Evidence for enhanced late-stage larval quality, not survival, through maternal carry-over effects in a space monopolizing barnacle

Understanding the effects of maternal and pelagic resource allocation on larval traits is essential to better understand population dynamics of marine benthic invertebrates. We tested how different levels of food supply to adult barnacles and their feeding larvae (nauplii) might alter survival to the settling cyprid larval stage and cyprid quality. Median development time did not vary, except when both parents and larvae were given a low food supply, which delayed the time to metamorphosis by over 40%. Survival to the cyprid stage was only affected by larval feeding, which doubled in better-fed nauplii. In contrast, cyprid size showed a more complex response, prone to additive effects of maternal and larval provisioning. Moreover, the resulting size-range observed for experimental cyprids (spanning over 70% of the minimum cyprid size) mirrored the variation found in the coastal plankton, suggesting that food supply may exert similar effects in nature. Given that barnacles nearly saturate available habitat under favorable conditions, maternal allocation resulting in enhanced late-stage larval quality may be adaptive since competition for available settling space is likely intense. On the other side, severe resource limitation through embryogenesis and larval development may impose delayed metamorphosis and thus enhanced potential for transport and the colonization of marginal habitats, where intraspecific competition may be lower and larval quality less critical.