All of the rave this year includes sexual selection explaining MHC polymorphism. MHC, also known as major histocompatibility complex, is a set of cell surface proteins that aid in the recognition of foreign particles in the body, as well as immune responses. There are two types of MHC classes. MHC class I recognizes antigens produced within the cells; however, MHC class II recognizes antigens that are introduced to the cell. Two types of strategies for sexual selection (inbreeding avoidance and parasite resistance) were used to argue in favor of MHC-related sexual selection. This study aimed to look at the differences in an allele counting strategy vs disassortative mating. This type of mating includes individuals with dissimilar genotypes/phenotypes that mate more frequently than expected.
This study uses female sticklebacks (Gasterosteus aculeatus) to test the preferred odor type in males. The males elicit a certain smell depending on the number of MHC class-IIB alleles, which females were exposed to. Females were then put into tanks and two different males were then placed in separate tanks, however a hose ran from the male tanks into the female tanks. This allowed for the odor of each male to be presented to the female, who then chose a scent that was more appealing to her. It was found that females did not prefer the odor of males with different MHC class-IIB alleles which rules out disassortative mating. It was also found that males with high MHC class-IIB heterozygosity had a higher chance of being infected by parasite which could be smelled by the females.
The results of this study begin to explain how MHC allele variation is used as a tool for sexual selection. Females were found to be choosier if they had less MHC allele variation. This shows that females look for males that have strong immune systems in order for the immunity to be passed on the offspring. On a more basic scale the purpose of this study is to increase fitness (reproductive success) and give offspring the best chance of survival. We look at studies such as this one to understand the mating process of animals and why they choose partners the way they do.
References:
Reusch, T. B., Haberli, M. A., Aeschlimann, P. B., & Malinski, M. (2001, November 15). Female sticklebacks count alleles in a strategy of sexual selection explaining MHC polymorphism . Retrieved October 8, 2017, from https://pdfs.semanticscholar.org/fddb/ce48d9088da6a3e432fa3c0e969464c054f7.pdf
