EMLET, R.B.; Univ. of Oregon, OIMB: Functional and ecological limits on size at metamorphosis of marine invertebrates

Just as egg size can influence many aspects of the larval stage, size and condition at metamorphosis have consequences for juvenile growth and survival. Here I examine several factors that may set the lower and upper limits to size at metamorphosis. Invertebrate larvae feed and swim with cilia or muscle and are small (≤ mmís). There is often a habitat transition that accompanies the transformation from larva to juvenile, and newly metamorphosed juveniles will grow larger (mmís to cmís) with relatively little change in form. Juveniles can be no smaller than what is required for survival in this new habitat. Lower limits to juvenile size may be set by requirements of sufficient energy reserves, requirements for juvenile feeding, growth, movement, and by competition. Upper limits to juvenile size may be set by larval form, mechanisms of larval swimming and feeding, and specific gravity of the competent larva including juvenile components. Because larger larvae and juveniles may be more easily seen, visual predation may also limit size at metamorphosis. I will present data from echinoderms and other phyla to explore patterns in size at metamorphosis in light of larval form and swimming mechanisms and juvenile feeding, attachment and movement.