SEXUAL AND ASEXUAL REPRODUCTION IN 2 SPECIES OF TETHYA (PORIFERA, DEMOSPONGIAE) FROM A MEDITERRANEAN COASTAL LAGOON

The sexual and asexual phases of reproductive cycles of two sponges, T ethya citrina and T. aurantium, living sympatrically in a Mediterranea n coastal lagoon (Stagnone di Marsala, NW Sicily), were studied from s amples collected over an 18-mo period. Both species are oviparous and gonochoric. They have a summer, partially overlapping, period of oocyt e production, although T. citrina appear to mature earlier. No males w ere found, possibly due to the very short period of spermatogenesis. B oth species produce asexual buds during the autumn/winter months. Howe ver, they seem to follow different reproductive strategies, with T. ci trina showing a significantly lower production of buds than T. auranti um; by contrast, egg production is significantly lower in the latter s pecies. The difference in the reproductive resource allocation is cons istent with data reported in the literature on the anatomy features, g enetic population structure and ecological distribution.