Search

The present study aimed at evaluating the effect of lethal doses of gamma radiation (LD25, LD50and LD75) on reproductive potential of females resulted from irradiated pupae, and the latent effect on first generation (F1). In addition, ultrastructure alterations in resulted female ovaries were studied using transmission electron microscope. The numbers of eggs laid were 158.3 and 70.0 eggs/5♀♀♀ at LD25and LD50, respectively, compared with 536.7 eggs/5♀♀ for control, and while no eggs were deposited by females resulted from pupae exposed to LD75of gamma radiation. Also, the sterility index recorded 94.0 and 77.7 at LD25, and LD50, respectively in F1 females. Otherwise, the growth index of F1 larvae and pupae recorded 7.2 and 6.4 at LD25and LD50, respectively, compared with 8.7 for control. Gamma radiation affected the ultrastructure of resulted female ovaries such as degeneration of ovarian sheath, distortion, and irregularities in the outlines of follicular epithelial cells and lysis of oocyte. Also, shrinkage nuclei with the unclear components were observed, as well as dispersion of vacuoles around cytoplasm with irregularity and shrinkage of nurse cells. So, these radiation doses can be used in the Sterile Insect Technique (SIT) programs against Musca domestica.

Laboratory male pupae of Culex pipienswere exposed to 23, 41, 74 and 128 Gy doses of gamma radiation according to the LD25,LD50, LD75and LD90calculation, respectively. The inherited deleterious effects of gamma radiation were observed in the F1, F2and F3generations. Levels of sterility index in the F1and F2were higher than those of untreated control but in the F3generation there was a semi-sterility compared with the control. Ultrastructure of normal males' testes of C. pipienswas studied using transmission electron microscopy. Histopathological responses were observed in the irradiated testes of C. pipiens. Gamma radiation had greatly affected the testes, such as (i) rupture, necrosis, degeneration and small vacuoles were reported in the testicular wall (ii) an abnormal distribution of the developmental stages of spermatogonia and spermatocytes leading to a general decrease in the rate of spermatogenesis; and (iii) deformity of sperm inhibitting the movements and the fertility of the sperm led to the decrease in the reproductive potential of C. pipiens. Consequently, these radiation doses are consistent with those used in the already established Sterile Insect Technique (SIT) programmes against Culex pipiens.

External morphology of males' hind legs of Spodoptera littoralissubjected to thermal treatment (33 °C and 37 °C) or/and irradiated with substerilizing doses of gamma radiation (75, 100 and 150 Gy) were studied using scanning electron microscopy (SEM) in the parental generation. Five types of sensilla have been distinguished; three types of trichoid sensilla (T1,T2and T3), sensilla basiconica and sensilla auricillica, which are considered as olfactory chemoreceptors. Moreover, sensilla chaetica are contact chemoreceptors, whereas sensilla styloconica are thermo–hygro/gustatory mechanoreceptors. The impact of thermal treatment or/and gamma irradiation reflect a clear morphological change in S. littoralislegs'sensilla, claws, spurs and scales. Otherwise, the degree of deformity was thermal and dose dependent, as it increased with an increase of the degree of temperature and dose of irradiation applied. Substerilizing doses 75 and 100 Gy, either alone or combined with thermal treatment 33 °C, have low undesirable effects on the hind legs with successful mobility or courtship behavior. Consequently, synergistic effect of gamma radiation and thermal stress induced successful application in the integrated pest management program for controlling S. littoralis.