WESTNEAT, M.W.; Field Museum, Chicago: Functional Morphology of Feeding in Fishes: Phylogenetic Trends in Mechanical Design of Cranial Levers and Linkages

Fishes have met the challenge of capturing or ingesting food in a sensational diversity of ways. One of the hallmarks of this diversity is the complexity of the kinetic skull in fishes which may have 20 or more major skeletal elements capable of movement, driven by a score of different muscles. The feeding system in fishes is one of the central model systems in the field of vertebrate biomechanics. Recent research has focused on biomechanical models of the jaws that represent hypotheses of how force and motion are transferred from muscle through tendon to bone. This study develops a more complete set of such models for the many movable elements in the skulls of fishes. The lever mechanism of the lower jaw is joined by lever mechanisms for the skull, maxilla, opercle, and pectoral complex. New morphometric protocols and software applications for analysis of lever and linkage design are introduced. The geometric position and contraction physiology of muscles are critical to accurate estimations of lever and linkage function. A survey of skull mechanical designs throughout the phylogeny of fishes reveals a wide range of strategies for transfering force and motion during feeding. For example, the mechanical advantage of the mandible ranges from 0.05 in gar to 0.70 in damselfishes. Major evolutionary changes in the feeding mechanisms of fishes are illustrated from a morphological and mechanical perspective.