A micronucleus assay in sea urchin embryos

We have developed a micronucleus assay for use in sea urchin embryos. The e mbryos at the early blastula stage (about 256 cells) were exposed to genoto xic chemicals overnight until control embryos have reached the gastrula sta ge. Then all embryos were suspended in 1 M urea, dissociated by pipetting, and fixed with methanol:acetic acid (9:1). The preparations were air-dried and stained with acridine orange. The test chemicals (mitomycin C [MMC], vi nblastine and 1-beta-D-arabinofuranosylcytosine [Ara C]) induced clear micr onuclei dose-dependently, The maximum frequency induced with MMC was 2-3% i n Clypeaster japonicus and 1-2% in Hemicentrotus pulcherrimus. (C) 1999 Pub lished by Elsevier Science B.V. All rights reserved.