The Pharyngeal Bone Musculature of the Carp,

The carp, Cyprinus carpio, was found to have eight pairs of muscles inserting on the pharyngeal bones. These were the levator arcus branchialis V, retractor 0 s pharyngeus superioris, retractor 0s pharyngeus inferioris, cleithropharyngeus superficialis, cleithropharyngeus profundus, coracobranchialis posterior, transversus ventralis V and subarcualis rectus communis. Complete morphoIogical descriptions of the muscles are given along with relevant osteological information. The pharyngeal muscles function in mastication by moving the bones and their attached teeth against the chewing pad so that crushing and grinding of food occurs during occlusion. In addition, certain pharyngeal bone muscles enlarge the lumen of the posterior pharynx thereby admitting food to the region of the teeth and chewing pad. The homologies of some of these muscles are considered along with the historical details pertinent to the establishment of a suitable nomenclature for the pharyngeal bone muscles. In the course of a detailed work on the pharyngeal bones and teeth of some cyprjnoid fishes (Eastman, '70), it became apparent that a thorough study of the musculature of the pharyngeal bones (i.e., the masticatory muscles) of these fishes had yet to be conducted. The published descriptions of these muscles are incomplete, in some cases inaccurate and subject to nomenclatural entanglements. It was deemed necessary to establish firmly the morphological basis of this musculature so that, in future papers, it would be possible to deal with adaptive radiation in muscle, bone and tooth structure and to attempt to relate masticatory function and dietary habits in cyprinid and catostomid species. The muscles of the pharyngeal bones of the carp, Cyprinus carpio Linnaeus, were examined in this study. This species was selected not only because of its large size and easy availability, but also because of its omnivorous feeding habits; a condition that would lead one to suspect that it possesses well-developed masticatory muscles. Historical background This review is concerned primarily with the pharyngeal bone muscles of cyprinids, but, for the sake of completeness and by J. MORPH., 134: 131-140. way of introduction, some general works on piscine myology will be mentioned first. The first volume of Cuvier and Valenciennes' Histoire Naturelle des Poissons (1828) contains a description of the muscles, including those of the pharynx, of the perch. Greene and Greene ('13) conducted a thorough study of the muscles of the king salmon, Oncorhynchus tschawytscha. Recently Branson ( '66) completed a brief survey of teleostean body musculature. Teutleben (1874) made a comparative study of the masticatory muscles among vertebrates, but his coverage of fishes was poor; descriptions were inadequate, no drawings were prepared and the scientific names of the fishes examined were not mentioned. Kesteven ('42, '43) speculated on the evolution of the cephalic muscles in the Chondrichthyes and Osteichthyes. The branchial muscles of some teleosts and their relation to the phylogeny of the class have been studied by Nelson ('67). Most of the muscles of the pharyngeal bones of cyprinids were first described by Vetter (1878) and Haempel ('08). Other workers, whose contributions vary greatly in quality and scope, tried to fill in their omissions: Arcangeli ('ll), Dietz ('14),