Tongue Morphology in Infant and Adult Bushbabies (Otolemur spp.)

Abstract

Lingual fungiform papillae are the only structures on the anterior two-thirds of the tongue that contain taste receptor cells and are the first gustatory structures to encounter food items. In humans, density of fungiform papillae is associated with taste sensitivity and food selection. Nonhuman primates also use the sense of taste to detect the nutritional contents of potential food items. The present study examines the ontogeny, distribution, and density of fungiform papillae in two species of greater bushbaby that differ in dietary specialization. Using light and electron microscopic methods, adult and infant cadaveric specimens (n = 4) of the frugivorous Otolemur garnettii and the exudativorous O. crassicaudatus were examined. The density of fungiform papillae was measured in an additional three adults of each species using 0.5% methylene blue. Observations by light and scanning electron microscopy (SEM) indicate that receptor pores are open in neonates. One adult O. crassicaudatus examined by SEM shows a high number of anterior fungiform papillae on which one or more open taste pores can be observed. The mean density of fungiform papillae was more than 50% greater in O. garnettii (162.4 ± 70.63/ cm 2 ) compared to that in O. crassicaudatus (101.9 ± 20.63/cm 2 ). These results suggest that greater bushbabies may have precocious ability to detect taste stimuli, based on the presence of open taste pores at birth. The apparent difference in fungiform papillae density between species requires further exploration.

Behavioral and Ecological Consequences of Sex‐Based Differences in Gustatory Anatomy in Cebus apella

“…Few studies have explored variations in TP density or count in nonhuman primates because TPs are difficult to view except by electron microscopy (Docherty et al,2010). We found that TP count within a single FP did not differ significantly between males and females.…”

“…However, these negative findings may be a result of histological section thickness (>20 μm) or too few serial sections (<15). Although TBs are rarely missed because they range between 10 and 20 μm, it is possible to miss one in intervals between stained sections (Docherty et al,2010). Because males in the study had smaller FP, but equal number of TPs per FP, males were documented to have significantly higher TP densities than females.…”

“…FPs surface area measurements, for example, can be compared to other studies using other methods. Moreover, TB pores are easily seen and will not be masked or clogged by gold and carbon sputter coating (see Docherty et al,2010). Based on the unique technology of the ESED, tongue samples do not require any additional preparation.…”

“…TB and TP counts can also vary across different papillae of the same type. For example, TB count can range between 0 and 5 per FP in nonhuman primates (Docherty et al,2010; Muchlinski et al,2010). In humans, ∼9% of FPs do not contain TBs.…”