Similarities and differences between the gastrointestinal microbiomes of wild and captive pantropical spotted dolphins (Stenella attenuata) in natural waters

Although there is a growing awareness of the importance of gut microbiomes, there is still a lack of understanding of marine mammal gut microbiomes due to the difficulty of sampling. As a common marine cetacean living in the tropics and subtropics, there is currently a gap in knowledge of the gut microbiology of pantropical spotted dolphins (Stenella attenuata). In this study, we collected opportunistically both wild and captive populations of pantropical spotted dolphins living in the southern waters of Hainan Island, China, which gave us the opportunity to understand the composition and diversity of the gut microbial communities of this cetacean species. At the same time, as these dolphins all live in the same waters, different food sources are the main differentiating factor between wild and captive pantropical spotted dolphins, which also provides us with good experimental material to study whether there are differences in the gut microbial community structure of the same marine mammal living in similar environments with different food sources. We found that the microbial community structure of the gastrointestinal tracts of wild and captive pantropical spotted dolphins differed significantly, both overall and at different sites, but no significant differences were observed in the microbial diversity of the gastrointestinal tracts of the two groups, so the differences in microbial communities were mainly in terms of microbial composition. In addition, we also detected a large number of potentially conditionally pathogenic bacteria, which suggests a comprehensive future study of marine mammalian gut microbiology, for example, by determining its health indicator factors. Our study not only provides complementary information on the gut microbiology of pantropical spotted dolphins, but also explores the similarities and differences in the gastrointestinal microbial communities of the same marine mammal when food source is a major factor of variation in its life.