Host use patterns and demography in a guild of tropical sponge- dwelling shrimps

Abstract

Demographic consequences of the commensal lifestyle for Synalpheus spp. were assessed by sampling sponges and coral rubble on reefs in Caribbean Panama. Eight of 22 species were found solely or primarily within the internal canals of sponges. Among these sponge-dwellers, host specificity ranged from generalism (occurrence in ≥4 host species) to specialization on a single host species. Parasitism by epicaridean isopods averaged six times higher in obligate sponge-dwellers (17%) than in free-living species (2.5%). Sponge species differed in the mean size and size range of habitable spaces they provide, number of potentially competing Synalpheus species they support, and vulnerability of associated shrimps to parasitism. Similarly, conspecific shrimp populations occupying different hosts differed demographically. Populations of Synalpheus brooksi in the sponge Spheciospongia vesparium were significantly less dense, less parasitized, had larger body sizes, and tended toward higher proportions of mature females than conspecifics in the co-occuring sponge Agelas clathrodes. -from Author