HUGE DISCOVERIES COULD COME FROM TINY TARDIGRADES.

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1 HUGE DISCOVERIES COULD COME FROM TINY TARDIGRADES.

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3 ~t-~----; , -1 [T:lr"""", I,' m;" I" -'~ljl'n "II', '. -" 1 "I -, " -~,.,.' ",,.....;..., '\"1... ~'=.. ~r '. I'", - J.-. '.....w.. I...-..,'.. :1',.- Iii'..,f _ '.. If\ii;;C; -, :'1" _..,..- 'fll~ ": ' ' I'~ 'I -.,' II I.' -.. ' '.., '..~:-:.t" -.~ _r,~_.~ ~lil~_.l I~ -,.,'.... J ardigrades are often called water bears, but they're not bears at all. They're invertebrates, meaning they have no backbone. And they're so small you need a microscope to see them. Yet, these tiny creatures are so tough that scientists are impressed-and eager to learn more. 12 Found in Water Everywhere Some water bears live in oceans and seas. Some live in fresh water. Still others thrive in water on tree mosses or in damp soil. So far, there are more than 1,000 known species of tardigrades. As a college student, Alex Young worked on a summer project with William Miller and other biologists in Kansas. Team members collected moss and lichen from trees. At a lab, they used dissecting microscopes to examine the samples for tardigrades. Research helped them classify what they found. Young found a population of tardigrades that did not fit any existing descriptions. More research followed. "It was a long, involved process," he says. When the team was ready to describe and name this new species, "it was definitely exhilarating," Young says. The team published its discovery in Miller, who teaches at Baker University in Kansas, has been involved in finding more than a dozen new species ofwater bears. Tardigrades are found on every continent, including Antarctica. But no clear patterns exist for the numbers or diversity of species at different places. As an ecologist, Miller says that's "sort of unsettling," Pudgy Uttle Animals Although types ofwater bears differ, they share common features. At an average of.02 inches (.5 mm) long, they are about the size of the period at the end of a sentence. They have soft, segmented, translucent bodies. Think of a tiny, pudgy animal in a puffy coat. These tiny animals have eight stubby legs with little claws, Some have a set of eyes. "They use their claws to latch onto their environment and to crawl around," explains Young. As it happens, the main part ofthe water bear's body is one big head, scientists reported in 2016,..~. I II!!I... Before half a billion years ago, water bears' ancestors probably looked more like worms but with lots oflegs, says Bob Goldstein. He's a biologist who worked on the study with Frank Smith and other scientists at the University ofnorth Carolina at Chapel Hill. Alex Young hoists himself up a tree in search of tardigrades near the top.

4 After many, many generations, though, water bears evolved. And, Goldstein says, it seems that "they just deleted a big part of the body." Now the tardigrade is "a little bit like a spider without its back end." Figuring out how these critters get around is a mystery. "We find more tardigrades and more diversity of species higher in the trees than we do at the bottom," Miller notes. "They didn't climb up there." Figuring out whether birds, wind, or other factors are giving them a lift will take more exploration. In his view, that's "part of the science of understanding the planet and how it works." Just Add Water Water bears must be in water for the active parts of their life. That's not really a problem for tardigrades in marine or freshwater habitats. But sometimes the environment gets too dry for many land-based species of the animal. "\Then that happens, their legs and the tip of their heads pull back tightly. Almost all the water goes out of their bodies, and they curl into small, dried husks. "It basically shrivels into what we call a tun," says Miller. It's like "a little flake of dust." At that point, the tardigrade is dormant-temporarily suspended-as if in a deep sleep. It becomes active again when conditions improve. The tougher the environment, the more successful water bears seem to be at the process of "sleeping" and "waking." "Those that live in the Arctic and Antarctic do it much better than those that live in tropical rainforests," Miller notes. Some tardigrades can stay frozen for very long periods too. Japanese scientists reported in 2016 that they had successfully revived a couple oftardigrades from a frozen moss sample' after more than 30 years. That's not all. Some water bear species can survive temperatures hotter than boiling water. Others can tolerate high radiation, a type of energy that's dangerous to humans... Tardigrades have even lived through a space launch and tests that exposed them to the vacuum, radiation, and extreme cold of space. Decoding Water Bears' Secrets To get a better idea of what makes water bears so tough, scientists are taking a close look at their genes. Genes are lengths of linked molecules called DNA. They provide the chemical code for all the traits of an organism. And that includes all the processes that let its body function. Takekazu Kunieda is a biologist at the University of Tokyo in Japan. In 2016, his team figured out the genome for a hardy tardigrade species. Then they got human cells grown in a lab dish to reproduce bits of that code. The researchers wanted to know how tardigrades protect themselves against such harsh conditions. Scientists call a dried-up tardigrade a "tun/'

5 ,.he scien-ailic nalne 'rarlll"ralla Ineans "slow walke." tl DO You can't take a closeup of a water bear with a regular camera. For a good look, you need a scanning electron microscope. Some of the cells with certain bits of the DNA made a protein that Kunieda's group called Dsup. After the team exposed groups of cells to radiation, the ones that had that protein suffered less damage from the radiation. The protein helped preventthe animal's DNA from breaking down. Ultimately, proteins from tiny water bears could lead to better medicines. "Once we know how those proteins work, we can either take those strategies or take the proteins themselves and use them to improve medicines," says Samantha Piszkiewicz. As a graduate student at the University of North Carolina, she studies the chemistry and physics of proteins that help water bears survive. Right now, she explains, some medicines must be kept cold or they will go bad. That makes it hard Which is cuter: this tardigrade hatchling or your baby photo? to get those medicines to remote areas, especially in developing countries. Tardigrade proteins might help, Piszkiewicz says. One protein, for example, makes ajell-o-like gel that protects other proteins. Maybe the protein could help scientists develop capsules to protect medicines from heat or other extremes. Discoveries from tardigrades might also lead to other exciting products or processes. But that all starts with basic science, says Miller. "Tardigrades are going to be part of the continued explosion of knowledge," and they may someday help save lives or provide clues to other new technologies, Miller says. "But if you dismiss them and if nobody spends any time on it, then we totally miss all of that knowledge." Goldstein adds another great reason to explore water bear science: "They're adorable!" Kathiann M. Kowalski is the author of more than 25 books and more than 650 articles. She loves getting out in the fi eld and into labs to lea rn about science.

6 The Wild Science of Searching for the Fish in the Desert Healing Waters Water Bears Source of Life Saving the Devils Elixir oflife or money All about tiny tardigrades Do microbes hold the key? Hole pupfish down the drain? by Kathiann M. Kowalski by Brittany Moya del Pino by Merry Dankanich by jennifer Connor-Smith