Gut microbiota of captive common bottlenose dolphins Tursiops truncatus gilli: investigation of age, sex, birthplace, and frequency of human contact influence

Dolphins are aquatic mammals, whose role in microbial ecology is not fully understood. It is critical to study the microbiota of dolphins kept in captivity, as close contact with humans could unpredictably affect both humans and animals health. In this study, we investigated the gut microbiota of 15 captive common bottlenose dolphins, and the relationship of microbial diversity and composition with animals age, sex, birthplace (dolphinarium or wildlife), and frequency of direct contact with dolphinarium visitors using metagenomic 16S rRNA sequencing. As a result, there was no association between gut microbiota composition and diversity and dolphins sex, and birthplace. However, there were significant differences in beta diversity in dolphins older than 20 years in comparison to adult dolphins (6-19 years), and a significantly higher relative abundance of Escherichia-Shigella taxa in adult dolphins in comparison to senior/old ones. Also, there was a significantly higher relative abundance of the Edwardsiella genus in dolphins that were in contact only with dolphinarium staff. These results show that dolphins born in wildlife and dolphinariums do not have significant differences in gut microbiota composition and the microbiota of captive dolphins can be affected by age and their contact with humans.