The intrasponge fauna of Spheciospongia vesparia (Porifera,Demospongiae) at Curaçao and bonaire

The infauna of 35 individuals of Spheciospongia vesparia (Lamarck, 1814) of different volumes and from different sites and depths have been inventoried and compared. The number of sponge-inhabiting taxa is logarithmically related to sponge volume. Biomass and total number of the animals contained in the sponge are directly proportional to sponge volume. Numerical and taxonomic composition of infaunas from different sampling sites is fairly constant. Biomass and total number of sponge-inhabiting animals is not significantly different for any of the 4 sampling sites. Several taxa, however, are more abundant in sponges from one or more localities. The ratio of total biomass to total number of intrasponge fauna is found to be significantly smaller for sponges collected in deep water than in shallow water. Differences from and similarities with Pearse's results (1932, 1950) on the infauna of the same sponge species at Dry Tortugas and Bimini are discussed. The relation of the number of contained taxa and the volume of a sponge is compared with the relation of island size and number of taxa present according to MacArthur and Wilson's island-theory (MacArthur, 1972). Finally the erratic occurrence of some taxa as opposed to the highly regular occurrence of some other taxa is discussed. It is concluded that the composition of the sponge-infauna in specimens larger than 11 is highly constant and that the sponge-inhabiting fauna constitutes an ecological community.