Meeting Abstract

83.6  Tuesday, Jan. 6  Hyoid And Pharyngeal Arch Function During Ventilation And Feeding In Elasmobranchs WILGA, Cheryl D.; Univ. of Rhode Island cwilga@uri.edu

The hypothesis that the mandibular and hyoid arches evolved from anterior pharyngeal arches to increase ventilation performance and subsequently became adapted for feeding is widely accepted. As jaws evolved, the morphology of the hyoid arch changed notably from that of a pharyngeal arch. Furthermore, hyoid arch morphology varies considerably among extant elasmobranch taxa and has been shown to be related to feeding style. Thus, the goal of this study is to determine whether the function of the hyoid and pharyngeal arches is altered between ventilation, the basal behavior, and feeding, the derived behavior. Four elasmobranch species with different hyoid arch morphologies are examined: Chiloscyllium plagiosum (CP), Squalus acanthias (SA), Leucoraja erinacea (LE), and Mustelus canis (MC). The hyoid arch is oriented more posteriorly while the pharyngeal arch is oriented more laterally in all of the species. CP has lateral and slightly anterior directed hyomandibulae (HY), SA has lateral and slightly posterior directed HY, LE has anterior directed HY, and MC has posterior directed HY. The epibranchial of the pharyngeal arches is the homolog of the HY and are directed posteriorly in all of the species. The kinematics of the hyoid and third pharyngeal arch during ventilation and feeding are quantified using sonomicrometry and the associated pressure generated at the arch is quantified using pressure probes. As expected, hyoid and pharyngeal arch vertical depth increases during ventilation and feeding in all species. However, hyoid and pharyngeal arch width and pressure differs among the species relative to hyoid arch orientation and feeding style. Hyoid and pharyngeal arch kinematics remain the same in some taxa but are altered in different ways in other taxa. Pressure varies between feeding style and ventilation.