"Temporary Ponds: a natural habitat to be protected!"

Crustaceans - Large Branchiopoda

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Large Branchiopoda (whose name means ‘branchia in the feet’) are characteristic of temporary ponds and are part of the Class Branchiopoda, a group of small crustaceans, which in turn are divided in five large categories (Orders), three of which are found in Portugal: Anostraca, Spinicaudata and Notostraca.

The Anostraca, commonly known as fairy-shrimp, can the easily distinguished because they swim belly up; the Spinicaudata are the clam-shrimp, since their whole body is protected by a bivalve shell, just like clams (bivalve molluscs); the Notostraca, commonly named tadpole-shrimp, have a large shield shape carapace covering the anterior part of the body resembling tadpoles (frog and toad larvae).

In the project’s intervention area the most emblematic specie of this large group is the tadpole-shrimp, Triops vicentinus (Notostraca), an endemic species of the southwest regions of continental Portugal. It is important to remind that the Branchiopods of the genus Triops have remained in these temporary ecosystems since before the Jurassic era (between 199 and 145 million years ago, approximately), the age of the great dinosaurs. There are fossil records of animals from this group dated from that geological era and also from posterior geological ages. These Triops are also the largest, reaching up to 7cm of carapace length, (not including cercopods).

However, the group of clam-shrimps is represented by two very interesting and also very resilient species of limited distribution: Cyzicus grubei and Maghrebestheria maroccana. These have also a very limited distribution like the Triops vicentinus, and their threatened status is the result of their survival to be dependent of temporary ponds, namelly the priority habitat of Mediterranean Temporary Ponds, where there is a constant shift between a flooded period in winter and a dry period in summer. This fact is explained by the nature of their cysts (eggs or resistant embryos), which require a dry period before hatching, as soon as the ponds floods again. In fact, those cysts may remain viable for several years in case of prolonged draught.

This latent stage of life shows a similar behaviour to seeds, which may be kept and sown only when the farmer desires so. This characteristics has also allowed these species of Large Branchiopoda to resist in time, fact that is vital to preserve by the conservation of the Mediterranean Temporary Ponds.

Photo of Margarida Machado, where it is possible to observe several specimens of dry clam-shrimp and tadpole-shrimps in the terrestrial phase of the Mediterranean Temporary Ponds.

Amongst the group of fairy-shrimps found in Portugal, namely the species Branchipus cortesi, Branchipus schaefferi, Chirocephalus diaphanus, Streptocephalus torvicornis, Tanymastigites lusitanica and Tanymastix stagnalis, some have a very interesting characteristic: they have very short life cycles, i.e. from their hatching from cysts until they die can all occur in just 8 to 15 days. They are truly ‘super-fast'. They have adapted to these temporary ecosystems in a way that allows them to make use of the water while it lasts.

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