Changes in phonotaxis by the female cricketAcheta domesticus L. after killing identified acoustic interneurons

Abstract

Phonotactic selectivity of female crickets to natural and model calling songs (CSs) has been well documented. No identified acoustic interneurons or groups of them exhibited sufficiently selective responses to CSs to explain this behavioral selectivity. In this study identified acoustic interneurons were killed and pre- and post-killing phonotactic responses to model CSs were compared. 1. Acoustic interneurons were iontophoretically filled with lucifer yellow. Surface illumination of the prothoracic ganglion with blue light (450 nm) stopped all EPSP and spiking activity and eliminated the membrane potential (Fig. 1). 2. Control females oriented normally to a CS after immobilizing, exposing the prothoracic ganglion, recording intracellularly, and killing an acoustic unit not related to phonotaxis (Fig. 3). 3. Killing one ON1 neuron resulted in an error angle when the female oriented to CSs with various syllable periods (SPs). However, direct orientation remained over a narrowed range of SPs, which were typical of an ‘ideal’ conspecific call (Figs. 4 and 5A). Elimination of both ON1s did not affect post-killing phonotaxis suggesting that the ON1 is not necessary for CS localization or recognition (Fig. 5B). 4. Killing one ON2 resulted in angular errors similar to those following unilateral elimination of the ON1, but only in response to post-test CS SPs that were most attractive in pre-tests. Good posttest phonotaxis occurred to CSs with SPs found to be only marginally attractive in pre-tests (Fig. 6). 5. Unilateral killing of AN2-type units produced post-test angular errors in orientation to all CS SPs. Presence of circling varied from animal to animal but if present occurred to all SPs (Fig. 7).