1. Antifreeze Proteins: Notothenioid fish produce unique proteins known as antifreeze proteins (AFPs) that prevent the formation and growth of ice crystals in their body fluids, including their blood, tissues, and organs. AFPs bind to the surface of ice crystals, interfering with their growth and preventing them from damaging the fish's cells and tissues. This adaptation is crucial in preventing them from freezing in sub-zero temperatures.
2. Reduced Membrane Fluidity: Fish in warmer climates possess cell membranes that are more fluid, allowing them to maintain flexibility in varying temperatures. However, notothenioid fish have evolved cell membrane structures with reduced fluidity, increasing their stability in the cold. By reducing the fluidity of their cell membranes, these fish can better withstand the detrimental effects of freezing temperatures and maintain cellular integrity.