Just add water
A desiccated husk that springs back to life with a little H2O inspires the admiration of MARTYN ROBINSON
So let’s roll out a few egg-shaped ‘tuns’ found in some century-old, dry herbarium moss specimens and see what happens if we add a little water. Soon, eight stumpy legs pop out and start waving, then tardigrades emerge. Feed them liquefied algae or moss, depending on the species, and then let them shrivel up and go back into dry storage. Tardigrades are the only known animal group that can remain in a state of suspended animation for years and, after a bath, return to full functionality.
The desiccated tuns (named for their barrel shape) are also tough in other ways. They can withstand temperatures close to absolute zero (–273°C) and above the boiling point of water (100°C), as well as radiation many times greater than is lethal to most animals, and vacuums like you find in space. Incredibly, they revive when rehydrated, and their eggs do this, too. Just as many seeds have an impervious husk that absorbs available water to start the process of growing, and protects its contents until this happens, the surface of the tun and the tardigrade egg manage to do the same.
Tardigrades are multi-cellular, like most larger animals, but at least as small as many single-cell animals such as amoebas and paramecia. The largest just make it into our naked-eye visual field, at about 1mm. Unlike most animals, whose cell numbers increase to keep up with growth in body size, they hatch with a full complement of cells, which just get larger as they do. Most are vegetarian, piercing plant, algal and fungal cells to feed on the fluid, but a few with bigger claws are predatory on equally tiny prey.
You can find tardigrades in your garden – particularly if you have moss (they’re also called ‘moss piglets’). They have been found in almost every habitat, from ocean to fresh water and on land. Try soaking moss in a little water, gently squeeze, then search the fluid under a low-power microscope.
Martyn gardens mainly on Sydney’s Northern Beaches Have you found something interesting in your garden? Send us a photo and Martyn will ID it. Email email@example.com with ‘Creature’ in the subject line.