Acorn worms live in burrows on the seafloor so you’re not likely to ever see one. But you may see their absolutely enormous piles of poop. Snorkelers and divers have noted them for years and Nat Geo WILD shared time lapse video of the process. Since acorn worm excrement is mostly sand, it looks like the seafloor itself is pooping.
Allegedly they get their name from the acorn-like shape of their proboscis, which extends out from a fleshy collar to siphon up sand. But it looks more like a penis to me. Perhaps the scientist who discovered and named acorn worms was trying to be discreet.
Most species of acorn worms feed by swallowing sand. They digest the organic material and then excrete most of the sand back out. This is called deposit feeding. Among the tiny particles of rock and shell that make up sand are materials like algae, microorganisms, and even fish poop. The provide nutrients to acorn worms. This is also how earthworms feed on land, swallowing soil and processing only the nutritious parts.
Some species of acorn worms live in the deep sea and move around on the seafloor instead of spending most of their time in burrows. The Monterey Bay Aquarium Research Institute (MBARI) has hundreds of videos of acorn worms taken by ROVs (remotely operated vehicles). Scientists will likely discover many more unknown species. MBARI shared a video on its Twitter account that shows an acorn worm pooping in a mesmerizing spiral pattern.
Beautiful spirals of.... poop?!— MBARI (@MBARI_News) April 25, 2019
This acorn worm (Tergivelum baldwinae) crawls over the surface of the mud, ingesting sediment, and leaving behind a sinuous “fecal trail”.
More on the amazing #deepsea animals MBARI researchers have discovered: https://t.co/Ua0QtzaovU pic.twitter.com/H5i1OAaZzx
These are not the only ocean worms that resemble a penis. The so-called penis fish sometimes washes ashore after storms, alarming beach goers. And they’re also not the only sea critter with interesting poop. The Monterey Bay Aquarium reports that comb jellies poops sparkles. Truly, the ocean is a mysterious place.
Featured Image: Nat Geo WILD
Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.