Lunging backward at the surface, a whale positions its lower jaw to scoop water and krill into its pleated pouch, which can quadruple in size.

• 蓝鲸在水面上后仰，调整下颚的位置，将海水和磷虾吞入满是沟褶的食袋（下），褶皱打开后，食袋的体积可变成原来的四倍。