Konrad Taube’s doctoral thesis explores how Eurasian perch adapt to different environmental conditions

The thesis was supervised by Professor Anti Vasemägi, Professor Riho Gross and Dr Kristina Noreikiene from Vilnius University, Lithuania. The opponent was Professor Jukka-Pekka Verta from Nord University, Norway.

Eurasian perch inhabit both clear-water lakes and dark, humic lakes in bogs and forests. These habitats differ in light conditions, acidity, oxygen availability and dissolved organic matter content. They therefore offer an opportunity to investigate how fish of the same species cope with contrasting conditions and which inherited traits help them survive and reproduce in their local environments.

In his doctoral research, Taube investigated how environmental conditions and parasites affect Eurasian perch. He combined analyses of genetic variation, gene activity and the way DNA is packaged within cells. This allowed him to examine both variation in the genetic information of the fish and how their cells use that information.

Genes work differently in perch from dark- and clear-water lakes

Comparisons between perch from humic- and clear-water lakes revealed substantial differences in gene activity. These were particularly pronounced in the gills and spleen and involved genes associated with oxygen uptake, ion balance, metabolism and immune defence.

Genes active in the gills and spleen also showed strong signatures of natural selection. This suggests that these tissues play an important role in adaptation to acidic, humic-rich waters.

The effects of parasite infection were more limited. Comparisons between fish infected and uninfected with the pike tapeworm, a parasite found in the liver of perch, revealed only minor differences in gene activity in the liver and spleen. This suggests that moderate parasite burdens may not trigger a strong physiological stress response under natural conditions.

Gene regulation offers further insight into adaptation

Gene activity is influenced, among other factors, by how DNA is packaged within the cell nucleus. In more open regions, DNA is more accessible to the proteins that regulate gene activity. Taube mapped these regions in different perch tissues and found that their distribution was largely tissue-specific and partly associated with environmental conditions.

The research identified candidate genes and regulatory regions potentially involved in adaptation, including those associated with stress responses, metabolism, vision and immune defence.

The thesis demonstrates that understanding adaptation in Eurasian perch requires examining both genetic differences and the regulation of gene activity. Combining several molecular approaches helps explain how wild fish populations cope with different habitats and respond to environmental change.

The doctoral thesis is available in the Estonian University of Life Sciences digital repository EMÜ DSpacelink opens in new page.