Induced expression of a vestigial sexual signal

Vestigial morphological traits are common and well known in a variety of taxa. Identification of vestigial genes has illustrated the potential for evolutionary reversals and the re-expression of atavistic traits. Here we induce expression of a behavioral sexual signal, male calling song, in a cricket species, Gryllus ovisopis, which lacks a functional calling song. We successfully used acetylcholine (Ach) injections in the frontal space of the head of male crickets to activate cerebral command neurons for cricket calling, and we recorded calling songs with a temporal chirp pattern similar to that of G. ovisopis’ close evolutionary relatives, G. firmus and G. pennsylvanicus, implying that the neural pattern generators which underlie cricket calling behavior persist in a vestigial state in G. ovisopis. To our knowledge, this is the first demonstration of the induced expression of a vestigial behavior in any organism. The retention of latent neural capacity to express sexual behaviors...