Oviposition Site-Selection by Bactrocera dorsalis Is Mediated through an Innate Recognition Template Tuned to γ-Octalactone

Kamala Jayanthi Pagadala Damodaram,Vivek Kempraj,Bakthavatsalam Nandagopal,Ravindra Kothapalli Venkataramanappa,Toby Bruce,Ravindra Mahadappa Aurade,Abraham Verghese,Frederic Marion-Poll

doi:10.1371/journal.pone.0085764

Abstract

Innate recognition templates (IRTs) in insects are developed through many years of evolution. Here we investigated olfactory cues mediating oviposition behavior in the oriental fruit fly, Bactrocera dorsalis, and their role in triggering an IRT for oviposition site recognition. Behavioral assays with electrophysiologically active compounds from a preferred host, mango, revealed that one of the volatiles tested, γ-octalactone, had a powerful effect in eliciting oviposition by gravid B. dorsalis females. Electrophysiological responses were obtained and flies clearly differentiated between treated and untreated substrates over a wide range of concentrations of γ-octalactone. It triggered an innate response in flies, overriding inputs from other modalities required for oviposition site evaluation. A complex blend of mango volatiles not containing γ-octalactone elicited low levels of oviposition, whereas γ-octalactone alone elicited more oviposition response. Naïve flies with different rearing histories showed similar responses to γ-octalactone. Taken together, these results indicate that oviposition site selection in B. dorsalis is mediated through an IRT tuned to γ-octalactone. Our study provides empirical data on a cue underpinning innate behavior and may also find use in control operations against this invasive horticultural pest.

Highlights

Insects make vital decisions about selection of food, mates or oviposition sites through pre-constructed recognition templates [1,2]
The flies laid 100% of their eggs into the treated non-hosts and no eggs were recorded in untreated non-hosts. These results show that the Innate recognition templates (IRTs) is strongly tuned to c-octalactone and this compound mediates the oviposition response in the Oriental fruit fly, B. dorsalis
The placement of eggs by gravid females is a crucial step that decides the fitness of B. dorsalis larvae [23]

Summary

Introduction

Insects make vital decisions about selection of food, mates or oviposition sites through pre-constructed recognition templates [1,2]. Innate recognition templates (IRTs) are embedded into the genome of insects and are transferred genetically to offspring so that when they are exposed to a fixed cue, or a fixed set of cues, a particular behavior is elicited without having to be learnt. Such recognition templates in insects are thought to be numerous; there is a paucity of information about the cues that trigger them. The oviposition-stimulants to which insects have developed IRTs remain elusive [13]

Methods

Results

Conclusion