Ultrastructural comparison and distribution of sensilla on male and female antennae of the sand fly Phlebotomus papatasi (Diptera: Psychodidae): the vector of cutaneous leishmaniasis in Egypt

Abstract

Background: Since sand flies are insects of medical importance and most of its sensilla were found on the antennae, the present investigation was designed to characterize the ultrastructure of the antennae of males and females and the sensilla distribution using scanning electron microscopy (SEM). Results: The filiform antenna of males and females consisted of a scape, pedicel, and flagellum. Male antennae appeared longer than those of females and exhibited obvious sexual dimorphism. In addition to the microtrichiae, six cuticular sensillary types, namely trichoid, coeloconic (subtype the common grooved coeloconic), chaetic, campaniform, squamiform, and the basiconic, were identified. The trichoid sensilla occurred in five subtypes, namely long blunt-tipped trichoid, short sharp-tipped trichoid, short blunt-tipped trichoid, medium pointed-tipped trichoid, and apical trichoid. Little changes in the number and distribution pattern of same sensillar types between males and females were revealed. Trichoid sensilla were the most abundant of all sensillar types. The short sharp-tipped trichoid sensilla were observed on the pedicel of males, while in females they were found on both scape and pedicel. The position of the apical trichoid sensilla on the last flagellomere differs in males than in females. Conclusions: The current study is the first to describe differences in the last three flagellomeres between males and females. Our results could provide a foundation for further research on sensory organs and approaches for the control of sand flies and enable for the use of new taxonomic characters to differentiate among species.