GENETIC MANIPULATION OF THE MANILA-CLAM (TAPES-PHILIPPINARUM) USING CYTOCHALASIN-B TO INDUCE TRIPLOIDY

In eight semi-commercial scale trials, in which Manila clam (Tapes phi lippinarum Adams and Reeve) eggs were treated with 0.5 mg cytochalasin B l-1, 70-77% of the embryos produced were triploids. Mean survival t o the D-larva, or straight hinge larva stage, of eggs treated with cyt ochalasin B was 45% (expressed as a % of initial egg numbers) compared to 67% in diploid controls. Subsequent growth and survival of putativ e triploids during hatchery culture were similar to the diploids. When reassessed in 8-15 mm seed, percentage triploidy in most experimental batches ranged from 15 to 80%. In the experimental batches, the relat ive viability of triploids was positively correlated with survival to the D-larva stage. A reliable and inexpensive method of assessing trip loidy in seed by measuring the diameter of nuclei in gill tissue cells is also described.