Bacteria in Abnormal Eggs of Chinese Giant Salamanders (Andrias davidianus) May Derive from Gut

Abnormal embryos of Chinese giant salamander (Andrias davidianus, CGS) were observed in an imitating ecologic breeding system at 20°C. The aim of the present study was to investigate the relationship of bacterial infection on the early embryonic development of CGS. The ratio of abnormal embryos at 10 days after embryos incubated was 35.0% ± 2.1%, 35.6% ± 2.3% and 34.7% ± 3.4% in six breeding system farms of Hanzhong city in the years 2014, 2015, and 2016, respectively. However, in the standard imitating ecology breeding mesocosm, the proportion of abnormal embryos was about 5%. Six bacteria species in the egg water of the early-dead embryos and eight bacteria species in the gut of healthy CGSs were detected and identified by PCR and 16S rRNA gene sequence homology analysis. All bacteria species in the egg water were also found in the cloaca contents. Cetobacterium somerae and Hafnia alvei, which individually can cause embryo death, were first isolated from egg water and gut of CGSs. Further, the egg jelly membrane and the egg water of embryos did not inhibit bacteria survival and the bacteria could individually lead to CGS larva death. These results suggest that bacteria in the eggs of CGS may derive from the gut and that high-velocity flow of water through nest may decrease bacterial infection of egg in the imitating ecologic culture system.