PACE, C. M.*; GIBB, A. C.; Northern Arizona University: Feeding kinematics of the pike killifish, Belonesox belizanus, a predominantly piscivorous poeciliid.

The pike killifish, Belonesox belizanus, is the largest member of the Poeciliinae and the only species in this subfamily that is predominantly piscivorous. It shares morphological traits such as an elongate fusiform body, large jaws, and posteriorly placed fins with other piscivorous fishes such as needlefish and barracuda. This represents a deviation from the typical morphology and behavior of the members of the subfamily Poeciliinae, most of which are omnivorous. Therefore, we asked the question does Belonesox share key kinematic parameters with its closest relatives or is it functionally similar to other piscivores? We hypothesized that feeding mechanics in Belonesox are similar to those seen in other piscivores, but shared ancestry with poeciliids may generate novel aspects of feeding behavior. To test our hypothesis, feeding sequences from juvenile Belonesox were captured in lateral and ventral views with digital video at 500 frames/second. X, Y, and Z coordinates were collected from these images using a custom digitizing program. We predicted that Belonesox would share functional characteristics with other piscivores such as ram feeding, a large gape and rapid jaw movements. We found that Belonesox is a ram feeder, while other poeciliids are suction feeders that prey on invertebrates (i.e., Gambusia affinis) or grazers that scrape food from the substrate (e.g., Poecilia sphenops). In addition, maximum gape in Belonesox is 49% of head length, which is similar to maximum gape in the barracuda (46% of head length). Finally, the feeding behavior of Belonesox is much more rapid than that seen in other poeciliids of a similar size. Thus, our preliminary analysis suggests that Belonesox feeding behavior is more similar to other piscivores than to other poeciliids.