EFFECTS OF CHRONIC IRRADIATION ON THE REPRODUCTIVE SUCCESS OF THE POLYCHAETE WORM, NEANTHES ARENACEODENTATA

Effects of lifetime exposure to chronic irradiation on reproductive su ccess were assessed for laboratory populations of Neanthes arenaceoden tata. Exposure was initiated upon the spawning of the parental (P-1) f emale and was terminated upon spawning of the first filial (F-1) gener ation female; broods from the F-1 pairs were sacrificed before hatchin g occurred. Groups of worms in the experiments received either no radi ation (controls) or 0.19, 2.1 or 17 mGy h(-1). The total dose received was either background or approximately 0.55, 6.5 or 54 Gy, respective ly. The mean number of embryos in the broods from the F-1 females expo sed to 17 mGy h(-1) was statistically significantly different from the mean number of embryos from control females; however, the mean number of embryos in the broods from the F-1 females exposed to 0.19 and 2.1 mGy h(-1) was not significantly different from the mean number from c ontrol females. For all the radiation-exposed groups, there was a stat istically significant reduction in the number and percentage of live e mbryos in the broods from the F-1 pairs as well as a statistically sig nificant increase in the numbers and percentages of abnormal embryos. Results on embryo abnormalities and mortalities indicate that dominant - and recessive-lethal mutations were most likely induced in the germ cells and that these mutations had an adverse effect on reproductive s uccess by affecting the survival of early-life stages. Except for pair s exposed to 17 mGy h(-1), there was no evidence of gamete killing or reduced fertilization success, because the number of developing embryo s in the broods did not decrease with increased dose. Data for the est imated hatch number and actual hatch number indicated that doses as lo w as 0.19 mGy h(-1) can reduce significantly the number of larvae that hatch when lifetime doses are given.