Reproduction cycles and strategies of the cold-water sponges Halisarca dujardini (Demospongiae, Halisarcida), Myxilla incrustans and Iophon piceus (Demospongiae, Poecilosclerida) from the White Sea

The reproductive development of the Demospongiae species Halisarca dujardin i (Halisarcida), Myxilla incrustans and lophon piceus (Poecilosclerida) fro m Chupa Inlet (Kandalaksha Bay, the White Sea) was studied histologically d uring 1982-1994 and 1997. These species are all viviparous. Halisarca dujar dini inhabits shallow waters (1.5-5 m); M, incrustans and I. piceus are com mon in a more stable environment at depths between 15 and 25 m. Initiation of sexual reproduction stages is dependent upon water temperature. Reproduc tive effort is low in Myxilla incrustans and I. piceus (reproductive elemen ts contribute 7.3% and 12% of maternal tissue volume respectively), but muc h higher in H, dujardini (up to 69% of the parental tissue volume). Reprodu ction leads to localized destruction of maternal tissue for M, incrustans a nd I. piceus and complete disorder of central and basal parts of the choano soma of H. dujardini after each period of reproduction. Myxilla incrustans and I. piceus reproduce throughout the hydrological summer, but reproductio n in H. dujardini is restricted to 3 weeks. The average life span of M. inc rustans and I. piceus is more than 4 years, and that of H. dujardini is abo ut 7-12 months. The data suggest that M, incrustans and I. piceus are K-str ategists, whereas H. dujardini is an r-strategist.