B06
B06
Genetic and phenotypic characterisation of immunological niche conformance in cavefish
Robert Peuß
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 whether adaption to environments with low parasite diversity affects the ability of the host to conform to other parasitological niches. If so, what are the physiological processes that potentially mediate this type of niche conformance to different parasitological niches of the host without developing immunopathological phenotypes? To answer these questions, we will investigate how local adaptation of the Mexican cavefish, Astyanax mexicanus, to different parasitological niches affects the niche conformance. Distinct populations of A. mexicanus are either found in cave environments (cavefish) with low parasite abundance and diversity, or rivers (surface fish) with high parasite abundance and diversity. The proposed project has two main aims. The first aim is to characterise the parasitological niches realised by different cave and river populations of A. mexicanus in the field by measuring the respective parasite abundance and diversity, and other environmental factors that could potentially affect individual immune phenotypes. We will also examine a variety of different immune phenotypes of individual fish to determine individuality within and among the different populations that may allow for the expression of niche conformance. For our second aim, we will use lab-reared populations of A. mexicanus derived from the respective field populations and investigate whether and to what extend they show conformance to different parasitological niches. In addition, we will study physiological underpinnings of niche conformance using single-cell RNA sequencing, by exposing individual fish to different field-collected parasites. This project will not only elucidate how parasite diversity affects niche conformance of the cavefish on the phenotypic and genetic level, but it will also provide insights into genetic frameworks that play a role in maintaining a functional immune phenotype of a host facing reduced parasite diversity.
