Abstract
To test whether insect antennae are necessary for eliciting courtship and aggression toward appropriate partners, we antennectomized adult male crickets (Gryllus bimaculatus) and observed their behavior toward other antennectomized males and intact females. At 7 days after removal of both antennae, pairs of antennectomized males were placed together; 80% displayed courtship behavior, generating courtship song by rubbing their forewings together, toward other antennectomized males, and 20% displayed aggressive behavior. Only 45% courted intact females. No intact males courted antennectomized males, and 80% displayed aggressive behavior. All intact males courted females. The results for males with one antenna removed were essentially the same as for intact males. These findings indicate that a high proportion of male crickets with both antennae removed court other males and fail to display maleβmale aggression, demonstrating that removal of antennae from male crickets induces maleβmale courtship and that an antenna is necessary for the expression of maleβmale aggression. Moreover, brain serotonin (5βhydroxytryptamine; 5βHT) levels in male crickets were significantly reduced at 7 days after removal of antennae. The reduction of 5βHT was detected primarily in the central body of the brain. Thus, 5βHT in the central body of the male cricket brain may be involved in the behavioral changes. Β© 2003 Wiley Periodicals, Inc. J Neurobiol 57: 110β118, 2003