GENETIC-VARIATION OF SOME PHYSIOLOGICAL TRAITS OF CLONAL AYU (PLECOGLOSSUS-ALTIVELIS) UNDER STRESSED AND NONSTRESSED CONDITIONS

Clonal and normal diploid ayu fish were used to determine the degree o f genetic variation in some haematological characteristics prior to an d after the application of standardized stressful conditions, using th e Genetic Variation Index (GVI) as an indicator of heritability. Shall ow water and high and low temperature shocks were applied as stressors and quantified the haematocrit, red blood cells, haemoglobin, mean co rpuscular volume and plasma glucose values as indicators of the stress response of the fish. The GVI values for the shallow water stressor e xperiments showed were relatively high for haematocrit (0.407), red bl ood cells (0.608) and haemoglobin (0.561). For the temperature stresso rs, generally lower GVI values for haematocrit (0.215 in average) were recorded, although the haemoglobin and glucose values from the low te mperature experiment were 0.499 and 0.427, respectively. These rather high GVI results may imply that the portion of the genetic variance in the physiological traits under study, may well be large enough as to be affected by the overall reduction assumed for the clonal fish, The usefulness of these isogenic organisms for identifying heritable trait s, became evidenced as well.