Amphipod community associated with invertebrate hosts in a Mediterranean marine cave

The present study explored the amphipod communities associated with the dominant host invertebrates inhabiting a marine cave of South Spain in order to describe their species composition and distribution patterns. Although they play a key role in the structure of mobile epifaunal communities inhabiting most rocky reef ecosystems, this component of marine caves communities has often been overlooked. Colonies of six sessile species were collected: Astroides calycularis, Parazoanthus axinellae, Pentapora fascialis, Aldeonella calveti, Filograna implexa, and Ircinia fasciculata. In each sample the mobile epifaunal community (mainly focusing on the amphipod group) was characterized, with Arthropoda and Amphipoda being the dominant phylum and order, respectively. Among amphipods, the gammarid Lembos websteri and the caprellids Phtisica marina and Pseudoprotella phasma were the most abundant species. The endangered coral Astroides calycularis showed the most distinctive amphipod community and multivariate analysis highlighted the existence of significant differences in the amphipod assemblages among invertebrate hosts in the cave. However, no host-specific species were found. Benthic hosts inside the cave are mainly used as a refuge by amphipods and all the sessile species studied seem to play an equivalent facilitation role. To what extent changes in the composition of sessile species may affect other associated species was also discussed.