THE EFFECTS OF BODY-SIZE ON MATE CHOICE IN A GRAPSID CRAB, GAETICE DEPRESSUS (CRUSTACEA, DECAPODA)

Male and female mate choices were investigated in the grapsid crab, Ga etice depressus (Crustacea, Decapoda) in a laboratory experiment. Male s mated indiscriminately with regard to the body size of the females, and frequently copulated with the first females they encountered. In c ontrast, females showed mate discrimination with regard to the body si ze of males. The females tended to sample potential mates prior to cop ulation, and showed both a preference for the larger males and a tende ncy toward the rejection of males with body sizes smaller than their o wn. However, they did not discriminate between two males that were eit her larger or smaller than they themselves. Mate choice by the females of this species is though to be based upon threshold-criterion tactic s, in which the body size of the female itself is used as a threshold value.