We were introduced to a fascinating couple who are both ecologists at Malilangwe Conservancy, and who have been there over 20 years. Sarah does the Rhino research of all the animals they have there, and Bruce studies a variety of different topics. During our evening game drive with them we got onto the topic of seasonal water. They mentioned that there were fairy shrimps and triops – living fossils – living in many of the seasonal pans around the country. We were fascinated and they promised to take us to find them the next morning.
As promised we met up the next day and headed to a pan which had been around for just over a week. We all discarded our shoes and armed with a net and containers, waded into the slimy, muddy pan. Their son began dragging the small net through the water close to the bottom and quickly turned up some miniature shrimps measuring about 2cm, with bright orange tails. It looked like they were swimming on their backs with lots of legs flailing about on top.
He also found us a Triop, a living fossil from the Carboniferous age, 300 million years ago. This strange creature had a rounded shell on its back, a longish tail and lots of legs. Among the haul was a few clam shrimps, tiny round things with legs. We put them all into a clear container so we could have a good look.
It was explained to us that these creatures had a life span of about 2-3 weeks in which they laid their eggs in the mud before being eaten by predatory birds or the water dried up. These eggs then stayed in the mud until it rained again and there was enough water for them to survive, (the pressure of the water had to be enough so as to trigger them to hatch). They explained how they were at first confused how these things were found all over the park, and had then discovered that when an animal had a mud bath, the mud that stuck to their bodies and later dropped off in another area, contained the eggs which if fell in an area where there was enough water, would hatch in the rains. Also through studies, they found that these shrimps were only found in seasonal water as the eggs needed a rest period and the adults were quickly eaten by birds and frogs, hence the very short life cycle. These little creatures were not found in water bodies that were there all year, and this highlighted the loss of this source of food for the birds and reptiles when a seasonal pan was converted to a perennial water source.
Who knew there were these fascinating creatures floating about in the muddy pans!