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Fish Evolved the Ability to Live on Land Multiple Times Throughout History

Elizabeth Fox
18th June, 2016

In a groundbreaking study that rewrites the story of evolutionary adaptation, researchers from the University of New South Wales have unveiled findings that significantly challenge the traditional understanding of how fish transitioned to land-dwelling creatures. Published in June 2016 in the journal Evolution, the study reveals that the ability of fish to live on land has evolved not just once but at least thirty times across different families of fish. Dr. Terry Ord and Dr. Georgina Cooke, the principal researchers behind this study, embarked on an exhaustive examination of the evolutionary relationships among all known species of fish that exhibit some form of terrestrial activity. Their research spanned various climates and aquatic environments, from freshwater rivers to the vast expanses of the ocean, uncovering that 33 different families of fish have species capable of performing terrestrial activities. Remarkably, these adaptations have likely evolved independently within these families, suggesting a more common and versatile evolutionary response to terrestrial environments than previously thought. The study focuses on understanding the environmental factors and evolutionary pressures that spurred such a widespread ability to transition between aquatic and terrestrial habitats. The researchers highlight the diverse range of climates, diets, and aquatic environments in which these fish reside, underscoring the ecological versatility and adaptability of fish. A particularly fascinating aspect of the research is the detailed observation of blennies, a group of intertidal fish. Blennies exhibit a wide range of behaviors related to land-dwelling, from species that never leave the water to those that spend their entire adult lives on land, navigating the splash zone on tidal rocks. In this family alone, an amphibious lifestyle has seemingly evolved between three and seven times, a testament to the evolutionary plasticity and repeated nature of terrestrial adaptation. This study's implications are profound, not only in understanding the evolutionary history of vertebrates but also in appreciating the dynamic and resilient nature of life. Over 350 million years ago, the emergence of fish onto land marked a pivotal moment in the history of life on Earth, leading to the evolution of all land vertebrates, including humans. This research challenges the notion that such transitions were rare, isolated events, instead presenting evidence that the leap from water to land has been a recurring theme in evolutionary history. The researchers note that while many species manage short stints on land, others, such as mudskippers and some eels, can survive for hours or days. This ability to overcome the significant challenges of breathing, moving, and reproducing on land indicates that the initial transition to terrestrial life may not be as daunting as once believed. However, the development of a fully terrestrial lifestyle likely hinges on overcoming the threat of desiccation, a critical challenge given the necessity of moist gills for respiration. This study opens new avenues for research into the evolution of terrestrial life and the adaptive strategies organisms employ to conquer new environments. It underscores the complexity of life's evolutionary journey and the remarkable adaptability of fish, offering new insights into our own origins and the evolutionary processes that shape the natural world. REFERENCE "Repeated evolution of amphibious behavior in fish and its implications for the colonization of novel environments", Evolution, June 2016.