Tiny NZ snail conquering the world

By Paul Harper

The mudsnail Potamopyrgus antipodarum, next to a pencil head for scale. Photo / Álvaro Alonso, Pilar Castro-Díez
The mudsnail Potamopyrgus antipodarum, next to a pencil head for scale. Photo / Álvaro Alonso, Pilar Castro-Díez

New Zealanders love to travel overseas - however, unlike friendly Kiwi tourists, New Zealand mudsnails are not welcome abroad.

Potamopyrgus antipodarum has invaded Europe, Australia, America and Asia. It is considered to be an invasive species because it has no natural predators and outcompetes native snails and insects for food.

New research has suggested a range of measures - including the use of scarecrows - to stem the spread of the mudsnail.

According to the Santa Monica Bay Restoration Commission, the New Zealand mudsnail can completely cover a streambed, crowding out the existing aquatic insects that provide food for native animals, including endangered species.

The spread of the aquatic snail is due in part to its ability to reproduce - females produce an average of 230 offspring per year.

While almost all of the non-native species are females, they are parthenogenetic and do not require males to reproduce.

However, it is its ability to tolerate air exposure which is the mudsnail's key to invading the foreign ecosystems.

The tiny snail - it measures no more than 10mm - travels the world attached to birds, fishing equipment and terrestrial animals, and it can also survive in the digestive tract of fish.

Spanish ecologists Alvaro Alonso and Pilar Castro-Diez from the University of Alcala, aimed to find out how long the mudsnail can be survive exposure to air.

The researchers exposed 120 snails to different periods of dehydration to see how long they would survive. The researchers found the snails could survive up to 48 hours out of water, with the molluscs springing back to life when placed back in liquid.

The researchers said the mudsnail's hard operculum - effectively a trapdoor which closes when the snail is within its shell - may contribute to its ability to tolerate exposure to air.

The findings have been published in the journal NeoBiota.

As a result of their findings, the researchers proposed several low-cost measures to restrict the spread of the mudsnail.

Firstly, they recommended fishing equipment and tools used in different aquatic ecosystems to be exposed to air for at least 53 hours to kill the snail. Secondly, they suggested using physical barriers or other methods to restrict the access of wild and domestic animals to waters infected with the snail, such as scarecrows for waterfoul.

"Avoiding the spread of invasive species is crucial for the conservation of aquatic native biodiversity" they concluded.

"These simple measures may reduce mudsnail translocations in early stages of invasion."

- Herald Online

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