hydracarian

例句：

1. 1. The hydracarians are a fascinating group of organisms that live in water.
   水螅是一种令人着迷的生物群体，它们生活在水里。
2. 2.Hydroids are common in marine environments and play important roles in the ecosystem.
   水螅在海洋环境中很常见，对生态系统起着重要的作用。
3. 3. The hydracarians have unique adaptations that allow them to survive in extreme conditions.
   水螅具有独特的适应能力，使它们能够在极端条件下生存。