Mediterranean worms thriving in Dublin

A thriving colony of Mediterranean French earthworms has been found on a farm in Dublin.

A thriving colony of Mediterranean French earthworms has been found on a farm in Dublin.

Global warming could explain how the worms swapped their home in sunny south-west France for Ireland, scientists believe.

Rising soil temperatures may be extending the habitat range of the Gallic worm, Prosellodrilus amplisetosus.

"Soil decomposer species including earthworms are frequently introduced into non-native soils by human activities like the transportation of nursery plants or live fish bait," said Dr Olaf Schmidt, from University College Dublin.

"There have been a few recordings of the earthworm P. amplisetosus outside of its native range in the Aquitaine region of south-western France, but now we have discovered a successfully thriving population in Ireland, about 1,000 kilometres north of its native habitat."

A study of the worms led by Dr Schmidt appears in the Royal Society journal Biology Letters.

Urban farms have higher temperatures than rural farms, which may have helped the worms become established in their new home, say the researchers.

The average annual temperature in Aquitaine is about 3C higher than in Dublin.

The discovery brings the total number of known earthworms living in Irish soils to 27.

According to the scientists, the French worm should not be regarded as an "invasive species", since it does not directly compete for resources with other native worms.

"By comparing the chemical composition of the worms, we discovered that the newcomers feed on a portion of the soil that the other resident earthworms do not use," said co-author Carol Melody, a Phd student also from University College Dublin.

"P. amplisetosus is a soil decomposer that eats organic carbon in portions of the soil to which the resident worm species don't have access."

But Dr Schmidt warned that the worm's feeding habits could lead to higher greenhouse gas emissions.

"If other soil decomposers like P. amplisetosus start to expand their habitat ranges we could see increasing amounts of carbon dioxide being released from the soil where previously this carbon had been locked up because it was inaccessible to native earthworm species," he said.

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