Induction of Dominant Lethal Mutations in Insect Oocytes and Sperm by Gamma Rays and an Alkylating Agent: Dose-Response and Joint Action Studies

Abstract

is generally recognized that certain types of chemicals cause biological effects I z o s e l y resembling those produced by radiation. Among these effects are the production of mutations, chromosome aberrations, and induction of sterility and cancer in animals. Our interest has been mainly to determine the effect of gamma radiation and alkylating agents upon growth and maturation of insect reproductive cells and the production of sterility by inducing dominant lethal mutations in these cells. In undertaking the studies reported herein we had several immediate objectives: ( 1 ) To determine dose-response curves for induction of dominant lethal mutations by either radiation or tretamine (2,4,6-tris (I-aziridinyl) -striazine) in meiotic oocytes and mature sperm for comparison of slopes, reaction kinetics and median lethal doses; (2) to compare response of different cell stages to either mutagen; and (3) to derive preliminary information from dose-response curves for later tests to determine potentiation of one agent by the other. No published study has come to our attention in which an inquiry was made into the combined action of a chemical mutagen and radiation in the induction of dominant lethal mutations. MATERIALS A N D METHODSAdult male and female screw-worm flies, Cochliomyia hominiuorax (Coquerel) (Diptera: Calliphoridae), were used in these experiments. The female reproductive system contains two ovaries, each consisting of 100 to 150 ovarioles in which egg development occurs synchronously. By treating one female, hundreds of oocytes, all in the same stage of development, are simultanzously exposed to the treatment. Gravid females deposit 200 to 250 eggs in a sagle mass.Three-day-old females reared at 80°F contain oocytes with the nucleus in early prophase of the first meiotic division, 4-day-old females contain almost fully mature eggs with the nucleus in metaphas2 I, and 5-day-old females contain a large number of fully mature eggs in which meiosis has progressed up to early anaphase I (LACHANCE and LEVERICH 1962). Further growth and changes in the egg and its nucleus are arrested in this stage until the egg is laid. Thus, the induction of dominant lethal mutations in meiotic oocytes can be detected by treating virgin females, mating them to untreated males, and scoring the hatchability of the eggs produced. Similarly, dominant lethal mutations in mature sperm are detected by treating 1-day-old males and allowing a single mating between treated males and normal females. Present address. Metabolism and Radiation Research Laboratory, State Cnirersity Station, Fargo, North Dakuta i8103.

Faunistic Study on Species Composition of Mosquitoes and Sand Flies around Mrima Hill a High Radiation Area in Kwale County, Kenya

“…It was observed the dengue virus mosquito Aedes aegypti [8] when exposed to gamma radiation, there is a significant reduction in fecundity, hatchability, adult emergence, sex ratio and longevity [9]. Ionizing radiation has also been shown to induce lethal mutations in insect life cycles [10]. In their natural habitats with high radiation such as Mrima Hill, no report on its effect on insect fauna has been reported.…”