This Workshop will bring together experts from a wide range of disciplines to examine the functioning of the vertebrate gastro-intestinal tract though the lens of integrative physiology. Until recently, the gut was the poor relation to other exchange sites with the environment (lungs, gills, and kidneys) in terms of scientific investigation. Indeed, it received scant attention from most comparative physiologists apart from the routine (but questionable) practice of starving their test animals prior to experimentation “so as to standardize their metabolic physiology”. However, many young researchers entering the field of gastro-intestinal physiology have radically altered the landscape, and many established researchers are now switching their focus to this area. Of particular significance has been the recent explosion of research on the importance of the microbiome for digestive health, not only in humans but in animals in general. The gastro-intestinal field is rapidly expanding, and now is a very appropriate time for the cross-disciplinary fertilization that this workshop will encourage.