Weird Marine Worms: Penis Fencers, Purple Socks and Toxic Ones 55 Meters Long

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Christmas Tree worms, kinds of bristleoworms

Among the longest-living animals on Earth are Escarpia laminata, a species of tube worm found in the Gulf of Mexico that has an average life span of about 300 years. Bristleworms are centipede-like creatures. Some 15-centimeter (six-inch) -long creatures have poison-tip spines that stick up from their bodies and produce an excruciating sting. Marine bristle worms and tube worms are members of the annelida phylum along with earthworms and leeches. They have long long flexible tubelike bodies divided into compartments. Some sea worms build their tubular homes with mucus, it, using it as cement.

Bermuda Glow Worm (Odontosyllis enopla) are small annelids — males are about 3.7 centimeters (1.4 inches) and females are twice as long — that come out to mate in huge swarms synchronized in phases with the full moon and they glow while they’re mating. “After sunset on the fifth day after the fullest of the full moons, the females will come up to the surface,” Dr. Mark Siddall, Curator of the Division of Invertebrate Zoology at the American Museum of Natural History,, told Mental Floss. “They’ll swim really fast in tight circles, and they’re [bioluminescing] a very bright blue. They look like little stars in the water.” This bright swarm attracts the males, who shoot up from the depths, also bioluminescing. “They come up really, really fast, like comets, jetting up to where the females are. When they get there, they dump their sperm in the water, and the females dump their eggs in the water, and that’s how they get the job done.” [Source: Erin McCarthy, Mental Floss, April 9, 2015]

Bloodworms (Genus Glycera) are commonly used by marine fishermen. They have a large proboscis equipped with four hollow pincers that are made out of a form of crystallized copper called atacamite. “The only other place you find [it] is in the Atacama Desert in Chile, where it’s formed by volcanoes,” Siddall says. “In order to be able to produce those fangs, it has to be able to withstand an enormous concentration of copper in its body, which can be toxic to other organisms.” Though scientists aren’t exactly sure why the worms have copper pinchers, some, according to Siddall, believe that the copper activates the creature’s venom. “They’ve got venom glands at the base of each of these fangs and they’ll grab onto prey and envenomate it,” he says. And as you might imagine, getting bitten by a bloodworm isn’t pleasant—which Siddall knows from experience. “When the proboscis comes out, it spreads the four fangs,” he says. “When they draw the proboscis in, those four fangs close on the spot. It’s like a grappling hook. It hurts like hell.”

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase; Encyclopedia of Life; Smithsonian Oceans Portal ; Monterey Bay Aquarium ; MarineBio; Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) ; International Coral Reef Initiative ; Coral Reef Alliance ; Global Coral reef Alliance ; Global Coral Reef Monitoring Network

Bobbit Worms

Bobbit Worms (Eunice aphroditois) are scary-looking, iridescent creature that get their common name from Lorena Bobbitt, the woman who cut off her husband’s penis in 1993. The worm buries its body — which can grow up to three meters (10 feet) long, making it one of the longest polychaetes in the world — in the sea floor, but leaves its head, with five sensory antennae and an open set of horrifying jaws, exposed. The ambush hunter waits patiently for prey to come within range. When prey gets close enough, the worm’s antennae sense it, and the jaws snap closed, like a bear trap, sometimes with enough force to cut a fish in two. [Source: Erin McCarthy, Mental Floss, April 9, 2015]

After that the worms pulls the prey into its lair. Luis F. Carrera-Parra and Sergio I. Salazar-Vallejo, who study annelid polychaetes at Mexico’s El Colegio de la Frontera Sur, told Wired, “We think that the eunicid injects some narcotizing or killing toxin in their prey animal, such that it can be safely ingested—especially if they are larger than the worm—and then digested through the gut.”

According to Scientific American, these worms can inflict a painful bite—but because they live on the ocean floor at depths between 10 and 40 meters (32 and 131 feet), humans rarely encounter them. Matt Slater, curator at Newquay's Blue Reef Aquarium in Cornwall, England, said his workers discovered a 1.2-meter (4-foot) -long bobbit worm in their tank and also discovered that the creature was “covered with thousands of bristles which are capable of inflicting a sting resulting in permanent numbness,” he told the Daily Mail. It is unclear where the worm’s common name comes form as females don’t cut off the male’s penish because they “don’t have penises,” Siddall says. “They’re broadcast spawners,” animals that release sperms and eggs into the water at the same time, letting nature take its course from there.

Scientists Find Lairs of 20 Million-Year-Old Bobbit Worms

Bobbit worm

Elizabeth Gamillo wrote in Smithsonian,org: Camouflaged in sandy loam, ancient giant worms waited for unsuspecting prey to swim within their reach and then suddenly emerge from the ground in a snap to pull fish to their demise. Now, 20 million years later, researchers have uncovered these colossal sea predators’ hideaways, according to a study published in January 2021 in Scientific Reports. The burrow may be the earliest known fossil of an ambush predator. [Source: Elizabeth Gamillo, Smithsonian,org, January 26, 2021]

The L-shaped lair found imprinted in ancient seafloor sediment from Taiwan measured about 7 feet long and one inch wide, reports Mindy Weisberger for Live Science. The worms that burrowed in these tunnels may have been the ancestors of modern Bobbit worms, Eunice aphtoditois. Bobbit worms or bristle worms have been around since the Cambrian period, reports Live Science, and they can be anywhere between a few inches to 10 feet long. The worms also have sharp teeth, hide within the ocean floor, and use their antenna to sense when prey is nearby. When the Bobbit worm feels something above them, it will lunge out of the sand to snatch and gobble up the ill-fated prey.

The trace fossils were first unearthed in the Yehliu Geopark and Badouzi promontory in Taiwan by accident. Kochi University biologist Masakazu Nara was looking at the rocky sediment for evidence of stingray feeding behavior. Instead, Nara found the secret caves of the ancient sea worms reports, Riley Black for National Geographic.

At first, scientists did not understand what constructed the underground burrows. Many other sea animals like clams, crustaceans, and sea urchins also burrow into the seafloor. From a total of 319 fossil specimens found, scientists saw the worms left a funnel-like structure at the start of the tunnel reports, Helen Thompson for Science News. The strange form hinted towards the animal living within these burrows was violent by nature, with the flared entrance likely a sign of a predator moving in and out of the den, reports Ian Sample for the Guardian. “It’s not one feature that convinced us this burrow was made by a worm but the combination of features. The funnels indicate a violent event,” paleontologist and study co-author Ludvig Löwemark tells National Geographic.

Researchers also found iron deposits along the top of tunnels’ walls, reports Science News. The iron deposits were most likely leftover from mucus used to reinforce damaged walls after the worms snatched up their prey, says Live Science. There are no fossilized remains of the worms themselves, however, because finding preserved soft-tissues is rare. The evidence found suggests that if the worms were the ones who made the tunnels, it could be an ancient example of invertebrates hunting vertebrates, reports Science News.

Penis-Fencing Flatworms

Deep on the ocean floor, hermaphroditic flatworms duel with their penises during the mating season. The loser has to take care of the eggs of the winner. Each worm has a pair of penises, which resemble white, thin-tipped daggers. They are filled with sperm and the first worm to stab the other injects his sperm into the loser’s body.[Source: Katherine J. Wu , Rachael Lallensack,, February 14, 2020]

Penis fencing is mating behavior practiced by many species of flatworm, such as Pseudobiceros hancockanus. The flatworms "fence" using extendable two-headed dagger-like stylets (“penises”). These stylets are pointed (and in some species hooked) in order to pierce their mate's epidermis and inject sperm into the haemocoel (the main body cavity) in an act known as intradermal hypodermic insemination, or traumatic insemination. Pairs can either compete, with only one individual transferring sperm to the other, or the pair can transfer sperm bilaterally. Both forms of sperm transfer can occur in the same species, depending on various factors. [Source: Wikipedia]

Unilateral sperm transfer takes place when one worm inseminate the other, with the inseminating individual acting as the "father". The sperm is absorbed through pores or sometimes wounds in the skin from the partner's stylet, causing fertilization in the other, who becomes the "mother". The duels last for up to an hour in some species. Many hermaphroditic species mutually inseminate, or trade sperm, rather than compete, The tiger flatworm, Maritigrella crozieri, for example, transfers sperm bilaterally. In many species that engage in bilateral insemination, sperm trading is conditional. If one partner "cheats", and does not transfer sperm, the other partner will either prematurely abandon the partner, or will engage in typical mating behavior without transferring sperm.

Purple Socks

Elizabeth Kolbert wrote in the New Yorker:“Xenoturbella profunda is a creature that looks like a discarded tube sock. First collected from a vent system in the Gulf of California in 2015, it has no intestines or central nervous system, and scientists aren’t even sure what phylum it belongs to. [Source: Elizabeth Kolbert, The New Yorker, June 14, 2021]

The common name of Xenoturbella profunda is the purple sock or sock worm. It is benthic, deep-water worm-like species that belongs to the genus Xenoturbella. It was discovered in eastern Pacific Ocean by a group of Californian and Australian scientists and was described in 2016 from seven specimens. X. profunda shares morphological similarities with other species of the genus Xenoturbella, and is known for lacking respiratory, circulatory and an excretory system. The purple soack was ultimately placed Xenacoelomorpha, a small phylum of bilaterian invertebrate animals, consisting of two sister groups: xenoturbellids and acoelomorphs.

Xenoturbella profunda individuals were sampled at depth of around 3,700 meters (12,140 feet) depth near a carbonate-hosted hydrothermal vent in the Gulf of California. The animal is 15 centimeters (5.9 inches) in length, with a uniform pale pink colouration. The body wall displays several furrows: on the circumference, on the side, and two deep, longitudinal, dorsal ones. The longitudinal orientation involves a rounded anterior end, while the posterior end gradually reduces in thickness. The mouth is orientated ventrally, anterior to the ring furrow. The live specimens exhibited an epidermal ventral glandular network branching over two-thirds of the ventral surface. The species is gonochoric, and gametes are present dorsally and ventrally in the body wall. Tissues contain exogenous DNA corresponding to a bivalve mollusk, the vesicomyid Archivesica gigas.

Giant Tube Worms of Deep Sea Hydrothermal Vents

Giant tube worms (Scientific name: Riftia pachyptila) live on the East Pacific Rise, more than 1.6 kilometers (a mile under the sea) under the surface in sulfide rich environments around hydrothermal vents on the ocean floor. The taxonomic status of this strange group of worms is still has n’t been worked out. There are several different scientific opinions about which group the worm species belongs to. [Source: Brent Privett, Animal Diversity Web (ADW) /=]

Adult giant tube worm has a tough chitonous tube that grows to over three meters tall. At the top of the tube is a large red plume containing hemoglobin that gives giant tube worm the appearence of a giant paintbrush . Inside the tube, the worm's body is colorless, and holds a large sack called a trophosome (along with its other organs). This sack contains billions of symbiotic bacteria that make food for the worm. The worm has no mouth, eyes, or stomach.

Giant tube worm depends on a symbiotic relationship with chemosynthetic bacteria for its food. Although it has no mouth or gut it is born with a mouth through which the bacteria enter. The tube worm uses a feeding sac (called a trophosome) to gather sulfuric chemicals that the bacteria uses to make food for the worm. /=\

During reproduction, females release lipid rich eggs which float slowly upward. Males release sperm bundles that contain hundreds of sperm cells. The sperm bundles then swim up to meet the eggs where they are fertilized. Larval Giant tube worm drift in the deep water, trying to find a hydrothermal vent that they can live near. They will settle down and attach to the rocky bottom when they detect the right chemicals in the water. They swim down near the hydrothermal vents and attach to solidified lava where they grow to form new tube worm communities.

Bootlace Worms — Toxic and Longer Than Blue Whales?

Bootlace worms (Lineus longissimus) by some reckonings are the longest animal on in the world. They are usually five to 15 meters (15 to 50 feet) in length, but can be up to 55 meters (180 feet) long. The 55 meter record is contested is it reportedly was obtaining by stretching out the very elastic and stretchable worm. Typically they one half to one centimeter (less than a third of an inch) thick. These worms are Nemertea, a phylum of invertebrate animals also known as ‘ribbon worms’ or ‘proboscis worms.’ They live in northern Atlantic Ocean and have been observed off the coasts of Norway, Britain, Denmark and Sweden. [Source: Sci News, March 27, 2018]

Sci News reported: The bootlace worm produces a neurotoxin that can kill both crabs and cockroaches, a team of Swedish scientists has discovered. When the bootlace worm is irritated, it releases large amounts of thick mucus that is poisonous for crustaceans. Professor Ulf Göransson of Uppsala University and co-authors extracted the most prevalent peptide toxin from the bootlace worm’s mucus and discovered that it could paralyse and kill crustaceans and cockroaches. “We already know that peptide toxins are found in, for example, cone shells that live in tropical waters,” he said. “This peptide toxin, named nemertide α-1, is the most poisonous substance to have been found in Sweden’s animal kingdom and the fact that it may be possible to use it makes the discovery even more exciting.”

Toxins often affect the ionic channels, that is, proteins that control the transport of different ions in and out of cells. Professor Göransson’s team showed that the isolated toxin impedes the inactivation of the sodium channels in three species of invertebrate animals: the German cockroach, fruit fly and Varroa mite. That causes continual electric signalling in nerves and muscles, which gives rise to paralysis. Laboratory tests were conducted to investigate how the toxin affects the sodium channels of mammals. There, the reaction was not nearly as strong. “Therefore, we believe nemertide α-1 is probably not poisonous for humans or other mammals,” the researchers said.

The team’s findings were published in the journal Scientific Reports. “Today, similar neurotoxins that have been extracted from snakes, spiders and cone shells are used, for example, as pharmaceuticals, pharmacological tools, in biotechnology and as agricultural insecticides.We believe that the toxins from the bootlace worm can also be used to develop new insecticides. Nemertide α-1 has a very powerful effect on crustaceans and cockroaches, which is why it could serve as a very effective insecticide,” Professor Göransson said.

Divers Come Face to Face with 8-Meter Marine Worm

In 2018, divers off the coast of New Zealand came face to face with a giant sea worm that was almost eight meters (26 feet) long. BGR reported: “The creature is called a pyrosome, and while it might look intimidating, it’s actually perfectly safe to approach. Pyrosomes are part of a family of sea creatures known as tunicates or “sea squirts”. They’ve also been called cockroaches of the sea, National Geographic notes, due to their ability to pull food from even the most inhospitable environments. [Source: Joshua Hawkins, BGR, November 28, 2021]

“Videographer Steve Hathaway, and his friend Andrew Buttle, discovered the pyrosome while filming a tourism promo in October of 2018. Hathaway says that Buttle was the first to notice the massive sea creature. He put on his scuba gear and dove in right after. The pyrosome they found was roughly 26-foot long. These translucent worm-like creatures can often glow and look similar to a plastic bag floating through the water. The two divers spent almost an hour swimming around the creature, taking photos and capturing video of it. Hathaway says that he’d been hoping to catch a glimpse of one for years.

Buttle told National Geographic that swimming next to it the pyrosome “was pretty incredible”. He also noted how they could see thousands of tiny creatures along the giant sea worm’s body, up close. That’s because pyrosomes are actually a free-flowing colony of hundreds or even thousands of individual organisms. These organisms are known as zooids. The small multicellular creatures pump water through their bodies to catch and feed on phytoplankton, poop particles, and other bacteria.

“Andrew Jeffs, a marine science professor at the University of Auckland says that the pyrosome and the salp, a cousin of the pyrosome, are both important to tropical waters as a food source. Other creatures like turtles and spiny lobsters cling to the tubes and can feed for weeks at a time. At night, pyrosomes swim to the surface of the sea. There they feed on whatever they can find in the water. Their bodies are very similar to gelatinous organisms like jellyfish. Additionally, they glow due to natural bioluminescence. While this one was 26-foot long, they can be as small as one centimeter in size. As long as the entire colony isn’t wiped out, they can theoretically live on forever.

Palolo Worms

Palola worms (Scientific name: Eunice viridis or Palola viridis) are also called Samoan palolo worms, balolo, wawo, or nyale. They are Polychaeta worms most often found in waters around Pacific islands such as Samoa, Tonga, Fiji, Vanuatu as well as islands of Malaysia, Indonesia, East Timor and the Philippines. [Source: Wikipedia]

Palola worms are about 30 centimeters (12 inches) long. They use their strong mandible to excavate a burrow for themselves in the hard coral reef, eating polyps as they go. Inside their coral burrows they are safe from predators and seldom venture out. They spend most of their time with their heads, called atokes, inside their burrows. [Source: Erin McCarthy, Mental Floss, April 9, 2015

During the year, the worm grows segments —epitokes — which eventually degenerate until they become, according to National Geographic, “little more than sacks engorged with either sperm or eggs.” According to the Natural History Guide to Samoa, “Each epitoke segments bear a tiny eyespot that can sense light”. This plays an important role in the breeding season when the worms release their epitokes, filled with sperm and eggs, in a “swarming, mucousy mass.” (See Below). The atoke section of the worms remains in the reef burrow during the mating madness. After their abdomens heal — a process that takes about a week — the atokes begin generating new epitokes for the next mating season.

Palola bodies are divided into segments like earthworms and each contains a set or organs necessary for life. Sex glands develop only in the segments in rear half. David Attenborough wrote: When breeding time comes the worm projects its rear end out of the tunnel and breaks it off. This then wriggles to the surface and there releases its sex cells. So the adult worm still in its burrow, has succeeded in spawning without putting itself at risk in any way. But the success of this technique depends on its timing. If the worms are to achieve cross-fertilization then all of them must detach their rear ends simultaneously, And they do — at dawn on the first three days of the moon’s third quarter in October, and then again at the same time in November. [Source: David Attenborough, “Life on Earth,” Little Brown & Co, 1979]

Samoan, Fijian Palolo Worm Party

Palolo worms live by the billions in the reefs off Samoa and Fiji. Samoans mark their new year on the one day of the year that Pacific palolo worms reproduce—the seventh day after the full moon after the autumnal equinox. Sections of the worms break from coral caves and rise to the surface where they spawn and die. Samoans scoop up the worms and serve them up at palolo worm feasts.

David Attenborough wrote: Palolo is greatly relished by both Samoans and Fijians and both peoples are able to predict the date when the worms will appear. The night before the rising is due, people from all over the islands travel down to the beaches. An hour or so before dawn a few of the most eager will be wading in the darkness, searching with torches for signs. Even before the night pales into dawn, green, wriggling strings materialize in the black water, spiraling upwards towards the lights. The call goes up that the worms have been seen and people who have been sleeping on the beach wade out, armed with nets and scoops. As dawn silvers the sea, the rising worms rapidly increase in numbers until great expanses of the water are covered in them. In good years, they may form curds many inches deep. With shrieks of excitement and jubilation, the people ladle them into buckets. Big fish swim in, darting among the legs of the waders, frenzied claiming their share of the bonanza. The thin body-walls of the palolo rupture in the waves and the eggs and sperm turn the water a milky blue-green. On the eastern horizon, the sun climbs out over the sea and withing half an hour of the worm’s first appearance, all is over. [Source: David Attenborough, “Life on Earth,” Little Brown & Co, 1979]

“Exactly how vast number of these lowly organisms achieve their synchronisation we still do not understand. It cannot be that each worm has within it and internal clock which triggers action every 365 days because the moon’s movements are not neatly synchronized with those of the earth, so the moon’s third quarter in October arrives ten or eleven days earlier each year. Nor can the worms judge the phase of the moon by its light for they spawn whether the sky is clear or completely overcast. One group of vigilante worms cannot be cuing others, for palolo on the reefs of Samoa and six hundred miles away around Fiji spawn at the same time. Furthermore the timing seems ti be quite arbitrary, without any celestial of oceanic logic, for the Pacific palolo has a close relative on the other side of the world around Bermuda and the West Indies, and although it too spawns at the third quarter of the moon, it chooses to do so not in October but in July. “

Pasola — the Sea Worm Festival in Sumba, Indonesia

Palola worms are the trigger of another even — the annual Pasola festival on the island of Sumba in Indonesia. Here the worms are called nyale. Usually held in February and March—Pasola features scores of colorfully-dressed horsemen battling with each other in a very serious way. During the war ritual, riders charge and fling blunt spears at one another. Sometimes two or more festivals are held at different times of the year, depending on several factors including the involvement of the government and the tides. Typically there is an event in February in Lamboyo and one in March in Guara and Honokaka. The battle begins several days after the full moon and coincides with the arrival strange multicolored seaworms. The festivals are held in wide lush green valleys. The exact dates are determined by shaman who disembowel live chickens and examine the entrails for omens after glowing worms burst forth in the sea.

Before the real Pasola there is a two-hour warm-up at the beach where the glow worms appear. The appearance of the worms is what signals the start of the event. Upon witnessing the arrival of the glow worms on the beach, Lawrence Blair wrote: "'Nyale! Nyale! the crowd began shouting, as the first rosy glow of dawn began creeping across the sea. But as I looked close I realized the redness was more than the dawn—the seaworms were swarming, wriggling multitudes staining the beach with every wave. The high priest was the first to wander sedately into the surf to sample this "gift of the Sea Goddess's body,' and to announce its portents to the crowd...'If the worms are healthy and plentiful, it will be a good year,' he said. 'If they fall apart at the touch , then enough rain can be expected to rot the rice on its stem. And if they are pitted and damaged, then a plague of rats or insects is probable.'...As soon as the priest had given his verdict, the crowd rushed into the surf themselves to scoop up the seaworms in their cupped sarongs or woven baskets for a holy breakfast, which they quickly cooked over small driftwood fires and ate." ♢

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023

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