Penis Worms Unseat Hermit Crabs as First to Live “Hermit Life”

Sorry hermit crabs, but you weren’t the first to steal other folk’s discarded homes and make them your own. That distinction now belongs to a rather suggestive looking creature who roamed the seas hundreds of millions of years before you, and word is he was a total d*ck. Okay, maybe he was nice, who knows, but he sure looks like one. Hence his name: penis worm.

“Hermit crabs are well known for employing snail shells as shelters against predators,” explains a press release from Durham University in the U.K., “but researchers have now found that penis worms invented the ‘hermit’ lifestyle hundreds of million years before hermit crabs first evolved.”


Before the recent study, which along with researchers from Durham included marine biologists from Yunnan University on Southern China, the first evidence of “hermit life” behavior seemed to indicate that the practice began around 170 million years ago.

In fact, modern day priapulids (the scientific name for penis worms) no longer exhibit hermit behavior, so the team did not expect to find it occurring with these organisms in the past.


In the study, the team from both universities reported on the remains of penis worm fossils that clearly show the ancient animal exhibiting hermit-like behavior over 500 million years ago. That period, known as the Cambrian, was significantly more violent and filled with predators than later eras, which is why the research teams believe the phallic shaped sea animals first adopted the behavior of hiding in the shells abandoned by other creatures.

“Perhaps it’s not a surprise that some priapulids became hermits when you think about what this predatory arms race was all about: eating, ducking and hiding,” said, Jakob Vinther, a paleontologist from the University of Bristol who was not part of the published research, in an interview with Science Daily.


With the results of their combined study published in the journal Current Biology, the team feels they have shown conclusively that although hermit crabs have been using the discarded shells of other animals as their homes for millions of years, the behavior was perfected hundreds of millions of years earlier.

“This represents the first direct evidence of a ‘hermiting’ life strategy — the adoption of a different organism’s exoskeleton — in the priapulans and within the Palaeozoic era,” the study abstract concludes.

Follow and connect with author Christopher Plain on Twitter: @plain_fiction