Wednesday, June 16, 2010

Alien Alert! Be Afraid,Be Very Afraid....


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.....

10 comments:

  1. Hi Phil
    They don't seem to have spread very much considering the "distribution network", does anyone know why not. I remember when they first appeared, although not the end of the world, the end of the earthworm was predicted.

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  2. Nasty little creature!Hope I never come across one.

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  3. I hope I never come across one.... it'll send my scoleciphobia raging again! I've come to like earthworms but I think I'd have difficulty becoming fond of this creature. :(

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  4. Hi John, they certainly did receive a lot of media coverage that seems to have died down. they made the local news here in Durham when they were first discoveredabout 15 years ago. I've heard various theories as to why that haven't fulfilled the dire prophecies - killed by hot summers or cold winters, for example - but neither of those seems very convincing. as with alot of alien introductions, I guess that eventually they reach an equilibrium with the native fauna.

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  5. Hi Keith, I certainly wouldn't want them in my garden. I have a pretty healthy worm population at the moment....

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  6. Hi Lesley, you've taught me a new word!

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  7. wow they are amazing.... that they can escape screw top containers? so amazing

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  8. They're the Houdinis of the flatworm world, verminous intoxication

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  9. Hi, I live in Fort Worth, Texas, where we have been invaded by a similar species, but from the tropics. I first found it under my children's wading pool and thought it was some horrible parasite. I put it in a jar and screwed a lid on, took to Dept of Agriculture for identification, and it had disappeared out of this tightly sealed jar! Just evaporated, impossible! So I drew a picture and described it. They didn't have a clue what it was. Took me two years to track down identification.
    PS Ours is uglier than yours - BIGGER

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  10. Hi Sharon, Glad to hear you were able to track it down. Sounds like a hideous beast! There are several other flatworms that have been brought to the UK from the Antipodes via the horticulture trade and there are some quite serious infestations now in some localities. best wishes,
    Phil

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