Mechanical properties of the rigid and hydrostatic skeletons of molting blue crabs, <i>Callinectes sapidus</i> Rathbun

Taylor, James B.; Hebrank, John H.; Kier, William M.

doi:10.1242/jeb.007054

Cited by 25 publications

(24 citation statements)

References 47 publications

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“…Mechanical testing shows that the flexural stiffness (composite variable EI) of the postmolt cuticle is four orders of magnitude lower than that of the intermolt cuticle, but the breaking strength (stress at fracture in tension) is the same. Thus, although the postmolt cuticle is unable to bear compressive or bending loads, this thin membrane can support large tensile stresses as is required for hydrostatic skeletal support (Taylor et al, 2007). This alternation between the two categories of skeletal support may be widespread for arthropods.…”

Section: Additional Examplesmentioning

confidence: 99%

The diversity of hydrostatic skeletons

Kier

2012

Journal of Experimental Biology

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Summary A remarkably diverse group of organisms rely on a hydrostatic skeleton for support, movement, muscular antagonism and the amplification of the force and displacement of muscle contraction. In hydrostatic skeletons, force is transmitted not through rigid skeletal elements but instead by internal pressure. Functioning of these systems depends on the fact that they are essentially constant in volume as they consist of relatively incompressible fluids and tissue. Contraction of muscle and the resulting decrease in one of the dimensions thus results in an increase in another dimension. By actively (with muscle) or passively (with connective tissue) controlling the various dimensions, a wide array of deformations, movements and changes in stiffness can be created. An amazing range of animals and animal structures rely on this form of skeletal support, including anemones and other polyps, the extremely diverse wormlike invertebrates, the tube feet of echinoderms, mammalian and turtle penises, the feet of burrowing bivalves and snails, and the legs of spiders. In addition, there are structures such as the arms and tentacles of cephalopods, the tongue of mammals and the trunk of the elephant that also rely on hydrostatic skeletal support but lack the fluid-filled cavities that characterize this skeletal type. Although we normally consider arthropods to rely on a rigid exoskeleton, a hydrostatic skeleton provides skeletal support immediately following molting and also during the larval stage for many insects. Thus, the majority of animals on earth rely on hydrostatic skeletons.

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Section: Additional Examplesmentioning

confidence: 99%

The diversity of hydrostatic skeletons

Kier

2012

Journal of Experimental Biology

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158

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“…The merus of the blue crab was tested by Hahn & LaBarbera [11], who loaded these limbs to failure in cantilever bending. Young's modulus and strength of material samples from the merus of this same species were measured in a different study [12], which found values of 318 and 9.9 MPa, respectively. These properties were measured in the transverse direction only; however, there is evidence to suggest that the material is isotropic.…”

Section: Experimental Datamentioning

confidence: 99%

“…The several limb segments distal to the merus can be simplified into one single, rigid segment, assumed fixed where it meets the ground. Using body measurements reported in the literature [11,12], we assumed that the merus had a length of 20 mm, a radius of 4.5 mm, a cross section of 15.25 mm 2 and a second moment of inertia (I value) of 135 mm 4 . The distance from the centre of mass of the body to the proximal joint was estimated as 40 mm, the merus was taken to be inclined at an angle of 458 to the horizontal and the joint angle at the distal end of the merus was taken to be 908 [30].…”

Section: Appendix a Stress Analysis Of The Locust Tibia And Crab Merusmentioning

confidence: 99%

Shape optimization in exoskeletons and endoskeletons: a biomechanics analysis

Taylor

Dirks

2012

J. R. Soc. Interface.

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This paper addresses the question of strength and mechanical failure in exoskeletons and endoskeletons. We developed a new, more sophisticated model to predict failure in bones and other limb segments, modelled as hollow tubes of radius r and thickness t. Five failure modes were considered: transverse fracture; buckling (of three different kinds) and longitudinal splitting. We also considered interactions between failure modes. We tested the hypothesis that evolutionary adaptation tends towards an optimum value of r/t, this being the value which gives the highest strength (i.e. load-carrying capacity) for a given weight. We analysed two examples of arthropod exoskeletons: the crab merus and the locust tibia, using data from the literature and estimating the stresses during typical activities. In both cases, the optimum r/t value for bending was found to be different from that for axial compression. We found that the crab merus experiences similar levels of bending and compression in vivo and that its r/t value represents an ideal compromise to resist these two types of loading. The locust tibia, however, is loaded almost exclusively in bending and was found to be optimized for this loading mode. Vertebrate long bones were found to be far from optimal, having much lower r/t values than predicted, and in this respect our conclusions differ from those of previous workers. We conclude that our theoretical model, though it has some limitations, is useful for investigating evolutionary development of skeletal form in exoskeletons and endoskeletons.

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“…molting) (Reaka, 1975). During molting, the cuticle that comprises the exoskeleton undergoes such dramatic changes in structure and mechanical properties, becoming as flimsy as plastic wrap before hardening, that animals must rely on hydrostatic skeletal support (Taylor et al, 2007;Taylor and Kier, 2003;Taylor and Kier, 2006). Newly molted animals cannot strike with their soft raptorial appendages and therefore tend to bluff or flee their cavities when threatened by intruders (Steger and Caldwell, 1983).…”

Section: Role Of the Telson In Ritualized Fightingmentioning

confidence: 99%

Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp's telson

Taylor

Patek

2010

Journal of Experimental Biology

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SUMMARY Resisting impact and avoiding injury are central to survival in situations ranging from the abiotic forces of crashing waves to biotic collisions with aggressive conspecifics. Although impacts and collisions in biology are ubiquitous, most studies focus on the material properties of biological structures under static loading. Here, we examine the mechanical impact properties of the mantis shrimp's telson, a piece of abdominal armor that withstands repeated, intense impacts from the potent hammer-like appendages used by conspecifics during ritualized fighting. We measured the coefficient of restitution, an index of elasticity, of the telson and compared it with that of an adjacent abdominal segment that is not impacted. We found that the telson behaves more like an inelastic punching bag than an elastic trampoline, dissipating 69% of the impact energy. Furthermore, although the abdominal segment provides no mechanical correlates with size, the telson's coefficient of restitution, displacement and impact duration all correlate with body size. The telson's mineralization patterns were determined through micro-CT (Computed Tomography) and correspond to the mechanical behavior of the telson during impact. The mineralized central region of the telson ‘punched’ inward during an impact whereas the surrounding areas provided elasticity owing to their reduced mineralization. Thus, the telson effectively dissipates impact energy while potentially providing the size-related information crucial to its role in conspecific assessment. This study reveals the mechanical infrastructure of impact resistance in biological armor and opens a new window to the biomechanical underpinnings of animal behavior and assessment.

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Mechanical properties of the rigid and hydrostatic skeletons of molting blue crabs, Callinectes sapidus Rathbun

Cited by 25 publications

References 47 publications

The diversity of hydrostatic skeletons

The diversity of hydrostatic skeletons

Shape optimization in exoskeletons and endoskeletons: a biomechanics analysis

Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp's telson

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