Repository logo

Motor control and directional accuracy of phonotaxis in female field crickets



Change log


Ntelezos, Athanasios 


This thesis addresses two aspects of the phonotactic behavior of female field crickets (Gryllus bimaculatus) as they orient towards singing males: the first one is how the auditory input is integrated into the motor activity underlying their walking responses, and the second one is how accurately they can localize a singing male in a dynamic stimulus situation. Although it has been established that the conspecific calling song is recognized via a circuit in the brain, it is not clear how pattern recognition is linked to descending motor control of phonotaxis. To analyze the auditory-induced motor responses, I recorded high-speed videos of crickets performing phonotaxis and tracked the movement of their bodies and appendages. The video analysis showed that when crickets commence phonotaxis, their body parts and appendages are activated and moved from anterior to posterior in the following order: antennae, head, prothorax, front legs, middle legs. During phonotaxis the antennae move continuously side-to-side in a rhythmic pattern, and on top of this rhythmic movement is superimposed a shift to the side the calling song is presented from. Moreover, the prothorax makes small rhythmic movements that are coupled to the stepping cycle, and on top of these rhythmic movements also steers towards the side the calling song is presented from.

Following up on the results of the video analysis, I recorded the activity of the antennal muscles of the scape in crickets that performed phonotaxis. The scape contains two muscles: the adductor muscle that adducts the antenna towards the median line, and the abductor muscle that abducts it laterally. The activity of the adductor muscle is coupled to the adduction movement of the antenna during the contralateral presentation of the calling song, while the activity of the abductor muscle is coupled to the abduction movement during the ipsilateral presentation of the calling song. The antennal movement and muscular activity – especially the abduction movement and the activity of the abductor muscle – are coupled to the calling song on a chirp-to-chirp basis. The neurites of the motoneurons of the antennal muscles are located in the deutocerebrum, while the ascending auditory pathway projects into the protocerebrum. I discuss that additional auditory brain interneurons must be involved for the transfer and processing of the auditory-to-motor signal from the protocerebrum to the deutocerebrum.

I also investigated the function of several thoracic muscles for potential contribution to the prothoracic movements contributing to phonotaxis. Of all the muscles tested, only the activity of pronotal muscle 56 was coupled to the prothoracic movements in crickets performing phonotaxis. Specifically, the activity of muscle 56 was coupled both to the rhythmic prothoracic movements that are coupled to the stepping cycle and to the auditory-induced steering of the prothorax. Like the antennae, the prothorax turns to the active speaker and also responds to the calling song on a chirp-to-chirp basis. I discuss that auditory input to the motoneurons of muscle 56 in the prothoracic ganglion is likely indirect via a pathway descending from the brain.

Finally, I tested the accuracy of female crickets walking on a trackball as they performed phonotaxis towards a speaker oscillating constantly between 45° left and 45° right relative to their long axis. In a group of crickets, I used a drop of wax to fix the prothorax against the mesothorax and test the effect of the immobilization of the prothorax has on auditory steering. The performance of the crickets with the fixed prothorax was not statistically different from the performance of the crickets that could freely move the prothorax, however, the crickets with the fixed prothorax generally understeered towards the more lateral angles of stimulus. Overall, in this dynamic situation the angular resolution of the crickets was 6-11° in their frontal range, which is less accurate than the previously reported 1-2° for phonotaxis towards a static sound source. The results show that crickets find orientation towards a moving sound source more challenging than towards a static one. This was further corroborated with tests where the crickets steered to the correct side when two speakers positioned 5° to the left and 5° to the right alternated in the presentation of the calling song, meaning their angular resolution for static sound sources was at least 5°.





Hedwig, Berthold


acoustic communication, cricket, motor control


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Jesus College (Embiricos Trust Scholarship)