Comparative Aspects of the Air-Breathing Transition in the Oxudercine Fishes

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Graham 9604699 The mudskipper fish are in the subfamily Oxudercinae of the family Goblidae. There are10 genera and about 25 species of oxudercines, including the mudskippers. This subfamily has a broad geographic range, from West Africa to Samoa, and most species live in shallow, warm, hypcxic tropical regions. The mudskippers (Periophthalmus, Periophthalmodon, Boleophthalmus, and Scartelaos) are distinguished from other oxudercines by their ability to live at the water surface, with their heads exposed to air, or to even leave water and live in the air for extended periods. Mudskippers accordingly have adaptations for air breathing, for terrestrial locomotion, and for aerial vision, as well as other specializations related to being out of water. This study will examine some of these adaptations and attempt to understand the macroevolutionary sequence of their acquisition, - - - that is to say, the point in the expansion of this group when adaptations related to air exposure appeared. This sequence is important to know because, while the current theory about the evolution of vertebrate life on land is replete with details, based on fossils, about the structural changes that accompanied the land invasion, much less detail is known about the changes that occurred at the behavioral, sensory, physiological and biochemical levels. Because the oxudercines contains species that never leave water and others that are highly terrestrial, this group provide a special window to the "bows" and "whys" of terrestrial invasion. This study will investigate the nature of the functional elements related to the transition from water to land, in particular, how access to aerial oxygen affected breathing and metabolism. The mudskippers, in an ecological sense, are exploiting an open ecological niche between water and land, one that was not filled by amphibians. The PI thus provide clues as to how ancient ancestors of ail land animals may have made the transition from living in shallow-water to living on land.