Crabs grab strongly depending on mechanical advantages of pinching and disarticulation of chela

Fujiwara, Shin-ichi; Kawai, Hiroki

doi:10.1002/jmor.20573

Cited by 19 publications

(11 citation statements)

References 53 publications

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“…The MA is a straightforward biomechanical metric which in a biological context was first introduced for vertebrates (Westneat 1995(Westneat , 2004 and was used since in many studies on vertebrate and arthropod jaw mechanics (Cooper and Westneat 2009;Sakamoto 2010;Habegger et al 2011;Dumont et al 2014;Senawi et al 2015;Cox and Baverstock 2015;Weihmann et al 2015b;Fujiwara and Kawai 2016;Blanke et al 2017a;Fabre et al 2017;Olsen 2017). The MA is defined as the inlever to outlever ratio.…”

Section: The Mechanical Advantage (Ma) As a Performance Metric For Inmentioning

confidence: 99%

The Early Evolution of Biting–Chewing Performance in Hexapoda

Blanke

2019

Insect Mouthparts

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Insects show a plethora of different mandible shapes. It was advocated that these mandible shapes are mainly a function of different feeding habits. This hypothesis was tested on a larger sampling of non-holometabolan biting-chewing insects with additional tests to understand the interplay of mandible function, feeding guild, and phylogeny. The results show that at the studied systematic level, variation in mandible biting-chewing effectivity is regulated to a large extent by phylogenetic history and the configuration of the mandible joints rather than the food preference of a given taxon. Additionally, lineages with multiple mandibular joints such as primary wingless hexapods show a wider functional space occupation of mandibular effectivity than dicondylic insects (¼ silverfish + winged insects) at significantly different evolutionary rates. The evolution and occupation of a comparably narrow functional performance space of dicondylic insects is surprising given the low effectivity values of this food uptake solution. Possible reasons for this relative evolutionary "stasis" are discussed.

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Section: The Mechanical Advantage (Ma) As a Performance Metric For Inmentioning

confidence: 99%

The Early Evolution of Biting–Chewing Performance in Hexapoda

Blanke

2019

Insect Mouthparts

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“…*See Supplemental Results (Methods S1) for an explanation of claw-face viewing perspectives. finger (dactyl) purely pivots about a single axis defined by two articulation points on the propodus (Figures 1A-1A'') [18][19][20]. Muscles attached to opposite sides of the pivot open and close the claw, respectively.…”

Section: Comparative Morphology and Evolutionary History Of Shrimp CLmentioning

confidence: 99%

Parallel Saltational Evolution of Ultrafast Movements in Snapping Shrimp Claws

et al. 2018

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How do stunning functional innovations evolve from unspecialized progenitors? This puzzle is particularly acute for ultrafast movements of appendages in arthropods as diverse as shrimps [1], stomatopods [2], insects [3-6], and spiders [7]. For example, the spectacular snapping claws of alpheid shrimps close so fast (∼0.5 ms) that jetted water creates a cavitation bubble and an immensely powerful snap upon bubble collapse [1]. Such extreme movements depend on (1) an energy-storage mechanism (e.g., some kind of spring) and (2) a latching mechanism to release stored energy quickly [8]. Clearly, rapid claw closure must have evolved before the ability to snap, but its evolutionary origins are unknown. Unearthing the functional mechanics of transitional stages is therefore essential to understand how such radical novel abilities arise [9-11]. We reconstructed the evolutionary history of shrimp claw form and function by sampling 114 species from 19 families, including two unrelated families within which snapping evolved independently (Alpheidae and Palaemonidae) [12, 13]. Our comparative analyses, using micro-computed tomography (microCT) and confocal imaging, high-speed video, and kinematic experiments with select 3D-printed scale models, revealed a previously unrecognized "slip joint" in non-snapping shrimp claws. This slip joint facilitated the parallel evolution of a novel energy-storage and cocking mechanism-a torque-reversal joint-an apparent precondition for snapping. Remarkably, these key functional transitions between ancestral (simple pinching) and derived (snapping) claws were achieved by minute differences in joint structure. Therefore, subtle changes in form appear to have facilitated wholly novel functional change in a saltational manner. VIDEO ABSTRACT.

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“…latro possesses a remarkable strength with a reported lifting force of up to 28 kg [8]. However, no previous study has reported the actual pinching force of this species, although a morphological study on crustaceans suggested that, among decapod crustaceans, the chelae of the coconut crab could generate the strongest pinching force [9]. In the present study, we aimed to (i) determine the pinching force of the wild coconut crab from measurement in situ and (ii) clarify how these animals acquired their mighty claw, using morphometric and ecological data.…”

Section: Introductionmentioning

confidence: 99%

A Mighty Claw: Pinching Force of the Coconut Crab, the Largest Terrestrial Crustacean

2016

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Crustaceans can exert a greater force using their claws than many animals can with other appendages. Furthermore, in decapods, the chela is a notable organ with multifunctional roles. The coconut crab, Birgus latro, is the largest terrestrial crustacean and has a remarkable ability to lift weights up to approximately 30 kg. However, the pinching force of this crab’s chelae has not been previously investigated. In the present study, we measured the pinching force of the chelae in 29 wild coconut crabs (33–2,120 g in body weight). The maximum force ranged from 29.4 to 1,765.2 N, and showed a strong positive correlation with body mass. Based on the correlation between pinching force and body weight, the force potentially exerted by the largest crab (4 kg weight) reported in a previous study would be 3300 N, which greatly exceeds the pinching force of other crustaceans as well as the bite force of most terrestrial predators. The mighty claw is a terrestrial adaptation that is not only a weapon, which can be used to prevent predator attack and inhibit competitors, but is also a tool to hunt other terrestrial organisms with rigid exteriors, aiding in these organisms to be omnivores.

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Crabs grab strongly depending on mechanical advantages of pinching and disarticulation of chela

Cited by 19 publications

References 53 publications

The Early Evolution of Biting–Chewing Performance in Hexapoda

The Early Evolution of Biting–Chewing Performance in Hexapoda

Parallel Saltational Evolution of Ultrafast Movements in Snapping Shrimp Claws

A Mighty Claw: Pinching Force of the Coconut Crab, the Largest Terrestrial Crustacean

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