Sexual Dimorphism

Sexual dimorphism in skate tooth morphology

We recently completed research which examined the differences in the tooth morphology of male and female specimens of the roundel skate (Raja texana). Previous studies suggested that the differences in tooth morphology may have been due to diverse prey preferences or an adaptation for males to effectively grasp females during mating. Jaws were removed from 109 (69 female: 40 male) R. texana, and morphological variations of male and female teeth were quantified. To account for intra-jaw tooth variations, lower jaw teeth were extracted using a dental pick at both a medial and lateral location. Teeth from both locations were photographed under magnification, and morphology software was used to denote landmarks and curves within each tooth. We compared tooth morphology variations between male and female roundel skates, as well as among mature and immature specimens at different sizes. A procrustes analysis was performed on these data to standardize differences in tooth size and orientation. Analysis of Variance was used to quantitatively compare the tooth shape from both jaw localities of male and female roundel skates. The results of this project were presented in poster form at this year's joint meeting of Icthyologists and Herpetologists. Future research will include expanding the roundel skate poster into a scientific paper and completing a similar anaysis of the spreadfin skate (Dipturus olseni).