Driving around the red rhyolite hills of Mt Ive Station back in November 2015. Heat haze rippled up from the ground with the car telling us the outside temperature was 44°C. We wandered our way along the dusty roads and through a stunning landscape of old warn down hills topped with yellow spinifex and sprawling plains covered with blue-grey bluebush. The station, a working sheep station, caters for the more adventurous traveller who is willing to get off the beaten track.
We were driving around early in the day trying to avoid the heat, looking for a spot that might attract some birds. Not long before we arrived there had been rain which can be sparse and unpredictable in the outback. A small rock walled dam between a couple of stunning spinifex clad hills called The Embankment had collected some water. We made our way up the slope and peered over the wall to find some turbid muddy water. Instead of finding the water only perturbed by the breeze we found a soup with bustling life. Abundant large tadpoles wiggled their way around and what appeared to be Fairy Shrimp fluttered about. But there was something else. Occasionally, dabbing the water’s surface then disappearing into the murky depths another crustacean lurked. After waiting a short while one emerged in the shallows releveling itself to me, a Shield Shrimp! I was very excited. Since hearing about them as a novelty pet in the aquarium trade I always wanted to see them in the wild. They are curious ancient looking creatures that have a very interesting lifecycle.
After it rains in the outback, dusty depressions, clay pans and dams like The Embankment fill up with water. The dust turns to mud and tiny packets of dormant life, the eggs (cysts) of the Shield Shrimp, hatch and spring to life. The larval stage (nauplii) quickly develop to adulthood and are able to reproduce within a few weeks. Life is quick because the water may not remain for long, evaporating in the harsh outback sun and being drunk by thirsty animals. The shrimp swim around their muddy soup using their oar-like limbs that have gills enabling them to breath. The adults can reach 90 mm long as they feed and prepare to lay eggs. The water levels become lower and lower the females disperse their eggs into the mud securing the next generation. As the water disappears the adults perish, and the mud turns to dust once again. The dust and eggs may be blown about for years or even decades experiencing harsh hot and cold temperatures waiting for the next rains so the cycle can start again.
If you are out and about in arid Australia after rain, check out some of the pools of water and you might find some of these fascinating and hardy little creatures that manage to persist in some of Australia’s harshest environments.