Morphology and distribution of antennal sensilla in a parasitoid fly, Gymnosoma rotundatum (Diptera: Tachinidae)

Abstract

Morphology of antennal sensilla and their distribution were investigated in male and female adults of the parasitoid fly Gymnosoma rotundatum (Diptera: Tachinidae) using scanning electron microscopy (SEM). The overall length and shape were not different between males and females from each other. Three basic types of sensilla (sensilla basiconica, s. chaetica, and s. coeloconica) were identified from both sexes, but with variations in numbers and distribution along the antennae. The s. basiconica and s. chaetica could be divided further into subtypes; s. basiconica into three subtypes and s. chaetica into two subtypes. All the basiconica subtypes 1, 2, and 3 were multiporous, indicating that their primary function was olfactory. The sensilla basiconica was most abundant on the antennae of both sexes. The abundance of s. basiconica subtype 1 was different, but other subtypes 2 and 3 were similar between males and females. There was no pore on the cuticular surface of the s. chaetica and s. coeloconica, suggesting that they are likely to be a mechanosensory or a thermohygroreceptory function. The abundance of the two sensillum types was similar between males and females. The morphological information obtained in our study provides a basis for future investigations into the sensory physiological function, and associated behaviors, of each type of sensilla in this parasitoid fly.