METHYL FARNESOATE LEVELS IN MALE SPIDER CRABS EXHIBITING ACTIVE REPRODUCTIVE-BEHAVIOR

The concentration of methyl farnesoate (MF) in the hemolymph and its s ynthesis by the mandibular organs (MOs) were investigated to determine whether this compound is related to the differences in the size of th e reproductive system and the mating behavior among male morphotypes o f the spider crab, Libinia emarginata. Large-claw abraded males displa yed mating behavior under competitive conditions. They have the larges t reproductive systems, their MOs synthesize large amounts of MF in vi tro, and the concentration of MF in their hemolymph is high. Small-cla w abraded males displayed mating behavior with receptive females only when isolated. These smaller crabs have intermediate-sized reproductiv e systems, their MOs synthesize the most MF, and they have the highest circulating level of MF relative to their body size. The unabraded ma les did not display mating behavior; their reproductive systems are sm aller; their MO activity is low, as is their circulating level of MF. The strong relationship between MF levels and the intensity of reprodu ctive behavior suggests that MF may be one of the driving forces behin d mating behavior in Crustacea. (C) 1994 Academic Press, Inc.