CONFLICT BETWEEN SOMATIC AND GONADAL GROWTH IN SEA URCHINS: IMPLICATIONS FOR AQUACULTURE

Studies on aquaculture of sea urchins have focused on production of large, high quality gonads by large individuals. Sea urchins must reach a threshold of body size before they are marketable. Decreasing the length of time required to reach this threshold is desirable for aquaculture of sea urchins. Somatic growth in sea urchins is great initially and then decreases with size as gonadal production occurs. Somatic growth in Strongylocentrotus intermedius is initially fast, then decreases after initial HD = ca. 15 mm with increasing size to an asymptote (Fig.1). Gonads of S. intermedius begin to increase greatly in size after a HD = ca. 15 mm (Fig. 2). The marketable size of S. intermedius is ca. 50 mm.

Gonadal production exceeds somatic production seasonally in species with annual reproductive cycles, suggesting conflict. Conflict between somatic and gonadal production requires limited common nutrient requirements. Independent processes would suggest differences in nutrient requirements or preferential allocation. Scheibling and Hatcher (2013) concluded there is apparent conflict between somatic and gonadal growth in strongylocentrotids but that the hypothesis that they are independent could not be rejected. Field and laboratory studies have shown both somatic and gonadal production are related to food availability and quality. Species with a low allocation to somatic production have faster growth and greater gonadal production, indicating a genetic basis for production. Intrinsic control (hormonal) of allocation to gonadal production but not to somatic growth has been reported. Rapid growth to a marketable size is important in aquaculture. The studies suggest feeding a high quality feed would increase the rate of somatic growth and decrease time to marketable size but the increase in gonadal growth would decrease cost effectiveness.