Résumé
To grow and develop, shrimps must shed their exoskeletons. In shrimp an inter-individual variability in molting time is spread over about a week. The genetic basis of this variability and its implications for selective breeding programs to improve growth or quality traits remains largely unexplored.
We estimated the effect of molting stage on genetic parameters of growth and color traits in the Pacific blue shrimp Litopenaeus stylirostris. As the variability of molting time may also be partly genetically determined, we estimated the heritabilities of molt stages and molting time under the hypothesis that some families may have the additive genetic potential to molt earlier (or later) than others.
To address these questions, 1200 shrimp progenies (mean body weight 14.5 g) from 49 full- and half-sib families, bred according to a partly factorial design with double-sire insemination, were phenotyped over 3 successive days, 3 to 5 days before the full moon. Body weight, body length, head length and molt stage were recorded on uncooked shrimp and external color traits on uncooked or both uncooked and cooked shrimp.
Molt stage had a significant phenotypic effect on all traits except for body length and head-to-length ratio. The heritability estimates for both growth and color traits were, however, similar in models with or without molting, and the estimated breeding values were highly correlated between these models.
The heritability of molt stage with a four-class threshold model was low (0.07 [0.02–0.28]). When the stage classes were combined into just two to simplify the description of the molting process, the heritability of early or late molting was intermediate (from 0.16 [0.10–0.28] to 0.22 [0.13–0.40]), indicating that this trait is partly under additive genetic determinism rather than solely under environmental control. The genetic correlations of molting traits with body weight were not different from zero.
These results are discussed for selective breeding practices and shrimp molting biology to consider in future study molting as a factor to improve selection practices for disease resistance, feed efficiency and robustness.
•First heritability of molting stages and time to molt in a shrimp species.•Molt stage significantly impacts growth, morphology and colors.•Genetic correlations are too imprecise to conclude on genetic interaction with growth.