Where do i find microbes like tardigrades in winter

Just bought a microscope and i want to see microbes like tardigrades. Where should i look? I have found many bacteria and what seems to be motionless single celled organism. I want to see movement and feeding. Ps snow on the ground and frozen ground

Tardigrades are best found by soaking moss in water. Even in the winter, under the snow, that is the best place to look. Let tap water sit overnight, uncovered before you add it to the moss to let the chlorine come out. And then strain the water with fine-mesh cloth to see what was in the moss. I would not call tardigrades "microbes" though. Even though "microbes" is not a scientific term, I think of microbes as bacteria, while tardigrades are microscopic animals.

The tardigrade in the ice hole: how extreme life finds a way in the Arctic

Tardigrades, nicknamed water bears or moss piglets, are less than 1mm in length and can enter cryptobiosis to withstand extreme conditions. Photograph: Science Photo Library - Steve Gchmeissner/Getty Images

Tardigrades, nicknamed water bears or moss piglets, are less than 1mm in length and can enter cryptobiosis to withstand extreme conditions. Photograph: Science Photo Library - Steve Gchmeissner/Getty Images

Tiny organisms nicknamed water bears offer clues about possible alien life but the changing climate means their habitat faces an uncertain future

Last modified on Sat 17 Oct 2020 16.07 BST

A s we make our way across Greenland’s ice sheets, I look around. We’re surrounded by numerous tiny black holes, some only a few centimeters in diameter, others up to 4-8in (10-20cm) wide. As we advance, we notice that more and more holes are magically appearing, and their edges are increasingly distinct. They’re called cryoconite holes.

Dotted across the surface of the glacier ice, these cylindrical holes are an oasis of life, the only place where life grows on polar ice caps. Despite the waters surrounding Antarctica being home to abundant life-forms, there is very little life on the landmass itself – and bear in mind it covers an immense expanse, one and a half times the size of the United States. It has the biggest freshwater reserve on the entire planet (70% of the world’s fresh water) but is anything but hospitable. Temperatures can drop to -89C (-129F), the lowest ever recorded on Earth, and winds blow – “rocket” might be more accurate – at speeds of up to 155mph (250km/h). Greenland is not that much different: all life on the island is confined to the few urban settlements along the coast.

We observe these glacial, geometric structures. Peering through the water filling them, we see something dark on the bottom. It’s cryoconite, a sludge made of dust, detritus, algae and bacteria, found not only in the Arctic and Antarctic but also in Canada, Tibet and the Himalayas. It collects in these holes because the detritus absorbs solar radiation, warming up the ice around it and causing it to melt. One of the first and most fascinating things to note about this detritus is that it’s not just from planet Earth: studies have shown that every 2lb (o.9kg) of cryoconite contains roughly 0.35 oz (10g) of sand of earthly origin and about 800 “cosmic spherules” (originating from comets, asteroids, or interstellar dust) and 200 partially molten micrometeorites.

A meltpool with cryoconite on Petermann Glacier. The dark rubble – mud, rocks, parts of meteorites and human pollution gather in heaps on the ice – as they are dark, they attract heat, and eventually melt neat holes in the glacier. Photograph: Dave Walsh/VW Pics/Universal Images Group via Getty Images

Even more spectacular is the fact that no one knew they existed until a century and a half ago. Nils Adolf Erik Nordenskiöld was the first to describe them, the same man who later set sail from Gothenburg on board the Vega, reached the Bering Strait via the northern coasts of Europe and Asia, and opened the famous North-east Passage. That was back in 1870, and the geologist (he had dual Finnish and Swedish nationality) and Arctic explorer was the first to publish a detailed description of the cylindrical melt-holes he witnessed in the ice.

Peering into the hole with my nose just centimeters from it, I ponder the doggedness of nature and its ability to surprise us, from penguins that cross the Antarctic peninsula solely to lay their eggs (when they would normally never leave their food supplies on the coast) to micro-organisms like the ones I’d come across, and others with names that sound straight out of The Lord of the Rings roundworms, or the phylum Nematoda – whose survival depends on their digging into the ice. The ability of some of the inhabitants of the melt-holes to adapt to this natural environment and evolve under such extreme conditions makes them ideal candidates for a study of extraterrestrial life.

In early 2016, in fact, a group of Japanese scientists managed to “resuscitate” two microscopic animals that had been in hibernation for more than 30 years in ice samples collected in the Antarctic. Yes, they had been in hibernation since Ronald Reagan’s day (6 November 1983, to be exact), and had “reawakened” from their long sleep on 7 May 2014, into a world of smartphones and social networks. The animals in question were Acutuncus antarcticus, a species of tardigrade – a microscopic (about 0.5mm long) creature with eight legs, four to eight claws on each leg, and an odd appearance (like a tiny mammal with its fur removed).

Tardigrades have also become a veritable internet sensation of late, nicknamed water bears or moss piglets. Why are they so popular? Because tardigrades are a bit like video game heroes – you can freeze them, boil them, crush them, starve them, and they just keep coming back to life. There’s no way to kill them! There could be no better candidate for a cryoconite hole. Water bears are one of the most fascinating creatures in the world for the way they can adapt to ultimate extreme environments. You can find them, for example, in the deepest ocean trenches or hottest deserts, on the frozen peaks of the Himalayas and in Antarctica. They have succeeded in outliving dinosaurs and are so hardy that they can survive in extraterrestrial environments in addition to boiling and freezing ones.

A microscope photo of a tardigrade. Photograph: Thomas Boothby/AP

The “defrosted” animals in the Japanese experiment had managed to survive through cryptobiosis, a process that causes their metabolism to slow to 0.01% of normal function. (Imagine your heart rate going from 60 beats per minute to only one every two minutes!) During cryptobiosis, all water in the body is released and the animal rolls itself up into a tiny, indestructible ball (the water in their bodies is sometimes replaced with a sort of natural antifreeze). Getting rid of water is the main priority, as it saves them, for example, from any cell damage caused by freezing.

The Japanese scientists described another, even more surprising tardigrade characteristic. One of the two animals (after being “defrosted”) managed to reproduce. Here’s what happened: the two animals – which the research team called Sleeping Beauty 1 and Sleeping Beauty 2 (SB-1 and SB-2) – were placed in two separate wells on a Petri dish to be monitored and fed. An egg was then found as the experiment progressed. The researchers placed it in another well and called it SB-3. To each well they added agar (a jellylike substance used in molecular biology), bottled water and chlorella algae (which contains chlorophyll). The ingredients were replaced weekly. More eggs were found over the course of time, all of which hatched safely.

I direct my gaze to the bottom of the holes again, mesmerized, despite there being little to see with the naked eye. Tardigrades are not alone in the cryoconite holes. They share the habitat with other equally fascinating organisms, which is a major difference between Antarctica and Greenland. In the former, the icy dens can resist for years, coming through the seasons intact and becoming a sort of mini testing ground for extreme life. The ice cover stops the sun’s rays from reaching the bottom of the cylindrical holes, with the result that photosynthesis cannot take place.

The existence of a different kind of life from what we are familiar with depends on a process known as bacterial chemosynthesis. Unlike photosynthesis, it exploits the energy generated in chemical reactions to produce organic substances. To put it more simply: these creatures are completely autonomous and self-sufficient, living their peaceful existence in complete isolation. Based on recent studies, the environmental factors in these landscapes and in these Arctic and Antarctic territories could be considered the closest to what we believe life would be like on other planets. Glaciers, especially the polar ice caps, are among the most extreme environments on our planet, not just because of the cold and isolation, but also because of the high levels of ultraviolet radiation, making them similar to planets or icy moons.

One of these would be Mars, or other icy celestial bodies like Europa, a satellite of Jupiter. Europa (discovered by Galileo Galilei in 1610) is a little smaller than the moon and mostly made up of silicate rock with a water-ice crust. The biological microsystems found in the ice are like “natural laboratories” helping us to understand alien life-forms. This is what makes them so important to astrobiology – the branch of science that studies life (or the possibility of life) on other worlds.

Measuring cryoconites on the Longyearbyen glacier in Svalbard. Photograph: Jevgeni Grudkin/Kertu Liis Krigul/WikiCommons

I stop for a second to contemplate the sky. When we look up at the stars at night, enchanted by the unknown universe above us, we may often wonder if there really is life up (or down) there – a form of life similar to ours. At least we know that the next time we stargaze with a scientific eye, we can draw on what we’ve learned from these monster-like creatures, the true magic of which is undoubtedly the greater secrets they are yet to reveal – secrets that bind us all together on the planet we share, floating in the dark cosmos along with billions of other creatures.

This is not my only thought, however. Cryoconite holes accelerate the rate at which the ice melts because of the dark color of the admixture inside them and the increased solar energy they absorb as a result. The curious holes have a limited life span, given the role water plays. For example, the more the ice melts, the more life inside them can proliferate – but when the glacier in which the holes have formed begins to melt, the proliferating life inside them will be swept away by the meltwater current, and the holes will disappear. This is where climate change also plays a part: the more the glaciers melt, the more difficult it will be for the cryoconite holes to survive. And the life-forms discovered within them will become ever rarer. Alternatively, it may be that the more meltwater there is, the more the holes will proliferate. The answer to this enigma is yet another mystery to be solved.

Ice: Tales from a Disappearing Continent, by Marco Tedesco with Alberto Flores D’Arcais, is available from Headline

A huge chunk of a tardigrade's genome comes from foreign DNA

A light micrograph of a tardigrade. Credit: Sinclair Stammers

Researchers from the University of North Carolina at Chapel Hill have sequenced the genome of the nearly indestructible tardigrade, the only animal known to survive the extreme environment of outer space, and found something they never expected: that they get a huge chunk of their genome - nearly one-sixth or 17.5 percent - from foreign DNA.

"We had no idea that an animal genome could be composed of so much foreign DNA," said co-author Bob Goldstein, faculty in the biology department in UNC's College of Arts and Sciences. "We knew many animals acquire foreign genes, but we had no idea that it happens to this degree."

The work, published today in the Proceedings of the National Academy of Sciences, not only raises the question of whether there is a connection between foreign DNA and the ability to survive extreme environments, but further stretches conventional views of how DNA is inherited.

First author Thomas Boothby, Goldstein and their collaborators revealed that tardigrades acquire about 6,000 foreign genes primarily from bacteria, but also from plants, fungi and Archaea, through a process called horizontal gene transfer - the swapping of genetic material between species as opposed to inheriting DNA exclusively from mom and dad. Previously another microscopic animal called the rotifer was the record-holder for having the most foreign DNA, but it has about half as much as the tardigrade. For comparison, most animals have less than one percent of their genome from foreign DNA.

"Animals that can survive extreme stresses may be particularly prone to acquiring foreign genes—and bacterial genes might be better able to withstand stresses than animal ones," said Boothby, a postdoctoral fellow in Goldstein's lab. After all, bacteria have survived the Earth's most extreme environments for billions of years.

The team speculates that the DNA is getting into the genome randomly but what is being kept is what allows tardigrades to survive the harshest of environments, e.g. stick a tardigrade in a - 80 celsius freezer for a year or 10 and it starts running around in 20 minutes after thawing.

This is what the team thinks happens: when tardigrades are under conditions of extreme stress such as desiccation - or a state of extreme dryness—Boothby and Goldstein believe that the tardigrade's DNA breaks into tiny pieces. When the cell rehydrates, the cell's membrane and nucleus, where the DNA resides, becomes temporarily leaky and DNA and other large molecules can pass through easily. Tardigrades not only can repair their own damaged DNA as the cell rehydrates but also stitch in the foreign DNA in the process, creating a mosaic of genes that come from different species.

"We think of the tree of life, with genetic material passing vertically from mom and dad," said Boothby. "But with horizontal gene transfer becoming more widely accepted and more well known, at least in certain organisms, it is beginning to change the way we think about evolution and inheritance of genetic material and the stability of genomes. So instead of thinking of the tree of life, we can think about the web of life and genetic material crossing from branch to branch. So it's exciting. We are beginning to adjust our understanding of how evolution works."

American Scientist

Tardigrades, I reply, are microscopic, aquatic animals found just about everywhere on Earth.

Figure 1. In this colorized electron micrograph (EM), which has the feel of a museum diorama, a tardigrade emerges from under a moss leaf to hunt for food or a companion. EMs are produced by layering a molecular film of metal on a sample. The technology gives a false sense of the “hide” of this tardigrade. In actuality, tardigrades are translucent and display a variety of colors—white, green, orange, red. In the microenvironments made by water that coheres in the fissures of mosses and lichens due to surface tension, tardigrades thrive by feeding on smaller organisms and by sucking contents out of plant cells. Their moist realm is transient, and in response tardigrades have evolved an array of strategies based on induced cryptobiosis—the suspension of metabolism by drying or freezing. In their cryptobiotic state, desiccated or frozen, they are astonishingly durable. These organisms survive extreme conditions—of temperature, pressure and radiation—to a degree unparalleled in nature.

Eye of Science/Photo Researchers

Terrestrial species live in the interior dampness of moss, lichen, leaf litter and soil other species are found in fresh or salt water. They are commonly known as water bears, a name derived from their resemblance to eight-legged pandas. Some call them moss piglets and they have also been compared to pygmy rhinoceroses and armadillos. On seeing them, most people say tardigrades are the cutest invertebrate.

At one time water bears were candidates to be the main model organism for studies of development. That role is now held most prominently by the roundworm Caenorhabditis elegans, the object of study for the many distinguished researchers following in the trail opened by Nobel Prize laureate Sydney Brenner, who began working on C. elegans in 1974. Water bears offer the same virtues that have made C. elegans so valuable for developmental studies: physiological simplicity, a fast breeding cycle and a precise, highly patterned development plan. Some species may, like C. elegans, be eutelic, meaning that the organisms retain the same number of cells through their development. Tardigrades have somewhere over 1,000 cells. I and others use water bears as a model educational organism to teach a wide range of principles in life science.

Tardigrades are nearly translucent and they average about half a millimeter (500 micrometers) in length, about the size of the period at the end of this sentence. In the right light you can actually see them with the naked eye. But researchers who work with tardigrades see them as they appear through a dissecting microscope of 20- to 30-power magnification—as charismatic miniature animals.

Most tiny invertebrates dart about frantically. Tardigrades move slowly as they clamber around on bits of debris. They were first named tardigrada in Italian from the Latin meaning “slow walker.” Tardigrades walk on short, stubby legs located under their bodies, not sticking out to the sides. These stout legs propel them unhurriedly and deliberately about their habitat.

Tardigrades have five body sections, a well-defined head and four body segments, each of which has a pair of legs fitted with claws. The claws vary in different species from familiarly bearlike to strangely medieval fistfuls of hooked weaponry. The hindmost legs are attached backwards, in a configuration unlike that of any other animal. These legs are used for grasping and slow-motion acrobatics rather than for walking.

Figure 2. Tardigrades’ appearance is not their only aspect that is reminiscent of macrofauna. A light-microscope image of the anterior end of a tardigrade (left ) shows the mouth stylets, strutures that help them feed the buccal apparatus, part of the digestive tract and the pharynx at the top of the alimentary system. A cross section of a generic water bear (right ) shows the relative positions of the organ systems. Lacking are circulatory and respiratory systems. At this tiny scale, an open hemocoel cavity is sufficient to distribute oxygen and nutrients through the organism.

Dr. David J. Patterson/Photo Researchers. Illustration at bottom by Tom Dunne, adapted from a figure by the author.

Inside these tiny beasts we find anatomy and physiology similar to that of larger animals, including a full alimentary canal and digestive system. Mouth parts and a sucking pharynx lead to an esophagus, stomach, intestine and anus. There are well-developed muscles but only a single gonad. Tardigrades have a dorsal brain atop a paired ventral nervous system. (Humans have a dorsal brain and a single dorsal nervous system.) The body cavity of tardigrades is an open hemocoel that touches every cell, allowing efficient nutrition and gas exchange with no need for circulatory or respiratory systems.

Taxonomists divide life on Earth into three domains: Bacteria, Archaea (an ancient line of bacterialike cells without nuclei that are likely closer in evolutionary terms to organisms with nucleated cells than to bacteria), and Eukarya. Eukarya is divided into four kingdoms: Protista, Plantae, Fungi and Animalia. Phylum Tardigrada is one of the 36 phyla (roughly, depending on whom one asks) within Animalia—making water bears a significantly distinctive branch on the tree of life.

Tardigrades are encased in a rugged but flexible cuticle that must be shed as the organism grows. Thus they have been placed among the phyla on the ecdysozoa line of evolution between animals such as nematodes and arthropods that also shed their cuticles to grow.

Animals grow in either of two ways, by adding more cells or by making each cell larger. Tardigrades generally do the latter. If an animal has a hard cuticle or exoskeleton, it must break out of that shell in order to grow. For example, in summer in many parts of the world, one encounters the shed exoskeletons of locusts on trees everywhere.

Tardigrades are divided into two classes, Eutardigrada and Heterotardigrada. As a general rule, the members of Eutardigrada have a naked or smooth cuticle without plates, whereas the Heterotardigrada boast a cuticle armored with plates.

Tough Customers

Tardigrades’ best-known feature is their brute, dogged ability to survive spectacularly extreme conditions. A few years ago, the Discovery network show Animal Planet aired a countdown story about the most rugged creatures on Earth. Tardigrades were crowned the “Most Extreme” survivor, topping penguins in the Antarctic cold, camels in the dry oven of the desert, tube worms in the abyss and even the legendarily persistent cockroach.

Figure 3. Tardigrades (left ) were for a time considered competitors with the round worm Caenorhabditis elegans (right ) and the fruit fly Drosophila melangaster as major invertebrate model organisms. Tardigrades have played that role less over the years, but research attention is increasing as new genetic research tools allow deeper inspection of their extreme durability and adaptivity in response to changing environmental conditions. Tardigrades are predators of nematode worms such as C. elegans . Under the microscope, tardigrade researchers occasionally encounter a water bear grabbing a nematode around the middle. The nematode wriggles furiously all over the dish, with the tardigrade hanging on like a bronco rider, until the drained nematode surrenders.

Photograph courtesy of Bob Goldstein and Vicky Madden of the University of North Carolina at Chapel Hill.

But extreme survivorship applies only to some species of terrestrial tardigrades. Marine and aquatic tardigrades did not evolve these characteristics because their environments are stable. It appears that the extravagant survival adaptations have been selected in direct response to rapidly changing terrestrial microenvironments of damp flora subject to rapid drying and extreme weather.

Terrestrial tardigrades have three basic states of being: active, anoxybiosis and cryptobiosis. In the active state, they eat, grow, fight, reproduce, move and enact the normal routines of life. Anoxybiosis occurs in response to low oxygen. Tardigrades are quite sensitive to oxygen tension. Prolonged asphyxia results in failure of the osmoregulatory controls that regulate body water, causing the tardigrade to puff up like the Michelin Man and float around for a few days until its habitat dries out and it can resume active life.

Cryptobiosis is a reversible ametabolic state—the suspension of metabolism—that has inevitably been compared to death and resurrection. In cryptobiosis, brought on by extreme desiccation, metabolic activity is paralyzed due to the absence of liquid water. Terrestrial water bears are only limnoterrestrial—aquatic animals living within a film of water found in their terrestrial habitats. Moss and lichens provide spongelike habitats featuring a myriad of small pockets of water and, like sponges, these habitats dry out slowly. As its surroundings lose water, the tardigrade desiccates with them. It has no choice. The creature loses up to 97 percent of its body moisture and shrivels into a structure about one-third its original size, called a tun. In this state, a form of cryptobiosis called anhydrobiosis—meaning life without water—the animal can survive just about anything.

Figure 4. Tardigrades have evolved a suite of survival tactics to escape the vagaries of their localized and vulnerable environments. Anoxybiosis and encystment, described in the upper part of this figure, are responses one might see in a variety of organisms. The bottom half of the chart shows three states of cryptobiosis, in which metabolism is suspended—an act usually diagnostic of death. Cryobiosis occurs in response to freezing, and anhydrobiosis in response to drying. During the latter, an organism surrenders its internal water to become a desiccated pellet. Both result in the formation of a durable shrunken state called a tun . More rarely, a tun is created to resist osmotic assault, which requires water. In the tun state, tardigrades can survive for many years, impervious to extremes far beyond those encountered in their natural environments.

Illustration by Tom Dunne.

Tardigrades have been experimentally subjected to temperatures of 0.05 kelvins (–272.95 degrees Celsius or functional absolute zero) for 20 hours, then warmed, rehydrated and returned to active life. They have been stored at –200 degrees Celsius for 20 months and have survived. They have been exposed to 150 Celsius, far above the boiling point of water, and have been revived. They have been subjected to more than 40,000 kilopascals of pressure and excess concentrations of suffocating gasses (carbon monoxide, carbon dioxide, nitrogen, sulfur dioxide), and still they returned to active life. In the cryptobiotic state, the animals even survived the burning ultraviolet radiation of space.

Challenging student scientists to ponder the astonishing durability of tardigrades brings their understanding of physics, chemistry and biology into play. They recall that water expands as it approaches the freezing point, which is why ice floats. At 4 degrees celsius the expansion of water exerts sufficient force to split boulders, rupture metal containers and explode living cells. A cell is more than 95 percent water. The rupturing forces and icy microshards that form in frozen cells are the same that cause frost bite.

The survival attributes of tardigrades are in fact quite appropriate for an organism that makes its home in mosses and lichens (bryophytes), which provide them with just a thin layer of protection. Bryophytes are subject to the environmental extremes experienced on a planet bathed in solar radiation. They may receive varying periods of direct ultraviolet exposure and are never far from drying out as ambient conditions change.

Improvise, Adapt and Overcome

Tardigrades exhibit distinctly different responses, grouped under the general name of cryptobiosis, to different sources of stress. Anhydrobiosis and cryobiosis lead to the formation of tuns, but they are not equivalent—they are different mechanisms for protection against different environmental assaults.

Figure 5. Eutardigrades lack armor, which appears to have done little to inhibit their evolutionary success. Larger eutardigrades—such as those of the genus Macrobiotus (shown above in active form and tun state)—are found in many habitats, where they consume smaller tardigrades as well as nematode worms and rotifers. Their large appetite for nematodes (they may consume many per day), and their resulting controlling role on the nematode population, indicates a significant role in the food web for tardigrades at the micro scale.

Eye of Science/Photo Researchers

Anhydrobiosis—metabolic suspension brought on by nearly complete desiccation—is a common state for tardigrades, which they may enter several times a year. To survive the transition, water bears must dry out very slowly. The tun forms as the animal retracts its legs and head and curls into a ball, which minimizes surface area. When nearly all of its internal water has been surrendered, the tardigrade is in anabiosis, a dry state of suspended animation. It is almost as if the animal preserves itself by becoming a powder comprised of the ingredients of life. When rehydrated by dew, rain or melting snow, tardigrades can return to their active state in a few minutes to a few hours.

In cryobiosis, another form of cryptobiosis, the animal undergoes freezing yet can be revived. Any temperature below the cell cytoplasm’s freezing point suppresses molecular mobility and therefore suspends metabolism. Deep-freeze temperatures could be expected to cause additional structural disruptions, yet tardigrades, as noted above, have survived the most drastic chills. It seems likely that survival is conferred by the release or synthesis of cryoprotectants. These agents may manipulate tissue freezing temperature, slowing the process and allowing an orderly transition into cryobiosis, and they may suppress the nucleation of ice crystals, resulting in an ice-crystal form that is favorable for subsequent revival with thawing.

Osmobiosis is a response to extreme salinity, which can cause destructive osmotic swelling. Some tardigrades exhibit strikingly effective osmoregulation, maintaining stasis in the face of steep osmotic gradients. Some others escape via formation of a tun that is impervious to osmotic transfer.

In 2007, tardigrades became the first multicellular animal to survive exposure to the lethal environs of outer space. Researchers in Europe launched an experiment on the European Space Agency’s BIOPAN 6/Foton-M3 mission that exposed cryptobiotic tardigrades directly to solar radiation, heat and the vacuum of space. While the experimental vessel orbited 260 kilometers above the Earth, the researchers triggered the opening of a container with tardigrade tuns inside and exposed them to the Sun. When the tuns were returned to Earth and rehydrated, the animals moved, ate, grew, shed and reproduced. They had survived. In summer of 2011, Project Biokis, sponsored by the Italian Space Agency, ferried tardigrades into space on the U.S. space shuttle Endeavor. Colonies of tardigrades were exposed to different levels of ionizing radiation. The damage is now being assayed to learn more about how cells react to radiation and, perhaps, how tardigrade cells fend off its damage.

Surviving intense radiation suggests an especially effective DNA repair system in an active organism. Effective osmoregulation in extreme salinity implies a vigorous metabolism—osmoregulation in the face of high environmental salinity is energetically extremely expensive as metabolic transactions go, requiring the pumping of ions against steep osmotic and ionic gradients. Thus, we see in tardigrades two opposing responses to environmental extremes: the passive response of dormancy in the form of cryptobiosis, balanced by the hyperactive responses of impressive DNA repair and high-performance osmoregulation. As practitioners of adaptive evolution, tardigrades are virtuosos.

Getting Around

Tardigrades have been discovered just about everywhere that anyone has looked, from the Arctic to the equator, from intertidal zones to the deep ocean, and even at the top of forest canopies. Their ubiquity is intimately linked to their survivorship. I am often asked how tardigrades manage to find their way to the canopy of towering trees. Most likely, wind carries them. In the tun state they are barely distinguishable from dust particles. But like spores, pollen and seeds, the tuns have a preference for where they land. Many microenvironments will be unsuitable habitats for freshly arrived tardigrades. Yet an unhappily placed tun can simply wait for a change in precipitation or perhaps a change in season. When conditions improve, life can begin again.

Figure 6. The armored Heterotardigrade of the genus Echiniscus in the active state (top ) and in the cryptobiotic tun state (bottom ). The armor of these tiny predators contains chitin, the same material incorporated in the cuticle of insects. The armor may slow the process of drying. In drier environments, heterotardigrades are predictably represented in larger numbers than are naked species. The armor plates may supply some degree of protection to the vulnerable active form.

Images courtesy of the author.

Contributing to their success as travelers is the fact that many tardigrades of moss, lichen and leaf litter are parthenogenetic, able to produce eggs without mating, and in a few cases are hermaphroditic, able to self-fertilize. A lone tardigrade on an ill wind—active, tun or egg—may be able to establish a population where it lands if the habitat is suitable. We may be under tardigrade rain right now.

Figure 7. These images of tardigrade claws are magnified 3,000 to 5,000 times. Even at so fine a scale, structures have developed that are distinctive to each genus, suggesting adaptations for different lifestyles. Tiny hooks suitable for spearing tiny hors d’oeurves contrast with bristling claws seemingly optimized for a raking, tearing attack. Little studied, tardigrades are far from understood. The diversity of claw types may have roles in mating, tun formation and other tardigrade activities that have not yet been discovered.

Images courtesy of the author and Clark W. Beasley of McMurry University.

At present there are about 1,100 described species of water bears, but not all are valid. Some descriptions are repeats and some are just plain flawed. Around 1,000 species have been properly identified and described. We have about 300 marine, 100 freshwater and 600 terrestrial species. But the land species are much easier to find and have been pursued by many more researchers over many more years. Still, my students have discovered and described four new species so far, and we are working to confirm another half dozen, including one found on the campus of Baker University in Kansas, where I am a faculty member. We believe there is an abundance of species yet to be discovered, especially in the nonterrestrial environments.

Finding a New One

Last summer, the student who inquired at my office, Rachael Schulte, became an intern working on our National Science Foundation grant under the Research at Undergraduate Institutions (RUI) program designed to teach research by exploring and expanding the biodiversity of the phylum Tardigrada in North America.

Figure 8. A light-microscope image reveals the dorsal plates and cirri, cuticular extensions, of what one day could be known officially as Multipseudechiniscus raney i. While working with the author, Baker University undergraduate Rachael Schulte found the organism in samples her teacher had collected in California. They have submitted a paper describing the organism for publication.

Image courtesy of the author and Rachael Schulte.

After a couple of weeks of practice on lichen from local trees, Rachael had become proficient with the tools of the tardigrade trade—the dissecting scope, the wire Irwin loop, slide preparation, imaging, record keeping and identification to the level of genus. She was ready to work on actual research material, so we set her up with samples collected a couple of years before on a transect from more than 9,000 feet up in the Sierra Nevada Mountains down to Fresno, California.

Just a week later, she came to me with a finely made slide.

In 1983, Giuseppe Ramazzotti and Walter Maucci published the monograph The Phylum Tardigrada. It was translated from Italian into English by Clark Beasley in 1985. It is now 27 years out of date and includes only half of the described species. But it remains the reference of first resort. We started with the genus Pseudechinsicus. As I read the diagnostic questions in the key, Rachel worked the microscope to answer them.

The animal looked like Pseudechinsicus raneyi, as described by Gragrick, Michelic, and Schuster in 1964. We pulled up a copy of the paper from the files (we have PDF files of 95 percent of all tardigrade papers) and read. The description matched our animal. We then looked at the 1994 list of species, along with the relevant research papers and geographic distributions, prepared by McInnes. There were only two listings for our species—the original description from California and Schuster and Gragrick’s entry in their 1965 classic work on the western North American tardigrades, which added Oregon to Pseudechinsicus raneyi’s known range. Searching through the more recent literature in our database, Rachael discovered that I had also found the creature in Montana during my master’s work at the University of Montana, Missoula, in the late 1960s, although I did not publish the record until 2006. Now after 40 years we had a fourth record and a new location for an uncommon regional animal.

During our literature review, we learned that the genus was described by Gustav Thulin in 1911, who gave high taxonomic value to the presence of the pseudosegmental plate. Then in 1987, Kristensen revised the family Echinsicidae, redescribed the existing genera and added four new ones to the list. Because this occurred after our creature was described, we needed to confirm the genus assignment by reviewing its characteristics against the amended, more detailed description.

We started down the list of characteristics under the genus Pseudechiniscus I read the first line:

Our specimens did not match the description of the genus Pseudechinicus. So we checked the other generic descriptions within the family the same way and concluded that our specimens matched none of them. We now thought there were enough significant deviations from the existing descriptions to merit describing and naming a new genus.

Over the next several months we borrowed the original type specimen of Pseudechiniscus raneyi from the Bohart Museum at the University of California at Davis and confirmed that it was the same as our specimens. Rachael and I made images of the slides, measured multiple characteristics on each specimen and developed a comparative table. We checked and double checked our specimens. As we started to pass the draft of a manuscript back and forth, I asked Rachael whether she wanted to be a coauthor describing the new animal or to have it named after her.

Rachael presented a poster about the discovery at the November 2010 Sigma Xi International Meeting and Student Research Conference in Raleigh, North Carolina, with 250 other undergraduate researchers. The new genus of water bear is shown in Figure 8. Our manuscript reporting the find is under review at a peer-reviewed journal.


The tardigrades are able to withstand such extreme conditions because they enter cryptobiosis status when conditions are unfavorable. It is an extreme state of anabiosis (decreased metabolism). According to the conditions they endure, the cryptobiosis is classified as:

    Anhydrobiosis: in case of environmental dehydration, they enter a “barrel status” because adopt barrel shaping to reduce its surface and wrap in a layer of wax to prevent water loss through transpiration. To prevent cell death they synthesize trehalose, a sugar substitute for water, so body structure and cell membranes remain intact. They reduce the water content of their body to just 1% and then stop their metabolism almost completely (0.01% below normal).

  • Cryobiosis: in low temperatures, the water of living beings crystallizes, it breaks the structure of cells and the living being die. Tardigrades use proteins to suddenly freeze water cells as small crystals, so they can avoid breakage.
  • Osmobiosis: it occurs in case of increase of the salt concentration of the environment.
  • Anoxybiosis: in the absence of oxygen, they enter a state of inactivity in which leave their body fully stretched, so they need water to stay perky.

Referring to exposures to radiation, which would destroy the DNA, it has been observed that tardigrades are able to repair the damaged genetic material.

These techniques have already been imitated in fields such as medicine, preserving rat hearts to “revive” them later, and open other fields of living tissue preservation and transplantation. They also open new fields in space exploration for extraterrestrial life (Astrobiology) and even in the human exploration of space to withstand long interplanetary travel, ideas for now, closer to science fiction than reality.

All about Waterbear (Tardigrade)

FACTS: One of the more fascinating organisms in the microsphere is the common tardigrade – technically speaking, “slow walker.” However, it is not the tardigrade’s sluggish speed that captures the attention, but rather the fact that as this miniscule creature lumbers along on its eight tiny legs, it bears an uncanny resemblance to, well, a bear.

First described in 1773 by Johann August Ephraim Goeze as “kleiner Wasserbär,” these “little Waterbears” are unusually hardy. By entering a state of cryptobiosis – a kind of super-hibernation where the metabolism becomes inactive – waterbears can survive in boiling water, and at temperatures very close to absolute zero. They can dry out and survive 99% dehydrated for decades. They can survive a thousand times more radiation than humans can. They can even survive in the vacuum of outer space!

Needless to say, with these death-defying abilities, waterbears are found all over the world, from the highest mountain peaks to the depths of the deep. But they are typically found nearby in the miniature rainforests created by common mosses (indeed, they are sometimes called “moss piglets”) – so backyard adventurers with low-powered microscopes can easily go on a waterbear hunt.

But never fear: although a few species (such as the grizzly Milnesium tardigradum) are aggressively carnivorous, as a whole, waterbears (including our own Hypsibius dujardini) are quiet herbivores who live gentle little lives, picnicking and playing – and taking long, slow walks.


Despite their overall abundance and cosmopolitan distribution, the Tardigrada have been relatively neglected by invertebrate zoologists. Because of difficulties in collecting and culturing the organisms and their apparent lack of economic importance to humans, our knowledge of tardigrades has lagged that of other groups. However, their importance in elucidating the phylogeny of the Metazoa, particularly the arthropods, has recently increased interest in this group. In addition, their development and ecology are poorly understood, and proper training of taxonomists skilled in identifying tardigrade species is essential for systematic, ecological, and molecular analyses.

Table 1. Subdivision of the Phylum Tardigrada with Habitat Classifications (Nelson, 2001)

Secrets of the amazing tardigrades revealed by their DNA

New genome sequences shed light on both the origins of the tardigrades (also known as water bears or moss piglets), and the genes that underlie their extraordinary ability to survive in extreme conditions. A team of researchers led by Mark Blaxter and Kazuharu Arakawa from the universities of Edinburgh, Scotland and Keio, Japan respectively, have carefully stitched together the DNA code for two tardigrade species, and their results are presented in an article publishing 27 July in the open access journal PLOS Biology.

Tardigrades are microscopic animals, justly famous for their amazing ability to withstand complete dehydration, resurrecting years later when water is again available. Once desiccated, they have been frozen in ice, exposed to radiation, sent into space vacuum. and still they spring back to life.

Tardigrades became more famous recently when it was suggested that their DNA was a mix of animal and bacterial segments, making them "Frankenstein" hybrids. The new research has now laid the Frankenstein idea to rest by arguing that tardigrade DNA looks "normal," with no evidence that these special animals use extraordinary means to survive. Previous ideas that they might have taken up large numbers of foreign genes from bacteria are shown to be due simply to contamination.

But what is "normal" to a tardigrade is still enigmatic and exciting. At less than a millimetre in length, tardigrades are too small to leave fossils, but using the new genomes, the scientists were able to explore what the DNA could tell them about where tardigrades sit in the tree of animal life. Tardigrades are a distinct type of animal whose closest relatives are arthropods (insects, spiders and their allies) and nematodes (roundworms). But which is closest? While the accepted view is that their four pairs of stubby legs make them more closely related to arthropods, the DNA evidence surprisingly strongly favoured a closer kinship with nematodes.

The researchers then looked at a set of genes -- the so-called HOX genes -- used to lay down the nose-to-tail pattern in embryos. There are usually about ten different HOX genes in animals, each involved with a different part of the nose-to-tail pattern. They found that tardigrades were missing five HOX genes, and that most nematodes also were missing the same five genes. This is either a coincidence or further evidence that tardigrades and nematodes are closely related.

It was also possible to identify the genes that tardigrades use to resist the adverse effects of desiccation. By asking which genes were turned on during the drying process, scientists could identify sets of proteins that appear to replace the water that their cells lose, helping to preserve the microscopic structure until water is available again. Other proteins look like they protect the tardigrades' DNA from damage, and may explain why they can survive radiation.

"I have been fascinated by these tiny, endearing animals for two decades. It is wonderful to finally have their true genomes, and to begin to understand them. It has also been great to work with Kazuharu Arakawa and his Japanese colleagues on this -- science is truly global, and together we achieved exciting things," Professor Mark Blaxter said. "This is just the start -- with the DNA blueprint we can now find out how tardigrades resist extremes, and perhaps use their special proteins in biotechnology and medical applications."

Frozen Siberian microbes just woke up from a 24,000-year nap—and immediately got busy

The microscopic organisms wasted no time cloning themselves.

Tiny microscopic organisms came back to life after they thawed out.

In 2015, a team of scientists extracted a core of frozen sediment from the permafrost in northern Siberia, near the Arctic Ocean. After getting thawed out in the lab, tiny microscopic organisms from that soil, called bdelloid rotifers, wriggled back to life—following what could be described as a 24,000-years-long nap, according to new research published in the journal Current Biology.

“It’s like a tale of Sleeping Beauty,” says coauthor Nataliia Iakovenko, a biologist at the University of Ostrava in the Czech Republic. Except instead of one hundred years of dormancy, these bdelloid rotifers were most recently kicking around in the Late Pleistocene. And instead of a cursed princess, we’re talking about some extremely hardy worm-like invertebrates, about a third of a millimeter in size, which do not exist in male form and reproduce by cloning themselves.

“The important message is these molecular mechanisms which help them to survive have a very long expiration date,” says Iakovenko.

When the researchers collected the permafrost samples, they used drilling and trimming techniques that helped reduce the risk of inadvertent mixing with modern-day microbes. To pinpoint the rotifers’ age, the scientists took adjacent material from the core and sent it to a lab in Arizona for radiocarbon dating, which revealed an age of 23,960 to 24,480 years. Meanwhile, the rotifers themselves, along with other soil organisms, sprung to life in the lab after defrosting into balmy 64-degree conditions. For contrast, when the researchers removed them from the permafrost the temperature of the frozen sediment was 21 degrees Fahrenheit, and average temperatures for the permafrost sit at around 14 degrees Fahrenheit.

These creatures can survive this type of extreme scenario because they are adapted to frequent or irregular drying or freezing, says Stas Malavin, a coauthor on the study and a researcher at the Institute of Physicochemical and Biological Problems in Soil Science in Russia. “From previous research on rotifers, we know that they are very tough animals, they can resist many different harmful conditions.” When frozen like this, the rotifers’ state can be compared to clinical death, says Malavin—but one that’s reversible.

This study is “one of very few studies that have demonstrated multi-thousand year survival of a eukaryote, an organism whose cells have a nucleus, wrote Peter Convey, a terrestrial ecologist at the British Antarctic Survey, in an email to Popular Science. Previous research has suggested that nematodes can survive for even longer, at over 40,000 years, while several studies on moss, for example, also found lengthy (though far shorter) survival times. Rotifers, tardigrades (or “water bears”) and nematodes are known for cryptobiosis, says Convey, meaning they can survive in a “suspended” state when exposed to serious stressors like sub-zero temperatures or desiccation.

“I guess one of the largest challenges with any such studies is that of contamination,” wrote Convey, who was not involved in the research. In other words, “how can you be absolutely sure that nothing has had the chance to percolate down through the [soil] over time, or how to be sure there have not been any events disturbing the continuity of permafrost over this time.”

These new findings, Malavin says, will help researchers figure out what specific mechanisms allow organisms to preserve themselves in such fatal conditions. Further research could eventually contribute to scientists’ understanding of how to better preserve human or endangered species sperm, says Malavin, or transplanted human organs like hearts, which can currently only be preserved for very short time periods.

While these rotifers may have technically survived for 24,000 years, their normal lifespan is quite brief. “Can you imagine,” Iakovenko mused, “that they can survive for 24,000 years frozen, but then they just live one month and die?”

Save the pangolins

Pangolins are one of the world's most interesting animals. They are the only mammals to be covered from head to tail in scales. Because they have no teeth, they will deliberately eat stones (and nibble their own scales) to break up food in their stomachs. When they roll up into a defensive position, their scales can withstand a lion or tiger's jaws and, a bit like skunks, they can emit a stinky fluid to deter any would-be predators.

Unfortunately, some species are on the edge of extinction. Education and awareness are important aspects of their protection.

Traditional Chinese medicine is far from a quaint, ancient wisdom. Instead, it's a multi-billion-dollar black market that tortures bears and skins pangolins. It's a leading factor driving the extinction of some species. Knowing this gives us the ability and tools by which to stop it. Law enforcement and anti-trafficking operations are insufficient. We must tackle the root causes of pangolin trafficking.

Jonny Thomson teaches philosophy in Oxford. He runs a popular Instagram account called Mini Philosophy (@philosophyminis). His first book is Mini Philosophy: A Small Book of Big Ideas.