Ultrastructure and electrophysiology of thermosensitive sensilla coeloconica in a tropical katydid of the genus Mecopoda (Orthoptera, Tettigoniidae)

Erik S Schneider,Christoph J Kleineidam,Gerd Leitinger,Heinrich Römer

doi:10.1016/j.asd.2018.08.002

Abstract

In many acoustic insects, mate finding and mate choice are primarily based on acoustic signals. In several species with high-intensity calling songs, such as the studied katydid Mecopoda sp., males exhibit an increase in their thoracic temperature during singing, which is linearly correlated with the amount of energy invested in song production. If this increased body temperature is used by females as an additional cue to assess the male's quality during mate choice, as has been recently hypothesized (“hot-male” hypothesis), thermosensory structures would be required to evaluate this cue. In the present study, therefore, we investigated the ultrastructure and physiology of thermosensitive sensilla coeloconica on the antennal flagella of Mecopoda sp. using a combination of electron microscopy and electrophysiological recording techniques.We could identify three distinct types of sensilla coeloconica based on differences in the number and branching pattern of their dendrites. Physiological recordings revealed the innervation by antagonistically responding thermoreceptors (cold and warm) and bimodal hygro-/thermoreceptors (moist or dry) in various combinations. Our findings indicate that Mecopoda sp. females are capable of detecting a singing male from distances of at least several centimetres solely by assessing thermal cues.

Highlights

In many acoustic insects, mate finding and localization as well as mate preferences are mainly based on variations in acoustic signals (Gerhardt and Huber, 2002)
Our findings indicate that Mecopoda sp. females are capable of detecting a singing male from distances of at least several centimetres solely by assessing thermal cues
The co in Mecopoda differ considerably from common np-is sensilla that have been described in the literature, especially regarding the following structural features: the dendritic outer segment (DOS) of all existing dendrites clearly extend into the peg distally

Summary

Introduction

Mate finding and localization as well as mate preferences are mainly based on variations in acoustic signals (Gerhardt and Huber, 2002). The calling songs represent the main signals produced during the initial stage of mate choice, during which the females phonotactically approach the males. During this stage, females potentially cover considerable distances by walking or by flight (Gerhardt and Huber, 2002). The acoustic signals carry important information about the Abbreviations: co, sensilla coeloconica; DIS, dendritic inner segment; DOS, dendritic outer segment; ds, dendritic sheath; np-is, poreless with inflexible socket.

Methods

Results

Conclusion