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Taylor, JRA.  2018.  Aquatic versus terrestrial crab skeletal support: morphology, mechanics, molting and scaling. Journal of Experimental Biology. 221   10.1242/jeb.185421   AbstractWebsite

The transition from aquatic to terrestrial environments places significant mechanical challenges on skeletal support systems. Crabs have made this transition multiple times and are the largest arthropods to inhabit both environments. Furthermore, they alternate between rigid and hydrostatic skeletons, making them an interesting system to examine mechanical adaptations in skeletal support systems. I hypothesized that terrestrial crabs have modified morphology to enhance mechanical stiffness and that rigid and hydrostatic skeletons scale differently from each other, with stronger allometric relationships on land. Using the aquatic blue crab, Callinectes sapidus, and the terrestrial blackback land crab, Gecarcinus lateralis, I measured and compared body mass, merus morphology (dimensions, cuticle thickness and the second moment of area I) and mechanics (flexural stiffness ElI, elastic modulus E, critical stress and hydrostatic pressure) of rigid and hydrostatic stage crabs encompassing a range of sizes (C. sapidus: 1.5-133 g, N <= 24; G. lateralis: 22-70 g, N <= 15). The results revealed that rigid G. lateralis has similar morphology (limb length to diameter LID and cuticle thickness to limb diameter TID ratio) to C. sapidus, and the mechanics and most scaling relationships are the same. Hydrostatic land crabs differ from aquatic crabs by having different morphology (thinner cuticle), mechanics (greater intemal pressures) and scaling relationship (cuticle thickness). These results suggest that the rigid crab body plan is inherently overbuilt and sufficient to deal with the greater gravitational loading that occurs on land, while mechanical adaptations are important for hydrostatically supported crabs. Compared with other arthropods and hydrostatic animals, crabs possess distinct strategies for adapting mechanically to life on land.

Lowder, KB, Allen MC, Day JMD, Deheyn DD, Taylor JRA.  2017.  Assessment of ocean acidification and warming on the growth, calcification, and biophotonics of a California grass shrimp. Ices Journal of Marine Science. 74:1150-1158.   10.1093/icesjms/fsw246   AbstractWebsite

Cryptic colouration in crustaceans, important for both camouflage and visual communication, is achieved through physiological and morphological mechanisms that are sensitive to changes in environmental conditions. Consequently, ocean warming and ocean acidification can affect crustaceans' biophotonic appearance and exoskeleton composition in ways that might disrupt colouration and transparency. In the present study, we measured growth, mineralization, transparency, and spectral reflectance (colouration) of the caridean grass shrimp Hippolyte californiensis in response to pH and temperature stressors. Shrimp were exposed to ambient pH and temperature (pH 8.0, 17 degrees C), decreased pH (pH 7.5, 17 degrees C), and decreased pH/increased temperature (pH 7.5, 19 degrees C) conditions for 7 weeks. There were no differences in either Mg or Ca content in the exoskeleton across treatments nor in the transparency and spectral reflectance. There was a small but significant increase in percent growth in the carapace length of shrimp exposed to decreased pH/increased temperature. Overall, these findings suggest that growth, calcification, and colour of H. californiensis are unaffected by decreases of 0.5 pH units. This tolerance might stem from adaptation to the highly variable pH environment that these grass shrimp inhabit, highlighting the multifarious responses to ocean acidification, within the Crustacea.

deVries, MS, Webb SJ, Tu J, Cory E, Morgan V, Sah RL, Deheyn DD, Taylor JRA.  2016.  Stress physiology and weapon integrity of intertidal mantis shrimp under future ocean conditions. Scientific Reports. 6   10.1038/srep38637   AbstractWebsite

Calcified marine organisms typically experience increased oxidative stress and changes in mineralization in response to ocean acidification and warming conditions. These effects could hinder the potency of animal weapons, such as the mantis shrimp's raptorial appendage. The mechanical properties of this calcified weapon enable extremely powerful punches to be delivered to prey and aggressors. We examined oxidative stress and exoskeleton structure, mineral content, and mechanical properties of the raptorial appendage and the carapace under long-term ocean acidification and warming conditions. The predatory appendage had significantly higher % Mg under ocean acidification conditions, while oxidative stress levels as well as the % Ca and mechanical properties of the appendage remained unchanged. Thus, mantis shrimp tolerate expanded ranges of pH and temperature without experiencing oxidative stress or functional changes to their weapons. Our findings suggest that these powerful predators will not be hindered under future ocean conditions.

Frank, MB, Naleway SE, Wirth TS, Jung JY, Cheung CL, Loera FB, Medina S, Sato KN, Taylor JRA, McKittrick J.  2016.  A protocol for bioinspired design: A ground sampler based on sea urchin jaws. Jove-Journal of Visualized Experiments.   10.3791/53554   AbstractWebsite

Bioinspired design is an emerging field that takes inspiration from nature to develop high-performance materials and devices. The sea urchin mouthpiece, known as the Aristotle's lantern, is a compelling source of bioinspiration with an intricate network of musculature and calcareous teeth that can scrape, cut, chew food and bore holes into rocky substrates. We describe the bioinspiration process as including animal observation, specimen characterization, device fabrication and mechanism bioexploration. The last step of bioexploration allows for a deeper understanding of the initial biology. The design architecture of the Aristotle's lantern is analyzed with micro-computed tomography and individual teeth are examined with scanning electron microscopy to identify the microstructure. Bioinspired designs are fabricated with a 3D printer, assembled and tested to determine the most efficient lantern opening and closing mechanism. Teeth from the bioinspired lantern design are bioexplored via finite element analysis to explain from a mechanical perspective why keeled tooth structures evolved in the modern sea urchins we observed. This circular approach allows for new conclusions to be drawn from biology and nature.

Naleway, SE, Taylor JRA, Porter MM, Meyers MA, McKittrick J.  2016.  Structure and mechanical properties of selected protective systems in marine organisms. Materials Science & Engineering C-Materials for Biological Applications. 59:1143-1167.   10.1016/j.msec.2015.10.033   AbstractWebsite

Marine organisms have developed a wide variety of protective strategies to thrive in their native environments. These biological materials, although formed from simple biopolymer and biomineral constituents, take on many intricate and effective designs. The specific environmental conditions that shape all marine organisms have helped modify these materials into their current forms: complete hydration, and variation in hydrostatic pressure, temperature, salinity, as well as motion from currents and swells. These conditions vary throughout the ocean, being more consistent in the pelagic and deep benthic zones while experiencing more variability in the nearshore and shallows (e.g. intertidal zones, shallow bays and lagoons, salt marshes and mangrove forests). Of note, many marine organisms are capable of migrating between these zones. In this review, the basic building blocks of these structural biological materials and a variety of protective strategies in marine organisms are discussed with a focus on their structure and mechanical properties. Finally, the bioinspired potential of these biological materials is discussed. (C) 2016 Elsevier B.V. All rights reserved.

Taylor, JRA, Gilleard JM, Allen MC, Deheyn DD.  2015.  Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica. Scientific Reports. 5   10.1038/srep10608   AbstractWebsite

The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 +/- 0.04) and reduced pH (7.53 +/- 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance.

Patek, SN, Rosario MV, Taylor JRA.  2012.  Comparative spring mechanics in mantis shrimp. The Journal of Experimental Biology.   10.1242/jeb.078998   AbstractWebsite

Elastic mechanisms are fundamental to fast and efficient movements. Mantis shrimp power their fast raptorial appendages using a conserved network of exoskeletal springs, linkages and latches. Their appendages are fantastically diverse - ranging from spears to hammers. We measured the spring mechanics of 12 mantis shrimp species from 5 different families exhibiting hammer-shaped, spear-shaped and undifferentiated appendages. Across species, spring force and work increase with size of the appendage and spring stiffness is not correlated with size. Species that hammer their prey exhibit significantly greater spring resilience compared to species that impale evasive prey (i.e., "spearers"); mixed statistical results show that species that hammer prey also produce greater work relative to size during spring loading compared to spearers. Disabling part of the spring mechanism, the "saddle", significantly decreases spring force and work in three smasher species; cross-species analyses show a greater effect of cutting the saddle on the spring force and stiffness in species without hammers compared to species with hammers. Overall, the study shows a more potent spring mechanism in the faster and more powerful hammering species compared to spearing species while also highlighting the challenges of reconciling within-species and cross-species mechanical analyses when different processes may be acting at these two different levels of analysis. The observed mechanical variation in spring mechanics provides insights into the evolutionary history, morphological components and mechanical behavior that were not discernible in prior single-species studies. The results also suggest that, even with a conserved spring mechanism, spring behavior, potency and component structures can be varied within a clade with implications for the behavioral functions of power-amplified devices.

Taylor, JRA, Patek SN.  2010.  Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp's telson. Journal of Experimental Biology. 213:3496-3504.   10.1242/jeb.047233   AbstractWebsite

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.

Taylor, JRA, Hebrank J, Kier WM.  2007.  Mechanical properties of the rigid and hydrostatic skeletons of molting blue crabs, Callinectes sapidus Rathbun. Journal of Experimental Biology. 210:4272-4278.   10.1242/jeb.007054   AbstractWebsite

Molting in crustaceans involves significant changes in the structure and function of the exoskeleton as the old cuticle is shed and a new one is secreted. The flimsy new cuticle takes several days to harden and during this time crabs rely on a hydrostatic skeletal support system for support and movement. This change from a rigid to a hydrostatic skeletal support mechanism implies correlated changes in the function, and thus mechanical properties, of the cuticle. In particular, it must change from primarily resisting compression, bending and torsional forces to resisting tension. This study was designed to explore the changes in the mechanical properties of the crustacean cuticle as the animals switch between two distinct skeletal support mechanisms. Samples of cuticle were removed from blue crabs, Callinectes sapidus, at 1 h (soft-shell stage), 12 h (paper-shell stage), and 7 days (hard-shell stage) following molting. We measured and compared the flexural stiffness, Young's modulus of elasticity (in tension), and tensile strength for each postmolt stage. We found that the hardshell cuticle has a flexural stiffness fully four orders of magnitude greater than the soft-shell and paper-shell cuticle. Although the soft-shell cuticle has a Young's modulus significantly lower than that of the paper-shell and hard-shell cuticle, it has the same tensile strength. Thus, the soft-shell and paper-shell cuticles are unable to resist the significant bending forces associated with a rigid skeletal support system, but can resist the tensile forces that characterize hydrostatic support systems. The mechanical properties of the cuticle thus change dramatically during molting in association with the change in function of the cuticle. These results emphasize the significant role that mechanics plays in the evolution of the molting process in arthropods, and possibly other ecdysozoans.

Taylor, JRA, Kier WM.  2006.  A pneumo-hydrostatic skeleton in land crabs - A sophisticated dual support system enables a crab to stay mobile immediately after moulting. Nature. 440:1005-1005.   10.1038/4401005a   AbstractWebsite

Like their aquatic counterparts, terrestrial crabs repeatedly shed their rigid exoskeleton during moulting. But in the case of land crabs, little water is available to provide a temporary hydrostatic skeleton before the new skeleton hardens, and air does not provide the buoyancy necessary to support the animal. Here we show that whenever its exoskeleton is shed, the blackback land crab Gecarcinus lateralis relies on an unconventional type of hydrostatic skeleton that uses both gas and liquid (a 'pneumo-hydrostat'). To our knowledge, this is the first experimental evidence for a locomotor skeleton that depends on a gas. It establishes a new category of hydrostatic skeletal support and possibly a critical adaptation to life on land for the Crustacea.

Taylor, JRA, Kier WM.  2003.  Switching skeletons: Hydrostatic support in molting crabs. Science. 301:209-210.   10.1126/science.1085987   AbstractWebsite

Skeletal support systems are essential for support, movement, muscular antagonism, and locomotion. Crustaceans shed their rigid exoskeleton at each molt yet are still capable of forceful movement. We hypothesize that the soft water-inflated body of newly molted crabs may rely on a hydrostatic skeleton, similar to that of worms and polyps. We measured internal hydrostatic pressure and the force exerted during claw adduction and observed a strong correlation between force and hydrostatic pressure, consistent with hydrostatic skeletal support. This alternation between the two basic skeletal types may be widespread among arthropods.