Notostraca
From Biocrawler, the free encyclopedia.
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 Triops longicaudatus | ||||||||||||
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Notostracans (often just called Triops, tadpole shrimp or shield shrimp) are small crustaceans, with internal compound eyes and a flattened shield covering the head and leg-bearing segments of the body. The order contains a single family, with only two genera. Their external morphology has not changed since the Triassic (appearance of Triops cancriformis around 220 million years ago). Triops cancriformis may therefore be the "oldest living animal species on earth" (Kelber, 1999).
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Way of living
Tadpole shrimps usually live near the ground of astatic pools, where they move with their ventral side down. However, lack of oxygen can force them to swim upside-down with their gill-like legs close under the surface of the water. Notostraca are omnivorous; they dig around in the mud using the frontal part of their shield, looking not only for plankton but also for larger prey such as worms, chironomid larvae and even weak tadpoles. Anostracans, often associated with notostracans, can also be a considerable part of their prey (especially when weak or dying).
Notostracans sometimes even cannibalize freshly moulted members of the same species. In northern and central Europe, with few exceptions, all tadpole shrimps are female, whereas sex ratios in southern and western Europe as well as in northern Africa are near unity. These "females" possess hermaphroditic glands, but instead of selfing, parthenogenesis takes place. Modified appendages of the 11th pair of limbs bear the ovisacs with the mature eggs.
Where they live
Notostracans can be found on virtually every continent.
In Austria, two notostracan species (one spring species and one summer species) were documented: Lepidurus apus (Linnaeus, 1758), Triops cancriformis (Bosc, 1801).
In America, several species were identified: Triops longicaudatus and Triops newberryi.
In Australia: Triops australiensis
Other common types are: Triops numidicus, Triops granarius.
Notostracans in the aquarium
These creatures are often sold to children over 6 years old in small packets as eggs as an interesting science project or as a beginner's kit to their first aquarium. One just pours distilled or spring water onto the eggs, and they will hatch out very quickly.
These creatures can make a useful addition to a freshwater aquarium, as they keep the substrate very clean and eat just about anything they find. They may, however pose a slight danger to very small fish or other shrimps, and may in turn be eaten by large fish. Also, they may damage the roots of aquarium plant they encounter if not kept well fed.
External links
- link Triops.cc (http://triops.cc)
- link triops.com (http://www.triops.com)
- link MyTriops.com (http://mytriops.com)
