Giant Floater Mussel, Pyganodon grandis
Let’s put it in the electron microscope!!
I had to break tiny parts of the shell off to fit it into the microscope, and one part of it broke off into little needle-like crystals. This is what they looked like up close. Nice!
I moved to an intact area, and saw these tightly-packed hexagon structures. Hmmmmmmmmm… I think those crystals in the top photo came from this anatomical feature of the shell. Let’s look at one of the opalescent areas!
Oh! Look at that! If you need help understanding the information at the bottom, this image is magnified 1350x. The scale bar in the lower left corner represents 50 microns. A human hair, on average, is 100 microns wide. If a piece of your hair was in this image, it would be twice as wide as that scale bar.
These little flaky things are interesting, let’s zoom in!
WOW!!! Now we’re zoomed in 2600x. These are crystals that make up the inner portion of the shell, but look: they’re thin plates, and they grow in layers! The size is interesting, too. You know how the insides of shells shine kinda rainbow-ey? I’m guessing it has something to do with the size–visible light is roughly 400 to 750 nm in wavelength, so physical structures in those sizes tend to do strange things with light (you think butterflies limit themselves to pigmentation? HA think AGAIN!). And these crystal plates are about the right size!
Here’s a different area with those crystals, but with mysterious holes! What are they for?!
ENHANCE. This was the zoomiest I could get. Look at those crystals! Nice!
Before I left, I needed to take a look at the outside of the shell.
Since the electron microscope looks at things so close up, it’s possible that this is all just sand. But it could also be minerals bound together with a protein matrix, which is what I believe the outer shell of these is! I was looking around for an area that looked more “shelly” and I found… this:
Uh… I have no idea what this is… But it was embedded in the outer shell of that mussel! UPDATE! IT’S A DIATOM!!!! 😀
If you have electron microscope requests, keep sending them in! I’ll keep doing these until they kick me out the door on Feb 28 OR until I quit which is HOPEFULLY way earlier than that!
December 7, 2018
@thatmcufangirl Oh boy prepare to clutch your pearls (I guess maybe literally if you’re doing oysters!) and be horrified. Here’s the sample before I switched to electron beam mode:
It ain’t coated. It’s not a “real” SEM in the sense that your lab has access to. We can’t get 20,000x either. The diatom is 13,500x, and that’s PUSHING our best resolution. We have a Phenom desktop SEM, but the cheapest model, and the charge reduction sample holder lets you throw samples in without coating them at all. We could probably get better resolution if we did coat them a little, but before I discovered the secret of that sample holder, our “brilliant” senior scientist (who was promoted to department director…) was having us coat everything in the gold sputterer for 20 minutes and our samples were coming out terrible because… uh… well… You can probably guess.
I don’t have any good tips based on what I know from experience BUT I would suggest possibly looking into other coatings (do you have access to carbon?). When I did nanowires and nanoparticles, before imaging in TEM, we coated them in carbon. Another possibility is 120s is too long. What do the other oyster people use? (Lit review time!)
December 7, 2018