SUPPRESSION OF 1ST CLEAVAGE IN THE NILE TILAPIA, OREOCHROMIS-NILOTICUS L - A COMPARISON OF THE RELATIVE EFFECTIVENESS OF PRESSURE AND HEAT SHOCKS

Evidence is presented for the successful suppression of first cleavage in Oreochromis niloticus L. and thereby the production of mitotic gyn ogens. The optimal parameters for UV irradiation of milt were 300-310 muW cm-2 for 2 min at 4-degrees-C. The optimal pressure shock paramete rs were 630 kg cm-2 (9000 psi) for 2 min at 28-degrees-C at 40-50 min after fertilization (AF) and those for heat shock were 41-degrees-C fo r 3.5 min at 27.5-30 min AF. Isozyme analysis of survivors at two loci , ADA and EST-2*, confirmed homozygosity and lack of paternal inherit ance.