Page last updated at 14:39 GMT, Thursday, 28 August 2008 15:39 UK

Rains revive prehistoric shrimp

Tadpole shrimp - Image PA/WWT
The tadpole shrimp has been in existence for 220 million years

Heavy summer rains have helped one of the UK's most ancient creatures to flourish in south west Scotland.

Specimens of the tadpole shrimp date back to at least 220 million years ago.

It is now almost extinct in the UK but recent heavy downpours have seen the creature flourish at the Caerlaverock reserve in Dumfries and Galloway.

Wildfowl and Wetlands Trust researcher Larry Griffin said that three-times the average rainfall for August created "ideal conditions" for the species.

The creature had been thought to be extinct in Scotland until it was found at Caerlaverock on the Solway Firth four years ago.

Mr Griffin, who spotted the tiny species in the same location in 2004, was "very excited" to see it return.

Flushed away

"We have had up to three-times the average rainfall this month," he said.

"So the ponds that dried out in early summer killing the fish and other invertebrates will have been drenched in August, flushing away the salt water to make the ponds much fresher.

"This will have created ideal conditions for the re-emergence of species such as the tadpole shrimp, like it did in 2004."

The tadpole shrimp lives in seasonal pools which dry out in the summer, killing predators and competitors.

Solway Firth
The shrimp was discovered in waters on the Solway Firth
It has evolved to produce two types of eggs, one which hatches soon after production if the conditions are right and the other which can lie dormant in dried-out pools for decades.

The shrimp, which resembles a small horseshoe crab, has a fast lifecycle - developing from an egg to an adult in several weeks with the right temperatures and living for just four to six weeks.

It had been previously found in nearby Preston Merse, Kirkcudbrightshire, in 1907, but the population was thought to have been wiped out when the ponds were lost to the sea in 1948.

The only other known UK population before the Caerlaverock discovery in 2004 was at the New Forest in England.

Fossilised remains prove tadpole shrimps were around 220 million years ago in the Triassic period - pre-dating the dinosaurs.

Experts say they do not appear to have changed in appearance since that time.

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