Abstract:
Hagfish are deep-sea craniates that have not evolved opposable jaws. Despite this, hagfish can “bite” forcefully, allowing them to utilize food sources ranging from marine worms to giant whale carcasses. Since hagfish do not have moveable jaws, their “bite” is created through a rasping motion of a tongue-like structure that contains a toothy dental plate. Hagfish protract and retract this plate using a feeding apparatus formed of elaborately arranged cartilages, muscles, and connective tissues. The rigid cartilages can be visualized using microCT scans, however, the soft tissues are often difficult to see. I solved this problem by imaging the soft tissues that join and actuate the rigid components using traditional histological techniques. I then created serial sections of multiple orientations to create a three-dimensional anatomical interpretation. This analysis indicated that the plates of the feeding apparatus are joined by connective tissue hinges and that the musculature is a multifunctional complex organized into antagonistic groups that allow the protraction and retraction of the dental plate.