Grit your teeth and chew your food: Implications of food material properties and abrasives for rates of dental microwear formation in laboratory Sapajus apella (Primates)

Abstract

Dental microwear analysis has been employed in studies of a wide range of modern and fossil animals, yielding insights into the biology/ecology of those taxa. Some researchers have suggested that dental microwear patterns ultimately relate back to the material properties of the foods being consumed, whereas others have suggested that, because exogenous grit is harder than organic materials in food, grit should have an overwhelming impact on dental microwear patterns. To shed light on this issue, laboratory-based feeding experiments were conducted on tufted capuchin monkeys [Sapajus apella] with dental impressions taken before and after consumption of different artificial foods. The foods were (1) brittle custom-made biscuits laced with either of two differently-sized aluminum silicate abrasives, and (2) ductile custom-made "gummies" laced with either of the two same abrasives. In both cases, animals were allowed to feed on the foods for 36 hours before follow-up dental impressions were taken. Resultant casts were analyzed using a scanning electron microscope. We asked five questions: (1) would the animals consume different amounts of each food item, (2) what types of dental microwear would be formed, (3) would rates of dental microwear differ between the consumption of biscuits (i.e., brittle) versus gummies (i.e., ductile), (4) would rates of dental microwear differ between foods including larger- versus smaller-grained abrasives, and (5) would rates of dental microwear differ between molar shearing and crushing facets in the animals in these experiments? Results indicated that (1) fewer biscuits were consumed when laced with larger-grained abrasives (as opposed to smaller-grained abrasives), but no such difference was observed in the consumption of gummies, (2) in all cases, a variety of dental microwear features was formed, (3) rates of dental microwear were higher when biscuits versus gummies were consumed, (4) biscuits laced with larger-grained abrasives caused a higher percentage of new features per item consumed, and (5) the only difference between facets occurred with the processing of biscuits, where crushing facets showed a faster rate of wear than shearing facets. These findings suggest that the impact of exogenous grit on dental microwear is the result of a dynamic, complex interaction between (at the very least) grit size, food material properties, and time spent feeding - which is further evidence of the multifactorial nature of dental microwear formation.

Keywords: dental impressions; ingestion; mastication; platyrrhine; scanning electron microscopy.

Figure 1.

Rates of microscopic wear on the molars of laboratory capuchin monkeys fed biscuits laced with either smaller- (180 μ) or larger-grained (1400 μ) abrasives.

Figure 2.

Rates of microscopic wear on the molars of laboratory capuchin monkeys fed gummies laced with either smaller- (180 μ) or larger-grained (1400 μ) abrasives.

Figure 3.

New features created during the consumption of biscuits (red boxes in “experiment 1” micrograph compared with “baseline” micrograph), and gummies (yellow boxes in “experiment 2” micrograph compared with “experiment 1” micrograph).

Figure 4.

Relative rates of microscopic wear (i.e., % new features / # items consumed) for laboratory capuchin monkeys fed biscuits laced with either smaller- (180 μ) or larger-grained (1400 μ) abrasives.

Figure 5.

Relative rates of microscopic wear (i.e., % new features / # items consumed) for laboratory capuchin monkeys fed gummies laced with either smaller- (180 μ) or larger-grained (1400 μ) abrasives.

Figure 6.

Estimated weekly rates of microscopic wear on the molars of laboratory capuchin monkeys fed either Brazil nuts or Mixed Foods (from Teaford et al., 2017, 2020) and Biscuits or Gummies laced with either smaller- (180 μ) or larger-grained (1400 μ) abrasives (from the present study).

Figure 7.

Estimated weekly rates of microscopic wear on the molars of laboratory capuchin monkeys fed either Brazil nuts or Mixed Foods (from Teaford et al., 2017, 2020) and foods laced with either Smaller- (180 μ) or Larger-grained (1400 μ) abrasives (from the present study).