Ribbon worm’s star turn shows its dynamic range

Published May 18, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott

A friend sent the link to the video above with a note: “This worm is trending on YouTube. Have you seen it?”

I have now, many times, because unlike unenlightened viewers who wrote “Gross!” “Creepy!” “Disgusting!” and worse, I loved it. This is why so many of us are crazy about marine biology. The animals are out of this world.

The video shows a ribbon worm in hunting mode.

Ribbon worms are carnivores that eat shrimp, crabs, clams and segmented worms (another kind of worm). Most are flat but thicker.

The video came from Thailand but ribbon worms are widespread. Researchers have identified about 1,200 species. Hawaii hosts 10.

Most are about 8 inches long, but some are so small they’re barely visible. At the other end of the spectrum is the bootlace worm, reaching the extraordinary length of 100 feet.

I imagined that a worm so outlandishly long would be rare. But no. Living in a twisted heap under rocks and in sand and mud, the bootlace worm is common along the shorelines of the British Isles.

Besides the huge range of sizes, ribbon worms also come in various colors and patterns. But all species of ribbon worms have one famous feature in common: a long flexible snout called a proboscis.

The snout isn’t a mouth, nor is it even connected to the digestive tract. A ribbon worm’s proboscis is an eye-popping tool that it uses to catch prey.

Inside the snout is a fluid-filled cavity holding a coiled, hollow, branched tube with an opening to the outside at the tip. Lining the inside of the convoluted tube is a sticky toxin. Some species have a barb at the far end of their tube to deliver their toxin by stabbing.

When the worm finds something live to eat, it contracts muscles around the snout, causing the tube to shoot out the hole inside out. (Picture blowing a latex glove inside out.) The tube’s gluey inverted branches wrap around the prey, and the toxin paralyzes it. In species with a barb, the worm injects its toxin.

Once the prey is immobile, the worm sucks the animal into its mouth, located on the underside.

As if that’s not enough coolness in one creature, when it comes to reproducing, ribbon worms take no chances. The worms are either male or female and can reproduce with sperm and eggs. But this is no hit-or-miss spewing in the water as is common in other marine animals. In some species, when the female finds a male, she builds a cocoon around herself and her mate. Thus enclosed, the sperm hits right on target.

Other species can clone themselves, handy when a member of the opposite sex isn’t available. The worm’s body breaks at preformed places that look like rings, and each piece grows into a complete worm.

I watched this 29-second video over and over — on mute because I disliked the creepy sound effects.

Ribbon worms are stunning designs of nature. I hope that someday we will live in a world where, about such extraordinary animals, people will write, “Fantastic!” “Brilliant!” “Excellent!”

And play Elvis Presley’s “Stuck on You.”


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2015 Susan Scott