Impact of Gamma Radiation on Male Proboscis of Rhynchophorous ferrugineus (Olivier, 1790) (Coleoptera: Curculionidae)

Abstract

Red palm weevil, Rhynchophorous ferrugineus (Olivier, 1790), (Coleoptera: Curculionidae) is the most dangerous pest for date palms in the Middle East, especially the Arab Gulf countries. The proboscis sensilla in males are studied by using Scanning Electron Microscopy (SEM) to assess the effect of gamma irradiation with different doses. Eight types of sensilla have been observed; four types of coeloconic sensilla (I, II, III, IV) are distributed on the lateral and frontal cuticular surface of the proboscis with a chemoreceptors function. Trichodea sensilla (I, II) and coeloconic sensilla (V) are concentrated on the dorsal surface of proboscis and are arranged in two rows to serve an olfactory and mechanosensory function. A very few number of squamiform sensilla (I) are scattered on the anterior-lateral side of proboscis to perform a mechanoreception function. Such malformation that gave rise to morphological structures of sensilla after exposing the pupae to the doses 10, 15, and 20 gray of gamma radiation are discussed. Irradiation with dose 10 Gy had a slight effect on the different types of sensilla as compared to the control, whereas at the radiation doses (15, 20 Gy) percentage of malformation are increased. The information gained from this study shows that the doses 15, 20 Gy have affected most types of sensilla and that the coeloconic sensilla (IV) are the only type that is not affected by any dose of irradiation.