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

View Article: PubMed Central - PubMed

ABSTRACT

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.

No MeSH data available.


Related in: MedlinePlus

Regression analysis of the maximum force per unit body weight vs. body mass across several animal groups, including coconut crabs.The shaded gray area represents the range of the maximum force exerted by various animal activities (running, jumping, pushing, pulling, swimming, flight, nipping, and biting) [11]. Colored lines were calculated based on the relationship between the closing forces of crustacean chelae, vertebrate jaws and body masses determined previously [1, 2].
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5120803&req=5

pone.0166108.g003: Regression analysis of the maximum force per unit body weight vs. body mass across several animal groups, including coconut crabs.The shaded gray area represents the range of the maximum force exerted by various animal activities (running, jumping, pushing, pulling, swimming, flight, nipping, and biting) [11]. Colored lines were calculated based on the relationship between the closing forces of crustacean chelae, vertebrate jaws and body masses determined previously [1, 2].

Mentions: The pinching force exerted by coconut crabs was extremely strong. Maximum pinching force ranged from 29.4 to 1765.2 N. The scaling factor in the allometric equation for pinching force and BW was 0.82 (Fig 2). This value was significantly greater than the predicted isometric scaling of pinching force (proportional to muscle cross-sectional area) against BW (a = 0.67 [11]). According to a previous study, the reported maximum BW of the coconut crab is 4 kg [12]. Applying our allometric scaling equation, the pinching force of the coconut crab of 4 kg BW was estimated to be 3300 N. This force greatly exceeds that in all other crustacean species that have been reported [1, 2], as well as the bite force for the majority of modern terrestrial predators, other than alligators [13–14]. The maximum force exerted by major muscle groups (in terms of force / body weight) usually ranges between 10 body mass-1/3 and 50 body mass-1/3 [11] (Fig 3). Among the force associated with the closure of crustacean chelae and vertebrate jaws [14] few exceed the upper range of these values, while the pinching forces of Cancer spp. [2] and the coconut crab do exceed the upper limit. The relative pinching force of the coconut crab was greater than the force of any animal above 0.14 kg BW, although coconut crabs less than 0.14 kg BW were inferior to Cancer spp. (Fig 3).


A Mighty Claw: Pinching Force of the Coconut Crab, the Largest Terrestrial Crustacean
Regression analysis of the maximum force per unit body weight vs. body mass across several animal groups, including coconut crabs.The shaded gray area represents the range of the maximum force exerted by various animal activities (running, jumping, pushing, pulling, swimming, flight, nipping, and biting) [11]. Colored lines were calculated based on the relationship between the closing forces of crustacean chelae, vertebrate jaws and body masses determined previously [1, 2].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120803&req=5

pone.0166108.g003: Regression analysis of the maximum force per unit body weight vs. body mass across several animal groups, including coconut crabs.The shaded gray area represents the range of the maximum force exerted by various animal activities (running, jumping, pushing, pulling, swimming, flight, nipping, and biting) [11]. Colored lines were calculated based on the relationship between the closing forces of crustacean chelae, vertebrate jaws and body masses determined previously [1, 2].
Mentions: The pinching force exerted by coconut crabs was extremely strong. Maximum pinching force ranged from 29.4 to 1765.2 N. The scaling factor in the allometric equation for pinching force and BW was 0.82 (Fig 2). This value was significantly greater than the predicted isometric scaling of pinching force (proportional to muscle cross-sectional area) against BW (a = 0.67 [11]). According to a previous study, the reported maximum BW of the coconut crab is 4 kg [12]. Applying our allometric scaling equation, the pinching force of the coconut crab of 4 kg BW was estimated to be 3300 N. This force greatly exceeds that in all other crustacean species that have been reported [1, 2], as well as the bite force for the majority of modern terrestrial predators, other than alligators [13–14]. The maximum force exerted by major muscle groups (in terms of force / body weight) usually ranges between 10 body mass-1/3 and 50 body mass-1/3 [11] (Fig 3). Among the force associated with the closure of crustacean chelae and vertebrate jaws [14] few exceed the upper range of these values, while the pinching forces of Cancer spp. [2] and the coconut crab do exceed the upper limit. The relative pinching force of the coconut crab was greater than the force of any animal above 0.14 kg BW, although coconut crabs less than 0.14 kg BW were inferior to Cancer spp. (Fig 3).

View Article: PubMed Central - PubMed

ABSTRACT

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.

No MeSH data available.


Related in: MedlinePlus