Scientists have finally tracked down the marine "unicorn," and it looks more like the stuff of nightmares than a famed fairytale creature.
Giant worms have been around for a long time, dwelling in the mud of the ocean floor and latching on sunken ships to munch on their wood.
The biggest and rarest of these fascinating marine creatures is Kuphus polythalamia, an enormous black shipworm that has managed to elude researchers for centuries — until now.
A team of marine biologists, led by Daniel Distel, from Northeastern University in Boston, eventually caught up with the mysterious creature in a sulfurous lagoon off the Philippines.
The Biggest Bivalve Mollusk On Earth
Kuphus polythalamia belongs to a class of invertebrates known as bivalve mollusks, which includes sea-dwelling creatures such as clams, oysters, mussels, and scallops.
All bivalve mollusks share a common feature: their soft bodies are encased and protected by an external covering, which is essentially a two-part hinged shell.
When Distel's team stumbled upon a group of giant shipworms, the mollusks, hidden in the mud, were only recognizable by their stick-like shells protruding from the muck.
To unravel their secrets, the researchers brought back a 3-foot-long specimen to the lab of Margo Haygood, a medicinal chemist from the University of Utah.
Thrilled by the amazing discovery, Haygood attests to the "mythical status" of the giant shipworm — the "unicorn" of the mollusk world.
Puzzle Solved: It's All About Bacteria Symbiosis
Upon studying the animal, researchers were intrigued to discover the shipworm's incredible size may be due to its peculiar feeding habits.
Just like all other shipworm species, which have developed a symbiotic relationship with bacteria to help them digest wood cellulose, Kuphus polythalamia relies on the aid of microbes for food.
However, as opposed to the majority of shipworms, this giant marine species greatly reduced its digestive organs and uses a different survival strategy. Instead of living trapped in the piece of wood that it chomps on, this creature buries itself in marine mud and depends on bacteria to cater to its needs.
Close examinations unraveled Teredinibacter turnerae bacteria living in the animal's gills process hydrogen sulfide — produced by decaying wood and plant material found plenty in the filtered water — and convert it into nourishing organic carbon.
Since the lagoon where the shipworm was found abounds in sulfide, the symbiotic bacteria were constantly exposed to this element and thus able to continuously feed the peculiar sea creature with a steady supply of food.
Distel believes this sulfur symbiosis may account for the marine worm's massive size, as it "provides them with plenty of nutrients and energy, allowing them to grow faster and larger than their relatives."
"There is not much to limit their growth, and they have a pretty unlimited source of energy from diffusing sulfide," he explained.
The researchers detailed their findings in paper, featured April 17 in the journal Proceedings of the National Academy of Sciences.