Walrus Lice

a scan of a louse
Vince Smith via Wikimedia Commons

The Echinophthiriidae are a family of lice that infect seals, sea lions, walruses, and otters, have invaded the sea like no other group of insects. While whales and manatees have lost much of their hair, these other marine mammals retained their furry bodies as they evolved from life on land to life at sea, meaning they have the perfect environment to harbor lice – except for their salty habitat. Like their hosts, these lice have evolved amazing capabilities that allow them to survive the hardships of life deep under sea, a place no other insects go. The lice go where their hosts go, which means they often make some of the deepest dives in the animal kingdom. The southern elephant seal makes dives to depths past 2,000 meters, a trip that can last over two hours, and the lice go along for the ride.