Extraordinary Clam Found Alive

By Frank Otto

Hiding inside a hard shell that’s up to four feet long and resembles an elephant tusk, there’s a dark-colored earthworm-like creature. At one end, the creature’s body forms a slight bulb. At the other, claw-like appendages. It doesn’t really eat on its own, but ingests products made by bacteria that live within it.

That sounds an awful lot like something leaked from a Comic Con panel on “Alien: Covenant,” doesn’t it?

Instead, it’s real, it’s related to run-of-the-mill clams, and we’ve known about it for centuries. It’s just that, now, we finally have seen one alive.

Kuphus polythamia, or giant shipworm, out of its shell.

Gary Rosenberg, PhD, professor in the College of Arts and Sciences and curator and Pilsbry Chair of Malacology at the Academy of Natural Sciences, was part of a team that examined and described the very first living specimen of giant shipworm, Kuphus polythamia, known to Western science. And, recently, he found specimens of his own in the Philippines.

Rosenberg gives us a closer look at the bivalve whose shells have been often found but mystified scientists for years.

Where were these first specimens finally found?

All the specimens studied for the paper I’m a co-author on were taken on Mindanao Island, in an area where it’s not safe for Westerners to travel, so our collaborators at Sultan Kudarat State University brought specimens to Manila for us to study. In this video, you can see the first one we saw alive.

Gary Rosenberg with the shell of a giant shipworm from the Academy’s Malacology Collection. Photo by Mike Servedio/ANS

You’ve since collected specimens yourself. How did you do that?

I hunted for sites where we could study Kuphus. For example, there were reports of them in the 1920s from Mindoro Island. I walked along the beaches near Puerto Galera with Joshua Torres, a graduate student at the University of the Philippines, serving as translator. We showed a Kuphus tube to fishermen, but no one recognized it, except those who had seen it in Mindanao.

Joshua and I also donned snorkeling gear and had ourselves towed by an outrigger along several miles of shoreline, looking for appropriate habitats, but without any luck.

Then, last year, I got lucky in choosing a site in southern Luzon where a member of our team finally found Kuphus alive, so we’ll be publishing follow-up reports about their ecology.

Why is Kuphus so hard to find?

They seem to be very patchy in distribution, so it’s hard to zero in on their habitat. Also, people prefer to sample on coral reefs and sandy bottoms, so the deep mud where Kuphus has been found doesn’t get much attention.

Since this is the first time we’re examining a live specimen, is there much that we know about them, like how they get around?

They probably can’t move much except to extend their burrows. To do that, they must shed the cap on their shell, extend their body, and then calcify new shell along the burrow. We can see signs of episodic growth on the shell and also imprints of the sediment that was against their body when the new shell formed.

But I still have lots of questions.

 

What are those questions? What do you hope to find out now that you know where to find live specimens of Kuphus?

Do the juveniles feed on wood like other shipworms, or have they shifted to relying on the sulfur-oxidizing symbionts [the aforementioned bacteria] throughout life?

How long do these animals live?

How fast do they grow?

Is gigantism in Kuphus associated with symbiosis, since the other largest living clams, Tridacna, the “Giant clams,” also have symbionts that provide energy to their hosts?

Kuphus had been reported from East Africa to the Solomon Islands and was first recorded in a scientific publication in 1705. Why hasn’t it been found alive before? It’s amazing that more than 300 years later, we are just beginning to understand its biology.

Kuphus polythamia samples being examined.

 

This post originally appeared on Drexel University’s News Blog.