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Wednesday, March 16, 2016

Big foot captured on video

Remember the Purple Sea Snail (Janthina umbilicata) I've shown several times during the past couple of months?

During certain conditions from late January-present, we've been finding quite a few of them washed up on the beach.  On 12 March 2016, we were walking along the beach counting them, when we noticed one snail that looked similar but slightly different.


It was larger, paler, more compressed (flattened from top-to-bottom), with a shorter spire (the first few whorls), and it had a more substantial float.  The striations (or lines) on the shell were also different — rounded all the way around, rather than angled.

Here's the same snail from below.  Although it's completely covered with sand grains, look for the float emerging from the shell:


It has been interesting enough to see one species of Janthina this year...and here was a second!  Although we need to confirm the identification with an expert, my best guess right now is that this is Janthina janthina. 

We didn't know if the snail was alive, and because this species is so rare in this area, we decided to bring it back to the lab for documentation.

The snail floated in sea water, so we left it in a tank overnight.  When I arrived the next day, this is what I saw:

  
The snail was alive and in about 12 hours it had created an impressive float made of very large bubbles. 

Here's a view from the side in a small aquarium:


The online record is incomplete, but in a quick search we could only find one entry for Janthina janthina in Northern California from 1935Its occurrence here this year is likely related to the current El Niño event.  We took some additional documentary photographs and video (see below).

One thing we noticed right away was how different the tentacles are between the two species.  Although they both have forked tentacles, Janthina janthina's tentacles are much more rounded.  They made us think of velvety deer antlers, or mittens (with thumbs)!

The next photo shows a close-up of the snail, emerging from its shell, with its broad foot gliding over its bubble raft.  Look for the tentacles on either side of the proboscis (left side of the photo they almost look like lobster claws). 


Eric was very fortunate to capture some nice footage of Janthina janthina working on its float.  In the video clip below, watch for:

The front of the foot expanding (tremendously!), then breaking the surface to grab a bubble of air and wrap it in mucus secreted by the foot.  (If you watch closely, you can even see the bubble below the foot as the snail attaches it to the float.)  

The snail's large black foot gliding over the float (applying another layer of mucus?)

A glimpse of the extended proboscis with sharp radular teeth exposed at the tip.




Amazing, right?  Not many people get to see these pelagic snails in action, so we hope this helps you visualize and wonder about their lives at sea.

P.S.  If you want to review the photos and video of the first species, Janthina umbilicata, click here.
 

8 comments:

Leth Benz said...

I AM ON THE LOOKOUT FOR JANTHINA JANTHINA RIGHT NOW!
The winds have been up on the windward side of Oahu and the full moon is coming. Conditions are just right.

Oh, the anticipation!!!

Thanks for temporarily quenching my search.

Jackie Sones said...

Hi, Beth! Let us know if you find them! If you do, we might have to consider a visit to Hawaii! You know, to see some friends who live over there (as long as they live near Janthina beaches!) ;D

Leth Benz said...

Oh man, I am definitely on the lookout!

Grace said...

Jackie, have you seen any purple ink at all??

Jackie Sones said...

Hi, Grace,

Yes, we have seen a few of the snails release a purple (I would probably say magenta) "ink." Some of them already have done so when we find them on the beach. Others have done it after we collected them, possibly in response to disturbance (e.g., being moved). Interestingly, it's been reported that the "ink" might serve as an anesthetic when feeding (subduing their prey?), but the few times we've seen them feeding, we haven't observed a release of "ink."

Thanks for your question!

:) J.

Leth Benz said...

I received word that their shells have been spotted on Kailua Beach and will report back soon!

John W. Wall said...

Congrats on the page in Bay Nature! It was fun to find that as I flipped through the pages.

Jackie Sones said...

Thanks, John! It was fun to facilitate a Bay Nature photo shoot. And I was happy that these beautiful and fascinating snails would be shared with a broader audience.