Survival and growth of induced tetraploid mud loach

Tetraploid mud loach (Misgurnusmizolepis) were produced by heat shock(40.5°C for 3 min, 28 minpost-fertilization) and their survival andgrowth up to 9 months of age were examined. Theincidence of tetraploidy in 1-month-oldsurvivors of the heat shock was 22.6%.Tetraploids had a mean erythrocyte nuclearvolume of 38.8 µm³, modal chromosomenumber of 4n = 96, and average DNA content of5.6 pg/cell, all of which were double those ofdiploid control values. The survival rate oftetraploids was similar to that of diploidcontrols throughout the experiment (from 1 to 9months of age; P > 0.05), but theheat-shocked group had significantly highermortality during early developmental stages(P < 0.05). Growth rates of tetraploidswere significantly depressed until 7 months ofage (P < 0.05), but were not differentfrom diploid controls at ages 8 and 9 months(P > 0.05).