Fish That Live In The Dark Have The Best Ears

The types of fish that Deng studies live in layers of the ocean that no sunlight can reach -- from 400 meters all the way down to depths of 4,000 meters. Biologists are currently unable to keep these mesopelagic and benthopelagic fish alive for very long at the surface, so knowledge about how they function comes from comparing their anatomy to other kinds of fish that live in surface waters.

Some of these deep-sea fish have adaptations similar to those of surface fish with heightened hearing: a connection between the swim bladder and the ears, which may help to amplify sounds to the ears; and elaborately-oriented hair bundles in the inner ear, which suggests better hearing than fish with less complex patterns. Some of the deep-sea fishes also have a variety of unusual structures not found in other types of fish, like exceptionally rigid ears and stalks projecting from stones in the ear. The functions of these newly-discovered parts are unknown.

Deng will present detailed images of these structures and discuss her plans to work out their physiological purpose. "We have already found many specializations and adaptations in the eyes and olfactory systems of deep-sea fishes; it is reasonable to think that their hearing should also be important in the dark," says Deng.

The talk "Comparative studies of the auditory periphery of deep-sea fish" by Xiaohong Deng  will be presented at the 157th  Acoustical Society of America Meeting to be held May 18-22 in Portland, Ore.