Tardigrades

Water Bears

Tardigrade – Water Bear A tardigrade is a member

of an obscure group of invertebrates (Tardigrada) located between the nematodes and the arthopods. They are microscopic animals that are found in marine freshwater and semi- aquatic environments.

Bear Claw

They are segmented invertebrate animals with eight legs. The name Tardigrada means “slow walker” and was given by Lazzaro Spallanzani in 1777. The name water bear comes from the way they walk, reminiscent of a bear. The largest adults may reach a body length of 1.5 mm. They occur over the entire world, from polar regions to the equator. (They can often be found by a soaking piece of moss in spring water.)

• Tardigrades are eutelic, with all adult tardigrades of the same species having the same number of cells. Some adults have 40,000 cells, while some have far fewer.

Tardigrade Plush

Water bears feed on the fluids of plant and animals cells.

They can live in extreme environments ranging from hot springs to solid ice. Without water they shrivel into a cask stage and survive long periods of desiccation in a stage called cryptobiosis (anhydrobiosis).

Tardigrades have been known to survive the following extreme conditions:

• Temperatures as low as -200 °C (-328 °F) and as high as 151 °C (304 °F);

• freezing and/or thawing processes;

• changes in salinity;

• lack of oxygen;

• lack of water;

• levels of X-ray radiation 1000x • the lethal human dose;

• some noxious chemicals;

• boiling alcohol;

• low pressure of a vacuum;

• high pressure (up to 6x the pressure of the deepest part of the ocean).

A grazing tardigrade