Deep-sea hydrothermal vents occur along the mid-ocean ridges and back-arc basins around the globe. There are very
few community analyses of vent meiobenthos. The central objectives of this study were to identify and quantify for the first
time the entire metazoan meiobenthic community associated with mussel aggregations of Bathymodiolus thermophilus
Kenk and Wilson, 1985 from the EPR, 111N and of Bathymodiolus puteoserpentis Cosel et al., 1994 from the Mid-Atlantic
Ridge (MAR), 231N. Using a quantitative sampling method, abundance, biomass, sex ratio, species richness, diversity,
evenness, and trophic structure were studied based on three samples from each site. Meiobenthic abundance in each sample
was unexpectedly low, but similar between sites. The community was composed of nematodes, copepods, ostracods, and
mites, with a total of 24 species at EPR vents, and 15 species at MAR vents. While most copepod species were vent
endemics within the family Dirivultidae, nematodes and harpacticoid copepods belonged to generalist genera, which occur
at a variety of habitats and are not restricted to hydrothermal vents or the deep sea. The meiobenthos of hydrothermalvent
mussel beds constitutes a unique community unlike those of other sulfidic habitats, including the thiobios of shallowwater
sediments and the meiobenthos of deep-sea, cold-seep sediments. The trophic structure was dominated by primary
consumers, mainly deposit feeders, followed by parasites. Predatory meiofaunal species were absent.