Morphological and Histochemical Characterization of the Dermal Plates of Pleco (Hypostomus plecostomus).

Studying the dermal skeleton in fish is valuable for phylogenetic specification. The current study describes the detailed structure of the plecostomus dermal skeleton, including its morphogenesis and distribution in the skin. The denticles have a crown and a basal part and are embedded in bony depressions, to which they are attached by denticle ligaments. During denticle morphogenesis, denticle papillae formed from denticle precursor cells align in two cellular layers: an outer ameloblast precursor layer and an inner odontoblast precursor layer. The ameloblast precursors and odontoblast precursors differentiate and secrete enamel and dentine, respectively. We used different histochemical techniques, including Crossmon's trichrome staining, Weigert-Van Gieson staining, periodic acid-Schiff (PAS) staining, combined Alcian blue (AB; pH 2.5)/PAS staining, Weigert-Van Gieson staining, Mallory trichrome staining, and AB staining to distinguish the dentine and denticle ligaments. We used acridine orange to detect lysosome activity during denticle eruption. Transmission electron microscopy was used to detect the denticle ultrastructure, and scanning electron microscopy was used to detect the topographic distributions of different types of dermal tissues in different anatomical regions.