Bootlace Worms Can Grow Longer Than Most Whales

Despite being as slender as a No. 2 pencil, this remarkable animal is one of the longest in existence, often matching or even exceeding the length of the majestic blue whale, which can grow slightly over 100 feet (30 meters).

This unique creature lacks a heart, spine, and segmented body. It hides in mud, sand, and rocky crevices across the North Atlantic. Its mucus is unexpectedly poisonous, and when it needs to feed, it deploys a complex, branching appendage that everts from its body.

Known scientifically as Lineus longissimus, the bootlace worm is a marine curiosity that could one day assist farmers in safeguarding their crops.

Blood Relatives

To truly understand the bootlace worm, one must examine its unique position on the evolutionary tree of life.

Lineus longissimus is the most prominent member of the Nemertea phylum, commonly referred to as "ribbon worms" or "proboscis worms." This group comprises roughly 1,200 known species. Unlike the segmented earthworms that enrich soil and supply bait shops, bootlace worms lack body segmentation.

Ribbon worms circulate blood through a network of vessels. Constriction of these vessel walls directs blood flow, enabling it to circulate throughout the body. Muscle movements from swimming or crawling aid this process, eliminating the need for a heart.

Probing for Supper

A hallmark feature of the Nemertea phylum is their tubular feeding apparatus, referred to as the "proboscis."

Typically stored within a specialized pouch, the proboscis is rapidly deployed when needed. By applying pressure, the ribbon worm everts the tube, effectively flipping it inside-out in a matter of seconds.

OK, but why?

Ribbon worms consume a diverse range of prey, including crabs, snails, and dead animals. Some species are even plant-eaters. Their rapid-fire proboscis is crucial for these limbless creatures to capture and handle their meals. While the bootlace worm lacks this feature, many other ribbon worms have a proboscis equipped with tiny, sharp barbs.

The proboscis also serves as a digging instrument and can startle predators attempting to prey on the worms.

It’s no surprise that other animals might feel bewildered or even threatened by this spectacle. Some ribbon worms can extend their body length twofold simply by deploying their proboscis.

If John Carpenter decides to remake "The Thing" once more, these worms would be perfect candidates for the role.

Ribbons of the Sea

Similar to most (though not all) ribbon worms, Lineus longissimus thrives in marine environments.

Bootlace worms are native to the northeastern Atlantic Ocean, inhabiting coastal regions of Iceland, Germany, the Netherlands, Scandinavia, Ireland, Great Britain, and the Baltic Sea.

These worms often coil themselves beneath large shoreline boulders. They also favor rock crevices, kelp beds, and tidal pools. Occasionally, they can be spotted gliding across muddy sands on beaches.

In deeper waters, bootlace worms are commonly found in sunlit seabed areas, weaving their elongated bodies through muddy and shell-covered terrain. Divers occasionally encounter them floating freely in the water as well.

Recognized for its dark complexion, Lineus longissimus displays hues of black and rich brown. Its skin may seem iridescent or striped to human observers. Unlike humans, ribbon worms cannot perceive images; instead, they sense light variations through basic sensory "eyespots."

A Giant in Scotland?

Despite being only 0.2 to 0.4 inches (5 to 10 millimeters) wide, the bootlace worm ranks among the longest animals on Earth.

Bootlace worms typically range from 16.4 to 32.8 feet (5 to 10 meters) in length, which is impressive for a worm, but this is only the beginning.

In a 2008 article published in Zoologische Mededelingen, biologists Adriaan Gittenberger and Cor Schipper noted that bootlace worms reaching up to 98.4 feet (30 meters) have been "frequently observed."

If the thought of a squirming worm longer than a New York City bus makes you uneasy, you might want to skip the next few lines. What follows is even more astonishing.

A massive bootlace worm carcass reportedly washed up on a Scottish beach in 1864. It was said to stretch over 180 feet (55 meters) from end to end!

Such claims should be approached with skepticism. As Gittenberger and Schipper pointed out, no preserved specimens of bootlace worms approaching this size exist in the scientific record.

This means the existence of a 180-foot-long (55-meter-long) Lineus longissimus remains unverified. Additionally, ribbon worms are highly stretchable and elastic, making it challenging to determine their true maximum lengths. Apologies for the disappointment.

The Benefits of Toxins

Interacting with bootlace worms is far from pleasant. To deter predators and curious humans, these invertebrates secrete copious amounts of thick, foul-smelling mucus when threatened.

However, this mucus holds more than just an unpleasant odor.

Researchers have found that the bootlace worm's defensive mucus contains potent peptide toxins. In 2018, a study revealed an entirely new category of these toxins, previously unknown to science.

According to researchers involved in the 2018 study, the most prevalent peptide, known as "nemertide α-1," is likely harmless to humans and other mammals. However, cockroaches should steer clear.

Laboratory experiments revealed that nemertide α-1 disrupts nerve and muscle activity in green crabs (Carcinus maenas) and Dubia roaches (Blaptica dubia), often resulting in death or permanent paralysis.

"Nemertide α-1 has a profound impact on crustaceans and cockroaches, making it a potential candidate for highly effective insecticides," explained Ulf Göransson, the study's lead author, in a 2018 interview with SciNews.

In the future, compounds derived from the bootlace worm's mucus could play a role in protecting farms and crops from destructive insects. After all, stranger innovations have emerged.