Lingual Surface Morphology in Delphinids: Structural Adaptations to Feeding Strategies

Tongue morphology in cetaceans may reflect functional adaptations related to different feeding strategies. This study compared the lingual surface morphology of four delphinids species with different feeding strategies: the short-finned pilot whale (Globicephala macrorhynchus), Risso's dolphin (Grampus griseus), Clymene dolphin (Stenella clymene), and spinner dolphin (Stenella longirostris). Macroscopic dissections, light microscopy analysis, histochemistry, and scanning electron microscopy (SEM) were performed on four tongues, one from each species. The short-finned pilot whale and Risso's dolphin, which are suction feeders, exhibited thicker and rounder tongues, whereas the Clymene dolphin and spinner dolphin, which are raptorial prehension feeders, showed thinner and more elongated tongues. Across all species, only two types of lingual papillae, marginal and vallate, were identified, both lacking taste buds. Differences were also observed in the distribution of lingual glands, with suction feeders showing glandular concentration in the root of the tongue, while raptorial prehension feeders exhibited glands distributed along the body and root regions. Histochemical analysis revealed that serous cells showed positive staining with Periodic Acid-Schiff, whereas mucous cells stained positively with Alcian blue. SEM assessments indicated surface structures consistent with keratinocytes and glandular pores. These findings highlight functional tongue adaptations associated with distinct feeding strategies in delphinids.