Wednesday, 21 April 2010

Native Snail

.....comes out of it's shell.

On 10th April I posted photos of a native snail feeding on fungi. I returned to the same location yesterday and while searching through some leaf litter, I came across another one. To my untrained eye looks to be the same species, Stenacapha ducani. This one was much less shy, coming out of it's shell and allowing me to get some better photos.

Edit: I told I had an untrained eye. This one turns out to be Stenacapha hamiltoni. See comments below for an explanation of differences in shell morphology.


(Click photos to enlarge)
#1- Stenacapha hamiltoni

#2- Stenacapha hamiltoni


#3- Stenacapha hamiltoni

#4- Stenacapha hamiltoni



7 comments:

  1. Hi Mosura.
    .
    Nice series of snail shots.
    I always thought those flattened snails (or ones designed on the slant, anyway) were supposed to be carnivorous.
    Probably just one of those stories which I accepted, for lack of contrary evidence.
    .
    I do know the local slugs and snails love to eat the fungi: Amanita muscari and the Lactaria deliciosa . Both introduced species and both associated with Pine Trees.
    Cheers
    Denis

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  2. Thanks Denis - According to my 'out of date' snail reference, this family, Charopidae, are believed to only eat fungi and decaying vegetable matter.

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  3. Lovely shots, Mosura. Charopidae is a group I back away from with eyes averted because they're all too small and tricky!

    Denis, I think most of the larger flat-shelled snails are carnivores (Rhytididae), but the smaller ones are not so easy to deal with.

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  4. Thanks Snail - I was happy with getting those shots. Charopidae are certainly too tricky for me. I had help from Kevin Bonham for the ID (see earlier post)

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  5. Hi Mosura,
    Snail postings are always fun.
    Thanks Snail.
    I had forgotten they were relatively small (7-8mm).
    It is good to have the existence of carnivorous snails confirmed.
    Cheers
    Denis

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  6. Wonderful pics. Especially the top one with the eyestalks low to the ground.

    Yes this is another Stenacapha and not a carnivorous rhytidid.

    Stenacapha ducani and S. hamiltoni are difficult to tell apart from photos (and sometimes difficult even from specimens) but although this may look extremely similar to the last one, this one is actually hamiltoni! One key difference between S. hamiltoni and S. ducani is the way the adult sculpture develops on the later whorls of the shell. On S. ducani the adult ribbing on the earlier whorls always becomes less prominent on the later whorls and I could see this starting to happen on your previous suspect, although it was sub-adult. This one has the ribs still quite prominent all the way around at over five whorls of growth. That rules out ducani and makes it hamiltoni. It is also just a slightly flatter, less chunky looking shell which is another difference that points to hamiltoni, although they do vary. It doesn't help that the two species will live together in the same habitat and may even be found munching from the same fungus or sheltering under the same log.

    Denis - the flattened ones on the slant in your part of the country are very likely to be carnivorous rhytidids. In most parts of Australia the charopids are very small and not likely to be confused with the carnivores (although there are some very small carnivores too). But in Tasmania we have the complication of Stenacapha, which is one of the world's largest charopids (S. ducani might even be the largest) and is much the same size and shape as our local carnivores. Nonetheless it is a harmless fungus grazer, and indeed is frequently eaten by the carnivorous species.

    I have seen large carnivorous rhytidids in Burnie Fern Glade - Victaphanta lampra and Tasmaphena sinclairi are both there but nowhere near as common as the Stenacaphas.

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  7. Thanks Kevin for a for your informative reply. I can see the difference now that you have explained it but would probably have never noticed otherwise.

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