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 ‘Polarstern’ in January–March 1996, several hundred hexactinellids 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 species of the genus Rossella. Egg numbers in intact hexactinellids ranged from about 800 to more than 8000. At two stations, pentacrinoids, the sessile stage of comatulid crinoid development were found attached to the inner dermal membrane of hexactinellids. This is the first time pentacrinoids have been documented from the high Antarctic. The pentacrinoids mostly formed small groups, but single individuals were found as well. Neither fish eggs nor pentacrinoids were observed in or on other structures or animals; these findings stress the overall importance of sponges, especially hexactinellids, as substrates for developmental stages of other members of the ecosystem. Received: 25 May 1996/Accepted: 22 July 1996