A narwhal's tusk isn't decoration — it's an antenna wired straight to its brain

The narwhal's long spiral tusk is an overgrown tooth riddled with millions of nerve endings. Research led by dentist-researcher Martin Nweeia found the tusk can sense subtle changes in water temperature and salinity, suggesting it works as a highly sensitive environmental probe rather than a weapon or ornament, as long assumed.

— Wikipedia contributors; research by Martin Nweeia, Narwhal — Findings presented c. 2014