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Parental genetic diversity of brown trout (Salmo trutta m. fario) brood stock affects offspring susceptibility to whirling disease.

Eszterbauer E, Forró B, Tolnai Z, Guti CF, Zsigmond G, Hoitsy G, Kallert DM - Parasit Vectors (2015)

Bottom Line: Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups.No external clinical signs were observed in the exposed brown trout groups.Our findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. eszterbauer.edit@agrar.mta.hu.

ABSTRACT

Background: Whirling disease, caused by the myxozoan parasite Myxobolus cerebralis, has high economical and ecological importance worldwide. Susceptibility to the disease varies considerably among salmonid species. In brown trout (Salmo trutta) the infection is usually subclinical with low mortality, which increases the risk of parasite dissemination, especially when farm fish are used for stocking natural habitats. The influence of intraspecific genetic differences (especially the level of homozygosity) on susceptibility is unknown. Therefore, we examined the possible correlations between parental genetic diversity and offspring susceptibility of brown trout stocks to whirling disease.

Methods: Two brown trout brood stocks from a German and a Hungarian fish farm were genetically characterized using microsatellite and lineage-specific genetic markers. The individual inbreeding coefficient f and pairwise relatedness factor r were estimated based on eight microsatellite markers. Brood stock populations were divided into groups according to low and high f and r value estimates and subjected to selective fertilization. The offspring from these separate groups were exposed to M. cerebralis actinospores, and the infection prevalence and intensity was measured and statistically analysed.

Results: The analysis of phylogeographic lineage heritage revealed high heterogeneity in the Hungarian brood stock since > 50% of individuals were Atlantic-Danubian hybrids, while only pure Atlantic-descending specimens were detected in the German population. Based on f msat and r msat estimations, classified non-inbred (NIB), inbred (IB) and a group of closely related fish (REL) were created. The susceptibility of their offspring varied considerably. Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups. In REL and IB groups, a high variability was observed in infection intensity. No external clinical signs were observed in the exposed brown trout groups.

Conclusions: Our findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.

No MeSH data available.


Related in: MedlinePlus

Frequency of the microsatellite-based individual inbreeding coefficient (fmsat) values among the examined brown trout brood stock. Data for female (a) and male (b) parents are displayed separately. The fmsat columns of non-inbred group are shown gray; those of the inbred group are black. Empty columns indicate the intermediate fmsat values excluded from the experiments.
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Fig1: Frequency of the microsatellite-based individual inbreeding coefficient (fmsat) values among the examined brown trout brood stock. Data for female (a) and male (b) parents are displayed separately. The fmsat columns of non-inbred group are shown gray; those of the inbred group are black. Empty columns indicate the intermediate fmsat values excluded from the experiments.

Mentions: The estimated fmsat values varied between 0 and 0.2091 for females, and 0 and 0.6197 for males. The examined brood stock specimens were divided into groups with relatively low and high individual inbreeding coefficients with thresholds resulting from the fmsat estimation. These were fmsat > 0.05 for more homozygous (IB) and fmsat < 0.02 for more heterozygous (NIB) females and fmsat > 0.1 for more homozygous (IB) and fmsat < 0.02 for more heterozygous (NIB) males. The latter threshold resulted from significantly higher individual fmsat values for NIB males, while fish with intermediate values were excluded from the experiments. The frequency distribution of fmsat values showed that while more than 40% of males could be classified as inbred based on our markers, only about 30% of females had fmsat values that made them candidates for the IB group (Figure 1).Figure 1


Parental genetic diversity of brown trout (Salmo trutta m. fario) brood stock affects offspring susceptibility to whirling disease.

Eszterbauer E, Forró B, Tolnai Z, Guti CF, Zsigmond G, Hoitsy G, Kallert DM - Parasit Vectors (2015)

Frequency of the microsatellite-based individual inbreeding coefficient (fmsat) values among the examined brown trout brood stock. Data for female (a) and male (b) parents are displayed separately. The fmsat columns of non-inbred group are shown gray; those of the inbred group are black. Empty columns indicate the intermediate fmsat values excluded from the experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4362631&req=5

Fig1: Frequency of the microsatellite-based individual inbreeding coefficient (fmsat) values among the examined brown trout brood stock. Data for female (a) and male (b) parents are displayed separately. The fmsat columns of non-inbred group are shown gray; those of the inbred group are black. Empty columns indicate the intermediate fmsat values excluded from the experiments.
Mentions: The estimated fmsat values varied between 0 and 0.2091 for females, and 0 and 0.6197 for males. The examined brood stock specimens were divided into groups with relatively low and high individual inbreeding coefficients with thresholds resulting from the fmsat estimation. These were fmsat > 0.05 for more homozygous (IB) and fmsat < 0.02 for more heterozygous (NIB) females and fmsat > 0.1 for more homozygous (IB) and fmsat < 0.02 for more heterozygous (NIB) males. The latter threshold resulted from significantly higher individual fmsat values for NIB males, while fish with intermediate values were excluded from the experiments. The frequency distribution of fmsat values showed that while more than 40% of males could be classified as inbred based on our markers, only about 30% of females had fmsat values that made them candidates for the IB group (Figure 1).Figure 1

Bottom Line: Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups.No external clinical signs were observed in the exposed brown trout groups.Our findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, 21 Hungária krt, H-1143, Budapest, Hungary. eszterbauer.edit@agrar.mta.hu.

ABSTRACT

Background: Whirling disease, caused by the myxozoan parasite Myxobolus cerebralis, has high economical and ecological importance worldwide. Susceptibility to the disease varies considerably among salmonid species. In brown trout (Salmo trutta) the infection is usually subclinical with low mortality, which increases the risk of parasite dissemination, especially when farm fish are used for stocking natural habitats. The influence of intraspecific genetic differences (especially the level of homozygosity) on susceptibility is unknown. Therefore, we examined the possible correlations between parental genetic diversity and offspring susceptibility of brown trout stocks to whirling disease.

Methods: Two brown trout brood stocks from a German and a Hungarian fish farm were genetically characterized using microsatellite and lineage-specific genetic markers. The individual inbreeding coefficient f and pairwise relatedness factor r were estimated based on eight microsatellite markers. Brood stock populations were divided into groups according to low and high f and r value estimates and subjected to selective fertilization. The offspring from these separate groups were exposed to M. cerebralis actinospores, and the infection prevalence and intensity was measured and statistically analysed.

Results: The analysis of phylogeographic lineage heritage revealed high heterogeneity in the Hungarian brood stock since > 50% of individuals were Atlantic-Danubian hybrids, while only pure Atlantic-descending specimens were detected in the German population. Based on f msat and r msat estimations, classified non-inbred (NIB), inbred (IB) and a group of closely related fish (REL) were created. The susceptibility of their offspring varied considerably. Although there was no significant difference in the prevalence of M. cerebralis infection, the mean intensity of infection differed significantly between NIB and IB groups. In REL and IB groups, a high variability was observed in infection intensity. No external clinical signs were observed in the exposed brown trout groups.

Conclusions: Our findings indicate that the allelic diversity of brown trout brood stock may constitute a significant factor in disease susceptibility, i.e. the intensity of parasite infection in the subsequent generation.

No MeSH data available.


Related in: MedlinePlus