Integrating feeding biomechanics and ecology to understand round goby predation on zebra mussels.
Morano, Janelle*,1, Grande, Terry1, Westneat, Mark2, 1 Loyola University Chicago, Chicago, IL2 Field Museum of Natural History, Chicago, IL
ABSTRACT- Feeding habits of the invasive round goby, Neogobius melanostomus, impact native Great Lakes fish eggs, fish larvae, and benthic invertebrates, but at approximately 70 mm SL, the round goby diet shifts to primarily invasive zebra mussel, Dreissena polymorpha. This shift to a specialized diet has implications for the ecosystem of the Great Lakes. Research in the functional morphology of the feeding apparatus of fishes clarifies the physical limitations of prey capture and processing, and provides a biomechanical basis to explain feeding preferences. Previous research has yielded insight into mechanisms underlying observed ontogenetic diet shifts of freshwater and marine fish species. Round gobies feeding on zebra mussels must use two jaw systems: the oral jaws to capture and remove attached zebra mussels, and the pharyngeal jaws to process and crush the mussels for consumption. These jaw systems are made of series of linkages and levers connecting muscles to bones to create a force for biting and crushing. This study investigates the biting force of the oral and pharyngeal jaws by testing the hypothesis that there is a difference in feeding performance (i.e. bite force) between pre-molluscivorous and molluscivorous round goby. To test our hypothesis, the oral and pharyngeal jaw musculature was examined in detail to identify and measure the muscular anatomy of these feeding systems, and a biomechanical computer model predicted the force exerted by the feeding apparatus during maximal oral jaw biting. Additionally, live feedings were recorded using high-speed videography to calculate kinematics of the feeding strike, which affects biting performance. We found that there is an increase in bite force as the goby increases in mass and length, with a maximum force of 2 N, and the mass of the muscles increases allometrically with goby growth. Additional data, including the dentition of the pharyngeal jaws, will further explain the role of the changing morphology of the jaws through ontogeny and its implications for the feeding ecology of round goby. Understanding this diet shift can elucidate the trophic dynamics of the round goby, and the potential dynamics of bite force capacity and its role in feeding upon the newest invader, quagga mussel, Dreissena bugensis.
Key words: ecological and functional morphology, predation, modeling
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