Jack W. Haynes

Sterilization of boll weevil pupae with fractionated doses of gamma irradiation

Fractionated doses of 6,250–8,000 rads of gamma irradiation when administered to pupae of the boll weevil, Anthonomus grandis Boh., sexually sterilized both sexes. Mortality of males thus treated with 6,250 and 8,000 rads via fractionation was 14% and 27% respectively, by 5 days posttreatment compared with 46% mortality when an equivalent acute dose was administered to newly emerged adults. Pheromone production of males irradiated at 6,250 rads was one‐third that of the control for the first 4 days, but equal that of the control during 5–11 days posttreatment. This procedure lends itself to the large‐scale sterilization of weevils needed in an eradication program. This technique is applicable to other insects that are highly susceptible to acute doses.

FRACTIONATED VS ACUTE IRRADIATION: THE EFFECTS OF TREATING ADULT BOLL WEEVILS (COLEOPTERA: CURCULIONIDAE) AT DIFFERENT AGES

When 6–7‐days old mass‐reared ebony boll weevils, Anthonomus grandis Boheman, were given 25 doses of γ‐irradiation totaling 6625 rads, mortality was 14%–15% less 1 week later than when young weevils (1–2 day‐old) were similarly treated. However, giving older weevils an acute dose of 6625 rads did not reduce mortality. Seven‐day‐old weevils receiving the acute treatment mated 10% more than weevils that were 3 days old at the time of treatment. Seven‐day‐old male weevils exposed to the fractionated treatment transferred sperm to 12% more females than 7‐day‐old males exposed to the acute treatment.

Differential enzyme activity in normal and sterile boll weevils

Abstract 1. 1. Whole-body homogenate and hemolymph enzyme profiles of normal and γ-irradiated boll weevils were compared. 2. 2. The specific activity of homogenate lactic dehydrogenase (LDH) in treated males was significantly lower than that in normal males ( 73 ± 3 vs 104 ± 3 mU/mg protein ). 3. 3. The specific activity of homogenate acid phosphatase (AP) in treated females was significantly lower than that observed in normal females ( 89 ± 5 vs 109 ± 5 mU/mg protein ). 4. 4. Hemolymph LDH and AP showed a comparable activity pattern to homogenate LDH and AP activities. 5. 5. The homogenate LDH activity in normal males correlated well with egg production and egg hatching by females after mating with normal males. 6. 6. Low LDH activity corresponded with very low egg production and no egg hatching in irradiated males. 7. 7. LDH and AP may be monitored to assess the sterility of the boll weevil after γ-irradiation.

A quick staining procedure to determine the testicular damage to boll weevils sterilized with busulfan

In eradication programs involving the release of sterilized male insects, the insects must be adequately sterilized. The usual procedure for determining sterility involves crossing presumptively sterile males with untreated virgin females and determining egg hatch and adult emergence. However, with the boll weevil, Anthonomus grandis Boheman, a period of 2--3 weeks is required before sterility can be determined in this way. As we considered the possibility of finding a faster method of evaluating the degree of sterility induced in boll weevils, we noted three facts: Mitlin & Wiygnl (1971) had found that busulfan 3) inhibits D N A synthesis in the boll weevil; Reinecko et al. (1969) determined (by the Feulgen procedure) that busulfan affected gonadal development and spermatogenesis in the weevil; and Mitlin et al. (unpubl.) had observed that incorporation of radiothymidine was reduced significantly in the testes of weevils treated with busulfan, indication of presumptive reduction in D N A synthesis. We, therefore, developed a gross morphological staining procedure to demonstrate testieular damage as a result of sterilization and made a study to determine whether the staining procedure could be correlated with the standard quality control to assess the degree of sterility in treated male boll weevils. Methods. Newly emerged male ebony weevils reared by Gasts method (1966) were sterilized by incorporating 0.1% busulfan in the diet for 6 days (MeHaffey et o2., 1972). Testes from treated weevils and from similar untreated weevils were dissected and fixed in Carnoys fixative (absolute ethanol-chloroform-acetic acid, 6 : 3 : 1 ) for a minimum of 1--1.5 hr. The fixed testes were stained by the Feulgen procedure (Gurr 1958). The staining pattern was examined either soon after staining or after d~hydration and the cleaning of tissue in xylol. Also, each day after the feeding with busulfan began, two groups of 10--15 males were withdrawn: one group was allowed to mate individually with virgin females for 24 hr; the 2nd group was left with females for 7 days. The males were removed and dissected at the appropriate time, and the testes were fixed and stained as described. The stained testes were rated on the basis of staining pattern by independent obsexvers. The females were allowed to oviposit for 7, 14, and 21 days, and egg hatch was scored. An attempt was made to correlate the ratings of the testes with the egg hatch and with sterility in general. Results. Fig. 1 shows the pattern of staining of normal and treated testes. The region surrounding the germarium of a normal untreated testis (Fig. la) is intensely stained and appears as a discrete band in the middle region. This region is constituted of sperrnatocytes in various stages of development (Reinecke et al., 1969). In the treated testis, this region has disintegrated, since the identity of the discrete band is lost (Fig. lb), probably because of the disappearance of the spermatocytes. All areas of treated testes took less stain than untreated testes, an