Dietary analysis on the shallow-water hydrothermal vent crab Xenograpsus testudinatus using Illumina sequencing

Environmental conditions in hydrothermal vents are considered to be unsuitable for most marine organisms due to discharge of hot and acidic water with high sulfur content. The crab Xenograpsus testudinatus is endemic to the shallow-water hydrothermal vents of Kueishan Island, Taiwan. This study aimed to provide detailed information on the composition of eukaryotes and prokaryotes in the gut and stomach of X. testudinatus by using Illumina sequencing of the 16S and 18S ribosomal RNA genes. The mangrove crab Perisesarma bidens was also studied to compare the diet and gut microbial fauna of crabs from different habitats. X. testudinatus was found to feed on a wide array of organisms including algae, fishes, bivalves, copepods, and anthozoans, whereas P. bidens was found to feed mainly on Magnoliopsida plants. Soil bacteria such as Rodobacteraceae and cyanobacteria such as Oscillatoriphycidae were present in both crabs, but Mycoplasmataceae and Helicobacteraceae were found only in X. testudinatus. Our findings suggest that both X. testudinatus and P. bidens are scavengers feeding on both prokaryotes and eukaryotes. The results facilitate understanding of the feeding ecology of X. testudinatus and provide a database for the food web dynamics of shallow-water hydrothermal vents.