Skip to main content

penis worms

Leading academics from our Department of Earth Sciences in collaboration with counterparts from Yunnan University in China have identified that a ‘hermit’ lifestyle was invented by ancient penis worms first, rather than by hermit crabs.

The researchers point out that penis worms (Priapulida) invented the ‘hermit’ lifestyle, some 500 million years ago during the rise of the earliest animal ecosystems in the Cambrian period.

‘Hermit’ lifestyle

Hermit crabs are well known for employing snail shells as shelters against predators, but researchers have now found that penis worms invented the ‘hermit’ lifestyle hundreds of million years before hermit crabs first evolved.

During the Cambrian age, penis worms used snail shells as their home to take permanent shelter from predators.

The researchers established that Cambrian predators were plentiful and aggressive, that forced the penis worms to move into empty shells, leading to the invention of ‘hermit’ lifestyle.

Examining fossil deposits

Our pioneering academics studied collections of the Guanshan fossil deposits – famous because they preserve soft tissue (such as the bodies of worms) alongside the shelly material that makes up the conventional fossil record. 

Researchers found four specimens of the penis worm Eximipriapulus inside conical shells of a long-extinct fossil group, known as hyoliths.

They explain that the penis worms are always sitting snugly in the same position and orientation within the same type of shells.

The study further highlights the key role of predators in shaping ecology and behaviour in the very early stages of animal evolution.

Find out more