Volatiles from the burnet moth Zygaena filipendulae (Lepidoptera) and associated flowers, and their involvement in mating communication

Abstract

The burnet moth Zygaena filipendulae L. contains the cyanogenic glucosides linamarin and lotaustralin, which can be degraded to the volatiles hydrogen cyanide (HCN), acetone and 2-butanone. Linamarin and lotaustralin are transferred from the male to female during mating and thus are considered to be involved in mating communication. Because volatile semiochemical cues play a major role in mating communication in many insect species, the emissions of HCN, acetone and 2-butanone from Z. filipendulae are characterized in the present study, aiming to determine the interplay between the degradation products of cyanogenic glucosides and pheromones. The volatile emissions from Z. filipendulae and flowers inducing mating are measured using headspace solid-phase micro-extraction and gas chromatography-mass spectrometry analysis. All Z. filipendulae life stages emit HCN, acetone and 2-butanone. Virgin females show higher emissions than mated females, whereas mated males have higher emissions than virgin males. Hydrogen cyanide is only rarely detected in the course of male-female copulation. These observations indicate a role for the cyanogenic glucoside derived volatiles in female calling and male courtship behaviours, although not as a defence during copulation. Males rejected for mating by a female are accepted after injection of linamarin or lotaustralin, demonstrating that cyanogenic glucosides are also important for female assessment of the fitness of the male. Volatiles from flowers occupied during mate calling are also analyzed, and emissions from males and females result in the identification of novel putative pheromones for Z. filipendulae.

Sex differences but no evidence of quantitative honesty in the warning signals of six-spot burnet moths (Zygaena filipendulaeL.)*

“…, ), a bias which can be overcome if the males are injected with extra cyanogenic glucosides or painted with linamarin (Zagrobelny et al. ). While females are thought to use compounds deposited on male abdominal brushes, or corremata, to assess male quality, chemical cues are not always reliable: in fact, males emit higher levels of HCN after mating, due to the presence of residual compounds on their corremata, despite having fewer cyanogenic glucosides left to offer (Zagrobelny et al.…”

“…While females are thought to use compounds deposited on male abdominal brushes, or corremata, to assess male quality, chemical cues are not always reliable: in fact, males emit higher levels of HCN after mating, due to the presence of residual compounds on their corremata, despite having fewer cyanogenic glucosides left to offer (Zagrobelny et al. , ). Since the cyanogenic glucoside reserves of older males are more likely to have been depleted by successive matings, wing color could assist female choice as a useful proxy for male age.…”

“…Further research into the volatiles emitted by zygaenids, including degradation products of cyanogenic glucosides such as HCN and ketones (Zagrobelny et al. ) and pyrazines (Rothschild ; Rothschild et al. ; Moore et al.…”

“…Conspicuousness of prey against the natural backgrounds on which they are found is a key component of aposematic signaling (Stevens and Ruxton 2012;Arenas et al 2015;Arenas and Stevens 2017), which should more often be measured in empirical studies of honest signaling (Arenas et al 2015). To address this issue, chromatic and luminance contrasts were calculated between the moth's wing markings and three likely natural backgrounds: the leaves and flowers of their principal host plant, Lotus corniculatus (Fabaceae), and a popular nectaring flower, field scabious (Knautia arvensis, Dipsacaceae) (Naumann et al 1999;Zagrobelny et al 2015). Five plants of each species were collected for analysis in Cornwall (UK).…”

Sequestration and functional diversification of cyanogenic glucosides in the life cycle of Heliconius melpomene

“…How and why the butterflies catabolize the dihydrogynocardin obtained from larval sequestration are unanswered questions and further investigations are necessary. Perhaps they degrade dihydrogynocardin to release volatile cyanide and ketones/aldehydes during calling and courtship behaviour, as seen in Z. filipendulae (Zagrobelny et al, 2015). The cyanide emitted by these moths might allow them to estimate the CNglc content of their peers, as females of Z. filipendulae will only copulate with males having a high CNglc content.…”