They feed on dead whales (Vigtorniella), have squid-like tentacles to collect falling debris (Squidworm), and make their homes in hydrothermal vents, the hottest submarine environments on earth (Pompeii worm). Meet the polychaetes, marine worms with body segments covered in bristles known as chaetae. Weird, colourful and varied, their scientific class is used to describe more than 10,000 known species that inhabit different layers of the ocean. Polychaetes are incredibly strategic too: because the journey to mate at the surface of the water is long and treacherous, the syllis ramosa - a polychaete that inhabits a deep-sea sponge - will develop a head with no mouth and large eyes on its tail-end, known as the stolon. Its gut disintegrates to make room for eggs or sperm, and when the time comes, the stolon is released to the ocean’s surface to procreate before dying - but no matter; down under, its original body is alive and thriving, able to make more stolons to be deployed the next time mating season comes around.