On the spot: utilization of directional cues in vibrational communication of a stink bug

Janez Prešern,Jernej Polajnar,Maja Zorović,Maarten De Groot,Meta Virant-Doberlet

doi:10.1038/s41598-018-23710-x

Abstract

Although vibrational signalling is among the most ancient and common forms of communication, many fundamental aspects of this communication channel are still poorly understood. Here, we studied mechanisms underlying orientation towards the source of vibrational signals in the stink bug Nezara viridula (Hemiptera, Pentatomidae), where female vibrational song enables male to locate her on the bean plant. At the junction between the main stem and the leaf stalks, male placed his legs on different sides of the branching and orientation at the branching point was not random. Analyses of signal transmission revealed that only a time delay between the arrival of vibrational wave to receptors located in the legs stretched across the branching was a reliable directional cue underlying orientation, since, unexpectedly, the signal amplitude at the branching point was often higher on the stalk away from the female. The plant and the position of the vibrational source on the plant were the most important factors influencing the unpredictability of the amplitude cue. Determined time delays as short as 0.5 ms resulted in marked changes in interneuron activity and the decision model suggests that the behavioural threshold is in the range between 0.3 and 0.5 ms.

Highlights

Substrate-borne vibrations are among the most ancient and widespread modalities used to gather information present in the environment[1,2,3,4], yet many fundamental aspects underlying behaviour guided by vibrational signals/ cues are still virtually unexplored
We combined the analysis of orientation behaviour at branching points on a bean plant (Phaseolus vulgaris), which is one of the preferred host plants of N. viridula, with the analysis of transmission of vibrational signals through this plant species in order to obtain the information on availability, reliability and utilization of directional cues
Since propagation measurements revealed time difference as an available and reliable directional cue, we investigated whether biologically relevant time difference (0.5–1 ms) is detected and processed in the central nervous system of N. viridula

Summary

Introduction

Substrate-borne vibrations are among the most ancient and widespread modalities used to gather information present in the environment[1,2,3,4], yet many fundamental aspects underlying behaviour guided by vibrational signals/ cues are still virtually unexplored. To get a proper insight into mechanisms underlying orientation towards the source of vibrational signals, one should analyse the behaviour, identify the potential directional cues and link them to the physical properties of the natural environment, as well as to receptor mechanisms and processing in the central nervous system. While such integrative approach has been applied to studies of insect audition[12], comprehensive studies on model species relying on vibration communication are still lacking. To support our experimental findings, we modelled the ratio of possible decisions based on the data on propagation of naturally emitted FCS and compared the results with observed behaviour

Methods

Results

Conclusion