Shield Shrimp (Triops australiensis) are one of the most bizarre and enchanting creatures found in inland Australia, a region that teems with the bizarre!
They are crustaceans and live in the temporary pools of water after good summer rains.
After extensive rains they may number in their millions but are sadly not always noticed. The muddy, silt filled water camouflages their presence and it’s only when their temporary homes start to dry out that people start to notice them.
They are usually coloured brown or olive green and can reach 7 centimetres in length but are generally seen just a few centimetres long.
They can be found in any temporary waterhole, puddle or claypan and once they hatch from their egg the race is on to reach maturity.
They feed on small microorganisms and bacteria in the warm waters and breathe using a series of external gills along their feet.
The males and females are almost identical, except if the female is carrying her eggs. These are attached to the underside of her body until they are ready to be cast off into the world.
When it comes to the eggs, that’s when Shield Shrimp get seriously amazing!
The female spreads the eggs around the pool of water as it dries up. The eggs dry as the summer sun beats down on them and they enter a stage called diapause, a type of suspended animation.
They will only be triggered to start developing again once good summer rains falls.
Only some of the eggs will be triggered while others will wait it out, often for many years, until the next rains.
This neat evolutionary trick allows the Shield Shrimp to avoid extinction during extended low rainfalls periods.
Winter rain will not trigger the eggs…who wants to wake up to a cold puddle with little food?
It might be years later when the dried eggs get flooded, triggering the small Shield Shrimp to emerge and repopulate the shallow pools again!
Shield Shrimp are often called "living fossils" as very similar looking creatures can be found in the fossil record dating back 200 million years ago.
Their taxomony has been little studied but recent genetic analysis has suggested the single Australian species could actually be 20 or more species scattered across Australia.