10 Bizarre Worm Survivalists

Copyright by Gary L. Pullman

Life, whether on land or in the sea, isn't easy. Survival isn't a matter merely of eating or being eaten. It's a matter, also, of finding food and acquiring food, which aren't always simple tasks. It's also a matter of reproducing. Various environments present different challenges. Organisms that adapt generally fare well. Those that don't may become extinct.

Surprisingly, it's often the simpler animals that are most effective in developing the abilities necessary to ensure their survival. Worms, in particular, have evolved some bizarre, sometimes astonishing, abilities to enhance their chances of survival, including photosynthesis; sociability; bioluminescence, astounding mimicry; sophisticated predatory capabilities; marvelous regenerative powers; extraordinary life cycles; unusual offensive, defensive, and even digestive secretions; host-specific behaviors; and incredible feeding methods.

Here are 10 bizarre worm survivalists.

10 Mint-sauce Worms

Their ability to photosynthesize or to feed on organic matter and their sociability make mint-sauce worms well adapted for survival.

Mint-sauce worms

Known as a “plant-animal” in the early 20^th century, Symsagittifera roscoffensis is now known informally as the “mint-sauce worm.” In the clusters they form, the tiny worms resemble this sauce. Their green color comes from the algae in their bodies, which allow them to photosynthesize. In groups, the worms tend to move in clockwise circles. Although their behavior remains a mystery, scientists believe it may benefit them to form 'biofilms” by binding themselves to one another using the “mucus” they “secrete.” Nigel Franks, of the University of Bristol, describes them as behaving “collectively as a social seaweed.”

To test whether the worms' behavior is “random,” Franks simulated the behavior of worms of a “similar” size and speed of movement, comparing the simulations to the actual behavior of the mint-sauce worms. He found the mint-sauce worms “interacted” more frequently than the “digital worms,” indicating the mint-sauce worms' activity is “not random,” but social, in nature. 

Scientists believe “such large-scale social behavior may be the key to the tiny animals' survival.” The worms' circular motion has four effects. First, it creates a “vortex,” which causes the worms to collect in large “aggregations.” Second, it may provide “safety in numbers.” Third, it helps to “stabilize” the worms “in shallow waters.” Fourth, it allows them to “form a more efficient solar panel.” Researchers suggest the groups also allow the worms to “sunbathe” en masse while avoiding too much sun by burrowing beneath “their neighbors” whenever they need “shade.” 

9 New Zealand Glowworms

Their ability to imitate the starry heavens makes New Zealand glowworms fantastic survivalists.

Glowworm's imitation of the starry nighttime sky

Arachnocampa luminosa, more commonly known as New Zealand glowworms, have evolved a fantastic survival strategy: they imitate the starry nighttime sky. When they hatch from eggs, they adhere to cave walls, hanging “sticky spit around themselves.” Balls of mucus, strung along these strands of saliva, “magnify” the glowworms' bioluminescence. As a result, the walls are transformed into what appears to be a nighttime sky, full of stars and galaxies. Since “moths and insects” navigate by the light of the stars and the moon, they're attracted by the worms' luminescence and fly into the worms' traps. The worms wait until the prey exhausts itself in its struggle to escape. Then, the predators retrieve the strands and consume their prey.

They luminesce through catabolism, breaking down “a light-emitting protein.” The resulting glow, a “steady blue light,” is used as “bait.” This strategy is “rare,” scientists say. The balls of mucus aren't toxic, but they may suffocate the glowworm's prey. Scientists believe the mucus “may clog the breathing holes of insects.” As the glowworms retract the saliva strands into their mouths, they enjoy a meal while hydrating themselves, since the mucus balls “absorb water” from the cave's humid air. Typically, the prey is alive when it reaches the worms' mouths, but the predators' teeth “bore through” their victims' exoskeletons. Glowworm larvae live for a year; adults perish a week after their emergence. Since adults have no mouths, it's “doubtful they even eat.” There seems to be a cooperative interaction among glowworm “colonies,” which luminesce at different times, depending on when their “position in the cave” makes them “most attractive to prey.”

8 Volcanic Mud Worms

Their ability to form a symbiotic relationship with the bacteria that make volcanic mud worms their homes give the worms (and the bacteria) an edge when it comes to survival.

Volcanic mud worms

They don't have light, but they do have all the mud and methane gas they could ever want. Five huge volcanoes at the bottom of the Arctic Ocean spread their thick mixture of mud and methane over the ocean floor, attracting millions of tubeworms. Hardy, the worms can withstand tremendous submarine pressures and are well adapted to temperature differences. The worm lacks eyes. It also lacks a stomach and an anus. The worm doesn't need a digestive system, because it doesn't eat. The worms obtain their nutrients from the volcanoes' methane gas, through a process called chemosynthesis: bacteria inside the worms perform “chemical reactions,” releasing energy in the form of electrons.

The worms and the bacteria inside them live in a symbiotic relationship. The worms supply methane and oxygen, which the bacteria need. The bacteria synthesize “new organic matter.” These volcanic mud worms live in the Arctic Ocean's Beaufort Sea and the Norwegian Arctic and “are among the most amazing survivors of the ocean deep.” They're also likely to be among the planet's oldest livingorganisms. 

7 Planarian Worms

Planarian worms' amazing ability to regenerate themselves doesn't just make them incredible survivalists, but it also makes them virtually immortal.

 Planarian worm

The planarian worm is an amazing survivor. If it's decapitated, noproblem. It simply grows a replacement head, complete with its original memories. Its stem cells are always dividing, and they're able to become any of the planarian worm's other types of cells. The worm's Smed-prep A gene orchestrates the process so the “cells end up in the right place and have the correct size, shape and orientation.”

The planarian worm can also regenerate other body parts. It can even form complete worms from cut-up parts, all in only a few weeks. Although planarian worms avoid “bright lights and open spaces,” Tuft researchers trained them to accept both by spotlighting food in the center of their petri dish. Ten days later, after the worms had overcome their aversions, the scientists cut off their heads. In 14 days, their heads had regrown. Introduced to the same environment, the petri dish, the worms needed a day of retraining before they recalled the 10 days' training they'd received before their heads had been amputated. Scientists theorize the worms' memories may be stored in the neurons that make up the worms' nervous system, rather than in their brains. 

More research is needed to determine for certain what accounts for the planarian worms' ability to retain memories even after growing replacement heads. Planarian worms may be the key to our own survival, allowing us to overcome injuries and the effects of some diseases. Scientists envision new medical applications of their research, such as the regeneration of human organs and treatment for Alzheimer's disease.

6 Hammerhead Worms

Their regenerative abilities, their hunting prowess, and their reproductive capacities place hammerhead worms among the best of nature's survivalists.

Hammerhead worm

They look like part worm and part hammerhead shark; hence, their name, hammerhead worms. They're also giants, as worms go, attaining a length of 50.8 centimeters (20 inches) or more. Their presence in Alabama hasn't gone unnoticed. They live in soil, but they're flatworms, not earthworms. In fact, they eat earthworms. They leave a trail of slime in their wake, like snails or slugs. They're survivalists of the first order, too. Sometimes known as “land planarians,” they have amazing regenerative powers: cut one in half, and there will be two. Most people are taken aback at the sight of them, but they're harmless to humans and pets. 

The hammerhead is an accomplished hunter and a fierce predator. It follows an earthworm's path and seizes its prey, holding the earthworm fast with its muscles and a glutinous secretion. Then, secreting an enzyme through its extended pharynx, the hammerhead sucks up its prey's dissolved tissues. 

The hammerhead's versatile reproductive capabilities also enhance its survival. The worm can produce sexually, but it can also reproduce asexually. In the latter case, it anchors its posterior to the ground and then pulls itself forward, tearing itself apart. Headless, the posterior part moves away, under its own power. Within a week or so, the headless part has grown itself a head. This astonishing feat is nothing special for the hammerhead. The worm repeats the act twice a month. Oh, yes! In addition to earthworms, the hammerhead also stalks and devours snails, slugs, and insects. 

5 Ice Worms

As long as the temperature of their abode doesn't rise more than a few degrees, ice worms' ability to energize themselves, their symbiotic relationship with the bacteria inside them, and their life cycle, which includes time in a cocoon, make ice worms hardy survivalists.

Ice worm

Ice worms call glaciers their homes. They're nocturnal, boring their way to the surface from inside their icy abodes at night. They survive in freezing conditions by pumping up their energy level as temperatures drop. The colder it gets, the more energetic they become. Ice worms are extremophiles, organisms able to survive in extreme conditions. Their ability to adapt well to extremely cold environments has caught NASA's attention. By studying them, NASA hopes they can learn more about how and where life may be found on ice-bound worlds beyond our own. 

The tiny black worms eat the algae on glaciers, and the fact they don't need to eat very often also benefits their survival. However, although ice worms have mastered survival in extremely cold conditions, they don't fare well when temperatures rise above freezing. When things heat up, even a few degrees, above freezing, the worms dissolve. Symbiots, ice worms interact with the bacteria living inside them, providing them with a warm environment in return for assistance in breaking down the algae the ice worms consume. Ice worms evolved from their terrestrial counterparts (or from freshwater worms), but they couldn't have accomplished this feat alone. They needed the help of the bacteria which evolved alongside (or inside) them,.The bacteria are not present on the glaciers' surfaces, but are passed from ice worm to ice worm in the worms' feces, which are eaten by one another. Ice worms, it seems, are willing to do whatever it takes to survive in their frozen habitat. 

It's believed the worms traveled from southeast Alaska to Vancouver and Washington state's Olympic Peninsula by way of rosy finches and snow buntings who prey on the worms. As they eat the worms, the birds walk on their prey's cocoons. The cocoons stick to the predators' feet. When the rosy finches and snow buntings fly south for the winter, they take the cocoons with them. On their way south, strong winds force the birds to land on glaciers. Thus, the worms find new homes far from the beginning of their journeys. Even the ice worm's life cycle contributes to their survival. 

4 Ribbon Worms

Ribbon worm

Ribbon worms have a number of abilities that heighten their survival. These abilities include snaring prey, acting as a parasite, poisoning predators and prey, coating themselves in mucus, and regenerating parts of themselves.

No, the

Gorgonorhynchus species of ribbon worm doesn't really regurgitate. But it sure looks like it's vomiting. The marine worm stores its proboscis (nose) in a sac atop its gut. When it seeks prey, its “muscles contract quickly,” spewing the branching white appendage forth and trapping “crabs, fish, snails, or other worms.” 

Although the proboscides (also proboscises) of other ribbon may differ, all the worms are marvelous survivalists. Many members of the phylum use their proboscides to snare prey. Some wind their appendages around their victims and stab them to death. The proboscides of some of the 1,400 species are equipped with stylets, or piercing mouthparts, which, in some cases, are poison.

Other ribbon worms' proboscides are “sticky.” Still others possess “suckers.” Those with stylets lose them when they use them, but replacement stylets are stored inside “internal pouches” and are replenished on a regular basis. The proboscides can also be used to pull the worms forward. The worms themselves are poisonous and “taste bad,” which further increases their survival. Some ribbon worms obtain food through parasitism, rather than predation. One genus,

Carcinonemertes, lives on crabs, consuming its hosts' eggs and any animals on or near the crabs. The ribbon worms' secretions of mucus prevent them from dehydrating; the mucus also makes it difficult for their predators to seize. Many ribbon worms also have fantastic regenerative abilities, which further enhances their ability to survive. 

3 Zombie Worms

Their symbiotic relationship with bacteria, which allows them to eat, and their dual means of reproduction, which allows them to multiply, make so-called zombie worms effective survivalists.

Zombie worm

It seems unlikely an organism without a mouth or a gut could survive, but zombie worms thrive without a digestive tract. They accomplish this feat by dissolving bones. Specifically, they secrete an acid that dissolves whale bones. Members of the

Osedax genus, zombie worms obtain nourishment from whale skeletons resting on the ocean bed. It's believed the acid lets the worms access collagen (protein) and lipids (fats) inside the bones. Symbiotic bacteria contribute to the process, although scientists are not sure how. It's thought that “the bacteria metabolize bone-derived collagen into other diverse organic compounds,” which the worms then digest the bacteria for their own nutrition.”

Zombie worms secrete their acidic enzymes through “root-like” structures that bore into the whale's bones. After the proteins and fats inside the bones are dissolved, the worms suck them up, through the same tiny appendages, and the bacteria inside the worms convert these nutrients into energy. The fact that marks of zombie worms' feeding are discernible on the fossils of plesiosaurs and other prehistoric animals that lived in the ocean indicate they worms have survived for millions of years. In fact, scientists believe that 45 million years ago, zombie worms branched off from “cousins” who used chemosynthesis (the process by which chemical reactions produce organic material) to obtain food. 

Typically, male zombie worms are tiny, larval, and motionless, living as parasites inside the bodies of the much-larger females and fed internally by the females. Their only role is to supply the sperm to fertilize the female's eggs. The discovery of males who not only live separate lives from females but are also the same size as they are has astonished scientists, because this reversal in size constitutes a rare evolutionary event. Normally, due to disuse, the genes that produce “full-size males” would degenerate, but, in this case, they did not. The existence of independent males increases zombie worms' ability to survive by providing a second means of reproduction. To enable independent males to find females with which to mate, the males have developed the ability to stretch themselves 10 times their normal length. This ability earned them the scientific name

Osedax priapus, after the Greek god of fertility. 

2 Horsehair Worms

Horsehair worm

One reason parasitic horsehair worms survive is that their cysts are able to distinguish between suitable and unsuitable hosts and react accordingly. Specialized proboscides also enhance their ability to survive, as does their ability to absorb nutrients directly, though their cuticles (“outermost non-cellular protective coverings”). 

Nematomorpha are called horsehair worms because they resemble hair from the mane or tail of a horse. They're also called Gordian worms because, when they mate in water, they tend to twist themselves into spherical masses like the fabled “Gordian knot.” These worms grow inside specific hosts, such as beetles, cockroaches, crickets, grasshoppers, and katydids. After hatching, the worms' larvae form cysts on the leaves of plants. When eaten by a host, the cysts degenerate, and the larvae “burrow” through the host's “intestinal wall” to develop inside the “host's body cavity.” However, if it is eaten by an “inappropriate host,” a cyst, if it degenerates, may form another cyst in its host's tissues. (Some contend a cyst will form inside any host but will develop only inside beetles, cockroaches, crickets, grasshoppers, or katydids.) If, later, a host it can live in consumes the “inappropriate host,” the cyst degenerates, and the larvae resume their normal life cycles. Such behavior extends the possibility of their survival by allowing them multiple chances of development. The larvae “digest and absorb” its host's tissues. When it reaches its juvenile stage, the larvae “emerges from the host to mature.” The larvae are white, but soon “turn yellowish-tan to brownish-black,” furthering resembling horse's hair. 

Horsehair worms' spiny proboscides help them to penetrate the intestinal walls of their hosts and enter their blood. The worm has also evolved a way to absorb nutrients without the need of a digestive system, absorbing absorbs “nutrients directly through its cuticle.” After the larvae undergo several “molts” inside their hosts, they may “induce” them “to move to water,” where the larvae emerge to seek mates. Their emergence usually kills the host.

1 Five-face Worms

The five-face worm's ability to feed on a variety of foods within the same habitat greatly improves its survival. The way it accomplishes this feat is truly astonishing.

Five-face worm

Pristionchus borbonicus is probably the champion survivalist. It has five faces, one for each of its feeding needs. Initially, the roundworm was believed to have been five species, but scientists determined, by sequencing its genes, that they're dealing with only one species, Pristionchus borbonicus, with five faces or mouths. The worm lives in fig plants and has the mouth it requires for the food in its surroundings: two for bacteria, a third for yeasts, a fourth for other roundworms, and the fifth for beetles. It's believed the five-face worms “travel between fig flowers on pollinating fig wasps.” 

“An extreme example of evolutionary divergence within one species,” the five-face worm's ability to “exploit a large food spectrum” enhances its survival by allowing it to eat a variety of foods within the fig plants it inhabits. If one food source becomes scarce, the worm has other alternatives available to it. It wouldn't have these options if it weren't able to use different mouths to consume a variety of prey. Among the faces, or mouths, it can develop is “a short wide mouth or a long narrow one.” The former “variant” is equipped with one tooth used for “predatory attacks,” while the “narrow version” allows it to graze on bacteria. 

Thanks to its ability to develop different mouths, the worm has another advantage. Ralf Sommer, the director of the Department for Evolutionary Biology at the Max Planck Institute for Developmental Biology, says the worm's capability enables it to “divide and conquer the fig's resources; individual worms with different mouth forms can coexist by sharing diverse food sources found within a single fig.” How the worm is able to develop different mouths for a variety of foods is a mystery scientists have yet to solve.