Substrate vibrations mediate behavioral responses via femoral chordotonal organs in a cerambycid beetle.

Takuma Takanashi,Niels Skals,Kiyoshi Nakamuta,Midori Fukaya,Hiroshi Nishino

doi:10.1186/s40851-016-0053-4

Abstract

BackgroundVibrational senses are vital for plant-dwelling animals because vibrations transmitted through plants allow them to detect approaching predators or conspecifics. Little is known, however, about how coleopteran insects detect vibrations.ResultsWe investigated vibrational responses of the Japanese pine sawyer beetle, Monochamus alternatus, and its putative sense organs. This beetle showed startle responses, stridulation, freezing, and walking in response to vibrations below 1 kHz, indicating that they are able to detect low-frequency vibrations. For the first time in a coleopteran species, we have identified the sense organ involved in the freezing behavior. The femoral chordotonal organ (FCO), located in the mid-femur, contained 60–70 sensory neurons and was distally attached to the proximal tibia via a cuticular apodeme. Beetles with operated FCOs did not freeze in response to low-frequency vibrations during walking, whereas intact beetles did. These results indicate that the FCO is responsible for detecting low-frequency vibrations and mediating the behavioral responses. We discuss the behavioral significance of vibrational responses and physiological functions of FCOs in M. alternatus.ConclusionsOur findings revealed that substrate vibrations mediate behavioral responses via femoral chordotonal organs in M. alternatus.Electronic supplementary materialThe online version of this article (doi:10.1186/s40851-016-0053-4) contains supplementary material, which is available to authorized users.

Highlights

Vibrational senses are vital for plant-dwelling animals because vibrations transmitted through plants allow them to detect approaching predators or conspecifics
We investigated the behavioral responses of M. alternatus to vibrations and identified a chordotonal organ in the leg that detects vibrations transmitted through the tree
Monochamus alternatus exhibited startle responses and/or stridulation when subjected to vibrations at different frequencies (Fig. 2)

Summary

Introduction

Vibrational senses are vital for plant-dwelling animals because vibrations transmitted through plants allow them to detect approaching predators or conspecifics. Vibrations transmitted through plants propagate well, allowing plant-dwelling animals to detect approaching conspecifics or predators without relying on other signals [3, 4]. Insects exhibit a range of behaviors in response to vibrations [1, 2]. A ‘startle response’ is a fast jerky movement with short latency elicited by vibrations; it is considered to be a preparatory behavior that enables locomotion to follow in a smooth behavioral sequence [5,6,7]. Vibrations may elicit abrupt cessation of ongoing movements, such as freezing

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