COMPARISON OF HOLOCEPHALAN TENACULUM TOOTH MORPHOLOGY ACROSS DEPTH PROFILE AND FAMILY TYPE

Chondrichthyans (cartilaginous fishes that include sharks, rays, skates, and chimaeras) use internal fertilization as a mode of sexual reproduction. Male holocephalans (chimaeras) have an accessory copulatory structure called the cephalic tenaculum. The teeth of the cephalic tenaculum grasp the pectoral fins of females to remain attached during mating. The structure of the tenaculum has been described in only two of the 53 known species, Callorhinchus milii and Hydrolagus colliei, and the variation across taxa has not been described. This study focuses on describing the cephalic tooth morphology across the three families of Holocephalans and also investigates whether depth affects the tooth shape and structure. I used macrophotography to investigate cephalic tooth morphology including tooth: density, length, width, curvature, and sharpness for each of the three extant families: Callorhinchidae (n = 6), Chimaeridae species (n = 25), and Rhinochimaeridae species (n = 6). And found that tenacular tooth morphology is well predicted by family and depth profile. Mapping the surface anatomy of the cephalic tenaculum is an important first step to determining the functional anatomy relative to the morphology and depth profile of the animal. This research will provide the blueprint for future anatomical investigations in Holocephalan reproductive morphology and functional anatomy in relation to family classification and depth profile.