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Sunday, December 20, 2015

Calcareous


A pheasant snail (Eulithidium pulloides), grazing along a blade of surfgrass (Phyllospadix sp.).  I first showed pictures of the shells of these snails in April 2014, but I haven't shown the entire animal yet.  (They're hard to find because they're quite small only a few millimeters long.)

One of the interesting characteristics of this species is its operculum (or "trapdoor").  In most marine snails, the operculum is made of a protein material (think about a moon snail operculum).  But in some species, including these pheasant snails, the operculum is harder and made of calcium carbonate.  

See below for a close-up of the white, calcareous operculum:


Can you think of reasons why it might be helpful for a snail to have a calcareous operculum?  (One possibility is mentioned at the bottom of this post.)

If you're interested in finding a pheasant snail, try searching the bases of surfgrass clumps during a good low tide.  


P.S. Calcified opercula are thought to be a defense against predators.

6 comments:

Anonymous said...

Wow. They are beautiful Jackie. Thanks for sharing.

Alice Chan said...

What a lovely critter!

Jackie Sones said...

I'm so glad to hear others appreciating this little beauty! It's one of my favorite local snails. Thanks for the feedback!

:) Jackie

cricket said...

i love your blog and learn so much from it!

Gina said...

Are there other ways to tell these apart from Littorinidae, other than the calcareous operculum? Do they almost always have more elaborate shell colors than LIttorinids? I think I have found these in mid-intertidal mussel beds and only later realized they might not be Littorinid.

Jackie Sones said...

Hi, Gina!

In Northern California, Eulithidium pulloides is primarily and noticeably pink, whereas the littorines (e.g., Littorina plena, Littorina scutulata) are primarily black (sometimes with white markings). Not sure if there are littorines elsewhere that have pink coloration? I have not seen Eulithidium in mussel beds, but have found it lower in the intertidal zone near surfgrass.

Thanks for the questions!

Jackie