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Small but mighty! The tardigrade

Records are not reserved for the tallest and strongest: This article is dedicated to the tiny tardigrade, which for all its inconspicuousness is the world record holder in the discipline of "survival".

Who would have thought that behind the cute-sounding name “tardigrade” there was a world record holder? The tardigrade is easy to miss if you don't know about its existence, because it rarely grows larger than a millimeter. Nevertheless, there was an entry in the Guinness Book of Records - but not because of its size (or smallness), because there are numerous living things that are smaller than a millimeter. No, it is the unique ability to adapt to various extremes such as cold, drought, lack of oxygen or high salt content that makes the tardigrade so special.

After this text, read the article The Tardigrade - Strategies of a Survivalist to find out what is behind the super abilities of these animals!

A very special group of animals

Strictly speaking, there is no such thing as “the” tardigrade, but rather these creatures form their own tribe within the animal kingdom, to which various genera and species belong. The eight-legged tardigrade are closely related to the arthropod tribe, which includes insects, millipedes and arachnids. By the way, her German name can be explained quite simply by her bear-like appearance under the microscope and the clumsy walk; in English they are also called “water bears” or “moss piglets”. Its scientific name is Tardigrada and means something like "slow steps".

And where do you find these tardigrade? In fact, their representatives are spread all over the world. They live both on the bottom of water - be it in salt or fresh water - as well as on land, where they prefer moist places such as moss pillows. You can find them in the cold of the Antarctic and in tropical hot rainforests. Tardigrades also live in the highest mountains in the world, the Himalayas, and at the lowest point on the earth's surface, the Mariana Trench, 11,000 meters below sea level. Tardigrade seems to be able to colonize every corner of the world.

Tardigrade anatomy

The body of the tardigrade consists of four externally visible segments, each with a pair of legs. The skin that surrounds the tardigrade is called the cuticle and serves as an external protective shield against the environment. It consists mainly of chitin and glycoproteins (these are proteins to which carbohydrate groups are attached). Dyes can also be stored in the skin, which give the tardigrade their typical red, green, yellow or purple color, depending on the species.

To move the body and limbs, tardigrade have very fine longitudinal muscles, which consist of a single or a few muscle cells. The first three pairs of legs can be used if necessary, for example to climb over grains of sand. The fourth and rearmost pair of legs are not used to move, but to hold on to the ground. However, only very few tardigrade move actively and purposefully. Instead, they are mainly driven by the movement of wind or water. Another peculiarity of the tardigrade is that they lack actual respiratory organs. Instead, they cover their oxygen needs simply by diffusion through the skin.

The different species of tardigrade have very different dietary preferences. There are predatory tardigrades, for example, which hunt for single-cell organisms or roundworms, as well as omnivores, which eat organic waste along with the bacterial and fungal cells that live on it. Most tardigrade, however, have a vegetable diet, usually algae. But as everywhere in nature, the tardigrade also has to "eat and be eaten". Spiders, mites, earthworms, but also larger, predatory tardigrade species come into question as natural predators.

Involuntary inhabitants of the moon

In April 2019, the Israeli lunar module Beresheet transported not only scientific equipment but also several thousand dried tardigrade into space. The probe should have touched down gently on the moon, but crashed after a partial failure of the data systems on the moon's surface.

Whether the tardigrade survived this crash landing and would be viable again if the conditions were more favorable?