Did you know there were such things as tardigrades?
I’d certainly never heard of them, so allow me to fill you in. Tardigrades (also referred to as water bears) comprise a phylum of invertebrates similar to arthropods (insects, arachnids, crustaceans). These tiny animals are found almost all over the world, most commonly amongst lichens and mosses. Measuring between 0.1mm and 1.5mm in length, tardigrades must be viewed with a microscope and cannot be observed in the wild, so there is a dearth of information regarding tardigrade distribution.
While a number of different tardigrade species have been described to science, many countries – especially small islands – have not been assessed.
Island studies
This was the concern of Harry Meyer, professor of biology at McNeese State University in Louisiana. Mr. Meyer specialises in tardigrades and has taken samples on various Caribbean islands. He expressed an interest in working with the National Trust for the Cayman Islands while on vacation in January 2010.
Mr. Meyer explained that the best information about biodiversity is yielded by the least modified or disturbed areas -tardigrades of course, are no exception. As such, we chose sampling areas in the least populated districts – North Side and East End. The Mastic Trail and Salina Reserve were especially useful areas to visit, and we were kept busy searching for mosses and lichens. When these were discovered, usually on rocks or trees, they were peeled off and stuffed into envelopes.
At this point you’re likely wondering what the fuss is about, what use we could have for these microscopic creatures?
The interest in tardigrades stems from cryptobiosis. Many animals are capable of hibernation throughout the winter season. During this time of metabolic depression they don’t eat and experience reductions in both temperature and respiration rate.
By contrast, a state of torpor, though marked by similar reductions in temperature and metabolic rate, lasts for shorter periods of time. Torpor is usually triggered by extreme environmental conditions; for instance, lungfish go into torpor when their pool dries up, and green iguanas may go into torpor in particularly cool winters.
Death-like state
Tardigrades, however, take survival to another level altogether: cryptobiosis. This state has been described as “truly death-like,” and is characterized by virtually undetectable metabolic rates.
Experiments have shown that cryptobiosis allows tardigrades to survive a number of extreme environmental conditions. While in this state, tardigrades have survived being heated to 151C, and chilled to -272C. They have survived the vacuum of space, as well as the pressure of 6000 atmospheres.
Virtually indestructible
Tardigrades have survived nearly 10 years of total dessication. They can also survive exposure to radiation – more than 1000 times the dose that would prove lethal to human beings.
When undergoing cryptobiosis, a tardigrade dries out to the point that it can be spread around the world by the wind. All it takes is a little water for the tardigrade to revive itself.
The hardiness of tardigrades is a characteristic that is being studied closely by scientists. Possible applications include the preservation of larger organisms, and even the safety of humans during space travel. In fact, tardigrades will be part of the upcoming Living Interplanetary Flight Experiment.
Mr. Meyer identified two species of tardigrade from his trip to Grand Cayman: Minibiotus sp. and Macrobiotus cf. areolatus.
Paul Watler is environmental programmes manager designate at the National Trust for the Cayman Islands.
Related Videos
