Character Acquisition During the Transition to Amphibious Life in the Oxudercine Fishes

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0111241 GrahamThis study investigates the specializations for amphibious life and air breathing of fishes in the goby subfamily Oxudercinae. Included among the oxudercines are species such as the mudskippers, which are highly amphibious and air-breathing, as well as several less- and entirely non-amphibious species. The research studies the characters associated with mudskipper terrestriality and the sequence of change these characters have undergone within the Oxudercinae. DNA sequence analyses will confirm the phylogenetic relationships among the oxudercine species. Comparative study of different oxudercines examines the functional relationship between the gills and auxiliary air-breathing surfaces considering, for example, such questions as how the presence of dual respiratory surfaces affects properties such as respiration, ionic and acid-base balance, and nitrogenous waste excretion. Also studied will be how the gills and auxiliary air-breathing structures function in oxudercine recovery from exhaustive exercise. Comparisons of oxudercine eyes will reveal how changes related to aerial visual acuity developed. Fieldwork in both Japan and Australia will correlate species-specific specializations with behavior and microhabitat distribution in order to establish how different degrees of terrestrial adaptation affect oxudercine distribution and natural history. The oxudercines are unique among the vertebrates in providing evolutionary "snap-shots" along the phylogenetic continuum extending from aquatic to amphibious life, and are thus ideal for studying the sequence of character changes that occurred over the course of this transition. This study therefore contributes to an understanding of the suite of changes that occurred during the invasion of land by the vertebrates in the Devonian Period, 360 million years ago.