Greenland shark (Somniosus microcephalus) with copepod parasite. This shark, also known as the sleeper shark, is native to Arctic waters of the North Atlantic. It feeds on fish, seals and whale carcasses. An adult Greenland shark can measure up to 6.5 metres long. This shark species usually suffers from copepod parasites (seen here on shark's eye). The copepod is a crustacean that attaches itself to the cornea of the shark's eye and can grow up to 8cm long. Eventually the copepod renders the shark blind, however the shark is still able to hunt due to an acute sense of smell. Scientists are unsure how the shark, which is sluggish and slow swimming, is able to capture fast swimming prey such as salmon, squid and eals. The meat from this shark is toxic and must be carefully prepared by Inuit hunters.