MATING-BEHAVIOR OF A BROODING ANTARCTIC ASTEROID, NEOSMILASTER-GEORGIANUS

Spawning behavior and male-female superposition of Neosmilaster georgi anus, a common brooding asteroid, were observed both in the field and the laboratory at Palmer Station, Antarctica, during the austral sprin g of 1991. Pseudocopulation is preceded by exploration, contact, and m ounting of a female by individual or multiple males. Male pre-mating a ctivity in the field was initiated by the spawning of a nearby conspec ific female. However, in laboratory experiments a similar pattern of a ctivity was triggered by the presence of spawning conspecific males or male sea urchins, indicating the presumed inductive signal lacks spec ificity. Pseudocopulation in this species may ensure maximal fertiliza tion and enhance reproductive success. This is the first reported inst ance of aggregative spawning in an Antarctic echinoderm. Moreover, pse udocopulation is a rare phenomenon among echinoderms worldwide and N. georgianus is only the third asteroid described to utilize this fertil ization strategy.