Tambaqui (Colossoma macropomum) is the main native fish produced in continental aquaculture from South America. However, its production has been negatively affected by significant economic losses due to frequent outbreaks caused by the parasite Ichthyophthirius multifiliis. Genetic selection for I. multifiliis resistance may represent a sustainable and effective alternative to reduce mortality and, therefore, improve production of tambaqui. The estimation of genetic parameters is needed to validate whether I. multifiliis resistance can be included in genetic improvement programs. The aim of this study was to estimate variance components and heritability for I. multifiliis resistance in tambaqui, through experimental challenge of 218 individuals from eight full-sib families. Survival status (SS), time of death (TD) and parasite load (PL) of fish presenting clinical signs of I. multifiliis infestation were recorded in the cohabitation experimental challenge. The total cumulative survival rate varied significantly among families (16 to 100%) and TD ranged from 217 to 254 hours post cohabitation, which indicates the presence of significant phenotypic variation related to resistance to I. multifiliis infestation. High values for heritability were estimated for SS and TD (0.46 ± 0.09 and 0.60 ± 0.18, respectively). However, differences among families and heritability value were not significant for PL. This study represents the first report on genetic parameters for disease resistance against the parasite I. multifiliis in a Neotropical fish species. The results presented here suggest that resistance to I. multifiliis in tambaqui can be improved through selective breeding.

Tambaqui（Colossoma macropomum）是南美大陆水产养殖中生产的主要本地鱼类。然而，由于寄生虫多花鱼（Ichthyophthirius multifiliis）引起的频繁暴发，其生产受到重大经济损失的不利影响。多丝抗性的遗传选择可能代表了降低死亡率并因此提高坦巴基产量的可持续和有效选择。需要遗传参数的估计，以验证是否可以将多丝抗性纳入遗传改良计划中。这项研究的目的是估计多丝I.的变异成分和遗传力。通过对来自8个同胞家族的218个人进行实验性挑战，对tambaqui产生抗药性。在同居实验中记录了表现出多丝线虫感染临床症状的鱼的生存状态（SS），死亡时间（TD）和寄生虫负荷（PL）。不同家庭之间的总累积生存率差异很大（16％至100％），同居后的TD范围为217至254小时，这表明存在与抗多丝酵母相关的显着表型变异。侵扰。估计SS和TD的遗传力较高（分别为0.46±0.09和0.60±0.18）。然而，对于PL，家庭之间的差异和遗传价值并不显着。这项研究代表了关于新热带鱼物种中针对寄生虫多丝线虫的抗病遗传参数的第一份报告。此处显示的结果表明，可以通过选择性育种提高对tambaqui中I. multifilii的抗性。