Most Unwanted: New Zealand flatworm
Arthurdendyus triangulatus
Habitat: Terrestrial
Threat: Threatens the native earthworm and ecosystem functioning
Status: Established
The New Zealand flatworm was first recorded in Northern Ireland in 1963 where it may have arrived with a shipment of roses or bulbs from the Christchurch area in New Zealand (Nobanis). The species has now reached all parts of Northern Ireland and is spreading southwards in the Republic of Ireland as well as in Scotland and England.
This description, while focused on the New Zealand flatworm (Arthurdendyus triangulatus), also aims to raise awareness of and limit the spread of other predatory flatworms that target the native Earthworm.
What is it?
Unlike the well known native earthworm, the invasive New Zealand flatworm does not have the segmented body that is easily recognised. The flatworm does, as the name suggests, have a flattened body that is pointed at both ends and covered in sticky mucus. Colour can vary making it difficult for members of the public to identify but in general specimens are grey, or brown, with a pale yellow margin and underside covered by specks.
Impact
Earthworms form a pivotal function in terrestrial ecosystems in Ireland. They are responsible for aerating the soil and decomposing plant material while also regulating drainage to some extent by creating burrows. The New Zealand flatworm has been shown to significantly reduce earthworm numbers from both agricultural lands and gardens in Ireland.
Where is it from
A. triangulatus originates from New Zealand however other species of predatory flatworms originate from Australia and elsewhere.
Where are they in Ireland
The New Zealand Flatworm was introduced to Northern Ireland in the early 60’s. It is currently known from all 6 counties in Northern Ireland where it is generally concentrated around built up urban areas such as Belfast. The species is present in the Republic of Ireland but may be under recorded.
How did it get here
It is believed that this species arrived in Ireland by contamination of plant potting soil from New Zealand.
How are they spreading in Ireland
The species can move long distances by contaminating plant and soil transported by humans.
What you can do
Avoid moving material you know or suspect to be contaminated.
Report all sightings.
Additional reading
Habitas Invasive Alien Species in Northern Ireland
