A Preliminary Comparison on Faecal Microbiomes of Free-Ranging Large Baleen (Balaenoptera musculus, B. physalus, B. borealis) and Toothed (Physeter macrocephalus) Whales

Stefanie P Glaeser,Liliana M R Silva,Angel Franco,Carlos Hermosilla,Tobias Eisenberg,Mónica A Silva,Peter Kämpfer,Rui Prieto,Anja Taubert

doi:10.1007/s00248-021-01729-4

Abstract

Large baleen and toothed whales play crucial ecological roles in oceans; nonetheless, very little is known about their intestinal microbiomes. Based on striking differences in natural history and thus in feeding behaviours, it can be expected that intestinal microbiomes of large baleen whales and toothed whales are different. To test this hypothesis, the phylogenetic composition of faecal microbiomes was investigated by a 16S rRNA gene amplicon sequence–based approach for Bacteria and Archaea. Faecal samples from free-ranging large whales collected off the Azores Archipelago (Portugal) were used, comprising 13 individual baleen whales (one sei, two blue and ten fin whales) and four sperm whales. The phylogenetic composition of the Bacteria faecal microbiomes of baleen and toothed whales showed no significant differences at the phylum level. However, significant differences were detected at the family and genus levels. Most abundant phyla were Firmicutes, Bacteroidetes, Proteobacteria, Tenericutes and Spirochaeta. Few highly abundant bacterial genera were identified as key taxa with a high contribution to differences among baleen and toothed whales microbiomes. Only few archaeal sequences were detected, primarily Methanomassiliicoccales representing potential methanogenic Archaea. This is the first study that directly compares the faecal bacterial and archaeal microbiomes of free-ranging baleen and toothed whales which represent the two parvorders of Cetacea which members are fully aquatic large mammals which were evolutionary split millions of years ago.

Highlights

Baleen and toothed whales play essential roles in ocean ecosystem as apex predators, primary and secondary consumers and University of the Azores, Horta, Portugal 4 MARE—Marine and Environmental Sciences Centre, Lisbon, Portugal 5 Department of Veterinary Medicine, Hessian State Laboratory (LHL), Giessen, Germany are, suitable as indicators of ocean health worldwide [1, 2]
The concentration of bacterial and archaeal 16S rRNA gene copies in whale faecal samples was in the range of 109 to 1011 and 106 to 109 copies per g fresh weight of faeces, respectively (Fig. 1; Supplementary Table S2)
The sei whale faecal microbiome analysed in our study showed strong differences to the other two baleen whale species, which can be explained by different diet and spatial distribution

Summary

Introduction

Toothed whales evolved innovations combining echolocation and anatomical modifications, to target single prey items by raptorial biting or suction feeding, while baleen whales evolved keratinous plates (baleen) and modifications to the skull and mouth morphology, allowing bulk feeding on aggregations of small prey using filtration [6] These specialisations resulted in a marked trophic separation between baleen (mean trophic level: 3.35) and toothed (mean trophic level: 4.23) whales, despite all being carnivorous [8, 9]. Largely different intestinal microbiomes can be expected in baleen and toothed whales

Methods

Results

Discussion

Conclusion