Fecundity,fertility and reproductive recovery of irradiated Queensland fruit fly Bactrocera tryoni

Pupae of the Queensland fruit fly or Q‐fly Bactrocera tryoni (Froggatt) are irradiated routinely to induce reproductive sterility in adults for use in sterile insect technique programmes. Previous studies suggest that adult sexual performance and survival under nutritional and crowding stress are compromised by the current target dose of radiation for sterilization (70–75 Gy), and that improved mating propensity and survival under stress by irradiated males may be achieved by reducing the target sterilization dose without reducing the level of induced sterility. This raises the question of the amount by which the irradiation dose can be reduced before residual fertility becomes unacceptable. The present study measures the levels of residual fertility in male and female irradiated Q‐flies at different irradiation doses (20, 30, 40, 50, 60 and 70 Gy), and investigates the possibility that fecundity and fertility increase between 10–15 and 30–35 days post emergence. Male flies require a higher dose than females to induce sterility, with no residual fertility found in females irradiated at doses of 50 Gy or above, and no residual fertility found in males irradiated at doses of 60 Gy or above. Irradiated females are more fecund at 30–35 days post emergence than at 10–15 days. However, fertility does not increase between 10 and 15 days post emergence and 30–35 days, even at doses below 50 Gy. The present study shows that there is scope to reduce the target sterilization dose for Q‐flies below that of the current dose range (70–75 Gy) at the same time as retaining an adequate safety margin above radiation doses at which residual fertility can be expected.     

Irradiation of Anastrepha ludens (Diptera: Tephritidae) revisited: optimizing sterility induction

Irradiation doses currently applied to sterilize Mexican fruit flies, Anastrepha ludens (Loew) (Diptera: Tephritidae), for release under the sterile insect technique eradication campaign in Mexico, were reviewed in an effort to increase sterile male performance in the field. A dose maximizing sterility induction into wild populations was sought by balancing somatic fitness with genetic sterility. Doses of 40, 60, and 80 Gy induced 95% or more sterility in all males, which in turn induced similar degrees of sterility into a cohort of wild flies in the laboratory. However, a low dose of 40 Gy was sufficient to completely suppress egg production in females. Similarly, a mild carryover of genetic damage might have been transferred to the F1 progeny of males irradiated at 40 Gy crossed with fertile wild females. Our results suggest that the 80-Gy dose currently applied in Mexico can be lowered substantially without jeopardizing program goals. This view could be strengthened by comparing performance of males irradiated at different doses under more natural settings. In general, we discuss the value of determining irradiation doses for pest species where females are more radiosensitive than males, by selecting the dose that causes 100% sterility in females.     

Mass rearing history negatively affects mating success of male Anastrepha ludens (Diptera: Tephritidae) reared for sterile insect technique programs

Mating competitiveness and sterility induction into cohorts of wild Anastrepha ludens (Loew) (Diptera: Tephritidae) was compared among wild and laboratory flies reared for use in the sterile insect technique Mexican program. Laboratory flies stemming from an 11-yr-old bisexual strain were either not irradiated, irradiated at 3 krad (low dose), or irradiated at 8 krad. In 30 by 30 by 30-cm Plexiglas cages, where a cohort of laboratory flies (male and female) irradiated at different doses (0, 3, and 8 krad) was introduced with a cohort of wild flies, males and females of each type mated randomly among themselves. Compared with nonirradiated laboratory and wild males, irradiated males, irrespective of dose (3 or 8 krad), induced shorter refractory periods and greater mating frequency in wild females. Nevertheless, laboratory flies irradiated at a low dose induced greater sterility into cohorts of wild flies than laboratory flies irradiated at a high dose. In a 3 by 3 by 3-m walk-in cage, wild males gained significantly more matings with wild females than nonirradiated and irradiated laboratory males a finding that revealed a strong effect of strain on mating performance. Mating incompatibility of the laboratory strain might have obscured the effect of reduced irradiation doses on male mating performance in the walk-in cage. Our results highlight an urgent need to replace the A. ludens strain currently used by the Mexican fruit fly eradication campaign and at least suggest that reducing irradiation doses result in an increase in sterility induction in wild populations.     

Evaluation of partial sterility in mating performance and reproduction of the West Indian sweetpotato weevil,Euscepes postfasciatus

The sterile insect technique (SIT) is based on population and behavioral ecology and is widely used to suppress or eradicate target pest insect populations. The effectiveness of SIT depends on the ability of the released sterile males to mate with and inseminate wild females. The use of gamma‐radiation to induce sterility is, however, associated with negative impacts not only on reproductive cells but also on somatic cells. Consequently, irradiation for sterilization diminishes mating performance over time. In this study, we evaluated the balance between the irradiation dose and both fertility and mating propensity in Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae) for 22 days following irradiation. The mating propensity of males irradiated with a 150‐Gy dose, as currently used to induce complete sterility of E. postfasciatus in the SIT program in Okinawa Prefecture, was equal to that of non‐irradiated weevils for up to 6 days, and the mating propensity of males irradiated with a dose of 125 Gy was equal to that of non‐irradiated weevils for twice this period (12 days). The fertilization ability of weevils irradiated with a dose of 125 Gy was reduced by 4.6% in males and 0.6% in females, compared to the potential fertilization ability. We also discuss the possibility of the application of partially sterilized insects in eradication programs.     

Protein consumption by mated, unmated, sterile and fertile adults of the Queensland fruit fly, Bactrocera tryoni and its relation to egg production

Abstract. Female adults of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) at 25 °C require more than 0.1 mg of yeast autolysate per day to mature their oocytes to the vitellogenic stage and mate. Those given 0.2 mg per day from day 2 of adult life mated (when given the opportunity between 11 and 13 days) and each laid approximately 100 eggs (just over one egg per ovariole) by day 56. Females allowed to feed ad libitum from day 2, then 0 or 0.2 mg per day from day 14, laid approximately 75 and 100 eggs, respectively (after mating), whereas those fed ad libitum from day 2 to day 56 laid approximately 540 eggs after mating (averaging just over six eggs per ovariole). The developmental pattern of intake of normal females when on an ad libitum diet showed a rise to a peak at 5–7 days, followed by a decline to sustained low levels if not mated, but rising to a lower peak if mated between days 11–13 followed by a steady decline. Female flies that had been sterilized by 80 Gy gamma irradiation at the puparial stage had a pattern of food consumption similar to that of normal females mated at 7 days but they produced no yolky oocytes and had a darkened fat body. Normal and irradiated males had a feeding pattern similar to that of unmated nonirradiated females but at a lower level. The results are discussed in terms of the control of protein intake and the rate of its conversion to yolk.     

Irradiation of adult Epiphyas postvittana (Lepidoptera: Tortricidae): egg sterility in parental and F1 generations

Adult Epiphyas postvittana Walker were irradiated using a Cobalt 60 source to determine the dose needed to achieve complete egg sterility of mated female moths, and egg sterility of female moths mated to F1 generation males. Adult male and female E. postvittana were irradiated at 100, 200, 250, and 300 Gy and their fertility (when crossed with normal moths) was compared with nonirradiated moths. Viable progeny (determined by egg hatch) were found at doses of 100 and 200 Gy, but very little at 250 and 300 Gy. In particular, there was no survival of female progeny into the F1 generation. Males irradiated at 250 and 300 Gy had very low egg eclosion rates (2.25 and 1.86% at 250 and 300 Gy, respectively) when mated with normal females. The F2 generation from those male progeny had a mean percent hatched of < 1.02%. Based on our results, a dose of 250-300 Gy is recommended for irradiation of E. postvittana adults used for sterile insect technique (SIT) if sterility of parental moths is the desired outcome. Our data also suggests that inclusion of F1 hybrid sterility rather than parental generation sterility into programs using the SIT may allow for doses lower than what we have reported, especially during initial phases of an eradication program where increase fitness of moths might be desirable. Further research is needed to verify the use of F1 hybrid sterility in light brown apple moth SIT programs.     

Radiation biology and inherited sterility in false codling moth (Lepidoptera: Tortricidae)

False codling moth, Cryptophlebia leucotreta (Meyrick), male and female mature pupae and newly emerged adults were treated with increasing doses of gamma radiation and either inbred or out-crossed with fertile counterparts. For newly emerged adults, there was no significant relationship between dose of radiation and insect fecundity when untreated females were mated to treated males (N female by T male). However, fecundity of treated females mated to either untreated (T female by N male) or treated males (T female by T male) declined as the dose of radiation increased. A similar trend was observed when mature pupae were treated. The dose at which 100% sterility was achieved in treated females mated to untreated males (T female by N male) for both adults and pupae was 200 Gy. In contrast, newly emerged adult males treated with 350 Gy still had a residual fertility of 5.2% when mated to untreated females, and newly emerged adult males that were treated as pupae had a residual fertility of 3.3%. Inherited effects resulting from irradiation of parental (P1) males with selected doses of radiation were recorded for the F1 generation. Decreased F1 fecundity and fertility, increased F1 mortality during development, and a significant shift in the F1 sex ratio in favor of males was observed when increasing doses of radiation were applied to the P1 males.     

Prolongation of the effective copulation period by fractionated‐dose irradiation in the sweet potato weevil,Cylas formicarius

The sterile insect technique (SIT), based on the principles of population and behavioral ecology, is widely used to suppress or eradicate target pest insect populations. The effectiveness of SIT depends on the ability of released sterile males to mate with and inseminate wild females; however, the use of gamma radiation to induce sterility negatively affects both somatic cells as well as reproductive cells. Consequently, sterilization by irradiation drastically diminishes mating performance over time. It is well known that fractionated‐dose irradiation, in which a sterilizing dose is delivered via a series of smaller irradiations, reduces radiation damage. In the present study, we evaluated the effect of fractionated‐dose irradiation on fertility, longevity, and mating propensity in Cylas formicarius (Summers) (Coleoptera: Brentidae) for 16 days after irradiation. Fractionated‐dose irradiation with 200 Gy induced full sterility regardless of the number of radiation doses. Although the mating propensity of males sterilized by a single 200 Gy dose (the current standard of the Okinawa Prefecture SIT program) was equal to that of non‐irradiated weevils for the first 6 days, the mating propensity of males sterilized by a series of three doses was maintained for at least the first 12 days. These results demonstrated that fractionated‐dose irradiation can be highly advantageous in C. formicarius eradication programs.     

Behavioural switch of female Mediterranean fruit fly, Ceratitis capitata: mating and oviposition activity in outdoor field cages in Hawaii

1 Laboratory-reared normal, and wild female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), were assayed in outdoor field cages to assess the impact of a mating-induced behavioural switch on mating and subsequent oviposition activity. 2 Virgin females preferred interactions with males leading to mating over attraction to, and oviposition in, artificial yellow spheres containing guava odour or green apples hung in a guava tree. Laboratory-reared females previously mated with either laboratory-reared normal males or laboratory-reared irradiated (sterile) males showed little interest in remating with males and instead, were much more likely to be found arrested on artificial and real fruit and ovipositing. Oviposition on artificial fruit was five times greater by females that had mated with either normal or irradiated males than by virgin females. Wild females showed similar qualitative changes in the mating-induced behavioural switch; however, oviposition activity was significantly less than for laboratory-reared females. 3 These results confirm that mating has a profound effect on the behaviour of female Mediterranean fruit flies and that irradiated males are functionally equal with normal males (lab-reared or wild) in their ability to alter female behaviour. These results are discussed in the context of the sterile insect technique for control of Mediterranean fruit flies in the field.     

Effects of gamma radiation on spermatophore production and reception and subsequent fecundity and egg viability inAcarus siro L. (Acari: Acaridae)

Gamma radiation at doses higher than 10 krad significantly lowered the fecundity of the grain mite,Acarus siro. The fecundity of irradiated females was inversely correlated with dose, both when control or irradiated males were used in the pairing.Irradiation with ionizing radiation affected sexual activity of males. At doses above 10 krad the number of formed or observed spermatophores was lowered significantly.Sexual attractiveness of irradiated and control females to irradiated males was similar. However, non-irradiated males were observed mating more often with non-irradiated than with irradiated females.No correlation was found between the numbers of spermatophores present in the spermathecae of the female and the fecundity of the female. Irradiation had a greater effect on fecundity of the female than on sexual activity of the male; it did not affect the shape or behavior of spermatophores in the spermathecae of the female.Viability of eggs laid by females decreased by at least 50% when females or males were irradiated with doses above 20 krad. Irradiation also affected the survival of adults, but females were more sensitive than males. Net sterility index indicates that doses higher than 20 krad induce more than 90% sterility.     

Precocious Mexican fruit fly methoprene‐fed males inhibit female receptivity and perform sexually as mature males

The sterile insect technique (SIT) has been used successfully for the control of fruit flies. The efficiency of this technique can be significantly reduced when sterile released insects are exposed to adverse conditions and predators, as a great number of sterile insects die before reaching sexual maturity and thus fail to mate with wild females. Treatments with juvenile hormone (JH) analogues such as methoprene (M) significantly reduce the time to reach sexual maturity by sterile Anastrepha ludens (Loew) (Diptera: Tephritidae) males. In this study, we compared the sexual performance of non‐treated sexually mature males with young males that had been sexually accelerated with M. Furthermore, we compared the ability of M‐fed males in inhibiting female remating compared with sexually mature males. Results showed that at 5 days M‐fed males had lower mating success than mature males; however, 6‐day‐old (0.1%) M‐fed males had the same amount of matings as mature 13‐day‐old males. Young 5‐ to 10‐day‐old M‐fed males also had similar number of matings as mature non‐treated 12‐ to 17‐day‐old males. There were no differences in copula duration between treatments. Moreover, there were no differences between the fertility, fecundity or refractory period of females mated with either young male fed M or normal sexually mature males. These results indicated that young males that were sexually accelerated with M have the same sexual performance as non‐treated sexually mature males. Implications of using M as a pre‐release treatment for A. ludens controlled through SIT are discussed.     

Effects of delayed mating and male mating history on the reproductive potential of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

Abstract 1 Despite the importance of Leucoptera coffeella (Guérin‐Mèneville) in coffee production worldwide, there is a lack of information on its reproduction. This knowledge will help in mass rearing, and support the development of behavioural control techniques for this insect. The present study determined the effects of delayed mating and previous matings of male L. coffeella on fecundity, egg viability and frequency of female remating. 2 The highest levels of fecundity and egg viability were obtained from matings of 1–3‐day‐old females. When females mated at 5 days of age, there were reductions of 40% in oviposition and of 43% in egg viability. 3 Females mated with 2‐day‐old virgin males were more fecund than those mated with older males; egg viability was also low (18%) from females mated with older males. 4 Virgin females that mated with virgin males laid a greater number of eggs than those mated with previously copulated males. Egg viability decreased with the increase in the number of previous male matings. 5 Five‐day‐old females remated in greater proportion than 2–3‐day‐old females. Females that copulated with males that had previously mated three times had higher rates of remating than those that copulated with virgin males. 6 The results obtained indicate that 1–3 days after emergence is the optimum age for mating. The implications of these findings for the control of L. coffeella by synthetic sex pheromone are discussed.     

Effects of gamma irradiation on the life stages of yellow flower thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae)

Irradiation at a minimum absorbed dose of 250 Grays (Gy) has been approved by the USDA as a quarantine treatment for certain fruits in Hawaii to control four species of tephritid fruit flies. Subsequent research must determine whether this dose is sufficient to control other quarantine pests, such as mealybugs, thrips, mites, beetles, moths, and scale insects, on other commodities with export potential that are approved for irradiation treatment for fruit flies. This study demonstrated that irradiation at 250 Gy caused non‐emergence of eggs and pupae, failure of larval development, and sterility of adults of yellow flower thrips, Frankliniella schultzei (Trybom). Adults were the most resistant stage tested, with 100% mortality at 57, 36 and 30 days post‐treatment for the 250, 350 and 400 Gy treatments, respectively. Untreated adults survived up to 66 days. After receiving an irradiation dose of 250 Gy, no one‐ to two‐day old eggs hatched successfully, while 3–4‐day old eggs hatched but did not develop beyond the larval stage. Of the controls, 96.0% of 1–2‐day old eggs and 75.9% of the 3–4‐day old eggs hatched and survived through pupation. No first or second instar larvae treated with a target dose of 250 Gy were able to pupate. When pupae were irradiated at 250 Gy, 37% emerged as adults and all were sterile compared to 88.3% emergence of controls.     

Irradiation of Anastrepha obliqua (Diptera: Tephritidae) revisited: optimizing sterility induction

The effects of irradiation doses increasing from 0 to 100 Gy (1 Gy is energy absorbed in J kg(-1) of irradiated material) on fertility, flight ability, survival, and sterile male mating performance were evaluated for mass-reared Anastrepha obliqua (Macquart). High sterility values (> 98.2%) for irradiated males were obtained for doses as low as 25 Gy. Egg hatch was inhibited for irradiated males crossed with irradiated females at a low dose of 20 Gy. However, we estimated that to achieve 99.9% sterility (standard goal of many sterile insect technique programs), irradiation doses had to be increased to a dose between 50 and 75 Gy. At doses of 25 Gy and greater, we observed a decreasing trend in adult flight ability and an increasing trend in adult mortality. Such differences were greater for pupae irradiated at a young age compared those irradiated 24 h before emergence. Our single most relevant finding was that sterility induction (i.e., oviposition of nonfertilized eggs) was two times greater for males irradiated at low doses (40 Gy) than for males irradiated at high doses (80 Gy) when used at a 3:1:1 sterilized male to fertile male to fertile female ratio. Males irradiated at high doses may have been outcompeted by unirradiated males when courting unirradiated females. Implications of our findings for sterile insect technique programs are discussed.     

Effects of gamma radiation on the reproduction biology and mating competitiveness of citrus leafminer Phyllocnistis citrella Stainton

The citrus leafminer (CLM), Phyllocnistis citrella Stainton, is one of the most serious pests of Iran's citrus nursery stocks. In this study, the effects of gamma radiation at doses of 100–450?Gy on the biological and reproductive parameters of P. citrella were determined. The results showed that the mean percentage of pupal mortality increases with a rise in the dose. Also, the mean values of this parameter were higher for irradiated females, indicating higher sensitivity. The mean fertility of the irradiated females mated with normal males was affected drastically and reached zero at 300?Gy. The hatchability of the eggs laid by normal females mated with irradiated males dropped to 2% at the highest irradiation dose of 450?Gy. The results of this test showed that females have a higher radio-sensitivity than males. The competitiveness values fluctuated from 0.2 to 0.6 at doses higher than 200?Gy. The results showed that the male CLMs irradiated with sterilizing doses could compete suitably with the untreated males in laboratory conditions.     

Effects of radiation on the fertility of the Ethiopian fruit fly,Dacus ciliatus

The Ethiopian fruit fly, Dacus ciliatus (Loew) (Diptera: Tephritidae), is a significant pest of cucurbit crops in Asia and Africa and is currently controlled with insecticides. The sterilizing effect of gamma radiation on D. ciliatus adults was investigated to assess the suitability of sterile insect technique (SIT) for use as an alternative, non‐chemical strategy for the control of this pest. Late pupae (48 h before emergence) were irradiated with 60, 80, 100, 120, and 140 Gy of gamma rays emitted by a ⁶⁰Co source. Following emergence, the biological characteristics of the experimental cohorts (including all possible male‐female combinations of irradiated and untreated flies) were recorded. No significant negative effects of irradiation on pupal eclosion or the ability of newly emerged flies to fly were observed. Samples of eggs at reproductive fly‐ages (12‐, 15‐, and 17‐day‐old pairs) were collected and their hatch rates were assessed. At 60 Gy, females were completely sterilized, whereas complete sterilization of the males was observed only at 140 Gy (a small amount of fertility persisted even at 120 Gy). In addition to the above experiments, three fruit infestation trials were conducted with zucchini [Cucurbita pepo L. (Cucurbitaceae)] as the plant host and the pupae produced in those trials were collected and recorded. We observed significant (ca. 10%) infestation following treatment with up to 120 Gy and zero progeny only at 140 Gy, mirroring the egg‐hatch results. Our findings support the feasibility of SIT for the control of D. ciliatus.     

Is lack of mating competitiveness in spring linked to mating asynchrony between wild and mass‐reared codling moths from an operational sterile insect programme?

Mating competitiveness and pheromone trap catches of mass‐reared, male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), from the Osoyoos, British Columbia, Canada, mass‐rearing facility operated by the Okanagan‐Kootenay Sterile Insect Release Board, were compared to wild males using mark–release–recapture field experiments in spring, summer, and autumn at Summerland, British Columbia. In spring, significantly more wild diapause males mated with tethered, wild females than did non‐irradiated (0 Gy) or irradiated (100 or 250 Gy) non‐diapause, mass‐reared males. A lower dose of radiation did not improve mating competitiveness, nor catches of mass‐reared males released in spring. Median mating time for wild males was approximately 45 min earlier than mass‐reared males with most wild males (70.5%) mating before sunset and mass‐reared males mating at or shortly after sunset in spring. Superior mating competitiveness of wild males in spring was mirrored by greater recapture rates in pheromone‐baited traps. In summer, mating competitiveness of mass‐reared moths improved relative to wild males and there was a significant inverse relationship between radiation dose (0, 100, and 250 Gy) and competitiveness of mass‐reared males. In autumn, untreated, wild males were significantly more responsive to pheromone traps than non‐diapausing mass‐reared males receiving 250 Gy of radiation. Mass‐reared males, subjected to diapause‐inducing conditions as larvae and emerged from diapause before this irradiation treatment, were recaptured significantly more often than similarly irradiated, non‐diapause, mass‐reared males, but not more than untreated, diapause wild males. We hypothesize that differences between wild and mass‐reared males in daily timing or speed of responses to natural or synthetic pheromone sources under montane weather patterns typical of spring in British Columbia may partially explain poor activity of sterile males, and low sterile : wild overflooding ratios during spring when measured using pheromone traps by the sterile insect release programme in British Columbia.     

Studies on mutagen-sensitive strains of Drosophila melanogaster. II. Detection of qualitative differences between genetic damage induced by X-irradiation of mature spermatozoa in oxygenated and anoxic atmospheres through the use of the repair-deficient mutant mei-9a

Muller-5 males were irradiated with X-rays in nitrogen, in air or in oxygen (followed by nitrogen or oxygen post-treatments in the nitrogen and oxygen series) and were mated to females of a repair-proficient strain (mei+) or to those of a strain known to be deficient in excision repair of UV damage (in somatic cells). The latter strain, designated as mei-9a, is also known to be sensitive, in the larval stages, to the killing effects of UV, X-rays and to a number of chemical mutagens. The frequencies of sex-linked recessive lethals and autosomal translocations induced in the spermatozoa of males were determined and compared. The frequencies of sex-linked recessive lethals in the mei-9 control groups were consistently higher than in the mei+ groups. Irradiation in air or in nitrogen led to significantly higher yields of recessive lethals when the irradiated males were mated to mei-9 females, whereas, after irradiation in oxygen, the yields were similar with both kinds of female. No significant differences in the frequencies of reciprocal translocations were observed between the mei+ and mei-9 groups after irradiation of the males in nitrogen, in air or in oxygen. Likewise, no differential effects of the contrasting post-treatments (nitrogen versus oxygen), either for recessive lethals or for translocations, could be discerned. These results are considered to support the notion that the kinds of genetic damage induced in mature spermatozoa in air or in nitrogen are qualitatively similar (at least with respect to the component(s) that lead to the production of recessive lethal mutations), but clearly different when induced in an oxygen atmosphere. The enhanced yields of recessive lethals with mei-9 females (after irradiation of the males either in air or in nitrogen) has been interpreted on the assumption that the mei-9 mutant is also deficient for the repair of X-ray-induced, recessive lethal-generating premutational lesions. Possible reasons for the lack of differences between the mei+ and mei-9 groups with respect to translocation yields and for the absence of measurable differences in response between the contrasting post-treatments (after irradiation of the males in nitrogen) are discussed.     

Radiation biology and inherited sterility of light brown apple moth (Lepidoptera: Tortricidae): developing a sterile insect release program

The radiation biology of two geographically isolated populations of the light brown apple moth [Epiphyas postvittana (Walker)] was studied in Australia and New Zealand as an initiation of a SIT/F1 sterility program. Pharate and < or = 2 d pre-emergence pupae were exposed to increasing radiation doses up to a maximum dose of 300 Gy. Fertility and other life history parameters were measured in emerging adults (parental) and their progeny (F1-F3 adults). Parental fecundity was significantly affected by increasing irradiation dose in pharate pupae only. For both populations, parental egg fertility declined with increasing radiation. This was most pronounced for the irradiated parental females whose fertility declined at a higher rate than of irradiated males. At 250 Gy, females < or = 2 d preemergence pupae produced few larvae and no adults at F1. No larvae hatched from 250 Gy-irradiated female pharate pupae. At 300 Gy, males still had residual fertility of 2-5.5%, with pharate pupae being the more radio-sensitive. Radiation-induced deleterious inherited effects in offspring from irradiated males were expressed as increased developmental time in F1 larvae, a reduction in percent F1 female survival, decreased adult emergence and increased cumulative mortality over subsequent generations. Males irradiated at > or = 150 Gy produced few but highly sterile offspring at F1 and mortality was > 99% by F2 egg.     

Does exposure of male Drosophila melanogaster to acute gamma radiation influence egg to adult development time and longevity of F1–F3 offspring?

Two‐ to three‐day‐old male Drosophila melanogaster flies were irradiated with 1, 2, 4, 6, 8, 10, 20, 25, 30, 40 and 50 Gy doses of gamma radiation. The longevity and rate of development were observed for three successive generations to assess the impact of irradiation. The mean lifespan of irradiated flies was significantly increased at 1, 2 and 8 Gy, while it was vice versa for high doses at 30, 40 and 50 Gy. Paternal irradiation had an impact on F₁ generation, with significantly increased mean longevity at 2 (female), 4, 6, 8 and 10 and decreased mean longevity at 40 and 50 Gy (male and female). Significant increase in the longevity was observed in the F₂ generation of the 8 (male and female) and 10 Gy (male) irradiated groups, while decreased longevity was observed in F₂ female progeny at 40 Gy. In the case of F₃ progeny of irradiated flies, longevity did not show significant difference with the control. Paternal exposure to radiation had a significant impact on the mean egg to adult developmental time of the F₁ generation; it was shortened at 2 Gy and extended at 25, 30, 40 and 50 Gy compared to the control. Mean development time at 30, 40 and 50 Gy was significantly increased in the F₂ generation, while there were no significant changes in the F₃ generation. The present study concludes that the effect of acute gamma irradiation on longevity and “egg to adult” development time of D. melanogaster may persist to following generations.