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SCIENCE
 

Creature from the shallow lagoon: mysterious giant shipworm is found

The giant shipworm lives in a shell planted in the mud in shallow bays in the Philippines. It is about the size of a baseball bat. Photo: Marine Science Institute/Marvin Altamia.
The giant shipworm lives in a shell planted in the mud in shallow bays in the Philippines. It is about the size of a baseball bat. Photo: Marine Science Institute/Marvin Altamia.

About 3 feet long and glistening black with a pink, fleshy attachment, it looks like the guts of an alien from a bad horror film. But it's no alien. In fact, it is a giant shipworm.

Discovered in the mud of a shallow lagoon in the Philippines, a living creature of the species has never been seen before. However, its existence has been known for more than 200 years thanks to fossils of the baseball bat-sized tubes that encase the creature.

Although people have known these animals exist, "they didn’t know the simplest things about them,” said Dan Distel. He works for Northeastern University’s marine science center in Massachusetts and is co-author of a study published in the journal PNAS. “It was a very mysterious organism.”

Distel points out that a description based on a museum specimen was made decades ago, but adds that the creature was not well preserved. “We think, among living biologists, anyway, our group is probably the only group that has seen living specimens,” he said.

Living In A Tube In The Mud

With the classification Kuphus polythalamia, the creature lives in the mud inside a long tube made of calcium secreted by the animal. The tube forms a casing for the beast, including its head. “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,” said Distel.

The end of the tube, adds Distel, is Y-shaped and surrounds two siphons. Water is drawn in through one, pushed through the creature’s gills, then expelled through the other.

Despite being known as a shipworm – a nod to its relatives’ diet of submerged wood – the animal is actually a type of clam. It has a modified version of two clam shells at its head, while the body stretches out behind. “Its body has been stretched out through evolution so that it no longer fits between the two shells,” said Distel. 

The team stumbled across a clue to the creatures’ whereabouts thanks to a YouTube video of a Philippine television news report. They asked academics in the region about possible locations and subsequently located a crop of the tubes in a lagoon full of rotting wood. The location, adds Distel, remains a secret to prevent the site from being disturbed by shell collectors.

A Beefy Black Bivalve

Divers collected tubes found pointing up around 10 feet below the surface. “That tube is anywhere from maybe 75 percent to 80 percent buried in the mud,” said Distel. About half a dozen were shipped to the laboratory, where the team cautiously opened one.

“It was really quite amazing," said Distel. “I didn’t even have any idea how to open it, but I thought, ‘Carefully.’”

The appearance of the shipworm when it slid out of the tube came as a surprise to the researchers. “That color of the animal is sort of shocking,” Distel said. “Most bivalves are greyish, tan, pink, brown, light beige colors. This thing just has this gunmetal-black color. It is much beefier, more muscular than any other bivalve I had ever seen.”

But it isn’t just its discovery that stunned researchers. The giant shipworm is also surprising because of its mode of survival. A large size is usually an indication of ample food, said Distel. Other shipworms feed on submerged wood with the aid of wood-degrading bacteria that live in their gills, but the newly discovered specimen had only a tiny digestive system, while the fact that the creature was enclosed in a tube suggested it was not eating mud.

Relying On Bacteria To Live

The giant shipworm is about the size of a baseball bat. Image: University of Utah/Washington Post. [click to expand]

Further work revealed that the creature relies on bacteria that live inside its gills. The bacteria help the giant shipworm get energy from sulfur in the water. Some bacteria are able to oxidize hydrogen sulphide, from which the bacteria produce energy. 

That energy is then used to turn carbon dioxide into food for the shipworm. It is similar to the way plants get food through the process of photosynthesis, in which they take in carbon dioxide, water and sunlight.

The shipworm gives the bacteria a place to live and the bacteria feed the shipworm. This mutually beneficial partnership is called a symbiotic relationship.

"Like Finding A Dinosaur"

The discovery, Distel adds, sheds light on how symbiotic relationships between sulphur-oxidizing life forms and other creatures may have evolved over millions of years. The finding also backs up the possibility that sunken wood might have played a role in how such species ended up in locations such as deep sea areas. “To me it was almost like finding a dinosaur – something that was pretty much only known by fossils,” he said.

Simon Watt, biologist, TV host and president of the Ugly Animal Preservation Society, welcomed the discovery of the giant shipworm. “It might well be monstrous, but that does not mean that it isn’t marvelous,” he said. He pointed out that the creature has evolved to live in an environment that is also “pretty disgusting.” If you are down living among murky dirt, then looking good is surely not your top concern, he added.

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Anchor 4: Word Meaning & Choice

Read the selection from the section "Living In A Tube In The Mud."

The team stumbled across a clue to the creatures’ whereabouts thanks to a YouTube video of a Philippine television news report. They asked academics in the region about possible locations and subsequently located a crop of the tubes in a lagoon full of rotting wood.

How does the phrase "stumbled across" affect the meaning of the first sentence?

A

It suggests that the team was awkward at first as it searched for the clue.

B

It indicates that the team made an error when it found the clue.

C

It indicates that the team found the clue by accident.

D

It suggests that the team found the clue when it tripped over some rotting wood.

2
Anchor 4: Word Meaning & Choice

Read the sentence from the section "A Beefy Black Bivalve."

About half a dozen were shipped to the laboratory, where the team cautiously opened one.

In the sentence, the word "cautiously" connotes a sense of:

A

concern

B

competence

C

cooperation

D

commitment

3
Anchor 7: Multimedia

Read the first paragraph of the article.

About 3 feet long and glistening black with a pink, fleshy attachment, it looks like the guts of an alien from a bad horror film. But it's no alien. In fact, it is a giant shipworm.

Which statement accurately compares the graphic "Giant Shipworm" with the paragraph above?

A

The paragraph describes the appearance of the giant shipworm in exactly the same way it is portrayed in the graphic.

B

The paragraph focuses solely on how the giant shipworm looks and the graphic focuses solely on what the shipworm eats.

C

Except for the reference to size, the paragraph and the graphic are completely different in the type of information they present.

D

Except for the reference to a bad horror film, the paragraph and the graphic present exactly the same information.

4
Anchor 7: Multimedia

Which sentence from the article is BEST supported by information in the graphic "Giant Shipworm"?

A

The end of the tube, adds Distel, is Y-shaped and surrounds two siphons.

B

"It is much beefier, more muscular than any other bivalve I had ever seen.”

C

The bacteria help the giant shipworm get energy from sulfur in the water.

D

Some bacteria are able to oxidize hydrogen sulphide, from which the bacteria produce energy.

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