Meeting Abstract
Unlike other elasmobranchs, batoids exhibit a euhyostylic jaw suspension, characterized by a loss of an anterior connection between the upper jaw and cranium. This leaves the paired hyomandibulae as the sole suspensory elements. The reduced jaw suspension increases mobility of the individual jaw elements, allowing batoids to move their jaws more freely while capturing and processing prey. However, the extent of jaw mobility is difficult to visualize and quantify in 3-dimensions with traditional high-speed videography. We used marker based XROMM (X-Ray Reconstruction of Moving Morphology) to measure the motion of the cranium and the left and right palatoquadrate (PQ) and Meckel’s cartilage (MC) during prey processing in a freshwater stingray, Potamotrygon motoro. The resultant animations from feeding trials recorded at 200 Hz confirm previous observations that the jaws are highly mobile during processing. In 14 consecutive chewing cycles from one individual, we found that the jaw joint, and by proxy the mandibular arch, depressed ventrally up to 5.0 mm relative to the cranium. The PQ and MC rotated up to 40 and 30 degrees about their long axes, respectively. The left and right MC rotated up to 25 degrees about their symphysis, with substantial rotations about two axes: one oriented dorsoventrally and the other rostrocaudally. The distances between markers within each cartilage stayed consistent (+ 0.049 mm), indicating high precision in the XROMM animations, and suggesting high stiffness in the cartilages themselves. This first application of XROMM to study batoid feeding provides new quantitative insight into a highly kinetic system, and further validates the method’s effectiveness for the study of cartilaginous fish feeding.
