ID help pretty please?!

[sammi]

Hello,
I've been trying my hand at ID-ing these guys but am having some trouble. The majority of books I can get my hands on are extremely outdated with (lovely) hand drawings, so although pretty helpful, I'm still falling short.

Does anyone know what any of these are?

Thank-you!

[rjlittlefield]

#1 has the general layout of a rotifer, but it seems awfully small given that scale bar.

#3 looks like a mite of some sort.

The others, I don't have the foggiest idea.

What's the specimen prep on these?

--Rik

[sammi]

Thanks!
These are marine biofilm samples (grown on plastic), that have just been ethanol dehydrated and critical point dried. Although it's too late now (already prepared all my samples), would you have a suggestion for a better prep?

[discomorphella]

Hi Sammi--

Can't help you right away with IDs, but I could offer you some SEM suggestions. The EtOH appears to be serving as your fixative as well as dehydrating your specimen; it may be better to fix the films in some formaldehyde first, typically 4% paraformaldehyde, you can find the recipe in numerous places. Then you can dehydrate and dry it. From the image tags, it looks like you are using 10 kV accelerating voltage, and a working distance of approx. 8 to 9 mm. You'll get better imaging if you try to get a smaller WD, say 3- 4 mm or so. Additionally, you probably don't need 10 kV, although I don't know what make of SEM you are using, I bet 3 kV would be fine. What beam current are you running at? At the comparatively low magnifications you are using charging is not a big issue, but I think you may see some image improvement if you lightly coat your samples with some Au or Au/Pd or Rh. Not a lot, maybe 25 to 50A or so, just enough to get a light film of metal (about 10 mA for 10s on my sputter coater for example). It will be very helpful if you plan on going to higher magnification since the plastic films are good insulators.

Hope this helps.

David