First insights into the gut microbiomes and the diet of the Littorina snail ecotypes, a recently emerged marine evolutionary model

Abstract

Microbes can play a prominent role in the evolution of their hosts, facilitating adaptation to various environments and promoting ecological divergence. The Wave and Crab ecotypes of the intertidal snail Littorina saxatilis is an evolutionary model of rapid and repeated adaptation to environmental gradients. While patterns of genomic divergence of the Littorina ecotypes along the shore gradients have been extensively studied, their microbiomes have been so far overlooked. The aim of the present study is to start filling this gap by comparing gut microbiome composition of the Wave and Crab ecotypes using metabarcoding approach. Since Littorina snails are micro‐grazers feeding on the intertidal biofilm, we also compare biofilm composition (i.e. typical snail diet) in the crab and wave habitats. In the results, we found that bacterial and eukaryotic biofilm composition varies between the typical habitats of the ecotypes. Further, the snail gut bacteriome was different from outer environments, being dominated by Gammaproteobacteria, Fusobacteria, Bacteroidia and Alphaproteobacteria. There were clear differences in the gut bacterial communities between the Crab and the Wave ecotypes as well as between the Wave ecotype snails from the low and high shores. These differences were both observed in the abundances and in the presence of different bacteria, as well as at different taxonomic level, from bacterial OTU's to families. Altogether, our first insights show that Littorina snails and their associated bacteria are a promising marine system to study co‐evolution of the microbes and their hosts, which can help us to predict the future for wild species in the face of rapidly changing marine environments.

Ecological filtering and phylogeographic structuring of Psychrilyobacter within two closely related limpet species from the Southern Ocean

“…Among invertebrates, mollusks stand out as ecologically significant and diverse phyla, being Gastropoda the richest class regarding species diversity (Neu et al 2019). Although descriptions of marine gastropod microbiota are accumulating, they mainly focus on commercial and/or northern hemisphere species, excluding most gastropod diversity (Neu et al 2019;Maltseva et al 2021b;Panova et al 2022). Moreover, the contribution of host diversification in shaping gastropod microbiota assembly remains largely unexplored.…”

A decade of progress in marine evolutionary biology

“…As most organisms depend on symbioses to function, divergence in host‐symbiont relationships can be just as important to fitness as within‐species genomic divergence among ecotypes. The genomic divergence between ecotypes in Littorina was found to be mirrored by their gut bacterial community composition by Panova et al ( 2022 ). The authors found that the biofilm communities that Littorina saxatilis grazed on differed depending on habitat, which, in turn, explained gut community differences between snail ecotypes.…”

Gut Bacteriomes and Ecological Niche Divergence: An Example of Two Cryptic Gastropod Species

“…Library preparation and sequencing were performed as described before [35,36]. In short: genomic DNA was extracted using PowerSoil Pro Kit (QIAGEN, Hilden, Germany) according to the manufacturer's protocol.…”

“…While various trends accompanying divergence at the levels of whole genomes [34] and single genes [32] of the Littorina snails have been broadly investigated, their bacteriomes had been nearly ignored until recently. Over the past few years, general descriptions of bacterial microbiome analysis of the Littorina (Neritrema) species [35] and the ecotypes of L. saxatilis [36] were published. Moreover, a hypothesis was suggested about the role of symbionts in the reproductive barriers' formation in this group of species [37].…”

“…In particular, the impact of location and host species on freshwater mussel gut bacterial bacteriome composition [44]; the snails' ability to accumulate new bacterial communities depending on the bacteria availability [45]; and the possibility of OTU-based metagenomic functional predictions on snails' gut bacteriome [46] were convincingly demonstrated. In previous studies, we have shown the geographic and micro-niche variability in Littorina bacteriomes as well as the difference between these snails' gut and body surface bacterial microbiomes and between associated and environmental ones [35,36]. In this project, we aimed at comparing the composition and spatial/temporal plasticity of the gut bacteriomes between the two sympatric sister-species in search of a possible role of commensal bacteria in host adaptation to their specific niches.…”