Dental wear proxy correlation in a long-term feeding experiment on sheep (Ovis aries)

Arid, mosaic environments during the Plio-Pleistocene transition and early hominin dispersals in northern Africa

The earliest archaeological evidence from northern Africa dates to ca. 2.44 Ma. Nevertheless, the palaeoenvironmental setting of hominins living in this part of the continent at the Plio-Pleistocene transition remains poorly documented, particularly in comparison to eastern and southern Africa. The Guefaït-4 fossil site in eastern Morocco sheds light on our knowledge of palaeoenvironments in northern Africa. Our study reveals the oldest known presence of C4 plants in the northern part of the continent in a mosaic landscape that includes open grasslands, forested areas, wetlands, and seasonal aridity. This diverse landscape and resource availability likely facilitated the occupation of the region by mammals, including potentially hominins. Our regional-scale study provides a complementary perspective to global-scale studies and highlights the importance of considering the diversity of microhabitats within a given region when studying species-dispersal dynamics.

Mandible microwear texture analysis of crickets raised on diets of different abrasiveness reveals universality of diet-induced wear

Animals have evolved diverse comminuting tools. While vertebrates possess mineralized teeth, insect mandibles often bear metal-inclusion-hardened serrated cusps. Microscopic dental enamel wear (microwear) is known to be caused by contact with ingesta. To test if insect mandible microwear is also diet-dependent, we kept newly moulted adult two-spotted crickets (Gryllus bimaculatus) for four weeks on alfalfa-based rodent pellets with and without added mineral abrasives (loess, quartz, volcanic ash). Six crickets per diet were examined after 1, 3, 7, 14, 21 and 28 days. All diets induced progressive mandible wear, affecting specific locations along the distal tooth cusps differently. The depth of furrows increased on most abrasive-containing diets until day 21, while wear mark complexity increased from day 1 to 3 and 14 to 21. After 28 days, these parameter values for large volcanic ash and large quartz diets significantly exceeded those for the control diet. These results are comparable to observations from guinea pig feeding experiments with the same diets. Cricket mandible wear was affected by all abrasives. Notably, large volcanic ash and large quartz induced the deepest, most complex lesions, akin to observations in guinea pigs. This suggests a universal wear process, supporting that microwear analyses are suitable for inferring invertebrate diets.

Elemental Bioimaging of Sheep Bone and Articular Cartilage After Single Application of Gadolinium-Based Contrast Agents

BACKGROUND

Gadolinium-based contrast agents (GBCAs) are applied to enhance magnetic resonance imaging. Gadolinium (Gd), a rare earth metal, is used in a chelated form when administered as GBCA to patients. There is an ongoing scientific debate about the clinical significance of Gd retention in tissues after administration of GBCAs. It is known that bone serves as Gd reservoir, but only sparse information on localization of Gd in bone is available.

PURPOSE

The aim of this study was to compare Gd tissue concentration and spatial distribution in femoral epiphysis and diaphysis 10 weeks after single-dose injection of linear and macrocyclic GBCAs in a large animal model.

MATERIALS AND METHODS

In this prospective animal study, Swiss-Alpine sheep (n = 36; age range, 4-10 years) received a single injection (0.1 mmol/kg) of macrocyclic (gadobutrol, gadoteridol, and gadoterate meglumine), linear (gadodiamide and gadobenate dimeglumine) GBCAs, or saline. Ten weeks after injection, sheep were killed, and femur heads and shafts were harvested. Gadolinium spatial distribution was determined in 1 sample of each treatment group by laser ablation-inductively coupled plasma-mass spectrometry. All bone specimens were analyzed histopathologically.

RESULTS

Injection of GBCAs in female Swiss-Alpine sheep (n = 36) resulted in Gd localization at the endosteal and periosteal surface and in a subset of GBCAs additionally at the cement lines and the bone cartilage junction. No histopathological alterations were observed in the investigated tissue specimens.

CONCLUSIONS

Ten weeks after single injection of a clinically relevant dose in adult sheep, both linear species of GBCA resulted in considerably higher accumulation than macrocyclic GBCAs. Gadolinium deposits were restricted to distinct bone and cartilage compartments, such as in bone linings, cement lines, and bone cartilage junctions. Tissue histology remained unaffected.

The dental microwear texture of wild boars from Japan reflects inter- and intra-populational feeding preferences

Dental microwear texture analysis (DMTA) is rapidly expanding for the dietary estimation of extinct animals. There has been an extensive accumulation of microwear texture data from herbivorous mammals, especially for ruminant artiodactyls, but suids are still underrepresented. Microwear varies depending on the diet, and suids are naturally more flexible than other artiodactyls. Thus, their microwear is prone to greater variability. In this study, we examine the tooth microwear texture of wild boars from Toyama Prefecture, Japan, for which detailed ecological and dietary information by stomach content analysis is available. We first investigated 205 individuals of wild-shot Toyama boars with known sex, age class, localities (the eastern high latitude region vs. the western low latitude region), and season of collection. The tooth surfaces of boarlets were rougher than those of juvenile and adult animals. The decrease in surface roughness with age implied that the frequency of tooth-tooth contact, which seemed to result in cracking of enamels and thus rough surfaces, decreased after the boars started feeding on solid foods (food-tooth contact), with progressive involvement of rooting behavior in mature adults. We further found that surface roughness showed significant differences between localities, with the western Toyama boars having flatter surfaces, possibly because they were involved in more rooting and feeding on soil-contaminated rhizomes than the eastern ones, as implied by the available stomach content data. The frequency of rooting was also evident in the broader comparison among Japanese boar populations with different habitat environments. The mainland boars inhabiting deciduous broad-leaved forests had a flatter and less rough tooth surfaces than those in the subtropical evergreen broad-leaved forests of the southern islands. This corresponds to the fact that above-ground dietary resources were more abundant in the habitat of the southern island boars, where crops like succulent vegetables and fruits, as well as naturally fallen acorns, were abundant, whereas underground plant parts were the dominant diet component for the mainland boars. This study proved that DMTA can identify the difference in foraging modes in suids and make it possible to estimate the frequency of rooting, which is informative for inferring breeding methods of boars/pigs from archaeological sites.

Dental microwear texture analysis correlations in guinea pigs (Cavia porcellus) and sheep (Ovis aries) suggest that dental microwear texture signal consistency is species-specific

Dental microwear texture (DMT) analysis is used to differentiate abrasive dental wear patterns in many species fed different diets. Because DMT parameters all describe the same surface, they are expected to correlate with each other distinctively. Here, we explore the data range of, and correlations between, DMT parameters to increase the understanding of how this group of proxies records wear within and across species. The analysis was based on subsets of previously published DMT analyses in guinea pigs, sheep, and rabbits fed either a natural whole plant diet (lucerne, grass, bamboo) or pelleted diets with or without added quartz abrasives (guinea pigs and rabbits: up to 45 days, sheep: 17 months). The normalized DMT parameter range (P4: 0.69 ± 0.25; M2: 0.83 ± 0.16) and correlation coefficients (P4: 0.50 ± 0.31; M2: 0.63 ± 0.31) increased along the tooth row in guinea pigs, suggesting that strong correlations may be partially explained by data range. A comparison between sheep and guinea pigs revealed a higher DMT data range in sheep (0.93 ± 0.16; guinea pigs: 0.47 ± 0.29), but this did not translate into more substantial correlation coefficients (sheep: 0.35 ± 0.28; guinea pigs: 0.55 ± 0.32). Adding rabbits to an interspecies comparison of low abrasive dental wear (pelleted lucerne diet), the softer enamel of the hypselodont species showed a smaller data range for DMT parameters (guinea pigs 0.49 ± 0.32, rabbit 0.19 ± 0.18, sheep 0.78 ± 0.22) but again slightly higher correlations coefficients compared to the hypsodont teeth (guinea pigs 0.55 ± 0.31, rabbits 0.56 ± 0.30, sheep 0.42 ± 0.27). The findings suggest that the softer enamel of fast-replaced ever-growing hypselodont cheek teeth shows a greater inherent wear trace consistency, whereas the harder enamel of permanent and non-replaced enamel of hypsodont ruminant teeth records less coherent wear patterns. Because consistent diets were used across taxa, this effect cannot be ascribed to the random overwriting of individual wear traces on the more durable hypsodont teeth. This matches literature reports on reduced DMT pattern consistency on harder materials; possibly, individual wear events become more random in nature on harder material. Given the species-specific differences in enamel characteristics, the findings suggest a certain species-specificity of DMT patterns.

What about the buccal surfaces? Dental microwear texture analysis of buccal and occlusal surfaces refines paleodietary reconstructions

Objectives

This study analyzes and compares dental microwear textures on occlusal and buccal surfaces from the same tooth to determine if using these surfaces in tandem can provide complementary data for dietary reconstructions.

Materials and methods

Cova de la Guineu is a Late Neolithic‐Chalcolithic burial cave located in Font‐Rubí (Barcelona, Spain). The study sample consisted of 69 individuals represented by the lower left second molar. However, only 27 individuals had well‐preserved surfaces. Dental Microwear Texture Analysis was performed on both surfaces using a Sensofar® S Neox white‐light confocal profilometer following standard procedures. Toothfrax® software was used to quantify surface complexity and anisotropy.

Results

The bootstrap resampling analysis shows significant differences in complexity and anisotropy between surfaces. There is no correlation between surfaces for complexity or anisotropy. The occlusal surfaces exhibit high complexities and low anisotropies, which are similar to values observed in Late Neolithic farming groups from Belgium.

Discussion

The combination of occlusal and buccal microwear signatures provided important inferences regarding the studied sample. First, occlusal complexity and anisotropy values indicate an abrasive dietary regime. Second, we propose that the higher anisotropy values found on buccal surfaces, compared to those on the occlusal ones, are attributed to the specific mechanisms of microwear formation for each surface. Finally, combining both surfaces may increase the number of samples suitable for analysis. Further studies, with greater intergroup sampling, will help to understand how buccal microwear reflects or complements DMTA signatures on the occlusal surfaces.

Species-specific enamel differences in hardness and abrasion resistance between the permanent incisors of cattle (Bos primigenius taurus) and the ever-growing incisors of nutria (Myocastor coypus)

Hypselodont (ever-growing) teeth of lagomorphs or rodents have higher wear rates (of a magnitude of mm/week), with compensating growth rates, compared to the non-ever-growing teeth of ungulates (with a magnitude of mm/year). Whether this is due to a fundamental difference in enamel hardness has not been investigated so far. We prepared enamel samples (n = 120 per species) from incisors of cattle (Bos primigenius taurus) and nutria (Myocastor coypus, hypselodont incisors) taken at slaughterhouses, and submitted them to indentation hardness testing. Subsequently, samples were split into 4 groups per species (n = 24 per species and group) that were assessed for abrasion susceptibility by a standardized brush test with a control (no added abrasives) and three treatment groups (using fine silt at 4 ±1 μm particle size, volcanic ash at 96 ±9 μm, or fine sand at 166 ±15 μm as abrasives), in which enamel abrasion was quantified as height loss by before-and-after profilometry. The difference in enamel hardness between the species was highly significant, with nutria enamel achieving 78% of the hardness of cattle enamel. In the control and the fine sand group, no enamel height loss was evident, which was attributed to the in vitro system in the latter group, where the sand particles were brushed out of the test slurry by the brushes’ bristles. For fine silt and volcanic ash, nutria enamel significantly lost 3.65 and 3.52 times more height than cattle. These results suggest a relationship between enamel hardness and susceptibility to abrasion. However, neither the pattern within the species nor across the species indicated a monotonous relationship between hardness and height loss; rather, the difference was due to qualitative step related to species. Hence, additional factors not measured in this study must be responsible for the differences in the enamel’s susceptibility to abrasion. While the in vitro brush system cannot be used to rank abrasive test substances in terms of their abrasiveness, it can differentiate abrasion susceptibility in dental tissue of different animal species. The results caution against considering enamel wear as a similar process across mammals.