polychaetan

例句：

1. 1. Polychaetes are a diverse group of marine invertebrates that live in the sea floor.
   多毛虫是一类生活在海底的海洋无脊椎动物。
2. 2.The cnidarians have unique structures for capturing and digesting prey.
   水螅具有独特的结构来捕捉和消化猎物。
3. 3. Cnidarians are found throughout the ocean, from shallow waters to deep trenches.
   水螅遍布整个海洋，从浅海到深海都有分布。