Parasitism, commensalism or mutualism? The case of Scyphozoa (Coronatae) and horny sponges

The relationship between the scyphozoan Nausitoe punctata and the horny sponges Cacospongia scalans, Dys~dea avara and D. fragdis was analyzed. Evidence was found for utilization of the thecae of N. punctata as a substitute for skeletal fibres. Consequently some metabolic costs associated with skeleton-buildng may be reduced for the sponge. Further potential benefits for the scyphozoan, e.g. protection against predation and mechanical disturbance, and trophic advantages, are discussed This association is suggested to be non-parasitic and mutualistic, and widely distributed among 6 orders and 8 families of the Demospongiae which occur throughout the Northwestern Mediterranean.