Regenerated claws of the virile crayfish Faxonius virilis (Hagen, 1870) (Decapoda: Astacidea: Cambaridae) generate weaker pinching forces compared to original claws

Crustaceans are known for their ability to autotomize and regenerate their appendages. The appendages that are most often autotomized are their chela, often specialized as claws, which serve essential functions including foraging, fighting, mating, and predator defense. Crustaceans with autotomized or regenerated chelae may suffer decreases in their ability to perform these functions compared to individuals with intact or original claws. It is noteworthy that although regenerated claws can grow back to the expected size of an original claw, regenerated claws often differ from original claws in external morphology and internal musculature. Both male and female crayfishes wield a pair of enlarged claws. It surprisingly remains unknown how the regeneration of crayfish claws influences the claws' ability to generate pinching forces, which has previously been shown to influence the outcome of territorial contests. We investigated the relationship between claw regeneration and claw strength among male and female virile crayfish, Faxonius virilis (Hagen 1870). We found that maximal pinching forces of regenerated claws were weaker than the maximal pinching forces of original claws in both sexes (36% and 40% weaker in males and females, respectively). Further, regenerated claws had proportionally less muscle mass compared to original claws of equivalent size. These results present evidence of how claw regeneration influences pinching strength in crayfishes and suggest that such regeneration may be the functional mechanism that produces dishonest (large but weak) claws in crayfishes, but behavioral observations are required to support this hypothesis.