Abstract
Mammals host diverse bacterial and archaeal symbiont communities (i.e. microbiomes) that play important roles in digestive and immune system functioning, yet cetacean microbiomes remain largely unexplored, in part due to sample collection difficulties. Here, fecal samples from stranded pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales were used to characterize the gut microbiomes of two closely-related species with similar diets. 16S rRNA gene sequencing revealed diverse microbial communities in kogiid whales dominated by Firmicutes and Bacteroidetes. Core symbiont taxa were affiliated with phylogenetic lineages capable of fermentative metabolism and sulfate respiration, indicating potential symbiont contributions to energy acquisition during prey digestion. The diversity and phylum-level composition of kogiid microbiomes differed from those previously reported in toothed whales, which exhibited low diversity communities dominated by Proteobacteria and Actinobacteria. Community structure analyses revealed distinct gut microbiomes in K. breviceps and K. sima, driven by differential relative abundances of shared taxa, and unique microbiomes in kogiid hosts compared to other toothed and baleen whales, driven by differences in symbiont membership. These results provide insight into the diversity, composition and structure of kogiid gut microbiomes and indicate that host identity plays an important role in structuring cetacean microbiomes, even at fine-scale taxonomic levels.
Highlights
Microorganisms form symbiotic relationships with most animal taxa, from basal invertebrate phyla[1] to humans[2], and play important roles in the biology, ecology and evolution of animal life[3]
It has been suggested that K. breviceps may dive more deeply and be found further offshore than K. sima[32], but these species display a high degree of dietary overlap that indicates very similar foraging ecologies[27]
We examined fecal samples of stranded individuals of K. breviceps and K. sima to study kogiid gut microbiomes in a comparative context controlling for broad differences in diet and phylogenetic history
Summary
Microorganisms form symbiotic relationships with most animal taxa, from basal invertebrate phyla (e.g. sponges)[1] to humans[2], and play important roles in the biology, ecology and evolution of animal life[3]. We characterized the gut microbiomes of two closely-related species in the cetacean genus Kogia, K. breviceps (pygmy sperm whale) and K. sima (dwarf sperm whale), which exhibit similar gross morphology and ecological niches in open ocean habitats[27, 28]. Both species have a shark-like appearance, characterized by a blunt rostrum (or pointed snout), underslung jaw and cervical pigmentation pattern that resembles a gill slit[28]. We hypothesized that kogiid gut microbiomes would exhibit: (1) similar richness and diversity compared to other toothed whale species, (2) lower richness and diversity compared to baleen whale species, and (3) distinct community structure compared to other toothed and baleen whale species
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