When not in use, the fins are tucked into special grooves or depressions so that they lie flush with the body and do not break up its smooth contours.

当鱼不使用鱼鳍时，会将它们折叠起来，收回到特殊的沟槽或者凹陷部位；这样鱼鳍就可以与身体保持齐平，以维持它们平滑的外形。