Seeing spots

I looked through the microscope and all I saw was spots.  Bright orange spots!

 

I've seen lots of snail larvae, formally known as veligers, but I'd never seen one with orange spots on its velum!

Here's a closer view (below).  How many orange spots do you count?

 

We counted at least 13 spots.  This velum is divided into four large lobes (two on each side).  Three of the four lobes have three spots, while the fourth lobe (in the upper right corner in the photo above) has four spots. 

The next image shows the veliger and spots from a slightly different angle.  Note also the cilia along the edge of the velum.  The cilia beat very quickly to help the veliger swim.

 

Of course we wanted to know the identity of such an intriguing veliger.  However, we couldn't find a match in the Larval Marine Invertebrates of the Pacific Northwest or by doing quick searches online.  We have been narrowing down a possible identity in a somewhat unusual way.  

When I searched for "veliger with orange spots on velum," Google showed us a small portion of text from a book with a description that seemed to match but for which we couldn't see the species name.  Eric kept working on it and eventually figured out that the text was probably referring to a British snail known as Mangelia nebula.  Then he found a paper that described the eggs and larvae of the family of snails (the Turridae) that included this species.  The veligers of some British turrid snails (e.g., see Mangelia nebula below) look very similar to our mystery animal, with spotted velar lobes:

 

Modified from Lebour, M.V. 1934. The eggs and larvae of some British Turridae. Journal of the Marine Biological Association of the United Kingdom 19: 541-558 

So although we don't know for sure, our best guess right now is that this wonderful polka-dotted veliger could be some type of turrid snail.  [There are a number of turrid snails in California, so we're contacting experts to find out if this veliger could be a match for one of them.] 

To help with the identification, we also tried to get pictures of the snail's shell: 

 

Why does this veliger have such bright orange spots?  You might think that the orange would make it more visible to predators.  Could the spots be distracting?  Could they draw attention to the edge of the velum, rather than the shell?  Could they somehow look like surrounding particles in the water and help to camouflage the veliger?  Can you think of other reasons it might be valuable for a larval snail to have orange spots?

 

See below for a short video clip of this tiny snail veliger swimming:

spotted veliger from Jackie Sones on Vimeo.