Tardigrades > Education > What is a Tardigrade?
The Academy of Natural Sciences


Baker University

By William R. Miller

What is a Tardigrade?

Tardigrades are microscopic aquatic animals that need water to live, eat, grow, and reproduce. Without water they shrivel into a cask called a “tun” and survive long periods of desiccation in a stage called cryptobiosis. Tardigrades are found in marine, freshwater, and semi-aquatic terrestrial habitats. “Terrestrial” tardigrades occur in habitats that provide an aquatic world in their interior. Mosses, lichens, leaf litter, soil, and even the grains of sand on a beach are examples of such habitats.

Tardigrades are generally less than ½ a mm and a 40x dissecting microscope is necessary to observe them. But under such an instrument they look like little caterpillars or teddy bears. They have five body segments, four pairs of legs, and each leg ends in a set of claws. Tardigrades have a ventral nervous system with a brain and eyespots. They have well developed excretory, muscular, digestive, and reproductive systems. A characteristic of the phylum is the lack of both the circulatory and respiratory systems. They breathe through their cuticle and have a hemoceol for circulation.

SEM of cuticle SEM of claws Sem of eggs
Cuticle Eggs Claws

[Query - Pic315.tif, listed as "SEM Claws" appears to be SEM of eggs]

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