Parrotfish Teeth: Stiff Biominerals Whose Microstructure Makes Them Tough and Abrasion-Resistant To Bite Stony Corals

Marcus, Matthew A.; Amini, Shahrouz; Stifler, Cayla A.; Sun, Chang‐Yu; Tamura, Nobumichi; Bechtel, Hans A.; Parkinson, Dilworth Y.; Barnard, Harold; Zhang, Xiyue X. X.; Chua, Jia Qing Isaiah; Miserez, Ali; Gilbert, Benjamin

doi:10.1021/acsnano.7b05044

Cited by 50 publications

(60 citation statements)

References 68 publications

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“…This is in contrast to long-held views of parrotfishes as consumers of algae, a viewpoint that has yielded research questions focused on the top-down effects of parrotfish grazing rather than the influence of habitats and associated substrates on the distribution of parrotfishes (e.g., [48]). Rapid evolutionary diversification of parrotfishes has facilitated highly-specialized morphologies (e.g., C. microrhinos teeth represent one of the hardest biominerals ever measured; [54]) to exploit protein-rich microbial communities existing within and upon calcareous substrates [52]. Previous work on the GBR demonstrates a strong cross-shelf pattern in the detrital, epi-and endolithic microbial communities associated with wave exposure gradients [55][56][57].…”

Section: Discussionmentioning

confidence: 99%

Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

et al. 2019

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The structure and dynamics of coral reef environments vary across a range of spatial scales, with patterns of associated faunal assemblages often reflecting this variability. However, delineating drivers of biological variability in such complex environments has proved challenging. Here, we investigated the assemblage structure and diversity of parrotfishes—a common and ecologically important group—across 6° of latitude on the Northern Great Barrier Reef (GBR), Australia. Parrotfish abundance and biomass were determined from stereo-video surveys across 82 sites spanning 31 reefs and assessed against geographic, biophysical, and management-related factors in a multivariate framework to determine major drivers and associated scales of assemblage structure. Large cross-shelf variation in parrotfish assemblages pervaded along the entire Northern GBR, with distinct assemblages associated with sheltered and exposed reefs. Species abundances and diversity generally decreased with decreasing latitude. The gradient of explicit predator biomass associated with management zoning had no effect on parrotfish assemblage structure, but was positively correlated with parrotfish diversity. Our results highlight the ubiquitous presence of cross-shelf variation, where the greatest differences in parrotfish community composition existed between sheltered (inner and mid shelf) and exposed (outer shelf) reef systems. Prior attempts to explain linkages between parrotfishes and fine-scale biophysical factors have demonstrated parrotfishes as habitat generalists, but recent developments in nutritional ecology suggest that their cross-shelf variation on the GBR is likely reflective of benthic resource distribution and species-specific feeding modes.

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Section: Discussionmentioning

confidence: 99%

Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

et al. 2019

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“…The methods used here include polarization-dependent imaging contrast (PIC) mapping 40–43 , HR-SEM and HR-TEM. X-ray linear dichroism in apatite was discovered 44 and fully explored 35 recently. This effect enables the PIC mapping method used here.…”

Section: Introductionmentioning

confidence: 99%

“…This effect enables the PIC mapping method used here. PIC mapping has been used extensively for carbonates 40,45–49 , bone apatite 35,50 , entire teeth 31 , parrotfish enameloid 44 , and mouse enamel 35 . In coral 48 , sea urchin teeth 46,47 , mollusk shell nacre 45 , and prismatic calcite 49 the orientations measured by PIC mapping were confirmed in precisely the same regions with x-ray diffraction.…”

Section: Introductionmentioning

confidence: 99%

The hidden structure of human enamel

et al. 2019

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Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-μm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°–30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°–90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.

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“…Hence, a preferred alignment of the apatite crystallites toward the loading direction can promote stiffness in bioapatite-based mineralized tissues 37,41 . In contrast, woven and entangled microarchitectures are a common strategy for toughness enhancement in biomineralized tissues through promotion of crack deflection 5,42,43 . However, despite comprehensive recent work linking microarchitecture and mechanical properties of shark teeth 2,7,44 , to the best of our knowledge, there is no experimental evidence assessing the hierarchical interrelations of microarchitectural variations and multi-scale function of shark enameloid, particularly with regard to material performance and damage mechanisms in biologically relevant loading contexts.…”

Section: Resultsmentioning

confidence: 99%

“…Across vertebrate taxa, the contact layer of teeth (i.e., enamel/ enameloid) is comprised largely of the same basic components: a high percentage of calcium-phosphate mineral, and a small amount (<5%) of water and organic materials. In addition, despite some variation in the elemental composition of the inorganic phase (e.g., fluorine substitution in the teeth of sharks and some fishes 2,4,5 , or iron substitution in rodent incisors 6 ), its composition remains relatively consistent across vertebrate taxa, consisting of nanocrystalline apatite 5,7 . These unifying material similarities across vertebrates are surprising, considering the diversity in the lifespan of vertebrate teeth 8 .…”

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confidence: 99%

Shape-preserving erosion controlled by the graded microarchitecture of shark tooth enameloid

et al. 2020

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The teeth of all vertebrates predominantly comprise the same materials, but their lifespans vary widely: in stark contrast to mammals, shark teeth are functional only for weeks, rather than decades, making lifelong durability largely irrelevant. However, their diets are diverse and often mechanically demanding, and as such, their teeth should maintain a functional morphology, even in the face of extremely high and potentially damaging contact stresses. Here, we reconcile the dilemma between the need for an operative tooth geometry and the unavoidable damage inherent to feeding on hard foods, demonstrating that the tooth cusps of Port Jackson sharks, hard-shelled prey specialists, possess unusual microarchitecture that controls tooth erosion in a way that maintains functional cusp shape. The graded architecture in the enameloid provokes a location-specific damage response, combining chipping of outer enameloid and smooth wear of inner enameloid to preserve an efficient shape for grasping hard prey. Our discovery provides experimental support for the dominant theory that multi-layered tooth enameloid facilitated evolutionary diversification of shark ecologies.

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Parrotfish Teeth: Stiff Biominerals Whose Microstructure Makes Them Tough and Abrasion-Resistant To Bite Stony Corals

Cited by 50 publications

References 68 publications

Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

The hidden structure of human enamel

Shape-preserving erosion controlled by the graded microarchitecture of shark tooth enameloid

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