Differential feeding habits of the shallow-water hydrothermal vent crab Xenograpsus testudinatus correlate with their resident vent types at a scale of meters

Abstract

Abstract. The shallow-water hydrothermal vents (SVs) located off Kueishan (KS) Islet, Taiwan, are one of the most intensively studied vent systems. Here, two distinct vent types were identified as white vents (WVs) and yellow vents (YVs), based on the color, physical and chemical characteristics of vent plumes. The endemic vent crabs (Xenograpsus testudinatus) are abundant in both WVs and YVs. However, most research on the vent crabs was associated with WV or unspecified vent areas. Studies on crabs dwelling in other vent types are rare. Here, we investigated the feeding habit of crabs inhabiting YV and made a comparison with WV crabs. Specifically, we examined the benthic community of WV and YV, isotopic niche width, and protein expression patterns of the crabs from the two vent types at a distance of 100 m. The coverage of sessile organisms and low-mobility fauna in WV were more abundant than in YV. The δ13C and δ15N values were insignificantly different between crabs from WV and YV. The niche width of crabs from WV was significantly broader than those from YV, shown as SEAc areas of 3.62 ‰2 vs. 0.88 ‰2 (p < 0.05). The overlap percentages in WV and YV were 23.9 % and 97.9 %, respectively. The food sources of crabs in WV were more diverse than those in YV. Based on the protein expression patterns, the vent crabs were classified into WV- and YV-dwellings. Our results revealed that the feeding habits of the endemic vent crabs (X. testudinatus) are adapted to their vent types at a distance of 100 m, and the trans-vent movement is uncommon.