Freshwater molluscs have physical defences such as shells to protect their inner soft bodies from underwater predators. However, some predators have specialized mouthparts that can destroy the snail’s tough and/or spiral shells. Therefore, these snails could have evolved specific defences against their specialist predators. We observed the freshwater snail Austropeplea ollula (Pulmonata: Lymnaeidae) frequently climbing rice plants above the water in paddy fields in Shimane, central Japan. We also found the beetle larvae of Hydrophilus acuminatus (Coleoptera: Hydrophilidae), which are known as snail-eating specialists, in waters of the same paddy fields. We hypothesized that A. ollula climbs rice plants above the water to escape underwater predation by H. acuminatus and that the escape behaviour of snails may be specifically triggered by chemical cues from snail-eating specialists and/or killed conspecifics. To test both these hypotheses, we conducted laboratory experiments. The results demonstrated that chemical cues (e.g. body fluids) from killed conspecifics could trigger A. ollula to crawl above the waterline. Furthermore, chemical cues (e.g. scent and digestive enzymes) from H. acuminatus could promote the behaviour. Therefore, A. ollula can successfully escape from H. acuminatus by climbing the rice plants above the water.

中文翻译：

---

在水线上方攀爬水稻：食蜗牛的专家从水下捕食中逃脱淡水蜗牛

淡水软体动物具有诸如贝壳之类的物理防御能力，可以保护其内部软体免受水下掠食者的侵害。但是，某些食肉动物具有专门的口器，可以破坏蜗牛的坚硬和/或螺旋形外壳。因此，这些蜗牛可能已经进化出了针对其专业天敌的特定防御措施。我们在日本中部岛根市的稻田中观察到淡水蜗牛Austropeplea ollula（Pulmonata：Lymnaeidae）经常在水面上方爬稻植物。我们还在同一稻田的水域中发现了被称为蜗牛食食专家的亲水性甲虫（Coleoptera：Hydrophilidae）的甲虫幼虫。我们假设油曲霉将水稻植株爬到水面上方，以逃避水下捕食。H. acuminatus认为蜗牛的逃逸行为可能是由吃蜗牛的专家和/或杀死的同种动物的化学线索特别触发的。为了检验这两个假设，我们进行了实验室实验。结果表明，来自被杀死的同种菌的化学线索（例如体液）可能触发油曲霉爬到水线以上。此外，来自尖头嗜血杆菌的化学线索（例如气味和消化酶）可以促进这种行为。因此，通过将水稻植株爬到水面之上，圆头曲霉可以成功地从尖头H虫中逃脱。