THE EFFECTS OF ACUTE GAMMA IRRADIATION ON THE BRINE SHRIMP, ARTEMIA. I. LIFE SPANS AND MALE REPRODUCTIVE PERFORMANCE

¹ Genetics Department, North Carolina State University, Raleigh, North Carolina 27607

Life span of both sexes

Freshly matured male and female specimens of Californian Artemia (stock #3) were irradiated with acute doses of 0, 0.1 , 1, 2, 5, 10, 50, or 100 kR gamma radiation and pair-mated to untreated animals. Significant reductions in life span resulted after 50 or 100 kR to either sex. Reductions in female life span approached significance after 10 kR. This moderate radiosensitivity can be explained if cell proliferation in some adult tissues improves the probability of individual survival.

Male reproductive performance

Treated males were completely sterile after doses of 50-100 kR. Males which received doses of 5 or 10 kR had an initial fertility period lasting 12 days, followed by permanent sterility. After a dose of 2 kR, 7 out of a sample of 8 males demonstrated the same initial period of fertility, followed by a period of sterility. Two of the 7 subsequently recovered their fertility. No sterile period occurred after 0.1 or 1 kR. These results are interpreted as indicating spermatogonial stem-cell replenishment of the testicular epithelium in some males after 2 kR and in all males irradiated with 1 kR. It is further hypothesized that all spermatocytes were in some way incapacitated or destroyed following doses above 2 kR.

Hatchability data failed to detect induced dominant lethality in sperm (and perhaps spermatids) after 2 kR. Induced damage resulted in 73% dominant lethal events at 10 kR. No effect on other stages was observed at less than 2 kR.

In the X₁ generation, a dose of 10 kR reduced survival to adulthood, fertility, and adult life span. Similar, but less pronounced effects were obtained after 2 and 5 kR. These data indicate induced genetic damage. No significant alterations were observed in sex ratios.

X₁ sterility appeared to be greater than that observed for irradiated sperm. This point is being reinvestigated, and would be compatible with the reported holokinetic nature of the Artemia chromosome.