Abstract
In response to predation threats during the embryonic period, prey from diverse taxonomic groups exhibit plasticity in their hatching timing. In theory, predators of adult prey, as well as predators of eggs or embryos, can influence hatching timing. Similarly, not only embryos but also parents of prey can regulate hatching timing. However, research on the influence of adult predators and adult prey on hatching timing in species with separate predators for adults and eggs remains limited. To the best of our knowledge, no study has investigated this phenomenon in marine invertebrates under natural conditions. In this study, we investigated the effects of life-stage-specific predators (i.e., adult and egg predators) on the hatching timing of the pulmonate limpet (Siphonaria sirius), which undergoes planktonic development on an intertidal rocky shore. The presence of adult predators before and after egg-laying did not affect the hatching timing. Furthermore, while the egg predators present before egg-laying did not influence hatching timing, those present after egg-laying accelerated it. The results indicate that embryos, rather than their parents, determine hatching timing in response to their own predation risk. This finding highlights a strategy in which organisms with planktonic development rely on embryonic plasticity to mitigate strong predation risks during the egg stage. To understand how predation risk shapes predator-prey dynamics, it is critical to identify how predators, specific to each life-history stage of prey (such as adult and egg), interact with prey at different life-history stages during key events like reproduction.