Figure 2

Cranial dermal denticles develop through conserved odontode developmental stages. (A) ALP staining shows developing primary cranial dermal denticles. Eight cranial dermal denticles form on both the left and right sides. Scale bars: 0.5 mm. (B) Schematic illustration of the position of primary cranial dermal denticles. (C) HE-stained transverse section of Ancistrus sp. embryo at 8 dpf. Primary cranial dermal denticles form in the cranial epithelium and mesenchyme, being anchored to underling cartilages via the attachment fiber-like structures. Scale bars: 0.1 mm. The right panel shows higher magnification of the dotted box area in the left panel. Scale bars: 0.5 mm. (D) Schematic illustration of primary cranial dermal denticle positions (left) and their structure (right). (E) Bone and cartilage staining of a juvenile (TL: 3.5 cm) and adult fish (TL: 6 cm). The number of cranial dermal denticles increased with underlying dermal plate expansion from the juvenile to the adult stage. Each right panel shows higher magnification of the dotted box area in the left panels. Scale bars: 1 mm. (F) Secondary cranial dermal denticle development through the bud, cap, bell, and eruption stages in adult fish (TL: 6 cm). White dotted lines indicate the boundary between the surface epithelium and cranial dermal denticle germs. Black dotted line indicates the attachment bone. Scale bars: 100 µm. (G) Schematic illustration of the developmental stages of secondary cranial dermal denticles. At least two biological replicates were investigated in each experiment. LM late morphogenesis, ED early differentiation, LD late differentiation.