Sexual Dimorphism in the Dentition of Pelagic Stingrays, Pteroplatytrygon violacea

The elasmobranch fishes are a group of vertebrates that have evolved a multi-functional mouth that is involved in mating behavior. Sexually dimorphic changes have been observed, which include epidermal thickening in females and seasonal changes in male dentition. Male Atlantic stingray (Dasyatis sabina) dentition changes from molariform to pointed during the mating season, which allows them to better grasp the females to successfully mate . Pelagic stingrays (Pteroplatytrygon violacea) are in the same family (Dasyatidae) as Atlantic stingrays and are likely to undergo seasonal changes in dentition as well. However, pelagic stingrays possess pointed symphyseal teeth to aid in feeding on teleosts and squid. Therefore, it is unknown if pelagic stingrays also undergo seasonal changes in dentition to aid in mating. Pelagic stingray jaws were collected from commercial fisherman. Tissue was dissected from each jaw and the number of teeth in the files and rows was recorded. The tooth next to the symphyseal tooth in the second row of the upper jaw was extracted and photographed. Photographs were digitized and analyzed for shape with various software programs. Results show that sexual dimorphism in pelagic stingrays is seen between male and female teeth (P=0.01). There were no significant differences in males and females between mating and non-mating seasons (P=0.06, P=0.55). The number of tooth rows increased significantly according to disc width in upper jaws in both sexes. The number of tooth rows in the lower jaws of males also increased significantly. There is no significant difference in tooth files in upper or lower jaws in both sexes. However, number of tooth files are significantly different between males and females