Tardigrades - Some of the toughest, and smallest, animals on earth!

Tardigrades are some of the smallest animals on the planet. Most are around 500 microns (half a millimeter), but newly hatched tardigrades can be 10 times smaller than that. And the biggest ones only reach about a 1.5 millimeters. Tardigrades are more commonly known as water bears. This is because of their bear like appearance when they waddle around looking for food. But, unlike a bear, tardigrades have eight legs which all end in several claw-like toes. Most tardigrades are herbivores and eat thing like algae and other plant material. However, not all tardigrades are grazers, some are hunters and eat things like bacteria, single celled organisms, rotifers and even other tardigrades.

Living tardigrade from the genus Ramazzottius.

Tardigrade from the genus Milnesium mounted in hoyer's medium.

Tardigrades are sometimes referred to as extremophiles, due to their ability to survive extreme conditions like enormous amounts of pressure, temperatures from close to absolute zero to way past boiling as well as huge amounts of radiation. To test just how hardy these animals are, they were sent into space for 10 days back in 2007. Most of the tardigrades survived and were still able to reproduce afterwards, despite being exposed to the vacuum of space and blasted with cosmic radiation. But, to tolerate such extremes, the tardigrades need to enter an inactive state called a tun, where they lose almost all of their water and are essentially dead. When rehydrated, the tardigrades return from the dead and continue on with their lives as nothing had happened.

A narrated video of tardigrades seen with different kinds of microscopy 

techniques, brightfield, darkfield and polarized light microscopy.

Tardigrades are egg layers. Some species lay their eggs in the open. Other species lay them inside of their sheded skin called a cutile. When the eggs hatch the newborn tardigrades have them same number of cells as an adult, and now they just need to grow. These animals can live for up to two years in their active state. But if they enter the inactive state, they are able to survive for decades, maybe even centuries!