PROBLEMS ASSOCIATED WITH TETRAPLOID INDUCTION AND SURVIVAL IN GRASS CARP, CTENOPHARYNGODON-IDELLA

Heat and hydrostatic pressure shocks were used to induce tetraploidy in fertilized eggs of grass carp. Estimates of percent tetraploidy at 1 day post-hatch ranged from 25 to 100 (average 62.5) for pressure treatments of 9000 and 10 000 psi, initiated 36, 39 and 42 min after fertilization at 21°C. These optimal treatment times were generally 16-20 min before cleavage and suggested karyokinesis inhibition. Tetraploidy was also induced in multiple-cell zygotes pressure shocked (9000 and 10 000 psi) at 65, 66 and 70 min after fertilization. Heat shocks of 42°C for 1.25 and 1.5 min induced tetraploidy ranging from 0 to 100% over a broad range of treatment times (33-60 min after fertilization). A series of parallel 1-min heat shock treatments failed to produce tetraploids. Overall, percent hatch was quite variable, but was directly related to tetraploid conversion for most treatments. No tetraploid larvae survived longer than 50 days of age. The occurrence of aneuploids (hypotetraploids) and 2N-4N mosaics was considered at least partly responsible for the mortality. © 1990.