Aberrant defense displays of the big‐handed crab, Heterozius rotundifrons (Brachyura: Belliidae)

Abstract

The New Zealand big‐handed crab, Heteroziusrotundifrons, shows a full flexion display when mildly disturbed and a full extension lateral merus display in response to strong or prolonged disturbance. The full extension display is unusual since the crab maintains a cataleptic state during the display, which long outlasts the period of stimulation (maximum display time observed was 2612s). Tactile and disequilibrium stimulate on were most effective; their effects appeared additive. Light and water jets were less effective. Statocysts provide the major sensory input during disequilibrium stimulation. Dactyl closure reflexes of the claws were less frequent than normal during the full extension display. It is suggested that the function of this display is to render the crab unpalatable to intertidal fish predators.

Keywords:

• Heterozius
• crab
• catalepsy
• defense display
• behaviour, lateral merus display
• predation