WILLINK, P.W.: The intertwining influences of prey, head shape, and attack behavior on gill raker morphology

Gill rakers are believed to play a critical function during the feeding of fishes. The predominant view is that gill rakers strain prey from the medium. Long, closely-spaced gill rakers are correlated with feeding on small prey, whereas short, widely-spaced gill rakers are correlated with feeding on large prey. However, this view may be too simplistic. Based on data from sunfishes (Perciformes: Centrarchidae), it will be argued that gill raker morphology is dependent not only on prey size, but also on the interdependent factors of attack behavior and mouth structure. Species which ram feed tend to have larger mouths and hence longer gill rakers. The opposite is true for suction feeding species. Differences in the pattern of water flow past the branchial arches is hypothesized to be the primary causal agent for the various gill raker morphologies. These ideas may help explain the feeding structures of northwestern North America sticklebacks, Great Lakes coregonids, and many other fishes.