Abstracts Biological Sciences

Quantitative genetic analysis of growth and survival in Penaeus vannamei versus temperature

by Alvaro J De Tomas Kutz

Two 8-week laboratory experiments were conducted to evaluate quantitative genetic aspects of growth and survival in juveniles of the marine shrimp Penaeus vannamei versus temperature. Experiment I involved 4,486 progeny within 27 full-sib and 24 half-sib fan-milies, cultured at 20, 23, and 32 'C. Experiment 2 involved 4,624 progeny within 34 full-sib and 16 half-sib families, cultured at 20, 23, and 33 'C. As temperature increased, growth increased but survival decreased. The random effect of family within dam and sire populations of origin, and the fixed environmental treatment effect were significant for growth and survival. The interactions of genotype by environment were significant for growth in both experiments. However, for survival, the interaction was only significant in the second experiment. These interactions accounted for only 0.16 to 0.26 % and 1.63 to 2.03 % of the total variance in growth and survival, respectively. Heterosis values for the various crosses among three shrimp populations, as a fraction of the mean for the two pure parent populations, ranged from 0. 10 to 0.40 for final weight, 0.08 to 0.44 for weight gain, and from-0. 19 to 0.23 for survival. Heritability (h 2 ) estimates varied with temperature. For final weight, weight gain and survival, h 2 ranged from 0.22 to 0.73, 0.14 to 0.69, and 0.08 to 0.57, respectively. The highest estimates were obtained under conditions of high temperature. Disadvantageous genetic correlations were found between growth and survival at 20 'C. Unfavorable phenotypic correlations were observed between final weight and survival at 20 and 23 'C, and between weight gain and survival at all temperatures. I Estimated genetic gains per generation with a selection intensity of I % in both males and females ranged from 1.02 to 3.97 g for final weight, 0.50 to 2.96 g for weight gain, and from 5.33 to 79.15 % for survival. Thus, the opportunity for genetic improvement of aquacultural performance in P. vannamei appears to be very good.