Tadpole shrimps in Namibia’s puddles - News - Gondwana Collection


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Tadpole shrimps in Namibia’s puddles

Avatar of inke inke - 27. novembre 2018 - Environment

This triops or tadpole shrimp is just a little less than seven centimetres long. As yet the living fossils have not been researched in detail. According to current knowledge the tadpole shrimp found in Namibia is of the species Triops granarius, which also occurs in South Africa and northern Africa, China and Japan. Whether the animal on this photo is in fact of that species has not been proven.

Dirk Heinrich

In arid areas it often does not rain for years. When rain finally comes down in the form of light showers the parched soil absorbs the moisture immediately. Plants and animals barely benefit from the few millimetres of water which evaporates fast. But if the rain happens to be brief and vigorous, life seems to explode. After just a couple of days, for example, animals resembling tadpoles are frolicking in puddles.

The eggs of tadpole shrimps, or triops, can survive in the dusty soil of arid areas for years. The young shrimps hatch when heavy rain showers leave pools of water which do not dry out within a few days. These living fossils have inhabited the earth for more than 250 million years. They are a genus of small crustaceans in the order Notostraca. According to the Namibia Biodiversity Database, only two species are known in Namibia: Triops cancriformis, the tadpole shrimp, and Triops granarius.

When asking Prof. Michelle Hamer, the Director of Biosystematics & Research Collection Initiatives at the South African Biodiversity Institute (SANBI), about these shrimps it transpired that almost no research has been conducted in southern Africa so far. It has not been established for certain which species occur in this part of the continent. Triops granarius, which is found in Namibia and South Africa, also occurs in China and Japan, the professor said. DNA tests, conducted on a few specimens some time ago, showed that there should be four different species of tadpole shrimp. However, too little research had been done on too limited a number of specimens, she said. For scientific examination, triops would have to be collected in numerous places in Namibia alone. Apparently the South African ‘species’ is closer related to tadpole shrimps in Tunisia than to those in Namibia.

Little is known about these crustaceans. They probably feed on live and dead animal matter, and they grow rapidly in their temporary ponds. Since these living fossils are hermaphrodites they reproduce asexually and sexually. They seem to be depositing vast quantities of eggs which are then lying in the dry soil for years, waiting for favourable conditions to return. Larvae, so-called nauplii, apparently only hatch from some of the eggs at a time, however, to ensure survival of the species in emergencies.

In April this year I discovered numerous triops, together with tadpoles, in a puddle at a picnic spot on the C35 road between Kamanjab and Ruacana. At the first glance the prehistoric shrimps, which are up to seven centimetres long, were barely distinguishable from the tadpoles. Many years ago I found hundreds of triops in a large pool of water in the Kuiseb Canyon. There are no records yet about where exactly in Namibia these interesting creatures occur.

At first glance, triops or tadpole shrimps may be confused with tadpoles which are often found in the same temporary pond. It is not known which species has been captured in this picture.

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