A slimy black tube-shaped creature with size of a baseball bat has been eluding scientists for centuries. They have examined its external shell, but until now, they never laid eyes on the alien-like physique hidden.
Researchers have finally had a chance to study a living specimen of the giant shipworm (Kuphus polythalamia), which is not actually a worm despite its name, but a bivalve. It is kind of aquatic mollusc enclosed in its shell, and a decidedly mysterious breed at that.
Margo Haygood, marine microbiologist from the University of Utah told The Washington Post: “It’s sort of the unicorn of molluscs.”
“It’s quite heavy. It’s like picking up a tree branch or something even heavier. The living animal is just magnificent.”
Haygood and her team met the first living giant shipworm specimen after a tip-off about a segment on a Philippine TV documentary, which showed numerous shipworm shells sticking out of a shallow lagoon, like carrots planted in a bizarre, muddy crop.
The animal grows up to about 90 centimetres (roughly 3 feet) in length. It lives upside down in its shell, most of which is submerged beneath mud in shallow bays in the Philippines.
The head and mouth of this animal are located at the base of the shell, deep within the mud – and were it not for the tell-tale tip of the shell indicating where these planted molluscs were holed up, the giant shipworm might have successfully eluded scientists for another couple of centuries.
Daniel Distel, researcher from Northeastern University, says: “I’ve been studying shipworms since 1989 and in all that time I had never seen a living specimen of Kuphus polythalamia.“
“It was pretty spectacular to lift that tube out of its container for the first time. To see this giant gun-metal black specimen was amazing. On the one hand, I was pretty excited to see what it looked like inside. On the other hand it was a little intimidating to dissect this incredibly rare specimen.”
Other shipworms are light in colour like clams, being white, beige, or pink. But the giant shipworm is quite contrary, it is like a dark, slick alien – and another point of difference is how it stays alive.
The giant shipworm lives off hydrogen sulphide gas produced by the mud it calls home, unlike other species of shipworm, which burrow into timber that falls into water and end up digesting the wood.
Although it is only a hypothesis at the moment, the team thinks the giant shipworm might once have consumed wood like its cousins, before evolving to live off sulphur compounds in the gas.
To pull off this trick, bacteria that live in the animal’s gills use the hydrogen sulphide to produce organic carbon that feeds the shipworm.
This symbiotic relationship is enough to keep the giant shipworm alive – but the practice has left the creature’s internal digestive organs shrunken from lack of use.
This survival mechanism explains how the giant shipworm manages to eat, given the shell it secretes covers its whole head (and mouth).
“If they want to grow, they have to open that end of that tube, so somehow dissolve or reabsorb that cap on the bottom, grow, extend the tube down further into the mud, and then they seal it off again,” Distel told Nicola Davis at The Guardian.
Although there’s still a lot we don’t understand about this captivating creature, we have a fresh lead on where to find them it’s likely we’ll discover a lot more.
For the scientists who were involved in hunting the giant shipworm for decades, the result is basically mythical in proportion.
Distel says: “To me it was almost like finding a dinosaur, something that was pretty much only known by fossils.”