DIGGING IN SAND CRABS (DECAPODA, ANOMURA, HIPPOIDEA) : INTERLEG COORDINATION

摘要: Sand crabs (Decapoda, Anomura, Hippoidea) are highly specialised for digging into sand using their thoracic legs. Using video-recording and electromyography, we examined the leg movements of three species belonging to two families: Blepharipoda occidentalis (Albuneidae), Lepidopa californica (Albuneidae) Emerita analoga (Hippidae). The patterns all similar. ipsilateral legs 2 3 tightly coupled shovel forward from underneath animal, whereas 4 more variable, apparently stirring up providing purchase rearward descent sand. B. L. resemble each other than either resembles that E. analoga. In albuneids, cycles at same frequency as 3, both albuneid switch gait bilateral alternation synchrony midway through digging. analoga, right left always alternate. Legs can cycle about twice they tend move in during high-frequency (e.g. start digging); coupling becomes variable low-frequency movements. crab may have originated a modified form walking, but this behavioural innovation subsequently diverged superfamily.