SFB-TRR 212

Genetic and phenotypic characterisation of immunological niche conformance in cavefish

Host-parasite interactions are a major driver of evolution. Coevolutionary dynamics between hosts and parasites shape the evolutionary trajectory of complex host immune systems, such as the innate and adaptive immune systems of vertebrates. These dynamics establish the genetic basis for an individual host to conform to different parasitological niches, i.e. conform to fluctuations in parasite abundance and diversity. There is, however, increasing evidence suggesting that host-parasite coevolution also led to a dependency between host and its parasites to develop a functional immune phenotype. This ‘Old-Friends’ hypothesis is based on the observation that the decreasing parasite diversity in the environment of many human societies is accompanied by an increase of immunopathological phenotypes. This raises the question how does local adaption to environments that differ in parasite abundance and diversity affect the ability of the host to conform to different parasitological niches?

To answer these questions, we will investigate how local adaptation of the Mexican cavefish, Astyanax mexicanus, to different parasitological niches affects the niche conformance.

We will take a two-step approach:

1. We will analyse parasitological niches in various environments of different cavefish and surface fish population. We hypothesise that parasite abundance and diversity affect the individual immune phenotype of wild populations of A. mexicanus.
2. We will then pursue the question whether local adaptations to environments with low parasite abundance and diversity affect the ability of the host to adjust its immune phenotype upon changes in the parasitological niche (e.g. increase in parasite diversity). We hypothesise that the individual immune phenotype, more specifically the immune investment strategy, affects the degree and expression of niche conformance.

In Summary, we will investigate whether and how these immunological differences affect the ability of several A. mexicanus populations to conform to different parasitological niches.