Shape variation and functional adaptation in a structure involved in the feeding system of gobiid fishes

Fish are observed in different aquatic environments, including freshwater, marine and also intertidal zones. It is suggested that the urohyal bone is involved in the feeding function of fish. Information about the urohyal bone in different fish groups, including gobiids is rare. In the present study, changes in the shape of the urohyal bone were studied in seven gobiid fish from the intertidal environments of the Persian Gulf and the Gulf of Oman by applying shape analysis and geometric morphometric analyses. The results revealed that the shape of the urohyal bone in each species was distinct, which is almost consistent with their phylogenetic relationships.Periophthalmus waltoniinhabits often terrestrial habitats and requires a system to obtain food. The specific shape of the urohyal bone in this species probably results from a functional adaptation to obtain food from the terrestrial environment. Moreover, our results indicated that the shape variation in the urohyal bone of the studied species is linked to their feeding because the calculation of E index categorized those species with similar feeding regimes into one group. In conclusion, we assumed that the urohyal shape variation in the studied gobiid species is the result of compatibility to the various feeding regimes, and it is likely controlled by genetic factors. Furthermore, the results support the usefulness of the urohyal bone morphology in differentiating the studied gobiid species and highlighting the taxonomic value of the urohyal bone.