Tardigrade: Hardiest Critter on Earth
Meet the Tardigrade. This microscopic, multi-celled invertebrate animal, also known as a water bear or moss piglet, has been launched into space on projects to see how spaceflight affects organisms on the molecular level. Famous for being a polyextremophile, the water bear has been reported to live more than 100 years without food and water, by assuming a dehydrated, hibernation-like state called cryptobiosis.
“They roll up into a dried little ball, and just stay dormant, with no sign of life whatsoever. Scientists have rehydrated them from a piece of moss in a museum collection that was a hundred years old. They’ve been frozen and defrosted, put under pressure, subjected to very high temperatures, and zapped with X-Rays. They come out alive and well. Just add water.” – How to Find Tardigrades, by Michael Shaw.
But while water bears are famous for their ability to survive extreme environmental conditions, scientists actually know relatively little about their “down to earth” biology and biological diversity. What do tardigrades do for our local ecosystems, for example?
“Absolutely nothing,” laughs William R. Miller, director of biological research and assistant professor of biology at Baker University in Kansas. Tardigrades aren’t known to cause disease or benefit humans in any concrete way. In fact, their contribution to the ecosystems and environments they inhabit is poorly understood for an organism that is known to survive temperatures as low as -200 °C (-328 °F) and as high as 151 °C (304 °F), and pressures as low as the vacuum in outer space and as high as 6x the pressure of the deepest part of the ocean. While tardigrades are found just about everywhere on Earth, and terrestrial species living in the damp environments inside mosses, lichens, leaf litter and soil have been differentiated from species living in fresh or salt water, scientists know little about species diversity in different forms of these environments.
But that doesn’t mean tardigrades are useless or unimportant to study. Understanding just how tardigrades survive such extreme conditions could help biologists better appreciate the molecular changes that occur to other organisms placed in these extreme environments. Tardigrades eat other microscopic organisms, and are in turn digested by larger organisms, making them an important link in the energy chain, Miller says.. And Miller believes there are many species of tardigrades yet to be discovered, some of which may possess yet unknown properties that allow them to survive high doses of radiation, noxious chemicals and other extreme conditions.
The Hunt is On
This week, visitors to the North Carolina Museum of Natural Sciences were invited to bring samples of mosses or lichens from their backyards for tardigrade analysis in the Biodiversity Lab on the second floor of the Nature Research Center. Meg Lowman, Senior Scientist for the Museum and coordinator of the project, along with Miller and a group of visiting undergraduate students from Baker University, have been working this summer to define the taxonomy and distribution of tardigrades in tree canopies as part of a larger NSF-funded research project.
“Do more [tardigrades] live in the top versus the bottom of a tree?” Lowman asked in a recent Raleigh News & Observer article on the project. “Is there one species or 100 species? Do they prefer leaf surfaces, lichen, moss or bark habitat?”
These are just some of the questions the research group is looking to answer this summer. Undergraduate students participating in the project for the summer has already discovered what look like several new species of tardigrades, which seem to be environmentally segregated by height, from ground level to the tops of the trees sampled by the group. They have been posting pictures of the tardigrades they have found on a NC Museum of Natural Sciences webpage dedicated to the project.
If you are in the vicinity of Durham or Raleigh, North Carolina, visit the Museum on Thursday August 8th from 1-2pm or 5-6pm to hear students answer questions about water bears and the ecology of tree canopies.