Ultrastructure of the Olfactory Sensilla across the Antennae and Maxillary Palps of Bactrocera dorsalis (Diptera: Tephritidae)

Abstract

The sensilla on the antennae and maxillary palps are the most important olfactory organs, via which the insect can perceive the semiochemicals to adjust their host seeking and oviposition behaviors. The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is a major agricultural quarantine pest infesting more than 250 different fruits and vegetables. However, the sensilla involved in olfaction have not been well documented even though a variety of control practices based on chemical communication have already been developed. In this study, the ultrastructure of the sensilla, especially the olfactory sensilla on the antennae and maxillary palps of both males and females, were investigated with field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Three types of olfactory sensillum types including trichodea, basiconica, and coeloconica, and two non-olfactory sensilla including both chaetica and microtrichia, were observed. Each of these three types of olfactory sensilla on the antennae of B. dorsalis were further classified into two subtypes according to the morphology and number of receptor cells. For the first time, the pores on the sensilla trichodea and basiconica cuticular wall were observed in this species, suggesting they are involved in semiochemical perception. This study provides new information on B. dorsalis olfaction, which can be connected to other molecular, genetic, and behavioral research to construct an integral olfactory system model for this species.

Antennal Sensilla in Vespidae: A Comparison Between a Diurnal and a Nocturnal Polistinae Wasp

“…The presence or absence of sensilla may be associated with adaptations to insect lifestyle, as reported for the antennal sensilla of four fig wasps (Hymenoptera: Chalcidoidea) with coeloconic sensilla occurring only in that entering the fruit to lay eggs (Yang et al, 2018). The occurrence of chaetica sensilla only in the antennal scape and pedicel found for A. flavissima is similar to that reported for Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) (Fu et al, 2012) and Bactrocera dorsalis (Diptera: Tephritidae) (Liu et al, 2021). The absence of cuticular pores and the flexible socket at the base of that sensillum indicates that it is a mechanoreceptor such as reported for other insects (Keil & Steinbrecht, 1984).…”

Mortality of Fruit Flies (Diptera: Tephritidae) Exposed to Spinetoram Toxic Bait in the Laboratory

“…The antennae and the maxillary palps, covered by numerous sensilla, are the primary olfactory organs in fruit flies. The multiporous sensilla trichodea are responsible for detecting volatile plant compounds and pheromones [31]. The toxic baits were more attractive to medflies or slightly repellent to A. obliqua during periods shorter than 360 minutes (Fig.…”

Is the Natural Instinct to Oviposit in Mated Female Oriental Fruit Fly, Bactrocera dorsalis More of a Brain-Independent Act?

“…This was also evident from the fact that the excised ovipositor could respond to GOL in the EOG experiments. SEM studies done previously on different appendages of tephritids including B. dorsalis (Zhang et al, 2012;Liu et al, 2021) reported differences in the type and density of sensillae on antennae and ovipositor. Significant difference in the density of the sensillae on the ovipositor compared to the antenna did not abolish the ovipositor response to GOL, which was comparable to that of the antenna.…”