Comparison of urohyal bone morphology among gerreid fish (Perciformes: Gerreidae)

The urohyal bone, located in the central part of the mandibular skeleton, plays an important role in the mouth opening-closing mechanism of fish, and is considered a synapomorphy in teleostean fish. Morphology of the urohyal bone in six species of Gerreidae (Diapterus brevirostris , D. auratus , Eugerres lineatus , E. plumieri , Eucinostomus entomelas and Gerres cinereus) from the Pacific and Atlantic coasts of México was compared, using size and shape measurements. The main goal of the study was to explore the effectiveness of urohyal measurements in discriminating Gerreidae species. Morphological variation of urohyal bones, in terms of size and shape parameters, allowed species differentiation. Discriminant function analysis (DFA) significantly separated the six species with high classification rates (overall mean 92%). The G-test and Cohen’s kappa confirmed the high rates of classification success obtained by DFA. Circularity, Feret minimum, roundness, rectangularity and area were the main urohyal measurements explaining inter-specific variability. These results suggest the usefulness of urohyal bone morphology in differentiating Gerreidae species analyzed, highlighting the taxonomic value of the urohyal bone, until now never quantitatively evaluated as a diagnostic character in the classification of teleostean fish.