From a human viewpoint, the cold waters of deep sea and polar marine regions present an inhospitable and harsh environment for life. The study of organisms that have exploited this seemingly hostile ecological niche has revealed intriguing physiological adaptations. This volume summarizes the most recent information on the adaptations exhibited by representatives of the main groups of polar animals, including marine invertebrates, fish, mammals, and birds. The scales of adaptation range from the whole organism to the underlying molecular mechanisms. Unique in its breadth of coverage, this volume will provide an important resource for all those concerned specifically with how animals have adapted to life in extreme conditions.