Five Fishes, Five Faces: Comparative Functional Morphology of the Feeding Apparatus in Sculpins (Cottoidea)

Abstract

By studying variation in feeding apparatus morphology across similar sympatric species, we can better understand the evolutionary relationships and ecological niches of these species. The most common feeding technique among vertebrates is suction feeding, in which an animal rapidly expands its buccal cavity to create negative pressure and suck in prey. Suction feeders not only open their jaws quickly; they must also close them rapidly to prevent elusive prey from escaping. In this study, we compared jaw morphology and feeding kinematics of five species of Salish Sea sculpin. We used anatomical dissection to measure differences in jaw adductor morphology and jaw leverage, and we used Sonometric crystal implantation to measure gape change and muscle strain during feeding. Although we found high conservation of body length to muscle mass ratio among species, visual inspection of the head and jaw revealed important differences. We found that the red Irish lord (Hemilepidotus hemilepidotus) possessed the fastest jaw, as demonstrated by anatomical measurement of a small lever ratio, kinematic measurement of a large gape-change to muscle-strain ratio, and behavioral observation of the red Irish lord’s ambush hunting strategy. This study highlights the importance of including behavior and ecology in analyses of organismal morphology.