Cytological Attributes of Sperm Bundles Unique to F1 Progeny of Irradiated Male Lepidoptera: Relevance to Sterile Insect Technique Programs

Abstract

The unique genetic phenomena responsible for inherited F1 sterility in Lepidoptera and some other arthropods provide advantages for the use of inherited sterility in a sterile insect technique (SIT) program. Lepidopteran females generally can be completely sterilized at a dose of radiation that only partially sterilizes males of the same species. When these partially sterile males mate with fertile females, many of the radiation-induced deleterious effects are inherited by the F1 generation. At the appropriate dose of radiation, egg hatch of females mated with irradiated males is reduced and the resulting (F1) offspring are both highly sterile and predominantly male. Lower doses of radiation used to induce F1 sterility increase the quality and competitiveness of the released insects. However, during a SIT program it is possible that traps used to monitor wild moth populations and over-flooding ratios (marked released males vs unmarked wild males) may capture unmarked F1 sterile males that cannot be distinguished from wild fertile males. In this study we developed a cytological technique with orcein and Giemsa stains to distinguish adult F1 progeny of irradiated males and fertile males. Our observations on 6 pest species in 5 families of Lepidoptera indicate that F1 males (sterile) from irradiated fathers can be distinguished from fertile males by the nuclei cluster in the eupyrene sperm bundles. The nuclei cluster in the fertile males exhibited a regular and organized arrangement of the sperm and was homogeneously stained, whereas in F1 males the nuclei cluster of sperm was disorganized, irregular and unevenly stained.

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