The grooved throat wall of fin whales, Balaenoptera physalus, extends tremendously during feeding causing the whale to expand its profile from a cigar shape to the shape of an elongated, bloated tadpole. Ventral groove blubber associated with the engulfing feeding mechanism can be extended reversibly to as much as 4 times its resting length in the circumferential direction, and to 1.5 times its resting length along the long axis of the body. The muscle in the throat wall can be reversibly extended up to 3 times its resting length. Both these tissues have large amounts of the protein elastin in their microstructures that may function in retracting the expanded buccal cavity. Calculations of forces contributing to the expansion of the buccal cavity show that the engulfing process in feeding can be powered solely by the speed of swimming.

No abstract