KRAUS, Naomie J.; O’NEILL, Matthew W.; GIBB, Alice C.; Saint Norbert College; Northern Arizona University; Northern Arizona University: Sexual Dimorphism in the Feeding Kinematics of Betta splendens

Prey capture of the aquatic fish, Betta splendens, involves both ram (swimming over the prey) and suction (sucking in the prey), and is similar to the behavior of many other teleost fishes (for example, Wainwright et. al., 2001). The mechanism by which these fish capture prey involves upper jaw protrusion, lower jaw depression, hyoid depression, and cranial rotation. Interestingly, male Betta use their jaws in aggressive displays with other males and to build bubble nests for the eggs, as well as for feeding. Therefore, sexual selection may have produced gender-specific modifications of the head and jaws to facilitate these reproductive behaviors. Any modification of the head and jaws has potential consequences for feeding behaviors. Here we ask the question: Do male and females have similar feeding behaviors? Eight fish, four males and four females, were recorded while feeding using high-speed digital imaging and ten points on the cranium and jaws were digitized. Males and females showed differences in hyoid depression, lower jaw depression, and cranial rotation. They also demonstrated differences in the time needed to reach these maximum values. These differences suggest that that males and females do differ with respect to their feeding behaviors. These differences may be a consequence of the different reproductive behaviors required for males and females. Alternately, males and females may use these different behaviors to feed on different prey items in the wild. This is particularly interesting because sexual dimorphism in feeding behaviors of teleost fishes has never been reported.