Abstract
Pheromones are biologically important in fruit fly mating systems, and also have potential applications as attractants or mating disrupters for pest management. Bactrocera kraussi (Hardy) (Diptera: Tephritidae) is a polyphagous pest fruit fly for which the chemical profile of rectal glands is available for males but not for females. There have been no studies of the volatile emissions of either sex or of electrophysiological responses to these compounds. The present study (i) establishes the chemical profiles of rectal gland contents and volatiles emitted by both sexes of B. kraussi by gas chromatography–mass spectrometry (GC–MS) and (ii) evaluates the detection of the identified compounds by gas chromatography–electroantennogram detection (GC–EAD) and –electropalpogram detection (GC–EPD). Sixteen compounds are identified in the rectal glands of male B. kraussi and 29 compounds are identified in the rectal glands of females. Of these compounds, 5 were detected in the headspace of males and 13 were detected in the headspace of females. GC–EPD assays recorded strong signals in both sexes against (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-ethyl-7-mehtyl-1,6-dioxaspiro[4.5]decane isomer 2, (E,Z)/(Z,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, and (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane. Male antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-methyl-6-pentyl-3,4-dihydro-2H-pyran, 6-hexyl-2-methyl-3,4-dihydro-2H-pyran, 6-oxononan-1-ol, ethyl dodecanoate, ethyl tetradecanoate and ethyl (Z)-hexadec-9-enoate, whereas female antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and 2-methyl-6-pentyl-3,4-dihydro-2H-pyran only. These compounds are candidates as pheromones mediating sexual interactions in B. kraussi.
Highlights
Chemical communication plays an important role in the mating behaviour of tephritid fruit flies [1,2]
Studies of the volatile compounds emitted by dacine fruit flies have focused on the chemical profiles of males because they have been classically considered as the major sex pheromone producers [8]
Spiroacetals were the dominant class of compounds in male rectal glands, whereas esters of saturated/unsaturated fatty acids were the main class of compounds in female rectal glands
Summary
Chemical communication plays an important role in the mating behaviour of tephritid fruit flies [1,2]. Studies of the volatile compounds emitted by dacine fruit flies have focused on the chemical profiles of males because they have been classically considered as the major sex pheromone producers [8]. Bactrocera and Zeugodacus fruit flies are known to produce and emit diverse compounds, including aliphatic amides, spiroacetals, alcohols, pyrazines, dihydropyrans and esters of medium chain fatty acids [8,14,15,16,17,18,19,20,21,22,23]. The most commonly reported compound in Bactrocera and Zeugodacus rectal gland secretions is (E,E)-2,8-dimethyl-1,7dioxaspiro[5.5]undecane [8,15,16,19,20,22,23,24,25,26] This compound is known to occur in other insects, such as Polistes wasps and Ontholestes beetles [27,28]. The present study (i) describes the chemical profiles of rectal glands and headspace in males and females of B. kraussi, including re-description of male rectal gland contents, by using gas chromatography–mass spectrometry (GC–MS) and (ii) evaluates the antennal and palpal responses to each compound in natural blends by using gas chromatography– electroantennogram detection (GC–EAD) and –electropalpogram detection (GC–EPD)
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