Plasticity of the sergeant major damselfish, Abudefduf saxatilis, to thermal stress and habitat loss

Sea surface temperatures are rising at unprecedented rates due to anthropogenic activities. Reef-forming corals are particularly sensitive to warming and increases in temperature can lead to degradation of the complex three-dimensional habitats they form. Studies have shown that, for marine ectotherms, thermal stress leads to physiological and molecular changes. Hence, oceanic warming can produce challenging conditions to marine ectotherms due to changes in temperature, as well as the irreversible changes in complexity of reef structures. Despite recent advances evaluating the effect of temperature in ectotherms, questions remain on how these traits influence the molecular processes of the main sensory organ, the brain. Here, we evaluated how thermal stress and habitat loss are acting independently and synergistically as stressors in a damselfish of the Tropical Western Atlantic, Abudefduf saxatilis. For the experiment, 40 juvenile A. saxatilis were exposed to warm temperatures and simplified environments to evaluate molecular changes in the brain, and the oxidative stress of liver and muscle. The results indicate that warming resulted in increased oxidative damage in the liver (p=0.007) and changes in molecular pathways of the brain including neurotransmission, immune function, and DNA and tissue repair, while habitat loss effected synaptic plasticity and spatial memory. This study enhances our understanding of how fishes are responding to coral reef degradation, thermal stress, and how plasticity may enable generalist fish species to persist in a changing world.