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Tuesday, March 24, 2015

Just learning to sail

I was leading a field trip today when we encountered thousands of By-the-wind Sailors (Velella velella) washed up on the beach.  There were a variety of sizes, so later on I lined up some examples for comparison (see below). 

How many Velella do you count in this picture?


There are nine Velella in the photo above.  The largest (on the right) is about 37 mm long.  The smallest (on the far left, and barely visible) is only 3.4 mm long.

I was impressed with the number of very small Velella.  I spotted quite a few that were ~5 mm long.  And although hard to see, a few that were only ~3 mm long.  Below are close-ups of each.



So here's the crazy part.  I brought in a few pieces of driftwood with pelagic barnacles.  When I put them in water and looked under the microscope, I noticed a few things pop to the surface that I thought were bubbles.  I couldn't help saying, "Wow!" out loud when I realized they were very tiny Velella the smallest I've ever seen.

These Velella were just starting to form their sails (the ribbed, flexible feature at the top).  They don't have visible floats yet.  You can see the colorful rim of their mantle, and just a few tentacles hanging below.


So how small were they?


Only 1 mm long!


I'm including one more individual that was even slightly smaller:


Can you imagine these tiny Velella sailing on the high seas during a big storm?

You might have noticed that the 3-mm Velella in the third photo of this post did have a float.  So this means that the float is formed when Velella is between 1-3 mm long.

It would be hard to find a 1-mm long Velella in the field.  But I'm guessing you could find a 3-mm long Velella.  Here's one more photo the largest and smallest Velella in the field today: