Abstract
Diffusing fluid at a deep-sea hydrothermal vent creates rapid, acute physico-chemical gradients that correlate strongly with the distribution of the vent fauna. Two alvinocaridid shrimps, Alvinocaris longirostris and Shinkaicaris leurokolos occupy distinct microhabitats around these vents and exhibit different thermal preferences. S. leurokolos inhabits the central area closer to the active chimney, while A. longirostris inhabits the peripheral area. In this study, we screened candidate genes that might be involved in niche separation and microhabitat adaptation through comparative transcriptomics. The results showed that among the top 20% of overexpressed genes, gene families related to protein synthesis and structural components were much more abundant in S. leurokolos compared to A. longirostris. Moreover, 15 out of 25 genes involved in cellular carbohydrate metabolism were related to trehalose biosynthesis, versus 1 out of 5 in A. longirostris. Trehalose, a non-reducing disaccharide, is a multifunctional molecule and has been proven to act as a protectant responsible for thermotolerance in Saccharomyces cerevisiae. Putative positively selected genes involved in chitin metabolism and the immune system (lectin, serine protease and antimicrobial peptide) were enriched in S. leurokolos. In particular, one collagen and two serine proteases were found to have experienced strong positive selection. In addition, sulfotransferase-related genes were both overexpressed and positively selected in S. leurokolos. Finally, genes related to structural proteins, immune proteins and protectants were overexpressed or positively selected. These characteristics could represent adaptations of S. leurokolos to its microhabitat, which need to be confirmed by more evidence, such as data from large samples and different development stages of these alvinocaridid shrimps.
Highlights
Deep-sea hydrothermal vents are highly dynamic and unstable, both temporally and spatially
When aligned with 1,066 benchmarking universal single-copy orthologues (BUSCOs) from arthropods, 90.7% complete BUSCOs were found to be present in the transcriptome of A. longirostris and 89.6% in S. leurokolos (S2 Table)
The protein synthesis rate has a significant impact on thermal acclimation, the relationship between them is complex [40, 41]
Summary
Deep-sea hydrothermal vents are highly dynamic and unstable, both temporally and spatially. Fluids emitted from these vents, at temperatures ranging from approximately 20 ̊C to as high as 407 ̊C [1], mix directly with ambient seawater (~2 ̊C) and, create steep thermal and chemical gradients. S. leurokolos inhabits the central zone (defined as zone 2, 0.2–0.8 m from vent) together with the squat lobster Shinkaia crosnieri, while A. longirostris mainly inhabits the peripheral zone (zone 4, >2.5 m from the vent), far away from the active chimney, as do Bathymodiolus platifrons mussels. Shinkaicaris leurokolos exhibits a similar microhabitat preference to Rimicaris exoculata (Alvinocarididae, Rimicaridinae) [7]. S. leurokolos and R. exoculata, which occur in the vicinity of vent fluids, have evolved a degenerate rostrum and reduced external spines, both of which reduce the impact of strong turbulent fluid flows; they have a dorsal organ that is used for detecting dim light emitted from the vents inside their carapaces; A. longirostris does not have dorsal organs, and its rostrum and spines are well developed [11]
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