UNITY — In the woods of Unity College, students hunt for a tiny eight-legged animal that is capable of surviving in extreme environments, from outer space to the bottom of lakes and oceans to the peaks of the Himalayan mountains.

Tardigrades, also known as water bears or moss piglets, are among the world’s smallest animals. Their discovery in North America dates to the 1873 findings of a priest in the town of New Gloucester. For years, there were no further scientific studies of tardigrades in Maine until their recent re-discovery sparked an interest at Unity College, an environmentally focused liberal arts school with an undergraduate population of about 550 students.

On a recent snowy day, a group of students working with Emma Creaser, a professor of marine biology, poked through lichen, moss and leaf debris looking for tardigrades, which are compared to bears or piglets because they have stout legs and rotund bodies.

Humans can’t see tardigrades. At an average size of two-tenths of a millimeter, they are not visible to the naked eye, yet their ability to withstand extreme environments means they are capable of doing things that humans can’t. In 2007, tardigrades were the first animals to survive exposure in outer space, and the study of them has attracted scientists interested in unlocking the key to living forever, thanks to their ability to preserve their bodies for extended periods of time without food, water or oxygen.

Studies so far have shown that they are capable of living up to 10 years in a hibernationlike state called cryptobiosis, only to be revived with a single drop of water.

“They’re sort of everywhere, but they inhabit a microcosm that we don’t even know about,” Creaser said as she led the students through the woods, making notes of which trees they are collecting samples from.

Even though it is the middle of winter and 6 inches of newly fallen snow blankets the ground, the animals still can be found on moss and lichens, where they inhabit layers of water surrounding the plant. Little is known about tardigrades, but because scientists know the habitat they prefer, material can be gathered that probably will contain the animals, Creaser told the students as they collected the samples in brown paper bags.

Tardigrades are some of the smallest animals known to man. They’re classified as animals because they move, eat plants and animals, have the ability to reproduce either sexually or asexually, and have a nervous system and brain.

More than 1,000 species of tardigrades have been documented worldwide since their discovery in the late 1700s. Their discovery in North America is credited to a Maine priest, W.R. Cross, whose findings were documented in a December 1973 publication of The American Naturalist.

“It is white, about 14/1000 inch long, and has minute eyes composed of about ten irregular facets” is the way the animal is described in the journal, along with a drawing showing its eight legs, each with a set of four claws.

For decades, no one in Maine studied tardigrades — until 2011, when Harry Meyer, a scientist visiting Maine, wrote a research paper on samples he found in Bar Harbor.

The paper caught the attention of Creaser, who has since documented 11 species of the animal throughout the state, including two never-before discovered species in Rangeley and Hancock. Last summer they were documented in Acadia National Park. Creaser is working on a grant to study whether they can be found off the coast of Maine.

Her students are also excited about the project.

Ashleigh Munton, 20, a junior majoring in marine biology and secondary education, discovered a tardigrade by accident while looking at a slide of water from a mud puddle in a biology class.

“I saw this thing crawling around and didn’t know what it was. It was really hard to identify because our biology books didn’t include tardigrades,” she said.

Munton volunteers her time to work on the tardigrade research for no credit, but Creaser also teaches a class in invertebrate marine biology in which the creatures are studied. She has a small group of students who are working on the research outside of class.

She has to limit the number of students who can participate because the laboratory has only so many slides and a limited amount of equipment, although enthusiasm for the project is high.

Ben Sawtelle, 19, a freshman, said he hopes to work on the research for as long as the opportunity is available.

“It’s a real-world experience. We don’t know what the next step will be, and that’s the exciting part. Before we can design an experiment, we have to know what we are studying, and that’s what we’re doing now,” said Sawtelle, as he scraped a lichen off a tree and put it into a paper bag on a recent outing.

Sawtelle, who is among the small group of students working on the research with Creaser, doesn’t just collect samples on campus. He also is involved in helping procure them from sites around the state, including faraway places such as Caribou, where he has an aunt who sends him samples of moss and lichen to test.

Tardigrades can be collected almost anywhere and can survive in a paper bag for days before they are brought to the laboratory. They require water for life, but without water they are capable of preserving their bodies by entering into a state of cryptobiosis, in which they store sugars.

This process allows tardigrades to survive some of the harshest conditions, including temperatures ranging from 301 degrees F to negative 458 degrees F for short periods of time, irradiation, extreme pressure and lack of food or water.

The study of tardigrades is important for a few reasons. In general, the lower an organism is on the food web, the more essential it is in maintaining a stable ecosystem, Creaser said. That means that tardigrades and other micro-organisms play essential roles, even though we may not be sure yet of the extent of what they do.

“When we lose a predator, we tend to care because they’re quite visible, but life can go on quite happily without them. It’s the little things — the decayers and the recyclers — that are much more important,” Creaser said.

Tardigrades are also distributed via the wind, so their movement is linked to climate change and can help us understand environmental patterns, she said.

Rachel Ohm — 612-2368rohm@centralmaine.com