Most worms seem pretty harmless – no one ever worries about a nasty bite from an earthworm. But they’re not all so benign. Many species of polychaetes have fearsome jaws that they use to feed on unsuspecting prey – including other worms. These alien-looking gnashers are formed from strengthened collagen and can extend all the way along the worm’s throat. Even better (unless you’re a prospective prey item), many species are able to evert their jaws and pharynx (turn them inside out) to get a better reach at their meal. Some scale worms can even give human swimmers and rockpoolers a nasty nip. As well as apparently inspiring several horror films, polychaete jaws, or scolecodonts, can be invaluable to palaeontologists, as they often outlast the soft tissues of the rest of the body and are more easily preserved. Fossilised jaws can be used to identify and reconstruct ancient species, even when there’s nothing else left.

Polychaetes: a group of annelid (segmented) worms which have paired parapodia (false feet) and chitinous bristles called chaete, which give them their name.

Image courtesy of Barcroft Media.