Data from: A water-borne pursuit-deterrent signal deployed by a sea urchin

Selection by consumers has led to the evolution of a vast array of defenses in animals and plants. These defenses include physical structures, behaviors, and chemical signals that mediate interactions with predators. Some of the strangest defensive structures in nature are the globiferous pedicellariae of the echinoderms. These are small venomous appendages with jaws and teeth that cover the test of many sea urchins and sea stars. In this study, we report a unique use of these defensive structures by the collector sea urchin Tripneustes gratilla. In both the laboratory and the field, globiferous pedicellariae were unpalatable to fish consumers. When subject to simulated predator attack, sea urchins released a cloud of pedicellaria heads into the water column. Flume experiments established the presence of a waterborne cue associated with this release of pedicellariae that is deterrent to predatory fish. These novel results add to our understanding of how the ecosystem-shaping sea urchin T. gratilla is able to reach high densities in many reef habitats, with subsequent impacts on algal cover.消费者的取食选择推动了动植物演化出种类繁多的防御机制，这些防御机制涵盖介导与捕食者互作的物理结构、行为策略与化学信号。自然界中最为奇特的防御结构之一，便是棘皮动物（echinoderms）的具球型叉棘（globiferous pedicellariae）：这类结构是带有颌与齿的小型毒附肢，覆盖于多数海胆与海星的钙质壳（test）表面。本研究报道了刻肋海胆（Tripneustes gratilla，collector sea urchin）对这类防御结构的独特利用方式。无论是实验室环境还是野外实地，具球型叉棘均对鱼类捕食者具有拒食性。当遭遇模拟捕食者攻击时，海胆会向水体中释放一团叉棘头部。水槽实验（flume experiments）证实，该叉棘释放过程会伴随产生一种水源性信号（waterborne cue），该信号可对掠食性鱼类产生驱避作用。本研究的全新发现，加深了我们对生态系统塑造者刻肋海胆（T. gratilla）为何能在众多礁栖生境中达到高密度种群的理解，以及其对藻类覆盖度产生的后续影响。