Approaching “Old Friends” with a new model: How parasite diversity shaped the adaptation of Astyanax mexicanus to the cave

• Applicant: Dr. Robert Peuß
• Subject Area: Evolution, Anthropology
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392345736

Host-parasite interactions are a major driving forces in evolution. The loss of parasite diversity in modern societies in the last 200 years, however, strongly correlates with an increase of autoimmune diseases caused by immune-regulatory defects in humans. This indicates that these interactions between host and parasite not only created a co-evolutionary dynamic, but also represent a necessity for a vertebrate host to develop a functional immune phenotype. So far, this “Old Friends” hypothesis is largely based on descriptive correlational data from humans since there are no suitable model organisms available that have adapted to an environment with low parasite diversity. This proposal introduces Astyanax mexicanus as a new model for host-parasite coevolution and addresses the exciting question of how natural changes in parasite diversity alter the evolutionary trajectory of the host immune system. Here, we present first evidence of parallel evolution within specific immunological traits of two A. mexicanus cave populations, in response to changing parasite diversity in their environment. We found that not only key immunological functions such as phagocytosis are strongly decreased in cave populations of A. mexicanus, but inflammatory responses towards bacterial antigens are highly increased. Furthermore, we found striking differences in the organization of immune cell populations between cave and surface population of A. mexicanus. The aim of this proposal is to characterize the parasite diversity in different environments of A. mexicanus and investigate the distinct immunological phenotypes that result from genomic adaptation to these different environments. Future investigation in this direction will not only provide important insights into the immune system of the emerging model organism A. mexicanus in general, but will also help to elucidate the evolutionary trajectory of vertebrate hosts in an environment with low parasite diversity.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Nicolas Rohner