A Novel Hygrotaxis Assay for Assessing Thirst Perception and Water Sensation in .

Water is essential for the survival of terrestrial animals. Animals obtain water from their food, from metabolism and, more importantly, by drinking. It is therefore vital for dehydrated animals to efficiently locate water sources in the wild. Traditional paradigm for studying the genetic basis of humidity sensation and preference use an apparatus consisting of two chambers providing a binary choice between flows of dry and moist air that maintain steep humidity gradients. Here, we introduce a novel assay to study water-seeking behavior (hygrotaxis) in , in which dehydrated flies detect a humidity gradient and rapidly aggregate near an inaccessible water source. Our previous work using this method demonstrated that hygrotactic behavior relies on both specific sensory organs and central brain neurons.