Survival and growth of induced tetraploid mud loach

Tetraploid mud loach (Misgurnus mizolepis) were produced by heat shock (40.5 degreesC for 3 min, 28 min post-fertilization) and their survival and growth up to 9 months of age were examined. The incidence of tetraploidy in 1-month-old survivors of the heat shock was 22.6%. Tetraploids had a mean erythrocyte nuclear volume of 38.8 mum(3), modal chromosome number of 4n = 96, and average DNA content of 5.6 pg/cell, all of which were double those of diploid control values. The survival rate of tetraploids was similar to that of diploid controls throughout the experiment (from 1 to 9 months of age; P > 0.05), but the heat-shocked group had significantly higher mortality during early developmental stages (P < 0.05). Growth rates of tetraploids were significantly depressed until 7 months of age (P < 0.05), but were not different from diploid controls at ages 8 and 9 months (P > 0.05).