Simmonds, Monique S. J., Stevenson, Philip C. ORCID: https://orcid.org/0000-0002-0736-3619 and Hanson, Frank E. (2019) Rosmarinic acid in Canna generalis activates the medial deterrent chemosensory neurone and deters feeding in the tobacco hornworm Manduca sexta. Physiological Entomology, 44 (2). pp. 140-147. ISSN 0307-6962 (Print), 1365-3032 (Online) (doi:10.1111/phen.12284)

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Abstract

For all but a very few highly specialized insect feeders, Canna generalis L. (Cannaceae) is unacceptable as a food plant and is a highly potent feeding deterrent for the tobacco hornworm Manduca sexta Johan. (Lepidoptera). The present study describes the isolation of an active deterrent compound, rosmarinic acid (RA) from the ethanol extract of canna leaves. A two‐choice bioassay shows that RA is a feeding deterrent in the concentration range 0.3–3 mm. Bilateral ablation of the oral chemoreceptors eliminates this deterrence. The results reported in the behavioural literature show that only the epipharyngeal sensilla and the medial (but not the lateral) styloconica contribute to this deterrence elicited by canna foliage or extract, and the data obtained in the present study show the same results using RA. Electrophysiological recordings from the medial styloconica show that RA primarily stimulates the ‘deterrent neurone’ in a concentration‐dependent manner with a threshold of approximately 0.03 mm and a peak frequency of 69 spikes s–1 at 0.1 mm RA. An extract of canna leaves elicits similar responses. Adding RA to canna extract does not elicit another class of spikes, indicating that both stimuli activate the same neurone. We discuss the significance of the results with respect to furthering our knowledge about the sensory basis of food selection, and specifically about the range of compounds that stimulate deterrent chemosensitive neurones of lepidopteran larvae.

Item Type:	Article
Additional Information:	This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.
Uncontrolled Keywords:	Feeding behaviour, insect neurophysiology, Lepidoptera, phagodeterrents, phytochemistry, sensory coding
Subjects:	S Agriculture > S Agriculture (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > Natural Resources Institute Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department Faculty of Engineering & Science > Natural Resources Institute > Chemical Ecology Research Group
Last Modified:	14 Mar 2020 01:38
URI:	http://gala.gre.ac.uk/id/eprint/23232

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