Meeting Abstract
Otophysan fishes possess a number of unique morphological features associated with enhanced hearing. These features include a Weberian apparatus that is composed of three pairs of ossicles that link the swim bladder to the inner ear, modifications of the associated first four vertebrae, and a well-developed lagena. In addition, within the otophysan clade, characiform fishes possess a foramen in the prootic that is open to the utricle and may have an auditory function. Auditory cues are likely to have influenced the evolutionary morphology of fishes in the family Serrasalmidae (piranhas, pacus, tambaqui). These fishes have a variety of feeding ecologies and behaviors which include fish predation, scale and fin feeding, frugivory, and herbivory of aquatic macrophytes. Sound may be an important cue for finding food resources in some species. In addition, several rheophilic species occur in rapids of rivers, which are high noise environments. We are examining shape of the neurocranium, lagenar capsule (basioccipital and exoccipital), cavum sinus imparis, prootic foramen, and vertebrae (1-4) of 20 species of serrasalmid fishes obtained from microCT scans. Preliminary observations indicate wide variation in the relative size of lagenar capsules and prootic foramen shape. 3D Geometric morphometrics is being used to quantify shape variation among taxa. This study is expected to determine the degree of covariation of these features and reveal any patterns associated with phylogeny and ecology.
