Sperm Transfer in Normal and Gamma-Irradiated, Laboratory-Reared Mediterranean Fruit Flies (Diptera: Tephritidae)

Abstract

Normal, unirradiated females of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), were mated with normal or gamma-irradiated males. In natural uninterrupted matings, mean durations in copula for normal males and irradiated males were about 120 and 108 min, respectively. Ten to 38% of the females were not inseminated. Eighty to 99% of the sperm were found in spermathecae after 2 h of mating. Few or no sperm were found in the bursa copulatrix, oviducts, or accessory gland. Mean numbers of sperm per female were about 1,780 and 990 for normal and irradiated males, respectively. A power equation was used to relate duration of copula to number of sperm in the spermathecae. Results are discussed with respect to the sterile insect technique and development of quality control parameters. KEY WORDS Insecta, sperm, distribution, Ceratitis capltata THE EFFECTIVENESS of the sterile insect technique is based on the efficiency with which lethal sperm are transferred from sterilized male insects to wild females in the target population (Knipling 1955). Thus, the success or failure of a sterile insect pro-gram depends especially on the quality of the ster-ile insects and their ability to forage and mate competitively with their wild counterparts. In the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), sterilization is achieved by gamma irradiation of pupae 2 d before eclosion. The ir-radiation treatment destroys all or nearly all of the germinal tissues (Anwar et al. 1971, Williamson et al. 1985) so that no new sperm can be produced. As a result, numbers of sperm that can be trans-ferred by sterile males during mating are limited to the irradiated sperm already produced; appar-ently, this is sufficient for five to eight matings (Ohinata et al. 1978). Farias et aI. (1972) developed subjective ratings to estimate the number of sperm transferred to females by timed matings. A small sample of sperm was placed on a microscope slide, sperm were counted, and the density was noted. Samples were rated on a scale of 0 to 3. Results indicated that sperm transfer increased with longer time in cop-ula. Many protocols have been developed to measure the quality of sterile insects from mass rearings in This paper reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a rec-ommendation for its use by USDA.