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July 30, 2026Short & citedBlog
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Field Notes • Biology

Tardigrade

Tardigrades are a phylum of microscopic invertebrates known for their eight legs and extraordinary resilience.

Updated July 30, 20261 min readCited sources

Tardigrades are microscopic invertebrates with eight legs, known for surviving extreme conditions. They are also called water bears or moss piglets.

What it is

Tardigrades belong to the phylum Tardigrada, first described in 1773 by J. A. E. Goeze. They are tiny, segmented animals about 0.5 mm long, with four pairs of legs. Their name means 'slow stepping,' and they move with a bear-like gait, hence the common name water bear.

Why it matters

Tardigrades are famous for cryptobiosis, a dormant state where metabolism nearly stops. This lets them survive vacuum, radiation, dehydration, and extreme temperatures. They are studied in Canadian classrooms and university biology courses as examples of extremophile animals and microscopic invertebrate diversity.

Key details

Tardigrades live worldwide in water, damp moss, lichens, soil, freshwater, and marine environments, including polar regions and hot springs. Their lifespan in active conditions is months, but dormancy can extend survival for years or even decades.

In short

  • Tardigrades are microscopic invertebrates with eight legs and a bear-like appearance.
  • They can enter cryptobiosis to survive extreme conditions like space vacuum and radiation.
  • Found worldwide in damp habitats, including Canadian ecosystems.
  • Typically about 0.5 mm long, with a short active lifespan but long dormancy.
Canadian angle

Tardigrades are studied in Canadian classrooms and university biology courses as examples of extremophile animals and microscopic invertebrate diversity.

Quick questions

What is a tardigrade?
A tardigrade is a microscopic invertebrate animal in the phylum Tardigrada, known for having eight legs and a highly resilient body plan.
Why are tardigrades called water bears?
They are called water bears because their slow, bear-like walking style and appearance resemble tiny bears, and they are often found in water or damp habitats.
Can tardigrades survive in space?
Yes, some tardigrades have survived exposure to the vacuum of space and intense radiation in experiments, largely because they can enter cryptobiosis.

Sources

  1. Wikipedia — https://en.wikipedia.org/wiki/Tardigrade
    Supports: General description, common names, and typical size
  2. Merriam-Webster — https://www.merriam-webster.com/dictionary/tardigrade
    Supports: Definition, common name water bear, and habitat
  3. National Geographic Kids — https://kids.nationalgeographic.com/animals/invertebrates/facts/tardigrade
    Supports: Common name, size, habitats, and survival in space
  4. American Scientist — https://www.americanscientist.org/article/tardigrades
    Supports: Average length of about half a millimeter
  5. BBC — https://www.bbc.co.uk/programmes/articles/1T3nsvDlwBqDS8TBzSGZPrV/what-are-tardigrades
    Supports: Meaning of the name, water bear nickname, habitats, and long dormancy
  6. Carleton College — https://serc.carleton.edu/microbelife/topics/tardigrade/index.html
    Supports: First description, naming history, body form, and size range
  7. Carolina Biological Supply Company — https://knowledge.carolina.com/timeless-tips/tardigrades-little-water-bears/
    Supports: Species count, habitat range, and longevity estimates