Look away if you’re an earthworm

This post,  by Matthew Cobb, comes from his Zoology Z-letter, and he’s given me permission to repost it.

Spotted on Lucas Brouwers’ Twitter feed (@lucasbrouwers), this great video of a Powelliphanta snail from New Zealand snarfing an earthworm. Keep your eye on the video – it all happens incredibly quickly! Odd thing to say about a snail, but true.

According to this PDF from the NZ Department of Conservation, Powelliphanta snails can grow up to 9 cm across and are nocturnal. They are also endangered, primarily because of human activity, although a recent survey suggested they were making a slight recovery. According to Wikipedia, “There are 21 species and 51 subspecies within the genus. The relationship between the species is complex, and it has been suggested that the group Powelliphanta gilliesi-traversi-hochstetteri-rossiana-lignaria-superba forms a ring species.”

There are other carnivorous snails on NZ, including the Rhytididae, which seem to be particularly vicious, according the NZ Dept of Conservation:

“They can eat other snails by biting their heads off and then they carry them to a quiet spot on the back of their foot where they insert their tails up into the prey’s shell. The tail secretes a liquid that slowly dissolves the prey’s flesh and the calcium from its shell. The Rhytida snail then absorbs the dissolved nutrients. It can take the snail several days to actually complete such a meal.”

One rhytidid snail, Wainuia urnula urnula, seems to use a similar rapid action to that seen in Powelliphanta and probably has the same basis. According to Murray Efford in The Journal of Molluscan Studies, “In the laboratory, W. urnula urnula captured landhoppers by rapidly everting the TVU-section odontophore beneath the prey and immediately drawing it into the mouth in a single action.”

So that’s how they (probably) do it. No sucking, just incredibly rapid movement, using that odontophore…

22 Comments

  1. Michael Fisher
    Posted June 26, 2011 at 8:14 am | Permalink

    ❤ it !!!

    Efficient & 'Merciless'

    Creation is the Bee's Knees

  2. Torbjörn Larsson, OM
    Posted June 26, 2011 at 9:26 am | Permalink

    Wow, snail fast food!

    Btw, is it just me? But it was oddly disturbing to read the description as “ring species” right after watching that.

  3. Bacopa
    Posted June 26, 2011 at 9:45 am | Permalink

    Reminds me of my pet nudibranch. I had no idea any gastropod on land hunted like this.

  4. Gregory Kusnick
    Posted June 26, 2011 at 9:45 am | Permalink

    Many, many years ago I read a science fiction story in the Saturday Evening Post about a naturalist chasing down a rumor of giant man-eating snails on a remote island in the South Pacific. Yes, he finds them. No, he does not return to tell the tale.

    • Posted June 26, 2011 at 3:56 pm | Permalink

      Geeze, Gregory, give a guy a chance to post! I remember the same story, although I read it in a science fiction anthology or in Playboy. (Ha, me read something in Playboy? Busted!)

      Anyway, yes, he finds the snails and giant crabs, too, if I recall. The snails are slow but they never sleep. They have razor sharp teeth.

      Spoiler Alert! The story ends with the naturalist exhausted as a giant snail starts to munch on his shoulder.

      Gave me nightmares for years, such that I had to sleep with a Playboy under my pillow. For comfort.

    • Posted June 27, 2011 at 2:13 am | Permalink

      Any memory of the story title or the author’s name? Sounds like one I’d like to read!

      • Gregory Kusnick
        Posted June 27, 2011 at 11:11 am | Permalink

        Might have been called “The Snails”. No idea who the author was; sorry.

  5. Posted June 26, 2011 at 10:35 am | Permalink

    Too cool. That burst of speed took me completely by surprise!

  6. daveau
    Posted June 26, 2011 at 11:10 am | Permalink

    “Look away if you’re an earthworm”

    A lot of earthworms in your demographic?

  7. Dr. I. Needtob Athe
    Posted June 26, 2011 at 11:59 am | Permalink

    Did you say “According to Wikipedia”?

    I’m a bit disillusioned by that!

    • Posted June 26, 2011 at 12:03 pm | Permalink

      I don’t think it’s wise to dismiss Wikipedia as a source of information. In fact, in this case the Wiki information was substantiated (and indeed, probably came from) another source: here.

    • Dominic
      Posted June 26, 2011 at 12:32 pm | Permalink

      That is a long discussion! The wisdom of crowds etc …

      Would a Frenchman eat this?!

      • Posted June 26, 2011 at 6:31 pm | Permalink

        With garlic, butter, a loaf of fresh bread an two bottles of red, I’d eat it, and the worm and whatever it was sitting on. And it’s mum, too.

    • Grania
      Posted June 26, 2011 at 12:36 pm | Permalink

      There is nothing wrong with Wikipedia, so long as you realise it is a starting point and not an end point for information.

    • Matthew Cobb
      Posted June 26, 2011 at 1:06 pm | Permalink

      I didn’t have time to verify the information, and the Wikipedia page didn’t have a reference for the ring species info, so I indicated my source and let the reader decide. That was responsible, no?

    • Posted June 26, 2011 at 3:03 pm | Permalink

      Well, the wikipedia article is pretty accurate.

      If you really want to dig out the ‘ring species’ idea it’s from

      Climo FM (1978) The Powelliphanta gilliesi-traversi-hochstetteri-rossiana-lignaria-superba ring species (Mollusca: Pulmonata). New Zealand Journal of Zoology 5: 289–294.

      I’d love one day to get to use some molecular tools to see what’s going on there, but the bigger focus is keeping them alive at the moment.

      • Matthew Cobb
        Posted June 26, 2011 at 3:32 pm | Permalink

        Ooh. ta. This may replace those boring Arctic gulls in my first year lectures. If only so that I can show the video…

        • Posted June 26, 2011 at 3:41 pm | Permalink

          Ha! I’m actually teaching my first ever lecture next month. On the species problem and taxonomy – and you can be damned sure these guys will feature!

        • Dominic
          Posted June 27, 2011 at 1:43 am | Permalink

          Herring /lesser black-backed gulls are not boring 😦
          Or you meant just as examples?

  8. Grania
    Posted June 26, 2011 at 12:38 pm | Permalink

    This is nightmarish stuff, watching a snail swallow a worm in one gulp is somewhat like discovering a cute little lamb with a row of shark teeth.

    I will be a lot more careful around lambs from now on :p

    • Posted June 27, 2011 at 5:51 am | Permalink

      And to think, my daughter had a snail crawling up her arm the other day…

  9. Diane G.
    Posted June 26, 2011 at 10:59 pm | Permalink

    Very very cool!


%d bloggers like this: