Your experience with worms may extend only to seeing them on the sidewalk on a rainy day or trying to get one to stay connected to a fishing hook. Those types of worms come from the segmented variety. There is a whole other world of the wriggly, slippery things. Welcome to the wonderful, weird, and sometimes freaky world of the ribbon worm.
Ribbon worms (phylum Nemertea) are typically found in the ocean. More than 1,000 species offer an unending variety of appearances and capabilities.
Powerful Probing Proboscis Pummels Prey
The most notable identifier of the ribbon worm is its proboscis. Picture a rubber glove with one of the fingers turned inside out. That is how the proboscis appears most of the time. When the ribbon worm attacks its prey, it can extend the proboscis through its special muscular structure to grab its meal.
Different species have their own variation of proboscis. Some have suckers. Others are sticky. Some come with a sharp spike called a stylet that acts as a dagger.
The Long and the Short of It
Ribbon worms can be found in all sizes. The smallest is less than a centimeter in length. At first glance, you might mistake it for a discarded piece of thread. On the other side of the scale is the bootlace worm, (Lineus longissimus). It is possibly the longest animal on the planet, with specimens found that have reached 60 meters (197 feet) — even longer than the blue whale. Despite their length, they are less than an inch in diameter.
Using Muscles to Shrink, Rather Than Bulk Up
When threatened, ribbon worms use their muscles in a counter-intuitive way. Rather than make a show of force, the special muscle structure causes the worm to contract, shrinking to about one-tenth of its regular size.
When the Appetite is Bigger than the Stomach
We’ve all regretted those times when filling our plates with more than what we can reasonably consume. This is not a problem for the ribbon worm. The same musculature that allows the worm to shrink can cause it to expand to consume a meal that is more than double the width of its body.
The Myth About the Mouth
There is one “fun fact” about the ribbon worm that does seem to stand up to reality. If you search for “Fun Facts About Ribbon Worms” one of the most common results will be the tidbit that they are able to eat parts of their own bodies if sufficiently hungry. That, in fact, is what inspired this article in the first place. Sadly, there does not seem to be any documented evidence to support the claim.
For now, we are obliged to classify this supposed “fact” as an urban legend. If anyone has some hard evidence to tell us otherwise, please write or leave a comment below.
Leaving a Nasty Taste in Predators’ Mouths
Many ribbon worms generate deadly poisons. Some contain tetrodotoxin, the same venom that is found in pufferfish. Others may not be deadly to eat but they produce a vile flavor. While this might not be particularly helpful to the worm that gets gobbled up by a predator, its death will not be in vain, since the predator is unlikely to seek out any similar ribbon worms for a second bite.
Paralyzing Predators From the Deep
The way some ribbon worms capture their prey is the stuff of nightmares. To watch the spectacle, you might think you are witnessing the attack of a malevolent alien life form.
One species of ribbon worms likes nothing more than to snack on fiddler crabs. The way it does this is by burying itself in the sand, waiting for the unsuspecting crab to saunter by. Once the crab is within reach, the worm springs out of the sand, covers the crab with toxic slime from its proboscis, resulting in the crab’s immediate paralysis. Unable to resist, the crab must endure the waking nightmare of waiting for its attacker to worm its way into a crack in its armor shell and begin consuming the crab from the inside out.
Petrifying Parasites From the Deep
Not all ribbon worms are predators, but that doesn’t make the exceptions cute and cuddly. Some are parasites. The Carcinoemertes lives as a parasite on crabs and devours its host’s eggs before they can hatch.
Masters at Multiplication
Ribbon worms are nothing if not versatile. There are male and female worms, but they like to travel light, so their reproductive organs are temporary. When not needed, their organs are absorbed into the body.
Baby ribbon worms typically emerge from a fertilized egg, looking like a tiny version of their parents. With a creature as odd as this one, you can expect exceptions to every rule, and you find it here with the heteronemerteans. They emerge from the egg looking like little flying saucers. They remain this way for a few weeks, zooming through the ocean, while a small worm develops inside the saucer-like structure. When it is ready, the worm eats its way out of the saucer and falls to the ocean floor, where it lives out the rest of its life.
Experts at healing, many ribbon worms will grow back any part of their body that is removed. There is one species, however, that takes this to a whole new level. Ramphogordius sanguineus can grow a whole new worm off of just about any part of its body that is cut off. With the exception of its tail, which has no nerves, when a piece is cut off, it has the potential to grow into a new little critter. From one 15-centimeter (6 inch) worm, more than 200,000 clones can be cut off and generated.