Population differences in gonad and pyloric caeca cycles of the New Zealand seastarSclerasterias mollis (Echinodermata: Asteroidea)

Abstract

Inshore and offshore populations ofSclerasterias mollis (Hutton, 1872) were sampled on the outer continental shelf off the Otago Peninsula, New Zealand, and their nutritional and reproductive cycles are described from 1985–1986. Histological changes in the gonads are generally typical of other asteroids. The gametogenic cycle takes 12 mo. The gonad and pyloric caeca indices in both females and males had an inverse relationship.S. mollis accumulates nutrients in the pyloric caeca during summer and early autumn. The gonads develop in the autumn and winter. Offshore seastars were much larger and had significantly higher gonad and pyloric caeca indices than inshore individuals. These differences in body sizes and organ indices arise from differences in food availability and/or population density.