Evolution: Diet and evolutionary history shape the whale microbiome

The gut microbiota of baleen whales, which prey on fish and crustaceans, display similarities to those of terrestrial herbivores, reports a study published in Nature Communications. The findings support the notion that both diet and evolutionary history contribute to shape the microbial communities inhabiting the gut of mammals.

Diet is a major factor determining the composition of gut microbiota in mammals. However, the overall composition of the gut microbiota in some animals such as the bamboo-eating giant panda is similar to that of their close relatives (bears), even if their diets are completely different. Jon Sanders, Annabel Beichman, Peter Girguis and colleagues set out to explore whether this was also the case for baleen whales, marine carnivores that evolved from plant-eating terrestrial ancestors related to cows and hippopotamuses.

The researchers analysed microbial genes in faecal samples from 12 baleen whales of three different species. They then compared this information with similar data obtained from other marine and terrestrial mammals with various diets. They find that baleen whales’ overall microbiota composition and functional capacity resemble those of their terrestrial herbivore relatives. However, certain microbial metabolic pathways are more similar to those of terrestrial carnivores.

The study helps to clarify the complex interplay between dietary and evolutionary determinants of gut microbiota composition. The authors propose that, for baleen whales, the correlation between evolutionary relatedness and gut microbiota composition may reflect constraints imposed by the structure of the gastrointestinal tract, as both whales and their terrestrial relatives possess a multichambered foregut that acts as a fermentation chamber.