Ontogenetic development of hearing and sound communication in catfishes.

Abstract

Catfish possess a high diversity in accessory hearing structures, hearing sensitivities, and sound-generating mechanisms. Nevertheless, the ontogeny of their hearing and sound communication remains unknown. We investigated the development of Weberian ossicles and hearing sensitivity in the African bullhead catfish from postlarval stages up to adults and also examined the ontogenetic development of hearing and sound production in the yellow marbled squeaker catfish. In the smallest bullhead catfishes, the Weberian ossicles and interossicular ligaments are not fully developed. They are unable to detect sounds at low levels and high frequencies. In later stages of both species tested, hearing sensitivity increases with size at low frequencies and decreases at high frequencies. In the squeakers, the duration of stridulation sounds, sound pressure level, and pulse period increase, whereas the dominant frequency decreases with size. The most sensitive frequencies correlate with the dominant frequencies of stridulation sounds in all size groups, enabling all stages to detect communication sounds. Our studies show two different trends of changes in hearing sensitivity in catfishes: one prior to and the other after full development of the Weberian ossicles. Squeakers of all sizes are able to communicate acoustically. These results contrast with prior findings in teleosts. [Work supported by FWF.]