Functional Morphology of the Pharyngeal Jaw Apparatus

Abstract

This chapter presents the understanding of the functional morphology of the pharyngeal jaw apparatus (PJA) in perciform fishes. Much of the functional diversity seen in fish feeding systems lies in the mechanics of prey capture that involves the oral jaws and buccal cavity. However, an often-overlooked element of fish trophic diversity lies in the functioning of a second set of jaws, PJA, which is used primarily in separating food from unwanted material and a variety of forms of prey manipulation and processing behaviors. Fish trophic diversity is impacted by the PJA at two distinct levels. First, the presence of a second set of jaws in the feeding system promotes overall trophic diversity by increasing the range of musculo‐skeletal specializations for feeding. The PJA can be thought of as an additional independent axis of morphological diversity that fish lineages have explored during evolution. The structural independence of the oral and pharyngeal jaws permits potential autonomy in their evolution, and because the roles of prey capture and processing are potentially decoupled, the degree of specialization of each system is less constrained by the need to maintain secondary functions. Independent evolution of the oral and PJA has increased the range of fish feeding abilities and hence their feeding ecology. The second way in which the PJA influences overall fish trophic diversity comes about because this system is itself structurally complex.