Apareiodon ibitiensis (Campos)

Scharcansky, Alexandre & Lucena, Carlos Alberto S., 2008, Phylogenetic assessment of ultrastructural and histological characters of teeth in the Anostomoidea, Hemiodontidae and Parodontidae (Teleostei: Ostariophysi: Characiformes), Zootaxa 1948 (1), pp. 36-56 : 38-39

Apareiodon ibitiensis (Campos) ( Figs 1 and 2 )

Members of the Parodontidae lack dentary teeth; the description is therefore based on premaxillary dentition.

There is compact bone tissue without apparent alveoli close to the functional teeth. The replacement teeth are arranged in four to seven rows. The posterior teeth are least developed and aligned differently compared to the functional teeth, indicated by a pre-eruptive rotation. Histologically, replacement teeth in their final stage show a pattern similar to that of functional teeth from the exterior inwards: a narrow enamel layer (light area of the tooth, see Figure 2A, B ), demineralized due to the histological preparation process, surrounded by relatively short, narrow ameloblasts. Next are the dentin layer and the set of odontoblasts with spaced cells which are comparatively wider. Starting from the enamel layer, we see conspicuous periodontal ligaments already fully developed. Finally, the dental papilla (mesenchymal cells) forms a rectangular area.

The functional teeth are connected along the dentin layer to the premaxilla by long periodontal ligaments, since the bone is far from the teeth. The dentin layer is equally thick all around the teeth. The dental pulp, located along the horizontal line through the bone-tooth connection, is wide and much larger than the tooth base, being bordered posteriorly by the row of replacement teeth.

Figures

FIGURE 1. Apareiodon ibitiensis (Campos, 1944), MCP 14430, 98.26 mm SL - A: premaxilla and teeth, left side, frontal view. MCP: 14430, CP: 95.69 mm SL - B: premaxilla tooth, left side, frontal view, apical region detail. C: premaxilla tooth, left side, frontal view, median region detail. D: tooth-premaxilla bone attachment, left side, frontal view. E: premaxilla tooth, left side, SEM image showing the crystal apatite arrangement, labiolingual direction.

FIGURE 2. Apareiodon ibitiensis (Campos, 1944) MCP 14430, 98.26 mm SL - A. Premaxilla, cross section (10x). Arrow points to the bony bridge dividing the replacement teeth groups. B. Replacement teeth (20x). Arrow points to the apical region of replacement teeth. C: Replacement teeth detail (40x). D: Attachment region of functional teeth (20x). E. Premaxilla, cross section, rows of replacement teeth, each set is divided by a boney bridge (5x). Small arrow points to the bony bridge; larger arrow points to the replacement teeth. AM=ameloblasts; DF=functional teeth; DN=dentine; DS=replacement teeth; ES= enamel; LP=periodontal ligament; OD=odontoblasts; PA=dental papilla; PO=pulp; PMX=premaxilla; TC=connective tissue; TE=epithelial tissue; TO=bone tissue.