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

Environmental conditions in hydrothermal vents are considered to be unsuitable for most marine organisms due to discharge of hot and acidic water with high content of sulphur. The crab Xenograpsus testudinatus is endemic to the shallow-water hydrothermal vents of Kueishan Island, Taiwan. This study provides detailed information on the compositions of eukaryotes and prokaryotes in the gut and stomach of X. testudinatus using Illumina sequencing of 16S and 18S rRNA. The mangrove crab Perisesarma bidens was also studied to compare the diet and gut microbial fauna of crabs from different habitats. X. testudinatus feeds on a wide array of organisms including algae, fishes, bivalves, copepods and anthozoans, while P. bidens feeds 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 results suggest that both X. testudinatus and P. bidens are scavengers feeding on both prokaryotes and eukaryotes. The findings from this study will help to understanding the feeding ecology of X. testudinatus, as well as providing the database for the food web dynamics of the shallow-water hydrothermal vents.