Peracarid Crustacea Inhabiting Aegagropylae of the Red Alga Rytiphloea Tinctoria (Clemente) C. Ag. in the Stagnone Sound, Western Sicily, Italy

The peracarid Crustacea belonging to Cumacea, Tanaidacca, Isopoda and Amphipoda, inhabiting aegagropylae of Rytiphloea tinctoria were studied throughout a year in the Stagnone Sound (western Sicily, Italy). The dominant groups, tanaids (61.7%) and amphipods (32.8%), were represented by 6 and 28 species, and showed complementary trends during the 12 months, reaching their maximum of abundance in spring and autumn, respectively. Tanaids were mainly represented by Apseudes intermedius Hansen, 1895 and Parapseudes latifrons (Grube, 1864), and amphipods by Elasmopus pocillimanus (Bate, 1862), Leptocheirus guttatus (Grube, 1864), Lysianassa longicornis Lucas, 1849 and Maera inaequipes (A. Costa, 1857). These species, often found in open coastal waters, showed different seasonal trends in the Stagnone, probably in relation to their ecological requirements and life cycle. Evidence is provided that these aegagropyla formations are not only a temporary refuge for the peracaridan communities in the sometimes stressed environmental conditions of the Stagnone. In fact, they are a complex microcommunity where species are present constantly in both sexes and at all stages of development. The formations are also the result of an interaction between alga and peracarid crustaceans, which moreover play a major role among the other small invertebrates.