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Saturday, August 11, 2012

Gelatinous thimble

Here's a gelatinous beach find from 29 July 2012.  I didn't get a chance to post it then, but it's from an intriguing animal, so I thought it would be worth doing so now.

It was ~4 cm long.  Although it may be somewhat difficult to imagine, it has a thimble-like structure — hollow, and covered with small bumps or tubercles.  You could insert it onto the tip of your finger.  

This photo from March 2011 shows the tubercles:

Here's another view from above (the same individual as in the first photo):

Remarkably, this structure belongs to a pelagic snail, a species of pteropod called Corolla spectabilis.  Instead of having a hard, external shell, Corolla has a soft, internal pseudoconch ("false shell") that supports most of its internal organs or viscera.

The diagram below illustrates the position of the pseudoconch in relation to the rest of the animal.  It also shows the broad wingplate, a modified foot used for swimming and the reason for the name pteropod (ptero = wing, pod = foot).

Modified from The Light & Smith Manual: Intertidal Invertebrates from Central California to Oregon (2007)

The Light & Smith Manual says that Corolla spectabilis is "relatively common in the California Current.  Reported in the eastern Pacific between 20°N and 45°N.  Pseudoconchs occasionally found washed up on beaches." [Do you know the latitude of Bodega Head?  Answer at bottom of post.]

It's worth searching for images of Corolla spectabilis on the Internet, as it's truly a spectacular snail.  There's a pretty good one on The JelliesZone website.  And a few more shared by Kevin Lee (scroll through the images until you see Corolla spectabilis).

[Bodega Head is at 38°N]


Noni said...

They are called a Pyrosome. I found them all over Carmel River Beach, Friday, Dec. 16, 2016. I took pictures, they look exactly like these, thimble size too. I sent the pictures to Jim Covel at the Monterey Bay Aquarium. He was very kind and very informative. I can forward you his email. JCovel@mbayaq.org. Director of training. Pyrosome means fire body. They are luminescent.


Jackie Sones said...

Hi, Noni!

Thanks for your comment. The pictures in this post are the pseudoconch of a pelagic snail (Corolla spectabilis). Pyrosomes are different and are more related to sea squirts! To compare, look at the post from 8 December 2014:


To tell them apart -- Corolla pseudoconchs are open on one end (you can slip one over the tip of your finger), while pyrosomes appear solid. Corolla pseudoconchs are flexible, while pyrosomes are firm. And Corolla pseudoconchs are clear in color, while pyrosomes have a pinkish hue. There are more differences, but this is a start!

I'm happy to review any pictures if you want to send a few my way.


Jackie Sones

Noni Ethielle said...

Well, I would love to send you my pictures, but I don't know how to here. Mine are EXACTLY like yours, and your description is exactly so, as well.! I'm so excited to check it out on the internet. I'll tell Jim at the Aquarium .
I'm surprised you got my message at all, I didn't think I signed off correctly.?
How do I send pictures to you? I don't know about blogs.

Jackie Sones said...

Hi, Noni,

You can e-mail pictures to me at naturalhistoryphotos@gmail.com

:) Jackie