Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation

Weng, Zhiying; Liu, Z.Q.; Ritchie, Robert O.; Jiao, Dan; Li, D.S.; Wu, Huan; Deng, Leixiong; Zhang, Z.F.

doi:10.1016/j.jmbbm.2016.07.029

Cited by 44 publications

(29 citation statements)

References 57 publications

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“…Potential modern analogs of herbivorous mammals that evolved from omnivorous ancestors with thick enamel and bunodont molars include the giant panda Ailuropoda melanoleuca and the red panda Ailurus fulgens, both highly specialized independently on a diet of tough bamboo leaves requiring prolonged chewing and numerous repeated chewing cycles (e.g., 63,64 ). Both examples illustrate phylogenetic inertia, with evolution tinkering preexistent morphologies, which limits the range of possible adaptive traits in response to functional selective pressure and results in seemingly suboptimal morphologies for the realized diet.…”

Section: Methodsmentioning

confidence: 99%

A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

Caley

Extier

Collins

et al. 2018

Nature

101

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The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution. Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions or a stable hydroclimate. By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years. The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes, whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean. Here we show that the hydroclimate in southeastern Africa (20-25° S) is controlled by interplay between low-latitude insolation forcing (precession and eccentricity) and changes in ice volume at high latitudes. Our results are based on a multiple-proxy reconstruction of hydrological changes in the Limpopo River catchment, combined with a reconstruction of sea surface temperature in the southwestern Indian Ocean for the past 2.14 million years. We find a long-term aridification in the Limpopo catchment between around 1 and 0.6 million years ago, opposite to the hydroclimatic evolution suggested by records from Lake Malawi. Our results, together with evidence of wetting at Lake Malawi, imply that the rainbelt contracted toward the Equator in response to increased ice volume at high latitudes. By reducing the extent of woodland or wetlands in terrestrial ecosystems, the observed changes in the hydroclimate of southeastern Africa-both in terms of its long-term state and marked precessional variability-could have had a role in the evolution of early hominins, particularly in the extinction of Paranthropus robustus.

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Section: Methodsmentioning

confidence: 99%

A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

Caley

Extier

Collins

et al. 2018

Nature

101

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“…Tooth enamel has unique mechanical properties due to its structural complexity and layering, particularly anti-cracking properties. Compared with its main ingredient, HAP, it satisfies the mechanical requirements of millions of mastications over the organism's lifetime ( 9 , 13 – 17 ).…”

Section: Discussionmentioning

confidence: 99%

“…Like other carnivores, giant pandas have much shorter and simpler intestines than herbivores and can effectively digest bamboo ( 7 , 8 ), particularly the cellulose in its cell walls. To obtain enough energy from low-protein, high-fiber, and high-lignin bamboo, giant pandas need to consume large amounts of bamboo every day ( 9 ), placing huge pressure on their teeth. Consequently, relevant scientists are increasingly focusing their research on the tooth structure of the giant pandas.…”

Section: Introductionmentioning

confidence: 99%

Special architecture and anti-wear strategies for giant panda tooth enamel: Based on wear simulation findings

Liu

Yang

et al. 2022

Front. Vet. Sci.

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Giant pandas are the flagship species in world conservation. Due to bamboo being the primary food source for giant pandas, dental wear is common owing to the extreme toughness of the bamboo fiber. Even though research on tooth enamel wear in humans and domestic animals is well-established, research on tooth enamel wear in giant pandas is scarce. The purpose of this study is to evaluate tooth enamel wear resistance in giant pandas to provide a basis for a better understanding of their evolutionary process. From microscopic and macroscopic perspectives, the abrasion resistance of dental enamel in giant pandas is compared with that of herbivorous cattle and carnivorous dogs in this study. This involves the use of micro-scratch and frictional wear tests. The results show that the boundary between the enamel prism and the enamel prism stroma is well-defined in panda and canine teeth, while bovine tooth enamel appears denser. Under constant load, the tribological properties of giant panda enamel are similar to those of canines and significantly different from those of bovines. Test results show that the depth of micro scratches in giant panda and canine enamel was greater than in cattle, with greater elastic recovery occurring in dogs. Scratch morphology indicates that the enamel substantive damage critical value is greater in pandas than in both dogs and cattle. The analysis suggests that giant panda enamel consists of a neatly arranged special structure that may disperse extrusion stress and absorb impact energy through a series of inelastic deformation mechanisms to cope with the wear caused by eating bamboo. In this study, the excellent wear resistance of giant panda's tooth enamel is verified by wear tests. A possible theoretical explanation of how the special structure of giant panda tooth enamel may improve its wear resistance is provided. This provides a direction for subsequent theoretical and experimental studies on giant panda tooth enamel and its biomaterials.

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“…Cyanogenic glygosides are suggested to be present in many species of bamboos and their role as anti-herbivory agents by bamboo have been discussed 11 , 31 – 33 . It is probable that the removal of the outer skin of bamboo culm by the masticatory system may also serve as adaptation to avoid the intake of cyanogenic glucosides, in addition to removing the phytoliths which could cause wear of toughened enamel structure of teeth 34 .…”

Section: Discussionmentioning

confidence: 99%

Temporomandibular joint and Giant Panda’s (Ailuropoda melanoleuca) adaptation to bamboo diet

Vallittu

Varrela

Salo

et al. 2021

Sci Rep

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Here, we present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The giant panda in the wild and in captivity removes without an exception the outer skin of all bamboo shoots, rich in abrasive and toxic compounds, by the highly adapted premolars P3 and P4. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource.

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Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation

Cited by 44 publications

References 57 publications

A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

Special architecture and anti-wear strategies for giant panda tooth enamel: Based on wear simulation findings

Temporomandibular joint and Giant Panda’s (Ailuropoda melanoleuca) adaptation to bamboo diet

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