Basic Statistics. Linkage Analysis and Map Construction. Linkage Analysis with Recombinant Inbred Lines. Linkage Analysis for Distorted and Misclassified Markers. Special Considerations in Linkage Analysis. Marker Analysis of Phenotypes. Interval Mapping with Regression Analysis. Interval Mapping by Maximum Likelihood Approach. Threshold and Precision Analysis. These results are indicative of an additive response rather than a non-additive effect.
Mass had no significant effect on this trait Table IV. Plasma glucose concentrations were similar for all controls Fig. The glucose response was similar among the three purebred lines Fig. The only exception was the D R hybrid, which had a significantly higher glucose concentration after stress exposure Fig. There was no significant co-factor effect for mass Table IV. Following stress exposure, Laval fish had significantly higher plasma osmolality levels than controls while osmolality did not vary in the other two purebred lines Fig.
Pre-stress levels of plasma osmolality were similar to both parental lines in the D R and D L hybrids Fig.
After stress exposure, there was a significant increase in plasma osmolality in the D R hybrid while no change was observed in the parental lines Fig. As with the Rupert line, no osmolality change was observed in the L R hybrids Fig. The interaction between stress treatment and cross-type was significant for the blood haematocrit response Table IV. Blood haematocrit was similar among controls and increased only in the domestic line after stress exposure Fig.
However, the results for the secondary response show different tendencies Table VI : i there were significant effects of both dam and sire origin in the cortisol response, with fish issued from the Rupert strain having lower plasma cortisol than other fish Table VI ; ii no significant dam or sire effect was observed for the glucose response Table VI ; and iii there was a significant dam origin effect on the osmolality and haematocrit stress responses Table VI.
Progeny of Rupert dams had lower plasma osmolality following stress exposure than progeny of the other two strains when used as dams, and progeny of Laval dams had lower haematocrit after stress exposure than when domestic dams were used.
While our results revealed no clear evidence of heterosis, relatively high heritability was found for endocrine and physiological responses. A third objective was to compare the stress response between strains of brook charr. Inter- strain differences have been previously reported between unselected lines of fighting fish B. In these studies, the stress cortisol response varied by 1.
Our results indicate a similar range, with the Rupert strain response being about half those of the other purebred strains. The osmoregulatory disturbance in the Laval strain is not easy to interpret since a secondary stress response would have resulted in decreased osmolality in a freshwater fish. Here, only weak correlations were present between mass and either the primary or secondary stress responses, indicating a weak link and therefore limited effect of body mass on stress resistance in brook charr.
However, heterosis related to survival time tertiary response was reported in F1 hybrids after salinity stress in Poecilia reticulata Peters Chiyokubo et al. A non-additive component was also observed for plasma osmolality in D R and R L hybrids, but this is more difficult to interpret for the D R hybrid, as previously mentioned.
Our observations of non-additive components only at the secondary response level reveal the presence of genetic divergence in purebred strains at the physiological level rather than a neuroendocrine response to stress stimuli. Our results do not support any of these expectations according to genetic distance: 1 the Laval and Rupert strains were the most genetically distant strains Martin et al. In addition, the results obtained for the other hybrids do not support the hypothesis that the genetic distance would be the main effect involved in non-additive expression in our crosses.
Overall, the presence of non-additive genetic effects only in secondary stress responses suggests that the use of hybrids to improve transport stress resistance in aquaculture has limited potential.
The plasma cortisol concentration in hybrids was always similar to both parental lines. Both dam and sire origin significantly affected this trait, indicating the importance of an additive genetic basis underlying this stress response. Other studies on hybrids also revealed additive effects on plasma cortisol level after exposure to stress: Bryden et al.
The cortisol response to stress is already used for genetic improvement in other fish species, especially in rainbow trout O. The selection procedure for stress response in rainbow trout was based on the mean post-stress plasma cortisol response across five episodes of confinement stress testing on parental lines, with the highest responding HR or lowest responding LR individuals used to produce the next generation.
Our results suggest that such a program could also be applied in brook charr. The low heritability observed in carp could be related to the androgenetic design, i. This suggests that maternal effect should have a limited impact on our results. Future work should aim at determining whether the difference expressed among strains is the result of global stress sensitivity variations or if some stains are more sensitive than others to different types of stress.
On the opposite, hybridization does not seem to be a promising avenue to improve stress resistance in brook charr. Nevertheless, it would be worth further investigating this issue by comparing strains specifically selected for different sensitiviy to stress response which was not the case here.
Thus, fixation of alleles related to the stress response in different strains could produce different, non-additive physiological effects in mixed progenies. Morin, and J. St-Laurent for their help with sampling and technical assistance. In Basic biochemical methods. Wiley, J. Stress in fishes: A diversity of responses with particular reference to changes in circulating corticosteroids. Integrative and Comparative Biology 42, Physiological changes in fish from stress in aquaculture with emphasis on the response and effects of corticosteroids.
Annual Review of Fish Diseases 1, Genetic improvement of farmed tilapias: growth performance in a complete diallel cross experiment with eight strains of Oreochromis niloticus. Aquaculture , Genetic effects for response to live Edwardsiella ictaluri, killed E. Journal of the World Aquaculture Society 35, Performance and heterosis in farmed and wild Chinook salmon Oncorhynchus tshawyacha hybrid and purebred crosses.
Origin of thermal adaptations in northern versus southern populations of a unisexual hybrid fish. Evolution 36, Thermally induced chronic developmental stress in coho salmon: integrating measures of mortality, early growth, and developmental instability.
Oikos 81, Effect of stress on blood coagulation and haematology in rainbow trout Salmo gairdneri. Journal of Fish Biology 10, Genetic features of salinity tolerance in wild and domestic guppies Poecilia reticulata. Comparative study of biochemical parameters in response to stress in Oreochromis aureus, O. Aquaculture Research 35, Physiological performance of largemouth bass related to local adaptation and interstock hybridization: implications for conservation and management.
Journal of Fish Biology 59, Management of physiological stress in finfish aquaculture. North American Journal of Aquaculture 68, Aquaculture Research 27, Introduction to quantitative genetics. Essex, UK: Longman Group. Genetic and phenotypic parameters for cortisol and glucose stress response in Atlantic salmon and rainbow trout. Save to Library Save. Create Alert Alert. Share This Paper. Background Citations. Methods Citations. Results Citations. Citation Type. Has PDF. Publication Type.
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