鱼鳔是鱼游泳时的“救生圈”,它可以通过充气和放气来调节鱼体的比重。这样,鱼在游动时只需要最小的肌肉活动,便能在水中保持稳定状态。不过,当鱼下沉到一定水深(即“临界深度”)后,外界巨大的压力会使它无法再调节鳔的体积,这时,它受到的浮力小于 A fish scorpion is a “buoy ring” when a fish swims. It can adjust the weight of the fish by inflating and deflation. In this way, the fish need only minimal muscle activity when swimming, so that they can maintain stability in the water. However, when the fish sinks to a certain water depth (ie, “critical depth”), the huge pressure outside makes it impossible to adjust the volume of the quail. At this time, it receives less buoyancy than