The Gorgeous Sea Urchin Skeleton: An SEM Odyssey

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...

Image by Gripspix

Here's a nice macro shot of aforementioned "boss" (=the knob which connects with the spine).

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).

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...

Image by gary.brake

Image by Studio Jonas Coersmeier

Another view from a different perspective...

Image by particlesixtyfour

Image by monkey.grip

Closer...

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

Closer!

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...