Mouvements des mâchoires pharyngiennes pendant la prise de nourriture chez le Serranus scriba (Linné, 1758) (Pisces, Serranidae)

Abstract

According to the morphology of its pharyngeal jaw apparatus, Serranus scriba can be considered as an intermediate type within the Acanthopterygians. The lower jaws are united only at their fore end. The upper pharyngeal jaws do not articulate with the skull base. Each of them consists of pharyngobranchials 2 and 3 (the latter being well developed), bearing a tooth plate, and of one posterior tooth plate, associated with two smaller tooth plates supported by epibranchials 2 and 3. The branchial musculature is of a generalized perciform type. Muscle activity generates variable cyclic movements of the pharyngeal jaws for transporting prey from the buccal cavity to the oesophagus, in cases where the prey is provided with a shell or a cuticle. Masticatory movements are not stereotyped as in more specialized fishes such as Labridae. Prey transport is more efficient when the upper and lower pharyngeal jaws retract together, either in complete synchrony or with a phase shift. This is often accompanied by downward movements of the upper jaws. The amplitude of movements of the components of the upper pharyngeal jaw may vary within one cycle. For instance, pharyngobranchial 2 could be drawn more forward, while pharyngobranchial 3 could be drawn more backward and the posterior tooth plate could move up and down independently. These movements can be induced passively by the interactions with the prey and (or) eventually by specific muscular activity as well. Stereotyped movements of other species probably allow them to meet only the requirements of a specialized diet. In contrast, the flexibility of this movement pattern allows S. scriba to explore a wider range of food types.