Biol Bull. 2023 Apr;244(2):103-114. doi: 10.1086/725633. Epub 2023 Jul 26.
AbstractMarine invertebrates with biphasic life cycles feature life history transitions that coincide with habitat changes from benthic adults to planktonic embryos and larvae, then a return to the benthos as a juvenile at metamorphosis. The metamorphic transition exposes animals to a new suite of benthic predators, and high mortality often occurs in the hours and days following settlement. Juvenile invertebrates may produce phenotypically plastic morphological defenses when predator cues are detected. However, time lags inherent to phenotypic plasticity may delay the production of defenses until after the period of highest vulnerability. It should, therefore, be beneficial for planktonic larvae approaching settlement to detect waterborne cues from benthic predators and produce juvenile phenotypes appropriate for postmetamorphic survival. Echinoderms are useful models for testing transhabitat and trans-life history stage phenotypic plasticity because many species have larvae that construct their juvenile phenotype while still in the water column. In this study, we tested whether planktonic echinoderm larvae exposed to cues from benthic predators modified their juvenile phenotypes at settlement. Green urchin () and Pacific sand dollar () larvae were exposed to predatory green crab () or red rock crab () cues, respectively, from their early-stage juvenile rudiment formation through settlement. Green urchin larvae exposed to predator cues settled with significantly more juvenile spines compared to unexposed controls. Sand dollars exhibited earlier settlement, larger disk area, fewer spines, and shorter spines when exposed to benthic predator cues. Sand dollar larvae were also exposed to cues from planktonic crab larvae and in response settled sooner and larger, with even fewer and shorter spines than those exposed to benthic predator cues. These results suggest that echinoderm larvae alter their juvenile phenotype in response to predator cues, but the response varies between species, and responses to planktonic threats may be prioritized over benthic ones.
具有双相生活史的海洋无脊椎动物具有生命周期的历史转变，这些转变与从底栖成体到浮游幼体和幼虫的栖息地变化相吻合，然后在变态时返回到底栖环境成为幼体。变态过渡使动物暴露于新的一系列底栖捕食者中，并且在定居后的几个小时和几天内经常发生高死亡率。当探测到捕食者的线索时，幼年无脊椎动物可能会产生表型可塑性的形态防御。然而，表型可塑性固有的时间滞后可能会延迟防御的产生，直到最高脆弱期之后。因此，对于即将定居的浮游幼虫来说，检测来自底栖捕食者的水传播线索并产生适合变态后生存的幼体表型是有益的。棘皮动物是测试跨栖息地和跨生命史阶段表型可塑性的有用模型，因为许多物种的幼虫在水柱中构建其幼体表型。在这项研究中，我们测试了暴露于底栖捕食者线索的浮游棘皮动物幼虫是否会在定居时改变其幼体表型。绿海胆（）和太平洋沙钱（）幼虫分别暴露于来自其早期幼体雏形形成到定居的捕食性绿蟹（）或红岩蟹（）的线索中。与未暴露的对照相比，暴露于捕食者线索的绿海胆幼虫定居时带有明显更多的幼体棘刺。沙钱表现出更早的定居、更大的盘面积、更少的棘刺和更短的棘刺，当暴露于底栖捕食者线索时。沙钱幼虫还暴露于浮游蟹幼虫的线索中，并相应地更早和更大地定居，与暴露于底栖捕食者线索的幼虫相比，棘刺甚至更少且更短。这些结果表明，棘皮动物幼虫会根据捕食者的线索改变其幼体表型，但反应因物种而异，并且对浮游威胁的反应可能优先于对底栖威胁的反应。
