Classical olfactory conditioning in the oriental fruit fly, Bactrocera dorsalis.

Hiromu Tanimoto,Xin Nian Zeng,Jia Li Liu,Xiao Yan Chen

doi:10.1371/journal.pone.0122155

Abstract

The oriental fruit fly, Bactrocera dorsalis, is a serious pest of fruits and vegetables. Methyl eugenol (ME), a male attractant, is used to against this fly by mass trapping. Control effect may be influenced by learning, which could modify the olfactory response of the fly to this attractant. To collect the behavioral evidence, studies on the capability of this fly for olfactory learning are necessary. We investigated olfactory learning in male flies with a classical olfactory conditioning procedure using restrained individuals under laboratory conditions. The acquisition of the proboscis extension reflex was used as the criterion for conditioning. A high conditioned response level was found in oriental fruit flies when an odor was presented in paired association with a sucrose reward but not when the odor and sucrose were presented unpaired. We also found that the conditioning performance was influenced by the odor concentration, intertrial interval, and starvation time. A slight sensitization elicited by imbibing sucrose was observed. These results indicate that oriental fruit flies have a high capacity to form an olfactory memory as a result of classical conditioning.

Highlights

Learning, especially associative learning, tends to adapt an insect to its current environment [1]
The first trial was excluded from analysis because it was designed to have a null response, and null response first trial in other experiments was excluded from analysis
By comparing with a control group, the unpaired group, we demonstrated that the increased probability of eliciting a proboscis extension was conditional upon an association between the odor and the sucrose solution

Summary

Introduction

Especially associative learning, tends to adapt an insect to its current environment [1]. Insects learn to orient toward stimuli that are rewarding and away from stimuli that are punishing. The success of a foraging task strongly depends on learning [2, 3]. The learning processes underlying foraging behavior have been broadly studied in honey bees [4, 5] and bumble bees [6]. The recognition of learning as a source of behavioral plasticity in parasitoid foraging has increased [7, 8]. The oriental fruit fly, Bactrocera dorsalis (Hendel), is a serious quarantine pest of fruits and vegetables [9]. Males of B. dorsalis are strongly attracted to methyl eugenol (ME) [10,11], a naturally occurring compound found in varying amounts in more than 200 species from 32 plant families [12].

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