Reproductive cycles in two populations of the Pacific sand dollar Dendraster excentricus

Abstract

Populations of the sand dollar Dendraster excentricus (Eschscholtz) occur in different habitats along the west coast of the USA. Two subtidal populations from the San Diego, California, area, one from an exposed coastal location and a second from a protected tidal channel, were compared for several aspects of their population and reproductive biology. Both populations demonstrated a similar schedule of reproductive activity with peak gonad volumes occurring in the early spring. However, population reproductive readiness and individual reproductive effort and size varied considerably between the populations; individuals in the protected tidal channel were larger and produced proportionately larger gonads with ripe gametes for a longer period, than those on the exposed coast. The differences between the populations are explained by the greater demands of the rigorous exposed habitat for maintenance at the cost of reproductive effort and growth.