ARTICULATION OF THE PHARYNGEAL JAW DURING FEEDING IN SERRANUS-VERIBA (LINNEUS, 1758) (PISCES, SERRANIDAE)

According to the morphology of its pharyngeal jaw apparatus, Serranus scriba can be considered as an intermediate type within the Acanthopte rygians. The lower jaws are united only at their fore end. The upper p haryngeal jaws do not articulate with the skull base. Each of them con sists of pharyngobranchials 2 and 3 (the latter being well developed), bearing a tooth plate, and of one posterior tooth plate, associated w ith two smaller tooth plates supported by epibranchials 2 and 3. The b ranchial musculature is of a generalized perciform type. Muscle activi ty generates variable cyclic movements of the pharyngeal jaws for tran sporting 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. P rey transport is more efficient when the upper and lower pharyngeal ja ws retract together, either in complete synchrony or with a phase shif t. This is often accompanied by downward movements of the upper jaws. The amplitude of movements of the components of the upper pharyngeal j aw may vary within one cycle. For instance, pharyngobranchial 2 could be drawn more forward, while pharyngobranchial 3 could be drawn more b ackward and the posterior tooth plate could move up and down independe ntly. These movements can be induced passively by the interactions wit h the prey and (or) eventually by specific muscular activity as well. Stereotyped movements of other species probably allow them to meet onl y 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.