Graduation Year

2009

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Biology

Major Professor

Philip J. Motta, Ph.D.

Keywords

Biomechanics, Performance, Functional morphology, Scaling, Ecomorphology

Abstract

Functional morphologists have extensively used measurements of performance to investigate the relationship among form, function and ecology through ontogeny. Among different measurements of performance bite force play a crucial role influencing fitness. Although, bite force has been thoroughly investigated among vertebrates, the majority of the studies on fishes have been concentrated only in small species. Consequently, this is the first study that compares the bite force performance in two large marine predators, the great barracuda (Sphyraena barracuda) and bull shark (Carcharhinus leucas). Values of posterior bite force in S. barracuda varied from 3 - 258 N for an ontogenetic series of 27 individuals (23 - 130 cm, TL). Bite force as well as the majority of the biomechanical variables that contribute to it scaled with isometry in S. barracuda. Values of posterior bite force in C. leucas varied from 170 - 5,914 N for and ontogenetic series of 16 individuals (73 - 285 cm, TL). Bite force at the most anterior bite point scaled with positive allometry as well as the majority of the subdivisions of the adductive musculature that greatly contribute to bite force.

Bite force performance in this two species showed strong differences, where S. barracuda has one of the lowest relative values of bite force among fishes and C. leucas has one of the largest ones. Additionally, the scaling patterns for bite force and most of the biomechanical variables investigated in this study differed among these two species. These results suggest that predatory success may be acquired by different strategies, and that the same ecological role in a marine ecosystem may be reached by having different bite force performance.

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