[Unilateral change in color produced by ablation of the eyestalk of the crustacean Processa edulis (Decapoda, Natantia)].

A difference of expansion of erythrophores is observed between the left and right side of P. edulis after the removal of only one Eyestalk. It is the first time, in the Crustacea, that experiments lead to the conclusion that a sympathetic-like constrictor nervous action can exist in colour-change control; colour changes are particularly fast in this species.