The balloon, a transparent structure that varies in design according to the type of appendicularian inhabiting it, also protects the animal and helps to keep it afloat.

气球是一个透明的结构，根据栖息在气球上的阑尾鱼的类型，气球的设计也有所不同，它还能保护动物，帮助它们保持漂浮。