Since species abundance and distribution in marine ecosystems are mainly driven by the key abiotic factor temperature, it is important to profoundly understand the mechanisms shaping thermal plasticity of organisms to estimate their ability to cope with the ongoing climate change. Specialization to a particular environmental factor can only occur if evolutionary processes develop at a higher rate than the change of environmental conditions. In this case, adaptation opens the prospect of a sustained and successful niche occupation. Such specialization on niches is thought to have developed at the expense of a reduced or even lost ability (“trade-off”) to respond to changing environmental factors. However, ocean warming and acidification, as projected for the future, seriously challenge species that are highly adapted to their habitats as specialists. Within this presentation I would like to focus on mechanisms of evolutionary thermal adaptation in the Antarctic fish fauna through an overview from molecules up to whole animal level. More details are exemplified by species comparisons within the fish family of Zoarcidae inhabiting thermally distinct habitats and therefore providing an excellent model for studies on thermal plasticity. Transcriptomic sequences and their respective translations of the Antarctic eelpout exhibit signatures of molecular cold adaptation when compared to those of its temperate congener, the North-sea eelpout. Trends in the amino acid usage as well as in the codon usage promote a higher flexibility of macromolecules (DNA, RNA and proteins) in the cold. However, such adaptation becomes extremely unfavourable when higher temperatures are experienced. Further indicators for a functional impairment of large protein complexes (translation or transcription) were found through broad-scaled metabolic profiling using a species-specific microarray. These data offer a comprehensive picture which molecular processes are mostly affected by rising temperatures subsequently limiting the ability of such specialized species to acclimate to higher temperatures.