Range: Cosmopolitan Habitat: Bones on the ocean floor Size: Up to 2 inches (5cm) long Diet: Bones Threats: None known Life span: Unknown

Transcript:

Today on Animal Fact Files we’re talking about bone worms. Have you ever wondered why the ocean floor isn’t a graveyard of whale bones? In the same way terrestrial mammal bones are broken down by terrestrial creatures, whale bones are broken down by today’s subjects. Animals belonging to the Osedax genus may be commonly known as zombie worms, bone worms, bone-eating worms, or snot worms; and these organisms thrive on whale bones! Heck, they might be found on just about any bones that end up on the ocean floor.

There’s evidence in fossils of marine birds that these worms were even dining in prehistoric times. Around the turn of the 20th century, scientists of Monterey Bay Aquarium Research Institute discovered a whale carcass on the ocean floor. The exposed bones teemed with a red, flowing substance, and upon closer inspection, a new group of animals was discovered. Bone worms are classified in the same phylum as earthworms or leeches. Currently, there are somewhere around 20 described bone worm species but more research will likely lead to the classification of more bone worm species!

Whale remains that have fallen to the bottom of the ocean are known as “whale fall”. On a single whale fall there may be multiple bone worm species. These species come in different shapes, sizes, and colors, but there are generally two features that stand out as a similarity among all bone worm species.

First, bone worms don’t have a mouth or even a stomach. Technically bone worms don’t eat whale bones, but they eat bacteria that eat the bones! Bone worms can be thought of as plants with roots. The “roots” bore into bone while the “plant” is the little brightly colored filaments that hang out outside the bone. These “plant” structures collect oxygen for the bone worms and their mutualistic bacteria living in the roots. These bacteria dissolve the bones and gain nutrients. The bone worms provide them bacteria with oxygen and protection which allows the bacteria to multiply. Eventually there is so much bacteria that the bone worms digest the bacteria themselves for nutrients. It’s a cycle!

The second similarity among most bone worm species is that the males are microscopic. Female bone worms reach about two inches (5cm) in length, or just a bit smaller than the average human index finger; male bone worms, however, are regularly less than a millimeter in length. There is one currently known outlier species to this, but in the case of all other known bone worm species, the males live on, in, or very near the females acting as nothing more than sperm banks.

Bone worms begin life as eggs that quickly hatch into larvae. If a bone worm larvae lands on a whale bone, it will develop into a female bone worm; if a bone worm larvae lands on a female bone worm, it will develop into a male bone worm. Male bone worms end up gathering around individual females as time progresses. For their first few months of life, female bone worms are believed to be less reproductively successful because they haven’t collected enough males, but as they get older and have increased the size of their harem, the females become more reproductively successful - they have more access to more sperm. This is in opposition to many animal species who lose reproductive capability as they age!

The male bone worms end up subsisting only on the yolk they hatched from their eggs with and will perish once this yolk is depleted. How long females survive is still unknown, but a bone worm community may take decades to fully break down a whale fall - at which point they will all die due to lack of food.

Bone worms have been observed in varying oceans around the world including the Pacific and Indian oceans, but they are seldom observed. They’ve also been found less than 164 feet (50m) below the ocean’s surface to depths of around 10,000 feet (3048m).

For more facts on bone worms check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.