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

Abstract

Although gut microbes are regarded as a significant component of many mammals and play a very important role, there is a paucity of knowledge around marine mammal gut microbes, which may be due to sampling difficulties. Moreover, to date, there are very few, if any, reports on the gut microbes of melon-headed whales. In this study, we opportunistically collected fecal samples from eight stranded melon-headed whales (Peponocephala electra) in China. Using high-throughput sequencing technology of partial 16S rRNA gene sequences, we demonstrate that the main taxa of melon-headed whale gut microbes are Firmicutes, Fusobacteriota, Bacteroidota, and Proteobacteria (Gamma) at the phylum taxonomic level, and Cetobacterium, Bacteroides, Clostridium sensu stricto, and Enterococcus at the genus taxonomic level. Meanwhile, molecular ecological network analysis (MENA) shows that two modules (a set of nodes that have strong interactions) constitute the gut microbial community network of melon-headed whales. Module 1 is mainly composed of Bacteroides, while Module 2 comprises Cetobacterium and Enterococcus, and the network keystone genera are Corynebacterium, Alcaligenes, Acinetobacter, and Flavobacterium. Furthermore, by predicting the functions of the gut microbial community through PICRUSt2, we found that although there are differences in the composition of the gut microbial community in different individuals, the predicted functional profiles are similar. Our study gives a preliminary inside look into the composition of the gut microbiota of stranded melon-headed whales.

The intestinal microbiota of a Risso’s dolphin (Grampus griseus): possible relationships with starvation raised by macro-plastic ingestion

“…This is quite distinct from the microbial information of the Risso’s dolphin stranded in Korea waters, which was predominately Photobacterium (89.4%) (Kim et al 2019 ). The Risso’s dolphin shared common gut microbial members associated with Firmicutes with a wide range of toothed whales, including the Chinese white dolphin ( Sousa chinensis ) (Wan et al 2021 ), Yangtze finless porpoise ( N. a. asiaeorientalis ) (Wan et al 2016 ), bottlenose dolphin ( Tursiops truncatus ) (Wan et al 2022 ), melon-headed whales ( Peponocephala electra ) (Bai et al 2022 ), short-finned pilot whales ( Globicephala macrorhynchus ) (Bai et al 2021 ), pygmy ( Kogia breviceps ), and dwarf ( K. sima ) sperm whales (Erwin et al 2017 ), whereas at the genus level, the Risso’s dolphin diverged from other toothed whales. For example, unlike Halomonas , Photobacterium , and Cetobacterium , detected as abundant taxa in the marine dolphins and porpoises (Wan et al 2018 , 2021 , 2022 ), the Risso’s dolphin contained higher proportions of Vagococcus (5.94%) and Bacteroides (4.27%) (Fig.…”

Variations and Interseasonal Changes in the Gut Microbial Communities of Seven Wild Fish Species in a Natural Lake with Limited Water Exchange during the Closed Fishing Season

“…Additionally, it was found that C. somerae was able to promote the expression of insulin in zebrafish to lower blood glucose, and C. somerae was also able to activate the parasympathetic nervous system through the metabolite acetic acid, which promotes the expression of insulin and the ability of glucose utilization of fish and plays an important role in regulating the health of the fish [45]. Clostridium sensu stricto 1 is a common group in the gut microbial community of freshwater fish [10], but it is also frequently found in the gut of marine mammals [46][47][48], where it often appears as a potential pathogen [49,50]. Bacteria of the genus Romboutsia are Gram-positive bacteria, one of the common intestinal microorganisms, and most species of Romboutsia originate from the gut, although some isolated strains of Romboutsia have originated from diseased individuals, but recent reports have shown that this group of bacteria contains a polysaccharide-synthesizing enzyme that produces (1,3;1,4)-β-d-glucans, so the role of this group of bacteria in the human and mammalian gastrointestinal tract is less clear [51,52].…”

Fecal and skin microbiota of two rescued Mediterranean monk seal pups during rehabilitation

“…Streptococcus is another potentially detrimental group of bacteria, but it has not been directly related to pathogenesis in marine mammals; it has been found in the oral cavity and intestine of the Yangtze finless porpoise ( Neophocaena asiaeorientalis ) ( 51 ) and sperm whales ( Physeter catodon ) ( 52 ). Enterococcus has been reported to be among the dominant fecal bacteria of captive or stranded but not diseased cetaceans ( 42 , 52 – 56 ). In the present study, whether detrimental or not, the considerable decrease of Shigella (from 35.2% to 4.4%), Escherichia (from 5.5% to 0.7%), and Streptococcus (from 17.1% to 0.1%) in the second period after metronidazole admission reduced any potential risks from these bacteria.…”

“…Of similar abundance was the genus Bacteroides whose abundance increased from 0.1% to 5.3% between the first and second periods. This genus has been found in the oral ( 51 ) and fecal ( 53 , 54 , 70 ) microbiome of cetaceans. In humans, it is considered one of the commensal bacteria that first colonize the gut after vaginal birth ( 71 ), and this could be also the case for the M. monachus pups.…”