Search

ABSTRACTThe present study evaluated the efficacy of X-ray irradiation for the sterilization of Ceratitis capitata. Pupae were exposed to doses of 0 (control), 60.7, 137, 156.9, 237.7, 300.59 and 344.46 Gy to determine which dose would not affect viability of irradiated fruit flies but would result in their sterilization. Doses of 60.7 and 137 Gy were suitable as males emerging from irradiated 7-day-old pupae were 100% sterile but were otherwise viable. Light and transmission electron microscopy were used to examine the structure of normal and treated male C. capitatatestes. The testes of males originating from non-irradiated pupae of C. capitataconsist of a single long follicle that looks like a sac and is full of germ cells at different stages of development. In testes of males originating from irradiated pupae, the presence of lysosomes, many vacuoles, and irregular distribution of spermatogonia and spermatocytes, led to an overall slowed rate of spermatogenesis. Apparent degeneration and abnormalities of the sperms resulted in the production of non-functional sperm or to a reduction in sperm production. This study concluded that X-ray is an alternative irradiation method for the sterile insect technique used to control Mediterranean fruit fly populations.

Earlier investigations into the proteases indicated that protease in the mosquito is synthesized, and released into the gut lumen after the blood meal feeding. Likewise, the nuclease enzyme is stimulated if the blood meal contains a pathogen. To evaluate the effect of the Hepatitis C Virus (HCV) and gamma rays on egg oviposition, protease and nuclease enzymes secretion in the mid-gut of C. pipienswe designed four mosquito groups. The first group was fed on a sugar solution, the second was fed on blood meal, and both the third and fourth groups were fed infected blood meal with a viral load 1.3 × 106 IU/ml, and fourth group was also irradiated with the dose level 60 Gy. The results indicated that, there is a positive correlation between the blood meal feeding and mosquito reproductive potential. Fertility was significantly higher in the groups of mosquitoes given infected blood HCV virus. Otherwise, the reproductive potential of irradiated females that fed on the infected blood was drastically reduced. The value of protease activity in a sugar-fed mosquito is significantly low but there was a rapid increase in the enzyme activity post one day of blood meal feeding. After five days, the activity has decreased significantly but still above the residual value. Nuclease activity was very low post the sugar and blood meal feeding and there was no significant change (p ≤ 0.05) in the activity during the interval time. While, the infected HCV blood meal stimulated and increased the level of nuclease activity. Protease and nuclease activity in the irradiated mid-gut C. pipiens, that fed on infected HCV blood was lower than the non-irradiated insects. The reduction of protease and nuclease activity due to the influence of infected HCV blood meal and gamma irradiation, leads to a disorder of the immune system that protects the mosquito from the infection of a pathogen.

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.

Compatibility of gamma irradiation and entomopathogenic nematodes as a management program for management of Pectinophora gossypiellain the laboratory are a vital issue in research, but they are used as an alternative technique for insect management are still in its beginnings,Full-grown (6-days old) male pupae were irradiated with 4 sub-sterilizing doses: 30, 60, 90 and 120 Gy. The obtained results indicated the presence of an inverse relationship between the radiation doses and biological aspects of the pest where, the fecundity was decreased from 91.80 ± 56.51 to 20.8 ± 25.37 eggs/female. The mortalities in the larval population are significantly (p ≤ 0.05) increased with increasing doses as compared with the control to be 45.37, 47.37, 66.19, and 74.74% at doses of 30, 60, 90, and 120 Gy respectively, compared to 25.35% in the control group. To evaluate the compatibility and synergistic effects of gamma irradiation and EPNs in the management of Pectinophora gossypiella. Two different strains of EPNs namely Heterorhabditis bacteriophora(HB88) and Steinernema riobrave(Sr) were tested against irradiated and non-irradiated 4th larval instar and pupae of P. gossypiella. There was a positive relationship between the nematode concentrations, exposure time and mortalities of P. gossypiella.The mortality rate was 100% when 2,000 IJs were applied to both H. bacteriophoraand S. riobrave. While, the low concentration (125 IJs/ml) caused 53.3 and 60% mortality after 72 h post-treatment with H. bacteriophoraand S. riobrave,respectively in non-irradiated larvae. So, S. riobraveappeared to be promising in management of cotton bollworm. The combined effect of gamma irradiation with each type of entomopathogenic nematodes induced more remarkable effects on P.gossypiellaas compared to gamma irradiation or each type of entomopathogenic nematodes alone.

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.