Cause of Wear in Sheeps' Teeth

Baker, George; Jones, L. H. P.; Wardrop, I. D.

doi:10.1038/1841583b0

Cited by 242 publications

(153 citation statements)

References 3 publications

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“…Several characteristics of phytoliths would enhance their effectiveness as structural barriers to herbivory. They are the only substance hard enough to grind and abrade the tooth enamel of large grazers (28). The evolution of hypsodont dentition during the late Miocene, when open woodlands and savannas expanded globally at the expense of forests and C 4 grasses appeared, has long been adaptively linked to the high phytolith content of grass leaves (12,29).…”

Section: Discussionmentioning

confidence: 99%

Evidence for the control of phytolith formation in Cucurbita fruits by the hard rind ( Hr ) genetic locus: Archaeological and ecological implications

Piperno

Holst

Wessel-Beaver

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Many angiosperms, both monocotyledons and dicotyledons, heavily impregnate their vegetative and reproductive organs with solid particles of silicon dioxide (SiO 2) known as opaline phytoliths. The underlying mechanisms accounting for the formation of phytoliths in plants are poorly understood, however. Using wild and domesticated species in the genus Cucurbita along with their F 1 and F2 progeny, we have demonstrated that the production of large diagnostic phytoliths in fruit rinds exhibits a one-to-one correspondence to the lignification of these structures. We propose that phytolith formation in Cucurbita fruits is primarily determined by a dominant genetic locus, called hard rind (Hr), previously shown to code for lignin deposition. If true, this evidence represents a demonstration of genetic control over phytolith production in a dicotyledon and provides considerable support to hypotheses that silica phytoliths constitute another important system of mechanical defense in plants. Our research also identifies Hr as another single locus controlling more than one important phenotypic difference between wild and domesticated plants, and establishes rind tissue cell structure and hardness under the effects of Hr as an important determinant of phytolith morphology. When recovered from pre-Columbian archaeological sites, Cucurbita phytoliths represent genetically controlled fossil markers of exploitation and domestication in this important economic genus.

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Section: Discussionmentioning

confidence: 99%

Evidence for the control of phytolith formation in Cucurbita fruits by the hard rind ( Hr ) genetic locus: Archaeological and ecological implications

Piperno

Holst

Wessel-Beaver

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…The initial presumption of this classification scheme based on pit and scratch number was that biogenic abrasives are primarily responsible for scratch-dominated wear among modern grazers because of the high abundance of phytoliths in monocotyledonous grasses relative to dicotyledonous browse (Baker et al, 1959;Piperno, 2006). However, several studies examining the effects of biogenic and abiotic abrasives have cast doubt on the central role of biogenic silica in scratch accumulation (Covert and Kay, 1981;Kay and Covert, 1983;Maas, 1991Maas, , 1994Gügel et al, 2001;Mainland, 2003;Sanson et al, 2007;Lucas et al, 2013;Schulz et al, 2013;Müller et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Controlled feeding trials with ungulates: a new application of in vivo dental molding to assess the abrasive factors of microwear

Hoffman

Fraser

Clementz

2015

Journal of Experimental Biology

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Microwear, the quantification of microscopic scratches and pits on the occlusal surfaces of tooth enamel, is commonly used as a paleodietary proxy. For ungulates (hoofed mammals), scratchdominant microwear distinguishes modern grazers from browsers, presumably as a result of abrasion from grass phytoliths (biogenic silica). However, it is also likely that exogenous grit (i.e. soil, dust) is a contributing factor to these scratch-dominant patterns, which may reflect soil ingestion that varies with feeding height and/or environmental conditions (e.g. dust production in open and/or arid habitats). This study assessed the contribution of exogenous grit to tooth wear by measuring the effects of fine-and medium-grained silica sand on tooth enamel using a novel live-animal tooth-molding technique. It therefore constitutes the first controlled feeding experiment using ungulates and the first in vivo experiment using abrasives of different sizes. Four sheep were fed three diet treatments: (1) a mixture of Garrison and Brome hay (control), (2) hay treated with fine-grained silica sand (180-250 µm) and (3) hay treated with medium-grained silica sand (250-425 µm). We found a significant increase in pit features that was correlated with an increase in grain size of grit, corroborating earlier chewing simulation experiments that produced pits through grit-induced abrasion (i.e. the 'grit effect'). Our results support an interpretation of large silica grains fracturing to create smaller, more abundant angular particles capable of abrasion, with jaw movement defining feature shape (i.e. scratch or pit).

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“…Silica is deposited as phytoliths in leaves. These are harder than tooth enamel (Baker et al 1959), so they could potentially increase the abrasiveness of leaves and deter feeding (Vicari & Bazely 1993). However, currently the evidence supporting the effects of silica on the palatability of grasses to vertebrate herbivores is limited: there have been relatively few experimental studies and none which manipulate silica content and measure the subsequent changes in abrasiveness of leaves.…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of the antiherbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates

2006

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The impact of plant-based factors on the population dynamics of mammalian herbivores has been the subject of much debate in ecology, but the role of antiherbivore defences in grasses has received relatively little attention. Silica has been proposed as the primary defence in grasses and is thought to lead to increased abrasiveness of foliage so deterring feeding, as well as reducing foliage digestibility and herbivore performance. However, at present there is little direct experimental evidence to support these ideas. In this study, we tested the effects of manipulating silica levels on the abrasiveness of grasses and on the feeding preference and growth performance of field voles, specialist grass-feeding herbivores. Elevated silica levels did increase the abrasiveness of grasses and deterred feeding by voles. We also demonstrated, for the first time, that silica reduced the growth rates of both juvenile and mature female voles by reducing the nitrogen they could absorb from the foliage. Furthermore, we found that vole feeding leads to increased levels of silica in leaves, suggesting a dynamic feedback between grasses and their herbivores. We propose that silica induction due to vole grazing reduces vole performance and hence could contribute to cyclic dynamics in vole populations.

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Cause of Wear in Sheeps' Teeth

Cited by 242 publications

References 3 publications

Evidence for the control of phytolith formation in Cucurbita fruits by the hard rind ( Hr ) genetic locus: Archaeological and ecological implications

Evidence for the control of phytolith formation in Cucurbita fruits by the hard rind ( Hr ) genetic locus: Archaeological and ecological implications

Controlled feeding trials with ungulates: a new application of in vivo dental molding to assess the abrasive factors of microwear

Experimental demonstration of the antiherbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates

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