Evolution of hearing specializations in teleost fishes

Abstract

Among teleost fishes, the spectacular diversity of body forms, ecotypes, and behavioral repertoires is matched by a tremendous diversity of hearing mechanisms and, presumably, auditory function. Morphological specializations with the potential to enhance hearing have arisen as many as 20 times within teleosts. These specializations range from modest modifications of the buoyancy-regulating gas bladder to wholesale reorganization of the rostral vertebral column and posterior neurocranium. Since many of these specializations involve vertebral elements and/or cranial modifications, it is possible to recognize enhanced hearing in fossil taxa. Other specializations, like the rostral swimbladder extensions of some holocentrids, appear to provide similar, but more modest, enhancements. In other cases, however, rostral swimbladder extensions may only increase the upper frequency limit (as in some scaeinids) or somehow underlie improved spectral resolution (in notopterids). The functions of these and many other specializations await more complete functional characterization. For instance, the number, linkages, and robustness of Weberian ossicles vary considerable within Otophysi, and it is clear that hearing abilities differ widely, too. How and why individual Weberian apparatus morphologies confer differences in hearing abilities remains a critical issue in studies of fish hearing.