SEASONALITY OF REPRODUCTION IN THE CUSHION STAR ODONTASTER VALIDUS ATSIGNY-ISLAND, ANTARCTICA

The reproductive and larval biology of the common Antarctic cushion-st ar Odontaster validus Koehler (Echinodermata: Asteroidea) were studied in a shallow-water population at Signy Island in the maritime Antarct ic. The gonad index peaked in April/May, and injection with 1-methylad enine indicated that competence to spawn peaked in May/June. Gastrulae were first detected in May, and maxima; water-column larval densities were measured in July. Reproduction was therefore highly seasonal, al though not ail individuals appeared to spawn each year. The pyloric ca eca index increased in summer (typically November to March, but variab le between years) and decreased during winter (June to October), sugge sting that feeding activity was seasonal. Ail aspects of biology inves tigated showed significant interannual variability. Comparison with pr evious studies in the high Antarctic at McMurdo Sound indicated a simi lar if more pronounced seasonality at Signy. but the warmer seawater t emperatures in the maritime Antarctic (particularly in late winter/ear ly spring from September onwards) resulted in faster larval developmen t at Signy.