Effects of radiation on frequency of chromosomal aberrations and sister chromatid exchange in the benthic worm Neanthes arenaceodentata

Traditional bioassays are unsuitable for assessing sublethal effects of low levels of radioactivity because mortality and phenotypic responses are not anticipated. We compared the usefulness of chromosomal aberration (CA) and sister chromatid exchange (SCE) induction as measures of low-level radiation effects in a sediment-dwelling marine worm, Neanthes arenaceodentata. Newly hatched larvae were exposed to two radiation exposure regimes. Groups of 100 larvae were exposed to either x rays delivered at high dose rates (0.7 Gy min-1) or to 60Co gamma rays delivered at low dose rates (4.8 X 10-5 to 1.2 X 10-1 Gy h-1). After irradiation, the larvae were exposed to 3 X 10-5M bromodeoxyuridine (BrdUrd) for 28 h (x-ray-irradiated larvae) or for 54 h (60Co-irradiated larvae). Slides of larval cells were prepared for observation of CAs and SCEs. Frequencies of CAs were determined in first division cells; frequencies of SCEs were determined in second division cells. Results from x-ray irradiation indicated that dose-related increases occur in chromosome and chromatid deletions, but an x-ray dose greater than or equal to 2 Gy was required to observe a significant increase. Worm larvae receiving 60Co irradiation showed elevated SCE frequencies; a significant increase in SCE frequency was observed at 0.6 Gy. 49 references, 2 figures