The effects of injecting Juvenile Hormone III into the prothoracic ganglion on phonotaxis by female crickets Gryllus bimaculatus

Nanoinjection of Juvenile Hormone III (JH III) into the prothoracic ganglion causes virgin female crickets Gryllus bimaculatus De Geer to become more phonotactically selective for the syllable periods (SPs) of model calling songs. Females responding to all, or almost all, of the SPs presented before JH III injection significantly narrow their responses to a range of SPs that is usually centered on the SPs included in the conspecific males' calling song. Control injections of acetone (i.e. the solvent for JH III) into the prothoracic ganglion do not significantly change the recipient females' phonotactic responses. Injection of JH III into the metathoracic ganglion also has no effect the females' phonotactic choices.     

Processing of Song Signals in the Cricket and its Hormonal Control

SYNOPSIS. Phonotaxis by female crickets to the calling songof males, is an important model for investigating the neuralbasis of auditory behavior. Recent advances make it possibleto explain some components of this behavior and its hormonalcontrol, at the level of identified neurons and molecular expressionwithin those neurons Tonotopically arranged afferents from the cricket's ear, projectto local and intersegmental prothoracic interneurons. Bilateralprocessing of signals and some temporal-pattern specific processingoccurs in the prothoracic ganglion and influences acoustic informationthat is sent to the brain via ascending interneurons that aredemonstrably involved in phonotaxis. High, low and band- passinterneurons in the brain continue temporal pattern processingwhich matches the selectivity of phonotaxis and may be filtersfor recognition of the calling song. Neurons descending fromthe brain and prothoracic ganglion, direct multimodal signals(including auditory) to more posterior regions, possibly theleg motor neurons that are responsible for phonotaxis Age-related changes or artificially induced changes in JuvenileHormone III levels regulate the threshold for phonotaxis inAcheta domesticus, by varying the threshold of LI, a prothoracicascending interneuron that is necessary for phonotaxis to lowintensity calling songs. Results from in situ hybridizationsuggest that this might be accomplished, in part, by controllingthe levels of nicotinic acetylcholine receptor-like mRNA expressedin LI, presumably by increasing its neurotransmitter receptordensity. L3 is a prothoracic ascending interneuron that exhibitsbandselective response properties to the syllable period ofthe calling song. L3's response is age and JHIII related, andis correlated to phonotactic selectivity. These changes in L3might be accomplished, at least in part by JHIII regulatingthe expression of nicotinic acetylcholine receptor-like mRNAin L3