Not My “Type”: Larval Dispersal Dimorphisms and Bet-Hedging in Opisthobranch Life Histories

Abstract. When conditions fluctuate unpredictably, selec-tion may favor bet-hedging strategies that vary offspring characteristics to avoid reproductive wipe-outs in bad sea-sons. For many marine gastropods, the dispersal potential of offspring reflects both maternal effects (egg size, egg mass properties) and larval traits (development rate, habitat choice). I present data for eight sea slugs in the genus Elysia (Opisthobranchia: Sacoglossa), highlighting potentially adaptive variation in traits like offspring size, timing of metamorphosis, hatching behavior, and settlement response. Elysia zuleicae produced both planktotrophic and lecitho-trophic larvae, a true case of poecilogony. Both intracapsu-lar and post-hatching metamorphosis occurred among clutches of “Boselia ” marcusi, E. cornigera, and E. crispata, a dispersal dimorphism often misinterpreted as poecilogony. Egg masses of E. tuca hatched for up to 16 days but larvae settled only on the adult host alga Halimeda, whereas most larvae of E. papillosa spontaneously meta-morphosed 5–7 days after hatching. Investment in extra-capsular yolk may allow mothers to increase larval size relative to egg size and vary offspring size within and among clutches. Flexible strategies of larval dispersal and offspring provisioning in Elysia spp. may represent adapta-tions to the patchy habitat of these specialized herbivores, highlighting the evolutionary importance of variation in a range of life-history traits