Key Laboratory for Sustainable Utilization of Marine Fisheries Resources, Ministry of Agriculture, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Nanjing Road 106, Qingdao, 266071, China.
Function Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology (Qingdao), No. 1 Wenhai Road, Aoshanwei Town, Jimo, Qingdao, China.
Genet Sel Evol. 2020 Aug 8;52(1):45. doi: 10.1186/s12711-020-00565-3.
Competition is a common social interaction among shrimp and depending on its intensity, it can affect heritable variation and response to selection. Little is known about the variance of indirect genetic effects (IGE) under competitive and non-competitive conditions in shrimp. In this study, we used extended mixed linear models to estimate genetic parameters for the direct genetic effect (DGE) and IGE on body weight in Litopenaeus vannamei raised under ad libitum (AF, non-competitive environment) and restricted (RF, competitive environment) feeding regimes.
Estimates of heritabilities for body weight obtained with a traditional animal model (i.e. without accounting for IGE) were 0.11 ± 0.09 under AF and 0.25 ± 0.11 under RF. With extended animal models that accounted for IGE, the corresponding estimates for body weight were 0.07 ± 0.08 and 0.34 ± 0.11. Thus, heritabilities were higher under the RF regime than under the AF regime, regardless of whether IGE was accounted for or not. The log-likelihood ratio test revealed significant IGE under the RF regime. Although estimates of indirect genetic variance were low (0.0023 ± 0.0013 for AF and 0.0028 ± 0.0012 for RF), they contributed substantially to the total heritable variance: 66.8% for AF and 692.2% for RF. The total heritable variance was smaller under the RF regime (0.7 ± 1.3) than under the AF regime (5.8 ± 2.6) because of the high contribution of the negative covariance between DGE and IGE (- 7.03). Estimates of the correlation between DGE and IGE were 0.32 ± 0.47 under AF and - 0.93 ± 0.15 under RF, those of DGE and IGE for body weight between both regimes were 0.94 ± 0.07 and 0.67 ± 0.20, respectively, and those of IGE for body weight with DGE for survival were - 0.12 ± 0.22 under AF and - 0.58 ± 0.20 under RF.
These results indicate that strong competitive interactions occurred under the RF regime in L. vannamei. Significant reranking and variation in IGE of individuals were observed between the two feeding regimes. Strong competitive interactions reduced the total heritable variation for body weight when food was restricted. These results indicate that the extent of competition among L. vannamei depends on the feeding regime applied and that this competition affects the genetic basis of body weight.
竞争是虾类之间常见的社会互动方式，其强度会影响可遗传变异和对选择的反应。关于虾类在竞争和非竞争条件下的间接遗传效应（IGE）的方差知之甚少。在这项研究中，我们使用扩展的混合线性模型来估计凡纳滨对虾在自由采食（AF，非竞争环境）和限制采食（RF，竞争环境）条件下体重的直接遗传效应（DGE）和 IGE 的遗传参数。
传统动物模型（即不考虑 IGE）获得的体重遗传力估计值分别为 AF 下的 0.11 ± 0.09 和 RF 下的 0.25 ± 0.11。通过考虑 IGE 的扩展动物模型，体重的相应估计值分别为 0.07 ± 0.08 和 0.34 ± 0.11。因此，无论是否考虑 IGE，RF 条件下的遗传力均高于 AF 条件下的遗传力。对数似然比检验显示 RF 条件下存在显著的 IGE。虽然间接遗传方差的估计值较低（AF 下为 0.0023 ± 0.0013，RF 下为 0.0028 ± 0.0012），但它们对总可遗传方差的贡献很大：AF 下为 66.8%，RF 下为 692.2%。由于 DGE 和 IGE 之间的负协方差（-7.03）很高，RF 条件下的总可遗传方差（0.7 ± 1.3）小于 AF 条件下的总可遗传方差（5.8 ± 2.6）。AF 条件下 DGE 和 IGE 之间的估计值为 0.32 ± 0.47，RF 条件下为-0.93 ± 0.15，两种条件下 DGE 和 IGE 之间的体重估计值分别为 0.94 ± 0.07 和 0.67 ± 0.20，而 RF 条件下的 IGE 与生存的 DGE 之间的估计值为-0.12 ± 0.22，AF 条件下的为-0.58 ± 0.20。
这些结果表明，在 RF 条件下凡纳滨对虾之间存在强烈的竞争相互作用。在两种饲养方式下，个体的 IGE 出现了显著的重新排序和变化。当食物受到限制时，强烈的竞争相互作用降低了体重的总可遗传变异。这些结果表明，凡纳滨对虾之间的竞争程度取决于所应用的饲养方式，这种竞争会影响体重的遗传基础。
