metasicula

例句：

1. 1.The metasicula is a hollow organ that helps the fish swim.
   中空器官是鱼类用来游泳的空心器官。
2. 2. The metasicula is an important part of the fish's digestive system.
   中空器官是鱼消化系统的重要组成部分。
3. 3. The metasicula is responsible for filtering the water and removing waste from the fish's body.
   中空器官负责过滤水和去除鱼体上的废物。