Visit the deserts of Central Australia this week, and you'll be transported to the Triassic. Unusually heavy rains have left the region's red sands crawling with shield shrimp, the descendants of a family that dates back some 250 million years. 

Much like locusts, these distinctive desert dwellers (Triops australiensis) can lie dormant for years, emerging only when the time is just right. And when they do, their larvae can hatch by the millions!

With scorching days and cold (but equally harsh) nights, life in the desert is extreme – so shield shrimp eggs have become incredibly hardy over time. A special barrier layer separates the encased embryo from the elements, much like the eggs of brine shrimp (of Sea-Monkeys fame).

In fact, shield shrimp eggs are so resistant to desiccation that they can survive without water for up to seven years. And it's thought the extreme weather patterns actually help to disperse them.

"All these eggs get blown all over the place," Northern Territory Parks and Wildlife staffer Michael Barritt told ABC Radio Darwin after news of the latest hatching event surfaced. "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."

The muddy puddles that form after sporadic desert rains make the perfect breeding and feeding grounds for the tiny animals, who will dry out and die shortly after spawning the next generation. In their adult stage, shield shrimp get around on 60 frilled legs, which also act like gills, sucking up oxygen from the surrounding water.  

While the term "living fossil" is inaccurate and misleading, shield shrimp (which aren't actually true shrimp) haven't updated their look in about 70 million years. It's strange to imagine, but there were Triops much like these swimming around in pools of water when the first dinosaurs walked the earth! 

You've probably noticed that this body style – complete with beady, upturned eyes and a self-righting tail – is shared by many other ancient creatures, like trilobites and horseshoe crabs. There's a reason for that: it works! These animals are all perfectly formed bottom-dwellers.

Well adapted they may be, but Triops are also relatively defenceless. Birds and other predators often flock to mass hatching sites for a crustacean buffet.


Top header image: Tiffany Hoy, Flickr