Severe enamel defects in wild Japanese macaques

Plane-form enamel hypoplasia (PFEH) is a severe dental defect in which large areas of the crown are devoid of enamel. This condition is rare in humans and even rarer in wild primates. The etiology of PFEH has been linked to exposure to severe disease, malnutrition, environmental toxins, and associated with systemic conditions. In this study, we examined the prevalence of enamel hypoplasia in several populations of wild Japanese macaques (Macaca fuscata) with the aim of providing context for severe defects observed in macaques from Yakushima Island. We found that 10 of 21 individuals (48%) from Yakushima Island displayed uniform and significant PFEH; all 10 specimens were from two adjacent locations in the south of the island. In contrast, macaques from other islands and from mainland Japan have low prevalence of the more common types of enamel hypoplasia and none exhibit PFEH. In Yakushima macaques, every tooth type was affected to varying degrees except for first molars and primary tee..., Specimens studied originate from three Japanese islands and mainland (Yakushima: 21 individuals; Honshu: 10 individuals; Koshima: 19 individuals). All specimens are curated at the Primate Research Institute (PRI) (now the Center for the Evolutionary Origins of Human Behavior), Kyoto University, Japan. All 48 individuals studied lived in the wild, with those on Koshima (Kojima) Island provisioned regularly as part of a primatological study.
Enamel hypoplasia data was collected following Towle and Irish (2019). Teeth were held under a lamp and rotated allowing light to hit the surface at different angles. The smallest discernible macroscopic defect was recorded, with a hand lens used to rule out postmortem damage. Postmortem damage was distinguished from enamel hypoplasia by distinct characteristics, including sharp edges and contrasting coloration between the fractured enamel and the rest of the crown. These features seldom resemble common forms of enamel hypoplasia, such as pitting, lin..., , # Severe enamel defects in wild Japanese macaques

Specimens studied originate from three Japanese islands and mainland (Yakushima: 21 individuals; Honshu: 10 individuals; Koshima: 19 individuals). All specimens are curated at the Primate Research Institute (PRI) (now the Center for the Evolutionary Origins of Human Behavior), Kyoto University, Japan. All 48 individuals studied lived in the wild, with those on Koshima (Kojima) Island provisioned regularly as part of a primatological study. Enamel hypoplasia data was collected following Towle and Irish (2019). Teeth were held under a lamp and rotated allowing light to hit the surface at different angles. The smallest discernible macroscopic defect was recorded, with a hand lens used to rule out postmortem damage. Postmortem damage was distinguished from enamel hypoplasia by distinct characteristics, including sharp edges and contrasting coloration between the fractured enamel and the rest of the crown. These features seldom resemble co...