Delayed metamorphosis: Effect on growth and survival of juvenile sand dollars (Echinoidea: Clypeasteroida)

Delay of metamorphosis is an important aspect of the larval biology and ecology of many marine invertebrates. In most studies on delay of metamorphosis, the focus has been on the length of time that larvae could remain competent to metamorphose. The potential effects of delayed metamorphosis on postlarval juveniles have not been investigated previously. Results of studies on the sand dollars Dendraster excentricus and Echinarachnius parma, both of which have planktotrophic larvae, indicate that juveniles from larvae that metamorphosed soon after becoming competent tended to have higher growth rates than juveniles from larvae that metamorphosed after a prolonged period of competence. Juveniles that were fed cultured algae had higher growth rates but also higher mortality rates than unfed juveniles. Mortality rates in fed juveniles were correlated with length of delay of metamorphosis, but some mortality may have been an artifact of feeding. Unfed juveniles from larvae that had delayed metamorphosis for 4 to 7 weeks had low mortality rates suggesting that either the larvae had not utilized a significant amount of the lipid energy reserves needed by the juveniles to survive until they become self-sufficient or that energy reserves accumulated by larvae are not critical to early juvenile survival.