Meeting Abstract

P3.37  Jan. 6  Morphological Variation of the Weberian apparatus in Cypriniform Fishes BIRD, N.C.*; HERNANDEZ, L.P.; George Washington University; George Washington University nbird@gwu.edu

Cypriniform fishes, such as minnows, carps, loaches, algae-eaters, and suckers, represent one of the most diverse orders of fishes in the world. A number of evolutionary innovations key to improved hearing and feeding have likely played an important role in their invasion and dominance of freshwater niches in North America, Europe, and Asia. One such innovation, the Weberian apparatus, is a novel assemblage of vertebral elements that relay and amplify sound and pressure changes from the gas bladder to the inner ear. Although not unique to Cypriniformes, the Weberian apparatus has undergone dramatic morphological changes within Cypriniformes. As one of the most complex skeletal adaptations in fishes, we are interested in the mechanisms responsible for the origin, development, and subsequent evolution of the Weberian apparatus within Cypriniformes. Using cleared and stained specimens, we assembled a detailed morphological comparison of the Weberian apparatus of Cypriniformes. Data are presented regarding morphological variation within and among all major cypriniform families. Our comparative study identified diverse morphologies, as well as evidence of convergent evolution. For example, many divergent benthic fishes inhabiting swift-moving waters, such as some cobitids, balitorids, and gobionin cyprinids, have encapsulated gas bladders. Variation within the families Balitoridae, Gyrinocheilidae, and Catostomidae was minimal, whereas variation within the subfamilies Cyprinidae and Cobitidae was far more significant. Large-scale variation was found among families, with each family exhibiting unique structural adaptations. This variation and morphological divergence provide insight into how ancestral vertebral structures have been modified and adapted to produce a functional Weberian apparatus.