Microbial diversity and functional potential of the Halobates melleus (Heteroptera: Gerridae) microbiome from the Red Sea coastline.

Background: Halobates, commonly known as sea skaters, are predatory Hemipterans uniquely adapted to tropical marine environments. Their ability to thrive in oligotrophic and environmentally extreme habitats, such as the open ocean surface and marine coastal areas, suggests the evolution of specialised adaptations, possibly including symbiotic associations with microorganisms that can support nutrition, niche adaptation, and stress resilience. To explore this hypothesis, we analysed the bacterial communities associated with Halobates melleus, a species inhabiting the Red Sea coastal mangroves in Saudi Arabia.

Results: Amplicon sequencing of the 16S rRNA gene and metagenomic analyses of composite body and gut samples from adult H. melleus revealed a population-level bacterial community dominated by Wolbachia and Spiroplasma, consistent with patterns observed in several terrestrial predatory insects. Members of Providencia and Swaminathania were also detected, along with other minor taxa that may represent transient environmental commensals. The identified bacteria encoded genes for the biosynthesis of essential vitamins and prosthetic groups, such as riboflavin and heme-compounds typically not synthesised de novo by insects-as well as amino acids, likely contributing to the host's nutritional requirements. Notably, the Wolbachia metagenome-assembled genome from H. melleus clustered within the supergroup B, showing high genetic similarity to strains from phylogenetically distant Dipteran and Lepidopteran hosts that nonetheless inhabit common ecological niches, i.e., mangrove and tropical environments. This extends the known ecological breadth of Wolbachia symbioses to marine insects, underscoring their evolutionary and environmental versatility.

Conclusion: Our findings highlight the potential nutritional and metabolic roles of the Halobates-associated bacterial microbiome, particularly members of the Wolbachia genus. This emphasises the importance of microbial symbionts in the ecological success and adaptation of marine insects, offering a perspective complementary to previously studied terrestrial insect microbiomes.