Comparative functional tongue morphology in male omnivorous bogue (Boops boops) and carnivorous red porgy (Pagrus pagrus) in relation to feeding habits: A study using light microscopy, scanning electron microscopy, and morphometric analysis.

Understanding how feeding strategies influence oral morphology is fundamental to fish functional anatomy and trophic ecology. However, comparative data on tongue structure across dietary groups remain scarce in teleosts. This study examined tongue morphology in Boops boops (bogue), an omnivorous teleost with opportunistic feeding habits, and Pagrus pagrus (red porgy), a carnivorous benthic feeder with specialized prey preferences. By selecting species with distinct trophic niches, we aimed to elucidate how tongue architecture reflects dietary adaptations within teleosts. Morphometric analysis supported by light and scanning electron microscopy revealed that the bogue exhibited a higher tongue length-to-body weight ratio (34.1 %) than the red porgy (14.3 %). In contrast, the red porgy showed a greater tongue length-to-body length ratio (7.1 % vs. 5.4 %) and consistently broader tongue dimensions. The bogue tongue was sword-shaped with a pointed apex, while the red porgy's tongue featured a rounded apex. Papillary patterns differed markedly: the bogue displayed gustatory structures including fungiform papillae at the apex, mixed filiform and fungiform papillae in the body, and volcano-like filiform papillae at the root. In contrast, the red porgy exhibited predominantly mechanical structures, such as filiform papillae at the apex, dome-like filiform papillae in the body, and dome-to scale-like papillae at the root. Histologically, both species shared a common organization of mucosa, submucosa (with connective and adipose tissues), ento-glossal hyaline cartilage, and striated muscle fibers. However, the bogue's tongue showed stratified squamous epithelium with gustatory papillae, apical taste buds, and nerve endings. At the same time, the red porgy had abundant mucous cells and mechanical papillae concentrated at the root. Additionally, vascular channels with nucleated erythrocytes were observed in both species. These findings highlight distinct structural specializations of the tongue associated with omnivorous versus carnivorous feeding modes, offering new insights into the functional morphology and evolutionary adaptation of oral structures in teleost fishes.