The Composition and Function of Intestinal Microbiota Were Altered in Farmed Bullfrog Tadpoles (Aquarana catesbeiana) during Metamorphosis

The bullfrog <i>Aquarana catesbeiana</i> is one of the main farmed frog species in China, with a low overall survival of farmed bullfrogs from hatching to harvest since bullfrog tadpoles are fragile during the metamorphosis period. The intestinal bacterial community can play crucial roles in animal development; however, little is known about the alteration of the gut microbial community of <i>A. catesbeiana</i> during metamorphosis. The present study used 16S rRNA amplicon sequencing to investigate the intestinal bacterial community in <i>A. catesbeiana</i> at four distinct developmental stages. Moreover, we determined the bullfrog's body morphological parameters and the intestine histology at different developmental stages. The results showed a reduction in the total length and snout-vent length of <i>A. catesbeiana</i> during metamorphosis. The intestinal microbial composition of <i>A. catesbeiana</i> exhibited variation throughout the process of metamorphosis. The terrestrial stage showed shifts in the bacterial composition compared to the aquatic stages, including a reduction in <i>Bacteroidetes</i> and an increase in <i>Firmicutes</i>. Furthermore, the presence of <i>Prevotella</i>, <i>Bifidobacterium</i>, <i>Leucobacter</i>, <i>Corynebacterium</i>, <i>Bulleidia</i>, <i>Dorea</i>, <i>Robinsoniella</i>, and <i>Clostridium</i> in <i>A. catesbeiana</i> metamorphosis appears to be mainly related to the host's epithelial cells' height and total body mass. The results indicated that the intestinal microbial composition changed with the bullfrog-tadpole metamorphosis. The genera of <i>Prevotella</i>, <i>Bifidobacterium</i>, <i>Leucobacter</i>, <i>Corynebacterium</i>, <i>Bulleidia</i>, <i>Dorea</i>, <i>Robinsoniella</i>, and <i>Clostridium</i> might be potential probiotics.