Gut microbiota differences during metamorphosis in sick and healthy giant spiny frogs (Paa spinosa) tadpoles.

Gut microbiota plays important roles in host nutrition, immunity, development and health; therefore, disruption of the gut microbiota is closely associated with development of diseases in the host. In amphibians, metamorphosis is associated not only with extensive changes in the gut microbiota, but also with high mortality. Therefore, we hypothesized that unsuccessful restructuring of the gut microbiota during metamorphosis was an important factor that caused the fatalities. To test this hypothesis, we investigated the gut microbiota of apparently sick and healthy giant spiny frog tadpoles during metamorphosis, using high-throughput sequencing of the 16S rRNA gene. Our results showed that most dominant phyla differed significantly among developmental stages of sick and healthy Paa spinosa tadpoles. The differences in the dominant genera in sick and healthy tadpoles were the highest at the stage of degeneration of cloacal tube (TDCT). After the metamorphosis, the composition of the gut microbiota was more alike between healthy and sick tadpoles at the stage of forelimb emergence than at TDCT. These results imply that failed restructuring of the gut microbiota during metamorphosis caused the death of P. spinosa tadpoles. These results provided an important reference to prevent the high actual of P. spinosa tadpoles during metamorphosis. SIGNIFICANCE AND IMPACT OF THE STUDY: We investigated the gut microbiota of apparently sick and healthy giant spiny frog (Paa spinosa) tadpoles during metamorphosis, using high-throughput sequencing of the 16S rRNA gene. Our results showed that the differences in the dominant genera in sick and healthy tadpoles were the highest at the stage of degeneration of cloacal tube. After the metamorphosis, the composition of the gut microbiota was alike between healthy and sick tadpoles. These results imply that failed restructuring of the gut microbiota during metamorphosis caused the death of P. spinosa tadpoles.