The Epaulette shark is a hypoxia-tolerant representative of Elasmobranchs, a group of vertebrates that diverged from the lineage leading to tetrapods and teleost fishes around 450 million years ago. In hypoxia the vertebrates normally show an increase in extra- cellular adenosine concentration. Since adenosine is an inhibitory regulator of nerve function, such an increase will play a role in the hypoxia-induced inactivation of all tissues. The cellular effects of adenosine are mediated via adenosine receptors. Some adenosine receptors respond to hypoxia in mammals, but their presence and function have not been studied in detail in water-breathing animals, even though aquatic animals experience hypoxia more often and more severely than terrestrial animals. We exposed epaulette sharks to hypoxia either directly or after previous exposure to hypoxic conditions and collected brain, eye, gill and heart tissues. In ongoing experiments we use qPCR to evaluate if changes in the transcription occur in selected genes of hypoxia- inducible factor dependent pathway including adenosine receptors.