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Published on: November 5, 2019
MHC-linked susceptibility to a bacterial infection, but no MHC-linked cryptic female choice in whitefish
C Wedekind1, M Walker, J Portmann
1Swiss Federal Institute for Environmental Science and Technology, EAWAG, Kastanienbaum, Switzerland. claus.wedekind@cawag.ch
Abstract:
Non-random gamete fusion is one of several potential cryptic female choice mechanisms that have been postulated and that may enhance the survival probability of the offspring. Previous studies have found that gamete fusion in mice is influenced by genes of the major histocompatibility complex (MHC) region. Here we test (i) whether there is MHC-dependent gamete fusion in whitefish (Coregonus sp.) and (ii) whether there is a link between the MHC and embryo susceptibility to an infection by the bacterium Pseudomonas fuorescens. We experimentally bred whitefish and reared sibships in several batches that either experienced or did not experience strong selection by P. fluorescens. We then determined the MHC class II B1 genotype of 1016 surviving larvae of several full sibships. We found no evidence for MHC-linked gamete fusion. However, in one of seven sibships we found a strong connection between the MHC class II genotype and embryo susceptibility to P. fluorescens. This connection was still significant after correcting for multiple testing. Hence, the MHC class II genotype can considerably influence embryo survival in whitefish, but gamete fusion seems to be random with respect to the MHC.
Insights
In whitefish, the major histocompatibility complex (MHC) does not influence gamete fusion, but MHC genotype significantly impacts embryo survival against Pseudomonas fluorescens infection. This suggests MHC plays a role in offspring health, not fertilization choice.
Area of Science:
- Evolutionary biology
- Immunogenetics
- Aquaculture
Background:
- Cryptic female choice mechanisms, such as non-random gamete fusion, may enhance offspring survival.
- Major histocompatibility complex (MHC) genes influence gamete fusion in mice, suggesting potential species-specific roles.
Purpose of the Study:
- To investigate MHC-dependent gamete fusion in whitefish (Coregonus sp.).
- To determine the association between MHC genotype and embryo susceptibility to Pseudomonas fluorescens infection in whitefish.
Main Methods:
- Experimental breeding of whitefish and rearing of sibships under varying levels of Pseudomonas fluorescens selection pressure.
- Genotyping of MHC class II B1 in 1016 surviving whitefish larvae.
Main Results:
- No evidence was found for MHC-linked gamete fusion in whitefish.
- A significant association was identified between MHC class II genotype and embryo susceptibility to Pseudomonas fluorescens in one of seven sibships, even after correcting for multiple testing.
Conclusions:
- While MHC class II genotype significantly influences whitefish embryo survival against bacterial infection, gamete fusion appears to be random with respect to the MHC.
- The MHC plays a role in post-fertilization survival, not in mate choice via gamete fusion in this species.
