EARLY DETECTION OF TRIPLOIDY IN THE LARVAE OF PACIFIC OYSTERS, CRASSOSTREA-GIGAS, BY FLOW-CYTOMETRY

Triploidy may provide a means to neuter the Pacific oyster, C. gigas, genetically thereby increasing survival and marketability during periods of reproduction. Pressure treatments administered 10 min after fertilization for 10 min duration at 6000-8000 psi consistently produced triploids. The highest proportion obtained was 57%. Triploidy was assayed in all experiments at the larval stage and again as spat (metamorphosed larvae) using flow cytometery. A technique to assay larvae as small as 250 .mu.m is described. Results obtained by flow cytometry were verified by chromosome counts. Analysis of triploidy at the larval stage provides reliable estimates of the proportion of triploids, eliminating several weeks of culture time.