32 - Intraspecific Variation in Fungiform Papillae Density in Rhesus Macaques (Macaca Mulatta)

Poster Board Number: 32
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Abstract Body : Fungiform papillae on the tongue have recently been recognized as multimodal sensory organs. The density of these papillae on the anterior tongue is associated with taste sensitivity and tactile sensitivity thresholds. However, demographic variables (e.g., age, sex) can also affect fungiform papillae density (FPD) in humans. In this study, we investigated relationships between age, sex, body mass, and FPD in rhesus macaques (Macaca mulatta) at the Cayo Santiago Primate Field Station in Puerto Rico. We predicted that, controlling for body mass, FPD would decrease with increasing age, and that females would have higher FPD than males. We stained and photographed the tongues of 79 macaques (30 females, 49 males) of known body mass and age (range: 0.3-8.1 years). Two assessors each counted the number of fungiform papillae in a 6 mm diameter circle on the anterior tip of the tongue using ImageJ. We then calculated average FPD/cm2 for each individual and used multiple linear regression to evaluate the effects of body mass, age, and sex on average individual FPD. Overall, we found a high level of variation in FPD in our sample of infant to young adult macaques (x̄=151.6 ± 69.3 papillae/cm2; range: 42.5-342.3), which is comparable to that identified in humans. Age was the only significant factor in our regression model (p=0.006), with neither sex (p=0.442) nor body mass (p=0.138) having a significant effect on FPD. Consistent with our predictions, we found decreasing FPD with increasing age, as is observed in humans. Our results suggest that FPD variation in macaques is at a similar level and affected by similar demographic factors as human FPD variation. Macaques may be good models for future research exploring mechanisms affecting fungiform papillae density and lingual sensory sensitivities.