Tuesday, July 30, 2013

The Gorgeous Sea Urchin Skeleton: An SEM Odyssey

Sea Shell
Image by gary.brake
The Scanning Electron Microscope (SEM) is a wonderous device. Simply put, electron beams provide a highly detailed almost surreal image of the surface they are directed at.

But what happens we direct an SEM at animals that are ALREADY kind of weird? The striking beauty of sea urchins is revelaed!

The sea urchin skeleton. Also known as a TEST.  One of my many regularly repeated caveats- these are NOT shells. These are underlying skeletons which have a layer of skin which is typically removed to reveal the more aesthetic skeleton...

Here is an example from a cidaroid sea urchin.. Those round knobs or bosses?  Those are where the spines articulate with the body...
Cidaris 1
Image by Gripspix
Here's a nice macro shot of aforementioned "boss" (=the knob which connects with the spine).
test photos
Image by "Nervous System"
But what happens when we focus a Scanning Electron Microscope (SEM) on these surfaces?  (note that these images are a different species from the one above).
sea urchin
Image by Monkey.grip
Here's another view looking down. Note how the skeleton is actually porous! Echinoderm skeletons aren't simply inorganic calcium carbonate, they are actually infused with tissue...
Sea Shell
Image by gary.brake
sea urchin
Image by Studio Jonas Coersmeier
Another view from a different perspective...
Image by particlesixtyfour
sea urchin landscape
Image by monkey.grip
Image by particlesixtyfour
..and closer still!
Image by particlesixtyfour
right on top of it!
Image by particlesixtyfour

But wait! What about the SPINES???   I'm not sure which species these are from.. but they give you a good idea about the fine topology that one might not realize is present from simply looking at a spine with your eye... 
Image by particlesixtyfour
Image by particlesixtyfour
And finally... CLOSEST!!
Image by particlesixtyfour
And just to cap off the whole odyssey through a sea urchin spine... here is a cross section THROUGH a spine magnified 150X!!!   The final three images below are from the Biology Dept. at the University of Dayton! 
Here are the featured spines...
 and together to show perspective...


Amanda Kahn said...

These are beautiful! I read a neat paper by Dafni (1986) that talks about where test deposition occurs in the tissue, so some nice soft tissue work to go with the hard skeletons. Has anyone thought about why the tissue that deposits the skeleton is syncytial? Also, I posted a few SEMs from an irregular urchin a while back, if you want to see more SEM photos of urchin tests: http://bmscblog.wordpress.com/2012/09/08/getting-to-the-heart-of-urchin-spine-attachment/

Unknown said...

Dear Chris:

A. Gaudi would be as enthralled as any of your echinoblog regulars/enthusiasts about the biomimicry possibilities and about the wondrous biophysiology that such SEM micrographs begin to reveal. Thank you much. FS

Emily said...

These look a lot like three-dimensional fractal images:

ChrisM said...

Wow! thanks Emily!