heiss, Natchev, Gumpenberger, Weissenbacher, & Van Wassenbergh, 2013). Terrestrial amphibians are more tolerant to dehydration than other vertebrates (Hillyard, 1999). Specifically, the Chinese giant salamander seems to endure what appears to be osmotic stress under normal conditions (dry environment), making this species a valuable model for research on osmotic stress. However, the osmoregulatory capacity of the Chinese giant salamander is not yet well understood. The grass carp (Ctenopharyngodon idella) is one of the most important teleost species in the Chinese fishery industry, accounting for 18% of the freshwater aquaculture production, with an output of 4.22 million tons in 2010. Previously, we have used the grass carp C. idella kidney cell line (CIK), established in 1986 (Zuo, Qian, Xu, Du, & Yang, 1986), to examine the osmoregulatory response (Gui et al., 2016). The kidney plays a key role in maintaining osmoregulation in fishes (Varsamos, Nebel, & Charmantier, 2005) as in amphibians (Hillyard, 1999). For this reason, CIK cell line and Chinese giant salamander kidney cell line (GSK) (Yuan, Chen, Huang, Gao, & Zhang, 2015) were used to assess the osmoregulatory capacity of the kidney in freshwater fish and amphibian in vitro. Anisosmotic environments cause an imbalance between extracellular and intracellular compartments and cell morphology can be affected. In a previous study, we have described the effect of osmotic stress in kidney cell morphology (Gui et al., 2016). Here, we describe kidney cell morphology changes in the freshwater grass carp and the Chinese giant salamander after anisosmotic treatments detected by optical and transmission electron microscopy. The results show that freshwater fishes and amphibians have different osmoregulatory capacities.