The examined host species, all collected from Crete, Greece, are Ircinia fasciculata, I. oros, I. variabilis, and Sarcotragus spinosulus. In this study we have tried to answer some specific questions such as: a) Is there a host species specific footprint on microbial communities, b) if there is an East versus West Mediterranean footprint, c) if there are similarities or differences on the composition of Ircinia species and non-Ircinia species (species specificity, sponge specificity) and finally whether there is a tissue specific patterning effect of the symbiotic microbial communities of sponges under study