Extremophile Fishes

Extremophile organisms thrive under environmental conditions considered inhospitable for most eukaryotes due to the presence of physicochemical stressors. To cope with such stressors, extremophiles have often evolved complex adaptations. Naturally occurring extreme habitats can be regarded as evolutionary experiments that allow studying the ability of species to habituate and adapt to altered ecological conditions, which may allow generating projections about the potential of organisms to habituate and adapt to human-induced stressors as well. This introduction provides an overview of different chapters of this book, focusing on the ecology, evolution, and physiology of extremophile fishes from various extreme habitats. Chapters introduce the nature of the physicochemical stressors and the taxonomic diversity in the respective habitat type. Furthermore, each chapter reviews adaptations of fishes in terms of modification of biochemical, physiological, morphological, life-history, and/or behavioral traits. In several cases, evidence for reduced gene flow between different locally adapted populations, i.e., indications for incipient or ongoing ecological speciation, is being discussed.