Quantitative genetic architecture of parasite-induced cataract in rainbow trout, Oncorhynchus mykiss

Abstract

Parasites impose costs on their hosts. The capability to fight against them is of great advantage, but may also be traded off with other traits. Although often observed at the phenotypic level, our knowledge of the extent to which such trade-offs are genetically determined is relatively poor. We tested this possibility with a farmed rainbow trout population suffering from natural Diplostomum spp. infections that cause cataracts in fish. We estimated the heritability of cataract severity and examined phenotypic and genetic correlations between cataract and a set of performance traits measured three times during a 3-year rearing period. A cataract score was used as an indicator of the host's capability to resist and/or tolerate the parasite. Our results showed moderate heritability for the cataract. Nevertheless, we found no evidence for a genetic or phenotypic trade-off between parasite resistance/tolerance and the measured performance traits. Initial body weight was not correlated with the cataract score. Phenotypic and genetic correlations of cataract severity with body mass and condition measured in the second and third year were strongly negative, indicating reduced growth and condition in fish with a high cataract score. The reduced body size and condition in cataract-bearing fish were probably reflected in the phenotypic association between a high cataract score and delayed maturity age in females. Put together, our study did not provide evidence of genetic or phenotypic trade-offs between Diplostomum resistance/tolerance and a number of performance traits. Therefore, selection for lessened Diplostomum-caused cataracts is unlikely to have a negative impact on the studied performance traits.

Genetics of Ascites Resistance and Tolerance in Chicken: A Random Regression Approach

“…Likewise, the genetic correlation of heart ratio with body weight of ascites-free birds (trait INTERCEPT) was 0.15. A similar change in correlation structure during growth occurs for skeletal deformations (Kause et al 2005) and cataract induced by a parasite in rainbow trout (Kuukka-Anttila et al 2010). …”

Genetics of Microenvironmental Sensitivity of Body Weight in Rainbow Trout (Oncorhynchus mykiss) Selected for Improved Growth

“…in our population may create genetic variation in microenvironmental sensitivity. Some families remain uninfected while others have both infected and uninfected individuals, and the infected individuals exhibit reduced growth [48]. Third, social interactions associated with behavior and growth differences have also been found to create additional genetic variation in chicken and pigs [49], [50], and presumably in fish as well [51].…”

Genetic analysis of tolerance to infections using random regressions: a simulation study

“…1). The normal distribution covers burden traits that are normally distributed at least after a transformation, such as log-normally and normally distributed pathogen/parasite counts, production diseases such as mastitis in dairy cows or ascites measured as a heart ratio in broilers (Green et al, 2004 ;Zerehdaran et al, 2006 ;Kuukka-Anttila et al, 2010). The negative binomial distribution, in turn, is perhaps the most widely used distribution to describe empirical parasite/parasitoid burdens (Stear et al, 1995).…”

“…So far, the genetic analyses of tolerance/resistance to infections have assumed such a linear relationship (e.g. Mauricio et al, 1997;Simms, 2000 ;Koskela et al, 2002 ;Ra˚berg et al, 2007 ;Kuukka-Anttila et al, 2010). However, in reality, the relationship may be non-linear, for example, sigmoidal or plateaulinear.…”