Morphological changes induced by gamma radiation on the cuticle and antennal sensilla of Acanthoscelides obtectus adults.

Purpose: Acanthoscelides obtectus is considered as one of the most dangerous insect pest of stored legume crops. Scanning electron microscopy (SEM) was used to studying morphological changes induced by gamma radiation on the cuticle and antennal sensilla of A. obtectus adults.

Materials and methods: Antennal structure of the normal and irradiated A. obtectus adults as 1-2 days old pupae at four doses (50, 100, 150 and 200 Gy) was examined using SEM to study the changes in the antennal segments and associated sensilla.

Results: The antenna of A. obtectus is covered with a high density of sensilla. Five sensillum types have been observed in both sexes: Böhm bristles, sensilla chaetica, sensilla trichodea, sensilla basiconica and sensilla coeloconica. Due to the gamma radiation doses (50, 100, 150, and 200 Gy), morphological changes were observed in the antennal segments and their associated sensilla. These changes included shrinkage, sensilla curvature into different directions, irregular shape, swelling in certain areas, and sensilla gathered into dense collections. At 150 and 200 Gy doses, these alterations were clearly visible, while at case of irradiated pupae with 50 Gy, there were only minor abnormalities. Also, morphological changes caused in body cuticle were splitting between the elytra and between the thorax and elytra. Furthermore, a decrease in sensilla density was observed in certain areas of the elytra.

Conclusions: All these malformations may lead A. obtectus to not reaching the host, impeding their ability to infest the common bean seeds, and this is the primary goal of this investigation.