Estimates of heritabilities and genetic correlations for growth and gonad traits in the sea urchin Strongylocentrotus intermedius

The present study is the first estimate for the sea urchin, Strongylocentrotus intermedius, of genetic parameters for growth and gonad traits during the entire reproductive period. 21655764 sea urchins were sampled from 74 to 120 families at six different growth stages. Six hundred individuals were sampled from 20 randomly chosen families at harvest. Coefficients of variation for most growth and gonad traits were high (18.08-78.66%) suggesting a good variation foundation for breeding. Point estimate for heritabilities based on the sire components of variance were moderate to high for test height (0.24-0.39), test diameter (0.21-0.48) and body weight (0.16-0.49). Heritabilities of gonad wet weight, gonad index and gonad moisture at harvest were 0.17, 0.41 and 0.50 respectively (moderate or high). Gonad colour parameters, L* (lightness) and a* (redness) have a heritability of 0, while b* (yellowness) and colour difference Delta E1 and Delta E2 have very similar heritabilities of 0.2, 0.18 and 0.21 respectively. Heritabilities of beta-carotene concentration and content were 0.89 and 0.44 respectively. The genetic correlations between the two measured traits ranged from -0.984 to 0.999. Gonad wet weight, L*, b*, beta-carotene concentration and beta-carotene content had significant positive genetic correlations with all the growth traits. However, gonad index, gonad moisture and colour differences Delta E1 and Delta E2 had significant negative genetic correlations with growth traits. The present study indicates that growth, gonad yield and most gonad quality traits could be improved by selection with moderate to high potential. Indirect selection should be applied on gonad traits using growth traits as secondary traits. The present study provides important theoretical guidance for future selective breeding programmes for S. intermedius.