The jaws in the jaws: Morphofunctional analysis of the pharyngeal plates of Labrus viridis Linnaeus, 1758 (Teleostei, Labridae).

Functional morphology highlights the adaptive flexibility of fish feeding strategies across environmental gradients and seasonal variations, providing key insights for the management and conservation of ichthyofaunal communities and their habitats. Labridae fishes possess a specialized pharyngeal jaw apparatus (PJA) that enables them to crush and consume prey with heavily calcified or chitinized shells. This functional adaptation has expanded their dietary flexibility, promoted trophic specialization and enhanced the ecological diversity of wrasses. Here, we present the first comprehensive morphological analysis of the pharyngeal jaws of Labrus viridis Linnaeus, 1758, a labrid fish widely distributed in shallow coastal habitats of the Mediterranean Sea. The PJA was examined using micro-computed tomography (micro-CT), scanning electron microscopy and energy-dispersive X-ray spectroscopy. Stomach contents from eight specimens were also analysed to infer prey composition and feeding strategy. The pharyngeal jaws of L. viridis are characterized by unicuspid molariform and caniniform teeth, showing intraosseous tooth development, weakly developed plicidentine and a one-to-one tooth replacement. This heterodont dentition, together with the predominance of caniniform over molariform teeth and the diverse prey items identified in gut contents, indicates an opportunistic feeding strategy and a diet distinct from that of the congeneric Labrus bergylta. This work suggests the existence of ecological divergence among congeneric species. Moreover, our results provide a reference point for linking the morphofunctional traits to the dietary role of L. viridis, encouraging new investigations into the morphology of the PJA and trophic dynamics of other Mediterranean wrasses.