The role of chromosomal inversions in temperature and salinity adaptation in Atlantic cod (Gadus morhua) eggs

Abstract

Atlantic cod is an ecologically, culturally, and economically important species which is classified as endangered due to overfishing. Chromosomal inversions, on chromosomes 2, 7, and 12 in Atlantic cod (Gadus morhua), have been consistently associated with environmental gradients, particularly salinity and temperature, across the species' natural range. While these correlations suggest a role for local adaptation, the underlying selective mechanisms remain unresolved. Critically, few experiments have yet tested the fitness consequences of these inversions under controlled environmental conditions. First, we conducted an acute stressor experiment with ten treatments of combined temperature and low salinity stress. We found evidence that the inversions on chromosomes 2 and 12 might assist with temperature and salinity adaptation, respectively. Then, we conducted a buoyancy test on Atlantic cod eggs. There was evidence that ecotypes, but not inversions, impacted buoyancy. Our results have implications for the management and conservation of cod in future changing environments.