Specific Volatile Compounds from Mango Elicit Oviposition in Gravid Bactrocera dorsalis Females

Abstract

Selecting a suitable oviposition site is crucial to the fitness of female insects because it determines the successful development of their offspring. During the oviposition process, an insect must use cues from the external environment to make an appropriate choice of where to lay eggs. Generalist insects can detect and react to a plethora of cues, but are under selection pressure to adopt the most reliable ones to override noise and increase efficiency in finding hosts. The oriental fruit fly, Bactrocera dorsalis (Hendel), is a generalist that utilizes a multitude of fruits as oviposition sites. However, the identity and nature of oviposition stimulants for B. dorsalis is not well known. Recently, we identified a volatile compound γ-octalactone that elicits an innate oviposition response in B. dorsalis. We screened 21 EAD-active volatiles, identified from mango, for their oviposition stimulant activity. 1-Octen-3-ol, ethyl tiglate, and benzothiazole instigated oviposition in gravid B. dorsalis females. Flies deposited most of their eggs into pulp discs with oviposition-stimulants, and only a small fraction of eggs were laid into control discs. In a binary choice oviposition assay, 95.1, 93.7, and 65.6 % of eggs were laid in discs treated with 1-octen-3-ol, ethyl tiglate, and benzothiazole, respectively. Single plate two-choice assays proved that oviposition-stimulants were crucial in oviposition site selection by gravid female B. dorsalis. In simulated semi-natural assays, gravid B. dorsalis females accurately differentiated between fruits with and without 1-octen-3-ol, ethyl tiglate, and γ-octalactone by laying more eggs on the treated fruit. However, benzothiazole did not elicit an increase in oviposition when presented in this context. Our results suggest that the identified oviposition-stimulants are 'key' compounds, which the flies associate with suitable oviposition sites.

Odorant-binding proteins expression patterns in recently diverged species of Anastrepha fruit flies

“…In C . capitata , for instance, studies revealed that sexually mature virgin females are attracted to the odor of male-produced pheromone, while mated females are more interested in finding suitable oviposition sites and are therefore more attracted to the odor of host fruits 42–45 . Considering these findings, we suggest that OBP genes up-regulated in virgins, in comparison with immature flies, may be involved in pheromone perception.…”

Evolutionarily conserved odorant receptor function questions ecological context of octenol role in mosquitoes

“…First mentioned as a potential oviposition cue for Ae. aegypti 50 and later for T. amboinensis 51, it has also been implicated as an oviposition cue in other dipterans including the oriental fruit fly, Bactrocera dorsalis 52 and the bean seed fly, Delia platura 53. It therefore appears that octenol detection may be an ancestral cue in insects and an oviposition cue in Dipterans53.…”

Discovery of Chemosensory Genes in the Oriental Fruit Fly, Bactrocera dorsalis

“…dorsalis exhibits sexually dimorphic behavior, which is influenced by olfactory cues expressed during specific developmental stages [19,20,21]. When the male flies reach sexual maturity, they are strongly attracted to and compulsively feed on Methyl eugenol (ME) (non-host compounds), and this behavior is used to control B .…”