The Somniosus microcephalus, also known as the Greenland polar shark, is the oldest known vertebrate, with a life expectancy of at least 272 years. Its exceptional longevity may be explained by its very slow development (1 cm/year) or by life in cold waters, associated with a lower body temperature and slower metabolism. Although it is at the top of the food chain in its environment, this shark is at the mercy of a parasite that attaches itself to its cornea and eventually blinds it. Fortunately, it uses its overdeveloped sense of smell to hunt.  Photo: DOCLIGHTS/BLACK CORAL FILM AB