FISH EGGS AND PENTACRINOIDS IN WEDDELL SEA HEXACTINELLIDS - FURTHER EXAMPLES FOR THE STRUCTURING ROLE OF SPONGES IN ANTARCTIC BENTHIC ECOSYSTEMS

During the CS-EASIZ expedition (ANT XII/3) to the eastern Weddell Sea shelf with RF 'Polar-stern' in January-March 1996, several hundred hex actinellids from trawl catches were inspected for associated fauna. At one station, fish egg masses were found in the suboscular cavities of 18 specimens of hexactinellid sponges belonging to four different spe cies of the genus Rossella. Egg numbers in intact hexactinellids range d from about 800 to more than 8000. At two stations, pentacrinoids, th e sessile stage of comatulid crinoid development were found attached t o the inner dermal membrane of hexactinellids. This is the first time pentacrinoids have been documented from the high Antarctic. The pentac rinoids mostly formed small groups, but single individuals were found as well. Neither fish eggs nor pentacrinoids were observed in or on ot her structures or animals; these findings stress the overall importanc e of sponges, especially hexactinellids, as substrates for development al stages of other members of the ecosystem.