Despite sounding like a sci-fi creation, ten species of Osedax worms have been described since their discovery in California’s Monterey Bay in 2002. These curious polychaete worms feed on bones which have sunk to the bottom of the sea – mainly whale fall, but they have also been found in fish and cow remains. The worms live half-embedded in the bone, with their plumes protruding into the water and acting like an external gill for gas exchange. The other end of the worm (at the bottom of this image) feeds on the bone, but lacks a mouth or teeth despite their hardy diet. Instead, they have root-like structures which contain endosymbiotic bacteria and secrete acid. The acid begins the digestion of the bone, allowing the bacteria to access the proteins and fats within. Even more curiously, only the female Osedax feed this way – the males are much smaller and live within the gelatinous tube surrounding the females themselves, sometimes hundreds at a time, providing sperm when required.

Image courtesy of Norio Miyamoto/Naturwissenschaften.