Bootlace worms boast spooky-stretchy bodies. Their secret: They also secrete a family of toxins new to science. These poisons might one day inspire novel ways to control noxious pests, such as cockroaches.
Tests first identified the toxins in the mucus coating one bootlace species. It holds the record as the world’s longest animal, notes Ulf Göransson. At Uppsala University in Sweden, he studies medical products that come from natural sources. This champion marine worm, Lineus longissimus, can stretch up to 50 meters (164 feet). That’s longer than an Olympic-size pool. The worm coats itself in mucus that smells a bit like iron or sewage. This goo holds small toxic proteins that have now been dubbed nemertides. Those poisons also have shown up in 16 other species of bootlace worms.
Göransson and his colleagues shared their discovery March 22 in Scientific Reports.
These nemertides poison by attacking some of the tiny channels in cell walls. These channels control the flux — flow rate — of sodium moving in and out of a cell. Much vital cell business depends on the right flux through these sodium channels, as they’re called. Among that important business: cell-to-cell communication.
The researchers injected small amounts of one nemertide into invasive green crabs (Carcinus maenas). The toxin permanently paralyzed or killed these animals.
“This study certainly has a lot of novelty to it, since marine worms are a tremendously neglected area of venom research,” says Bryan Grieg Fry. He works at the University of Queensland in Brisbane, Australia. There, he explores how animal poisons appear to have evolved.
Unlike earthworms, the 1,300 or so species of bootlace — or ribbon — worms have no segments. Some scientists give these animals their own branch, call Nemertea, on the animal family tree. Bootlace worms have a brain but no lungs. Like many other slender marine creatures, these worms breathe directly through the skin. They predators that dine on crustaceans, mollusks and other worms.
One has to marvel at how they can expand and contract their bodies. A 10-meter [33 foot] L. longissimus “can be held in your hand as a slimy heap,” notes study coauthor Malin Strand. She’s a marine biologist at the Swedish University of Agricultural Sciences in Uppsala. She estimates these worms could live 10 years “or maybe much longer.”
How bootlace worms use their toxins isn’t clear. The stringy creatures aren’t easy to keep in captivity for study, Strand says. She has some worms in her lab that have chosen to eat no more than once in three to four years.
Göransson proposes that their toxic mucus might make a useful defense. He has seen videos with the worms stretched upon the seafloor. “If you’re a crab or a fish, it must be tempting to take a nip,” he says. However, there’s little sign of anything pestering these worms.
He once tried some bare-handed contact with a small lab specimen. He didn’t feel much of anything. He’s been warned, though, about “tingling.” Just in case, Göransson now wears gloves.
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biology The study of living things. The scientists who study them are known as biologists.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
coauthor One of a group (two or more people) who together had prepared a written work, such as a book, report or research paper. Not all coauthors may have contributed equally.
colleague Someone who works with another; a co-worker or team member.
compound (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.
crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
defense (in biology) A natural protective action taken or chemical response that occurs when a species confront predators or agents that might harm it. (adj. defensive)
earthworm A type of worm that lives in the soil. As it moves through soil, an earthworm creates burrows. These allow air and water to move more readily through the soil. The worms feed on decaying organic matter, which helps improve soil fertility.
evolution (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the particular conditions in which it developed.
flux A term for the flow of some liquid, sometimes described as a measured rate of flow (such as liters per hour). Or it can refer to a substance used to enhance the fusion of metals or minerals (such as the rosin used to aid in the soldering of metals).
green crab A species of crab (Carcinus maenas) that is native to the coasts of northern Europe. It has invaded areas outside its home range, both along the Atlantic and Pacific coasts. It is a voracious feeder and will eat many important species as it invades their habitats.
marine Having to do with the ocean world or environment.
marine biologist A scientist who studies creatures that live in ocean water, from bacteria and shellfish to kelp and whales.
mollusks Soft-bodied invertebrate animals that usually live in water and develop a hard protective shell. Examples include snails, shellfish (like clams and oysters), slugs, octopuses and squids.
mucus A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.
novel Something that is clever or unusual and new, as in never seen before.
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
Queensland One of the states that makes up the northeast corner of the country of Australia.
secrete (noun: secretion) The natural release of some liquid substance — such as hormones, an oil or saliva — often by an organ of the body.
sewage Wastes — primarily urine and feces — that are mixed with water and flushed away from homes through a system of pipes for disposal in the environment (sometimes after being treated in a big water-treatment plant).
sodium A soft, silvery metallic element that will interact explosively when added to water. It is also a basic building block of table salt (a molecule of which consists of one atom of sodium and one atom of chlorine: NaCl). It is also found in sea salt.
species A group of similar organisms capable of producing offspring that can survive and reproduce.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
toxin A poison produced by living organisms, such as germs, bees, spiders, poison ivy and snakes.
venom A poisonous secretion of an animal, such as a snake, spider or scorpion, usually transmitted by a bite or sting.
Journal: E. Jacobsson et al. Peptide ion channel toxins from the bootlace worm, the longest animal on Earth. Scientific Reports. Vol. 8, published online March 22, 2018. doi: 10.1038/s41598-018-22305-w.