The aim of the Eggtox project is to unravel the mechanistic effects of crude oil toxicity on early life stages of cold-water marine teleosts. This knowledge is vital for understanding the impact of accidental oil spills from offshore petroleum activities on fishes. The heart is the first organ to develop in fish larvae and its correct maintenance is crucial for survival into adulthood. Thus, a secondary goal is to define the mechanisms of crude oil toxicity on the electrical and contractile properties of the fish heart. To do this, scientists from IMR together with colleagues from the University of Manchester, UK, are working in the electrophysiology lab at Austevoll station investigating how various oil components affect the electrical activity if the cod and halibut heart. Specifically, we are studying the impact of a single component of crude oil with known cardiotoxicity, and two of its metabolic derivatives, with potentially potent cardiotoxic effects. A thorough understanding of cardiotoxic mechanisms will improve ecological risk assessments, environmental health monitoring, and the development of advanced technologies.