Limb loss in the poisonous crab Atergatis floridus (Linnaeus) : advantages of possessing toxins?

Abstract

To determine the effectiveness of possessing toxins as a defense mechanism in crabs, the level of limb loss was examined in a poisonous crab Atergatis floridus. Crabs were collected individually using SCUBA between June 1990 and December 1992. The sex ratio approximated 1:1. Significant levels of limb loss were observed in both males and females, but limb loss frequency differed between sexes. Higher frequencies of limb loss were found in males (41.3% with limb loss) than females (18.4%). Site of loss also differed between sexes, with males having a higher loss of the walking legs 1, 3 and 4 than the chelipeds and leg 2 (P<0.01). Females have a more random pattern of limb loss. In conclusion, A. floridus was found to have a similar degree of limb loss to other reported crab studies. In situ observations of the behaviour of A floridus and predator interactions suggest the ecological benefit from the possession of toxins as a primary anti-predation strategy may be less effective than initially suspected.