Tardigrade

Tardigrade

Tardigrades can survive in extreme environments, they can even stay alive in outer space.

Biology

Keywords

tardigrade, extreme environment, Repairing DNA damage, segmented body, direct development, tolerance, cuticle, chitin, eurytopic, arthropod, arthropods, animals, animal, biology

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Scenes

Tardigrade

Anatomy

  • 4 pairs of legs
  • cuticle - The outer covering of tardigrades. It consists of chitin and proteins and is moulted periodically.
  • mouth - The muscular, sucking pharynx serves food intake.
  • segmented body - The double ventral nerve cord possesses one ganglion per segment. The brain, located in the head, consists of multiple lobes.

Dehydration

  • normal state
  • dehydrated state - Under extreme conditions, tardigrades are capable of reversibly suspending their metabolism and going into this state by losing nearly 99% of the water content of their bodies, which helps survival. If they get back to an adequate environment, even years later, they rehydrate and revert to their normal state.

Repairing DNA damage

  • thymine - DNA consists of 4 types of nitrogen-containing nucleobases: thymine, adenine, cytosine and guanine. The order of the nucleobases encodes the amino acid sequence of proteins.
  • UV-radiation
  • thymine dimer - Upon exposure to UV radiation, they form in the DNA. This causes a disturbance in protein synthesis, which increases the risk of cancer. This is why too much exposure to solar radiation may cause skin cancer in humans. Tardigrades, however, are capable of efficiently repair damage to their DNA, using repair enzymes.
  • DNA repair enzyme

Animation

  • thymine - DNA consists of 4 types of nitrogen-containing nucleobases: thymine, adenine, cytosine and guanine. The order of the nucleobases encodes the amino acid sequence of proteins.
  • UV-radiation
  • thymine dimer - Upon exposure to UV radiation, they form in the DNA. This causes a disturbance in protein synthesis, which increases the risk of cancer. This is why too much exposure to solar radiation may cause skin cancer in humans. Tardigrades, however, are capable of efficiently repair damage to their DNA, using repair enzymes.
  • DNA repair enzyme

Narration

Tardigrades, also known as waterbears or moss piglets are micro-animals of about a half millimetre in length, typically living on mosses, but found in nearly all environments. They can survive extreme conditions that would be fatal for most life on Earth.

Under such conditions, they suspend their metabolism and go into a state of dehydration by losing nearly 99% of the water content in their bodies, which aids in their survival. When they are in an adequate environment, even years later, they rehydrate and go back to their normal state.

Their tolerance is illustrated by an experiment, in which dehydrated tardigrades were taken to outer space, where some individuals survived the combination of strong cosmic radiation and temperatures close to absolute zero. According to experiments, tardigrades are capable of withstanding temperatures between -272 and 151 °C, both in a vacuum and under extremely high pressure - up to several thousand times normal atmospheric pressure, which is several times the pressure of water in the deepest oceanic trench, the Mariana Trench. They can also survive radioactivity, and X-ray and UV radiation up to 1,000 times the lethal dose for humans.

Ultraviolet radiation damages the DNA of living beings. DNA consists of 4 types of nitrogen-containing nucleobases: thymine, adenine, cytosine and guanine. The order of the nucleobases encodes the amino acid sequence of proteins.

Upon exposure to UV radiation, thymine dimers form in the DNA. This causes a disturbance in protein synthesis, which increases the risk of cancer. This is why too much exposure to solar radiation may cause skin cancer in humans. Tardigrades, however, are capable of efficiently repair damage to their DNA, using repair enzymes. Similar enzymes can be found in other living beings, including humans, but they are much less efficient that they are in tardigrades. In dehydrated tardigrades this repair system is inactive, however, the DNA can be protected against UV radiation by 'wrapping' it up. In this case, thymine dimers are not produced, or if so, only in very low quantities.

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