A group of enthusiastic students carrying out a BioBlitz in Durham at the weekend found this remarkable animal. It's a New Zealand flatworm Arthurdendyus triangulatus, introduced into the UK in 1963 and now well established in Northern Ireland and Edinburgh - and also in Durham, where it was first found about 15 years ago. This species is a predator of earthworms and initially had a major impact on earthworm populations in areas where it became established, although recently these depleted earthworm populations seem to have recovered somewhat. It belongs to an animal phylum called the Platyhelminthes, that also includes a number of gruesome parasites, but this predator has a particularly horrific method of dealing with its prey. If you are of a sensitive disposition, you might wish to cease reading now....
The head-end of the N.Z. flatworm is the narrow tapered bit and they can change shape, making themselves very long and thin if necessary. This specimen, which I have on my desk in a securely sealed container as I write, currently looks much as it does in the photos here - coiled up and about 4cms. across, but occasionally it glides around the container and extends its length to about 15cm. This specimen was enclosed in a plastic screw top jar, tightly closed, but managed to escape by sliding along the screw-thread, between cap and jar. They have also been known to explore sewage systems and appear in toilet bowls, leading at least one unfortunate person to believe that they were afflicted with a horrendous intestinal parasite. When they encounter an earthworm N.Z. flatworms wrap themslves around it and them secrete powerful digestive enzymes that effectively reduce their prey to soup, which they ingest. When an earthworm is touched by one of these flatworms it - not surprisingly - reacts violently, as though it had been stung, thanks to the powerful enzymic secretions of the predator - which is why, if you find one, it's not a good idea to handle it with bare hands. They are most often found in cool, permanently moist spots under logs and stones; I know one old churchyard where it seems to like living under fallen gravestones. It seems likely that this alien predator was first introduced by the horticulture trade with plants imported from New Zealand. The wholesale- retail-gardener chain has since provided it with a perfect distribution network. If you find one, your first port of call should be the New Zealand Flatworm web page, where you can find expert advice on what to do next.....
Posts
