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Increased potential versatility in form and function of the feeding apparatus of cichlid fishes has led to a prodigious proliferation in the number of possible functional solutions to an increasing variety of biological problems. Optimal utilization of every conceivable trophic resource in lacustrine environments by just one fish family, the Cichlidae, has been achieved by eruptive evolutionary radiation within the characteristically cichlid body plan producing mechanisms which partition the diverse food resources with extraordinary efficiency therefore minimizing resource sharing. There is a direct relationship between the effectiveness of trophic resource exploitation and the functional integration of the cichlid body plan in which a minimum number of adaptive compromises are necessary to evolve optimal anatomical solutions by rapidly realizable changes Anatomical data presented here reveal that cichlids possess a specific kind of mosaic in which the basic percoid jaw apparatus permits unparalleled optimal adaptations by simple morphogenetic changes while unique and dramatically diverse patterns of muscular coordination involving degrees of synchrony and extensive modulating capabilities of antagonistic muscle groups have been discovered electromyographically. At the same time the highly integrated pharyngeal jaw apparatus is sufficiently specialized providing complete freedom for the jaws to evolve into refined collecting devices. The exceptional evolutionary success of lacustrine cichlids demonstrates how rare and very specific kinds of biologically versatile morphological mosaics represent the best preadaptations for the ancestors of major new taxa. Given identical ecological conditions and temporal factors, a group of organisms possessing such rare mosaics, in which optimal biological versatility is realizable by simple evolutionary mechanisms, will dominate newly formed environments to the detriment of taxa not so endowed.

Synopsis. Functional morphological analysis has revealed the existence of three functionally and morphologically different mechanisms underlying the tongue-parasphenoid and pharyngeal-parasphenoid bites in advanced teleost fishes. The bite is specialized differently in Pristolepis and the Anabantoidei, and in a primitive condition in both the Nandidae and Channiformes. These taxa belong to at least three unrelated lineages and do not share a common ancestry as was previously postulated. It has been possible to show how an originally primitive character can acquire a new biological and phylogenetic meaning by being integrated into a specialized functional complex. Based on functional data on the pharyngeal jaw apparatus, a new hypothesis is proposed stating that the Cichlidae, Embiotocidae, Labridae, Odacidae and Scaridae represent a monophyletic assemblage. This case study has demonstrated that reciprocal illumination of functional morphological and phylogenetic findings can lead to: (1) better tested and more precise phylogenetic hypotheses; (2) the construction of new hypotheses on the basis of specialized character complexes which were unrecognized by the use of a purely descriptive morphological approach.

Analyse anatomique de l'appareil pharyngeal du Perroquet de mer (scare). Demonstration de la specialisation des mâchoires broyeuses

SYNOPSIS. Structural and functional patterns in the evolution of the actinopterygian feeding mechanism are discussed in the context of the major monophyletic lineages of ray-finned fishes. A tripartite adductor mandibulae contained in a maxillary-palatoquadrate chamber and a single mechanism of mandibular depression mediated by the obliquus inferioris, sternohyoideus, and hyoid apparatus are primitive features of the Actinopterygii. Halecostome fishes are characterized by having an additional mechanism of mandibular depression, the levator operculi—opercular series coupling, and a maxilla which swings anteriorly during prey capture. These innovations provide the basis for feeding by inertial suction which is the dominant mode of prey capture throughout the halecostome radiation. A remarkably consistent kinematic profile occurs in all suction-feeding halecostomes. Teleost fishes possess a number of specializations in the front jaws including a geniohyoideus muscle, loss of the primitive suborbital adductor component, and a mobile premaxilla. Structural innovations in teleost pharyngeal jaws include fusion of the dermal tooth plates with endoskeletal gill arch elements, the occurrence of a pharyngeal retractor muscle, and a shift in the origin of the pharyngohyoideus. These specializations relate to increased functional versatility of the pharyngeal jaw apparatus as demonstrated by an electromyographic study of pharyngeal muscle activity in Esox and Ambloplites . The major feature of the evolution of the actinopterygian feeding mechanism is the increase in structural complexity in both the pharyngeal and front jaws. Structural diversification is a function of the number of independent biomechanical pathways governing movement.

SYNOPSIS. The actinopterygian fishes are an exemplary clade for the study of structural and functional evolutionary patterns. With over half of all vertebrate species, ray-finned fishes have diversified into a wide variety of habitats, and considerable progress has been made over the last fifteen years in understanding the genealogical relationships of actinopterygians. This symposium has contributed to our understanding of phylogenetic patterns in actinopterygians and to knowledge of the major structural and functional patterns in locomotor, auditory, trophic, and neural systems. A number of key areas for future research have been identified. (1) The relationships of “palaeonisciform“ fishes, (2) the study of trends in feeding and locomotor systems within a phylogenetic context, (3) the identification of primitive patterns of pharyngeal jaw movement and steady and unsteady locomotor patterns in actinopterygians, (4) the homologies, identification, and functional significance of neural pathways in the telencephalon, and (5) the comparative study of form-function relations in the auditory system. The study of teleost fish biology has proceeded at the expense of data on primitive actinopterygians ( e.g., Polypterus, Polyodon, Aapenser, Lepisosteus, Amia ) which are especially important in the analysis of structural and functional patterns in ray-finned fishes.