Evaluation of the Internal Morphology of Antennal Sensilla in Scirpophaga Incertulas for Male and Female by Scanning Electron Microscopy

Abstract

The Scirpophaga incertulas (Walker), trivial name Yellow Stem Borer (YSB) is a serious pest contributing to significant yield loss to rice. YSB detects host/mate cues through olfactory receptors (sensilla) on antennae, which is critical for its survival, adaptability, and perpetuation. Though YSB is a destructive pest, its mechanism of olfaction is poorly understood. Using a scanning electron microscope, it is attempted to detect distinct sensilla, decode their characteristics, and compare the antennal sensilla of both males and females. Sensilla trichodea (S.T), Sensilla chaetica (S.Ch), Sensilla styloconica (S.St), Sensilla squamiformia (S.Sq), Sensilla coeloconica (S.Co), Sensilla cavity, and Bőhm bristles (BB) are the seven distinct kinds and subtypes of sensilla are recognized. Sexual dimorphism was observed in the arrangement of scales over the antenna in males and females. Interestingly, among the subtypes, the S.T-I was observed only in males. Furthermore, Sensilla coeloconica without a fence (type II) noticed in our studies was also reported earlier in other monophagous lepidopteran pests. The statistical analysis of the number and size of sensilla clearly indicates their involvement in sexual differentiation. This study may help in better understanding the processes of communication, identification of plant volatiles, oviposit site, and mate in YSB.