Just add wa­ter

A des­ic­cated husk that springs back to life with a lit­tle H2O in­spires the ad­mi­ra­tion of MAR­TYN ROBIN­SON

Gardening Australia - - BACKYARD VISITORS -

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 your­say@gar­deningaus­tralia.com.au with ‘Crea­ture’ in the sub­ject line.

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