WICKMAN, K.L.*; GIBB, A.C.; St. Norbert College, De Pere, WI; Northern Arizona University, Flagstaff: Does parallel evolution of upper jaw protrusion result in similar prey capture kinematics? A comparative study of Danio rerio and Betta splendens

Upper jaw protrusion, an extension of the mouth during suction feeding, is hypothesized to improve prey capture performance and, in turn, the ability of teleost fish to survive and reproduce. Due to the advantages of upper jaw protrusion, the adaptation has evolved in at least two individual fish lineages, the order Cypriniformes and superorder Acanthopterygii. This parallel evolution leads to both similarities and differences in the mechanisms and behaviors of the independent lineages. In this study, we compared the feeding behavior of representatives of the two lineages, Danio rerio and Betta splendens. Through high-speed digital imaging, we captured feeding sequences from both species for analysis. From the images captured, various displacements of the head and jaw were quantified. Results indicate that the feeding behaviors of the two species are very similar, despite their independent evolution. However, observed differences in the degree of premaxillary protrusion, as well as the time to maximum premaxillary protrusion and maximum hyoid depression may be generated by differences in the underlying mechanisms of jaw movement. These results could also be attributed to ecological differences. For example, one species may feed regularly on more elusive prey, or jaw movements in Betta splendens may be modified for bubble nest production.