How small bristle worms keep the ocean clean of whale bones

Whales are incredibly large, and without a doubt the largest mammal on the earth. Some whale species are able to live for up to 200 years, but eventually they end up dying, so where do their bones go? For some time, people just believed they would lay at the bottom of the sea until erosion tore them apart, but research has shown us that some small bristle worms are doing an amazing job with getting rid of all the bones.

The bristle worms are called zombie worms or boneworms. Their latin name is Osedax sp., which translates into “bone eating”. This genus of Osedax sp. consists of at least 15 known species, but many of them have only recently been discovered, so there is a very high chance that we will see more members of this genus in the future.

Osedax frankpressi, one of the zombie worms species. Image by Robert C. Vrijenhoek, Shannon B. Johnson & Greg W. Rouse, posted with the Creative Commons Attribution 2.0 Generic license.

What is amazing about the zombie worms is that they are able to live completely of whalebones. There are many different animal and bacterial species that are able to live of the carcass of the dead whales, but it is very rare that animals are able to live completely of the bones themselves, such as is the case of the zombie worms.

The life of a zombie worm

When whales die, the carcass will eventually sink, and become what is known as a whale fall. This is usually located in the bathyal zone, which means it is somewhere in the range of 1,000 to 4,000 meters down into the sea, meaning it is mostly pitch black there. This whale fall creates a complex small-scale ecosystem that houses different species, and in time, the carcass will be reduced to only consist of the bones. At this point the zombie worms will thrive, and creates a network of “roots” that is filled with bacteria. This bacterium has a symbiosis with the zombie worms, and helps to break down the nutrients from the skeleton.

A whale fall community with lots of different species. Image by Craig Smith, posted as Public Domain.

The zombie worm will secrete acid to bore into the bones, and release nutrients. These nutrients are absorbed directly through the skin, since the worm lacks both a stomach, mouth and anus. Waste products are released the same way once the nutrients have been digested.

Experiments have shown that the zombie worms might be able to live of the carcasses of other mammals, but it is unlikely that there are enough non-whale mammalian carcasses in the sea to sustain an ecosystem of zombie worms. So with our current knowledge, we expect these bristle worms to only feed on the skeletons of whales, which is a pretty small niche.

I found these bristle worms to be pretty incredible, and being able to completely live off skeleton remains of whales is a very cool thing to do. What is actually really cool is that they are found all over the world, just like the whales, and finding a whale fall with these zombie worms is not really that rare. I think we will learn much more about this genus in the future, considering they were discovered only 14 years ago, so we have not had a lot of time to study them yet.

About the author

Hi, I’m @valth! I live in Norway with my girlfriend, our newborn son, and our two dogs, one of which is seen wearing a bow tie in the profile picture!

I am very passionate about nature and biology, and have been studying ecology for a few years now. My passions are mostly within conservation biology, mycology (the studies of mushrooms), animal behavior and general microbiology. I really enjoy both the theoretical aspect, as well as the more practical aspect of biology, and I spend about as much time in front of biology textbooks as I do spend on finding and identifying plant, mushroom and animal species in the forests.

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