Heavy rains across Central Australia have brought about the ephemeral phenomenon of tiny shield shrimps hatching from years of obscurity in the middle of the desert.

Yet these shrimps are more sea monkey than edible foodstuff.

"They're not a true shrimp," expert Michael Barritt told ABC Radio Darwin.

"So forget about prawns and that sort of look. They look a bit shrimp-ish but have this big shield across the tip of their bodies."

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Growing to seven centimetres at maturity, the shrimps are members of the crustacean family yet look more like an alien tadpole with a double-pronged tail.

A remnant of prehistoric times, on mainland Australia there is only one type of shield shrimp (triops australiensis) and it is commonly found across the middle section of the country.

While occasionally found in drainpipes or ditches all year round, the shield shrimps are most often found temporarily in bodies of water that periodically dry up.

"They can turn up in the absolute millions upon millions," Mr Barritt said.

"Even to the point of appearing on top of the rock of Uluru."

Where do these desert curiosities come from?

The shrimp's arrival after heavy rains — as seen recently across Central Australia with the flooding evacuation of one community — relies on their super-resilient eggs.

Fans of the retro toys sea monkeys might be familiar with the concept.

"Forget about your average egg," Mr Barritt said.

"These are eggs that can dry out and get blown by the wind. They deal with all the kinds of extreme temperatures that inland Australia gets, including high temperatures and low temperatures at night in wintertime.

"All these eggs get blown all over the place. Then when enough sufficient summer rain comes along, they hatch and go crazy trying to feed as much as they can on micro-organisms and bacteria in the water.

"They want to be able to have their eggs back into the drying surface before the waterhole dries out."

Shield shrimp seen after heavy rains near Numurkah in Victoria in 2016. ( Supplied: Leslie Bannon )

Despite their shields, the little critters are actually pretty defenceless and easy prey for fish and water birds.

"So that's why they're usually in waterholes that are shallow and drying out," Mr Barritt said.

After gorging, egg laying and a return of dry desert conditions, the newly laid shield shrimp eggs can last up to seven years buried in the sand or dirt, according to Mr Barritt.

"This gives them an opportunity to survive with the infrequent rains."

Mr Barritt said people currently in Central Australia would stand a chance at seeing the shield shrimps at Redbank Waterhole in Owen Springs Reserve, Palm Valley in Finke Gorge National Park and at Napwerte/Ewaninga Rock Carvings Conservation Reserve.

"And even at the top of Uluru," he added.

So how did the strange creatures end up in fleeting pools of water on top of a national icon 360 metres above the Gibson Desert?

The answer is unclear yet may lie in the eggs' ability to survive being carried long distances by the wind or perhaps hark back further to when Australia was a very different landscape.