saccoid gill

例句：

1. 1. The fish had a sac on its back that it could use to protect itself from predators.
   这条鱼在背上有一个袋子，它可以用来保护自己免受捕食者的攻击。
2. 2. The scientist discovered a new species of fish with sac-like gills.
   这位科学家发现了一种具有类似鳃盖状鳍的新鱼类。
3. 3. The fish's sac-like gills were used to filter the water and extract nutrients from it.
   这种鱼类的鳃盖状鳍用于过滤水并从水中提取营养。