This volume comprises selected contributions by internationally renowned researchers and represents the state-of-the-art in the field of hemoglobin function in vertebrates living in extreme and temperate environments. The topics have been covered from several viewpoints, including protein chemistry, molecular biology, and evolution. All the contributions chosen for publication focus on phenotypic and genetic adaptations to changing environmental conditions and on gene expression and regulation. The book provides the reader with an update in this field, which is presently enjoying a true renaissance following developments in recent years of powerful methodologies such as site-directed mutagenesis and discoveries of new roles, for example, as oxygen sensors and in nitric oxide metabolism.