A stiff challenge

Ready for your next mystery close-up challenge?

 

You may have seen a picture somewhat similar to this before.  Note the small, oblong, densely packed objects throughout.

Here's another view, a little further zoomed out.  All of these pictures were taken under a microscope.

 

The next image has slightly different lighting, and extends the view to show those long, slender tube-like structures. (Hint: "tube" is a clue!)

 

 

Do you have a guess yet?  

Warning: The next picture will reveal most of this organism.

 

And the answer is...the one that's been on the tip of your tongue...the one that you've been shouting out loud...a sea cucumber!  

This is a Stiff-footed Sea Cucumber (Eupentacta quinquesemita).  I couldn't fit the whole animal in the microscope view, but below is one more image showing almost the entire sea cucumber.  It was ~2.5 cm (~1 inch) long.

 

Eric spotted this distinctive sea cucumber in a Bull Kelp holdfast washed up on Salmon Creek Beach last weekend.  They're found along the West Coast from British Columbia to southern California.

The eye-catching football-shaped structures in the first few photos are called ossicles.  Remember that the skeleton of sea cucumbers has been reduced to these tiny perforated plates.  Stiff-footed Sea Cucumbers have so many ossicles that they're known for being rigid.  I don't know if anyone has proposed an adaptive explanation for why this species of sea cucumber has such densely-packed ossicles.  Do you have any ideas?

You can see more magnified views of ossicles (in a different species) and review information about another local sea cucumber in this post from 16 April 2013.