Comparative Study of the Gut Microbiota Among Four Different Marine Mammals in an Aquarium

Abstract

Despite an increasing appreciation in the importance of host–microbe interactions in ecological and evolutionary processes, information on the gut microbial communities of some marine mammals is still lacking. Moreover, whether diet, environment, or host phylogeny has the greatest impact on microbial community structure is still unknown. To fill part of this knowledge gap, we exploited a natural experiment provided by an aquarium with belugas (Delphinapterus leucas) affiliated with family Monodontidae, Pacific white-sided dolphins (Lagenorhynchus obliquidens) and common bottlenose dolphin (Tursiops truncatus) affiliated with family Delphinidae, and Cape fur seals (Arctocephalus pusillus pusillus) affiliated with family Otariidae. Results show significant differences in microbial community composition of whales, dolphins, and fur seals and indicate that host phylogeny (family level) plays the most important role in shaping the microbial communities, rather than food and environment. In general, the gut microbial communities of dolphins had significantly lower diversity compared to that of whales and fur seals. Overall, the gut microbial communities were mainly composed of Firmicutes and Gammaproteobacteria, together with some from Bacteroidetes, Fusobacteria, and Epsilonbacteraeota. However, specific bacterial lineages were differentially distributed among the marine mammal groups. For instance, Lachnospiraceae, Ruminococcaceae, and Peptostreptococcaceae were the dominant bacterial lineages in the gut of belugas, while for Cape fur seals, Moraxellaceae and Bacteroidaceae were the main bacterial lineages. Moreover, gut microbial communities in both Pacific white-sided dolphins and common bottlenose dolphins were dominated by a number of pathogenic bacteria, including Clostridium perfringens, Vibrio fluvialis, and Morganella morganii, reflecting the poor health condition of these animals. Although there is a growing recognition of the role microorganisms play in the gut of marine mammals, current knowledge about these microbial communities is still severely lacking. Large-scale research studies should be undertaken to reveal the roles played by the gut microbiota of different marine mammal species.

Gut Microbial Characterization of Melon-Headed Whales (Peponocephala electra) Stranded in China

“…Due to the difficulty of sample collection, studies on cetacean gut microbes are usually from animals in zoos and oceanariums (e.g., [ 13 , 14 , 32 ]), or stranded cetaceans (e.g., [ 16 , 17 , 19 ]). To date, there are very few, if any, reports on the gut microbial communities of melon-headed whales.…”

“…Although most Bacteroides are symbiotic in the intestine, several species can also cause infections, including Bacteroides fragilis, Bacteroides distasonis, Bacteroides ovatus, Bacteroides thetaiotaomicron, Bacteroides vulgatus , and Bacteroides uniformis , with significant morbidity and mortality [ 35 ]. The genera Clostridium sensu stricto are other common microorganisms in the gut of cetaceans, for example, beluga whales Delphinapterus leucas , Pacific white-sided dolphins Lagenorhynchus obliquidens , common bottlenose dolphins Tursiops truncatus , and short-finned pilot whales [ 13 , 16 ]. Clostridium is one of the most common genera of cetacean gut microorganisms, while some studies suggest that members of Clostridium have low virulence and can pose a potential threat to unhealthy cetaceans [ 33 , 36 ].…”

“…Clostridium is one of the most common genera of cetacean gut microorganisms, while some studies suggest that members of Clostridium have low virulence and can pose a potential threat to unhealthy cetaceans [ 33 , 36 ]. The members of Enterococcus can also be found in the gut of some cetaceans, such as pygmy sperm whales Kogia breviceps , Pacific white-sided dolphins, and common bottlenose dolphins [ 13 , 16 ].…”

“…PCR products were prepared for library construction using the TruSeq DNA sample preparation kit (Illumina, San Diego, CA, USA) in accordance with the manufacturer’s instructions. The libraries were sequenced at MajorBio Co. Ltd. (Shanghai, China) using the HiSeq platform (Illumina, San Diego, CA, USA) with reads of 250 bp at the paired end [ 13 ].…”

“…According to previous reports, gut samples from cetaceans are mainly obtained from three approaches: (1) feces in the wild just post-defecation. For example, Sanders et al [ 12 ] investigated the microbial diversity and function of gut microbiomes in baleen whales feces and found them harbored unique gut microbiomes whereas still kept a functional capacity similar to that of both carnivores and herbivores; (2) fecal samples from human cared animals, such as studies on belugas ( Delphinapterus leucas ), Pacific white-sided dolphins ( Lagenorhynchus obliquidens ) and common bottlenose dolphins ( Tursiops truncatus ) [ 13 , 14 ], and Yangtze finless porpoises ( Neophocaena phocaenoides asiaeorientalis ) [ 15 ]; and (3) from dead, stranded animals. A few of studies sequenced along the gastrointestinal tracts of stranded cetaceans to investigate the distribution of microorganisms in different gut regions [ 16 , 17 , 18 , 19 ].…”