Impact damage and repair in shells of the limpet <i>Patella vulgata</i>

Taylor, David

doi:10.1242/jeb.149880

Cited by 13 publications

(17 citation statements)

References 18 publications

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“…However, these studies have focused primarily on relatively high forces (≥65% of the one-time breaking force) and relatively low cycle numbers (mostly <1000), as they have considered fatigue in the context of predation. A few studies have also examined how repeated impacts damage mollusk shells (Crane et al, 2018;Taylor, 2016), but again, these have focused on a few, high-force impacts (<120 impacts). None of this research has developed a broader framework to examine how a wide range of potentially fatiguing forces affects animal survival.…”

Section: Introductionmentioning

confidence: 99%

Mechanical fatigue fractures bivalve shells

Crane

Denny

2020

Journal of Experimental Biology

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Mollusk shells protect against diverse environmental and predatory physical threats, from one-time impacts to chronic, low-magnitude stresses. The effectiveness of shells as armor is often quantified with a test of shell strength: increasing force is applied until catastrophic fracture. This test does not capture the potential role of fatigue, a process by which chronic or repeated, low-magnitude forces weaken and break a structure. We quantified the strength and fatigue resistance of California mussel (Mytilus californianus) shells. Shells were fatigue tested until catastrophic failure by either loading a valve repeatedly to a set force (cyclic) or loading a valve under constant force (static). Valves fatigued under both cyclic and static loading, i.e. subcritical forces broke valves when applied repeatedly or for long durations. Stronger and more fatigue-resistant valves tended to be more massive, relatively wider and the right-hand valve. Furthermore, after accounting for the valves' predicted strength, fatigue resistance curves for cyclic and static loading did not differ, suggesting that fatigue fracture of mussels is more dependent on force duration than number of cycles. Contextualizing fatigue resistance with the forces mussels typically experience clarifies the range of threats for which fatigue becomes relevant. Some predators could rely on fatigue, and episodic events like large wave impacts or failed predation attempts could weaken shells across long time scales. Quantifying shell fatigue resistance when considering the ecology of shelled organisms or the evolution of shell form offers a perspective that accounts for the accumulating damage of a lifetime of threats, large and small.

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Section: Introductionmentioning

confidence: 99%

Mechanical fatigue fractures bivalve shells

Crane

Denny

2020

Journal of Experimental Biology

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“…This may explain why some limpets were unable to repair holes even after long periods. Similarly, the apex seems to act as a sacrificial point in the shell [17], absorbing most of the damage. This is remarkably similar to 'crumple zones' in cars, a structural safety mechanism that serves to absorb, like the apex, energy in an impact, preserving more important structures within.…”

Section: Discussionmentioning

confidence: 99%

“…After inflicting damage, and waiting for a chosen repair period, the limpets were removed from the rocks using sharp knives, before removing the animal inside and cleaning the shell and storing it for subsequent testing. In a previous study [17], we devised a method of impact testing which was also used here (see below). We found that the energy required to cause failure when the shell was impacted on its apex was related to the size of the shell raised to the power of 4.6 [17].…”

Section: Experimental Methodsmentioning

confidence: 99%

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Repair and remodelling in the shells of the limpetPatella vulgata

O’Neill

Mala

Cafiso

et al. 2018

J. R. Soc. Interface.

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Limpets and other molluscs rely on shells to protect them from physical damage, predation, dehydration, etc. If the shell becomes damaged, this may significantly impair its function. In this work, experiments were carried out to investigate the effect of damage on the strength of shells of the common limpet () and their ability to repair this damage effectively. Shells were damaged in three ways: (i) low-energy impacts; (ii) abrasion of the outer layer; and (iii) creation of a small hole in the apex of the shell. Shells were left to repair for several time periods (0, 10, 30 and 60 days). The mechanical strength was evaluated by impacting the shells with a weight dropped from a known height. The damage reduced the strength (defined as impact energy to failure) by 50-70% depending on damage type. After 60 days, limpets in all three groups had repaired their shells significantly, bringing their strength to 79-91% of the control value (in each case, samples were statistically indistinguishable from their control counterparts). Measurements of the thickness of the shell at the apex suggest that the main effect of low-energy impact and abrasion is reduction in thickness, which correlates linearly with the impact energy needed for failure. The method of repair is believed to be by the growth of fresh shell material on the inside of the shell, though we could not identify this new material specifically. Even after 60 days, the shells were still statistically thinner than the controls. Consequently, there may be some other strengthening mechanism at work. This work has demonstrated the remarkable ability of limpets to detect the mechanical weakening of their shells caused by relatively subtle forms of damage and to take appropriate action to restore shell strength.

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“…Predators often attack certain regions of the shell or apply other behaviors such as peeling or impacting, which are not captured in the typical two-plate test. Using multiple methods to quantify strength of the limpet Patella vulgata, Taylor (2016) demonstrated differences between the impact strength, quantified by dropping rods onto shells, and the strength as measured with a more traditional two-plate crushing test.…”

Section: Introductionmentioning

confidence: 99%

Smashing mantis shrimp strategically impact shells

Crane

Cox

Kisare

et al. 2018

Journal of Experimental Biology

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Many predators fracture strong mollusk shells, requiring specialized weaponry and behaviors. The current shell fracture paradigm is based on jaw- and claw-based predators that slowly apply forces (high impulse, low peak force). However, predators also strike shells with transient intense impacts (low impulse, high peak force). Toward the goal of incorporating impact fracture strategies into the prevailing paradigm, we measured how mantis shrimp () impact snail shells, tested whether they strike shells in different locations depending on prey shape ( spp., , spp.) and deployed a physical model (Ninjabot) to test the effectiveness of strike locations. We found that, contrary to their formidable reputation, mantis shrimp struck shells tens to hundreds of times while targeting distinct shell locations. They consistently struck the aperture of globular shells and changed from the aperture to the apex of high-spired shells. Ninjabot tests revealed that mantis shrimp avoid strike locations that cause little damage and that reaching the threshold for eating soft tissue is increasingly difficult as fracture progresses. Their ballistic strategy requires feed-forward control, relying on extensive pre-strike set-up, unlike jaw- and claw-based strategies that can use real-time neural feedback when crushing. However, alongside this pre-processing cost to impact fracture comes the ability to circumvent gape limits and thus process larger prey. In sum, mantis shrimp target specific shell regions, alter their strategy depending on shell shape, and present a model system for studying the physics and materials of impact fracture in the context of the rich evolutionary history of predator-prey interactions.

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Impact damage and repair in shells of the limpet Patella vulgata

Cited by 13 publications

References 18 publications

Mechanical fatigue fractures bivalve shells

Mechanical fatigue fractures bivalve shells

Repair and remodelling in the shells of the limpetPatella vulgata

Smashing mantis shrimp strategically impact shells

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