066 -- Feeding Morphology of Deep-Sea Demersal Fishes

Deep-sea inhabitants survive high pressure, limited food availability, lack of sunlight, and cold temperatures. These deep-sea conditions have spurred adaptations that allow organisms to fill an array of niches. For example, distinctive feeding modes and jaw morphologies enable organisms to utilize the food resources available in their environment. Here, we investigate feeding biomechanics in deep-sea fishes across three families of fishes, the rattails (Macrouridae), snailfishes (Liparidae), and cutthroat eels (Synaphobranchidae). Each of these families exist in abundance and occupy important ecological roles in their environment. We compare jaw morphologies and mechanics between families to gain insights into feeding mode, including ram feeding, suction feeding, and manipulation. Mechanical advantage, measured here, is the ratio of the output force to the input force, indicative of the total force applied by an apparatus (like a set of jaws). High mechanical advantages in the jaws indicate greater force transmission, characteristic of fishes that manipulate prey, while low mechanical advantage indicates greater velocity transfer, common to suction feeders. We compare tooth shape between the oral jaws and the pharyngeal jaws, the latter of which aid in prey processing. Members of the Synaphobranchidae family had a lower mechanical advantage in their oral jaws, indicating their scavenging feeding mode requires a lower force transmission than active prey capture and manipulation. Macrourids had larger pharyngeal jaws than their liparid counterparts, suggesting that pharyngeal jaw size is a function of prey type. This research helps characterize ecological roles and describe the organismal interactions that govern the deep sea.