Tardigrades Temporal range:
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Milnesium tardigradum, a eutardigrade | |
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Echiniscus succineus, a heterotardigrade | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Subkingdom: | Eumetazoa |
Clade: | ParaHoxozoa |
Clade: | Bilateria |
Clade: | Nephrozoa |
(unranked): | Protostomia |
Superphylum: | Ecdysozoa |
(unranked): | Panarthropoda |
Phylum: | Tardigrada Spallanzani, 1777 |
Classes | |
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Tardigrades ('water bears') are microscopic, segmented animals.[1] They live in water. They are members of the tactopod phylum Tardigrada, part of the superphylum Ecdysozoa. They are also known as water bears or moss piglets.[2][3]
Tardigrades were first described in 1773.[4] Their name means "slow stepper". There are more than 1000 different species of tardigrade.[5]
Tardigrades have a cylindrical shape with four segments, each with two legs. Each leg has little claws.[5] The biggest adults may reach a body length of 1.2 mm, the smallest below 0.1 mm. Freshly hatched larvae may be smaller than 0.05 mm.[4] Tardigrades feed on plant cells by penetrating the cell wall and eating what is inside. Some tardigrades are carnivores.[6][5]
Tardigrades are eutelic: all adult tardigrades of the same species have the same number of cells. Some species have as many as 40,000 cells in each adult, while others have far fewer.[7][8]
Tardigrades can be found in many habitats: in moss,[6] freshwater,[6] the Himalayas,[4] and the ocean.[4] They are one of the few animals that can be found on the highest mountains and the deepest seas.[4] About 83% of the known species live on land, the other 17% live in water.[5]
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