Meeting Abstract

20-4  Monday, Jan. 4 11:00  Prey material properties and the evolution of the feeding apparatus in stingrays KOLMANN, MA*; SUMMERS, AP; LOVEJOY, NR; KOLMANN, Matthe; University of Toronto Scarborough; Friday Harbor Labs, University of Washington; University of Toronto Scarborough

Stingrays have diversified to fill an array of trophic niches across freshwater, estuarine, and marine systems despite lacking the prey-processing pharyngeal jaws of bony fishes. Several species have evolved to be “durophagous,” feeding on prey like mollusks; while some freshwater rays are the only insectivorous elasmobranchs. We present data on prey processing in insectivorous and durophagous rays in two families, the freshwater potamotrygonids and the marine, pelagic myliobatids. Muscular hypertrophy and a reinforced jaw skeleton enable myliobatids to generate high bite forces over their ontogeny and resist stresses incurred during feeding on stiff prey. Asymmetrical jaw protrusion and substantial lateral movement of the jaws are typical of feeding on tougher prey items like insects. The shape of myliobatid tooth arrays does not affect crushing performance on bivalve and gastropod prey, even as teeth become stiffer over ontogeny. Insectivorous rays can behaviorally reorient their teeth from flattened occlusion to occluding cusps when feeding on tough prey, as the dental ligament is contracted. Despite simple jaw morphology these fishes accomplish impressive post capture prey manipulation and processing by combining hydrodynamic forces with complex movements of the jaws.