Figure 5

The relationship between forces produced by the claw and resistance of the cuticle. Each symbol represents a species average ± 1 S.E.M. (A) The relationship between the force estimated at the tip of the claw and the force required to indent the carapace (closed squares) and the force required to indent the manus (closed circles). The black line is an x=y relationship. Species averages that fall above the line (i.e. all of the manus values) are examples where the claw tip cannot produce enough force to puncture the cuticle. Species averages that fall below the line (i.e. all of the carapace values) can be punctured by the claw tip. (B) The relationship between force produced at the claw tubercle and the force required to indent (closed squares) and crack (open diamonds) the manus cuticle. Again, the black line is an x=y relationship. Indentation forces fall around the line and suggest that crabs can produce approximately enough force to indent the manus of a conspecific. However, crabs cannot produce enough force at the tubercle to crack the cuticle and cause catastrophic damage (i.e. these values fall above the x=y line).