The goal of our project is to compare the ability of symbiotic crabs to recognize their hosts visually, and to compare these behavioral results with a microscopic analysis of their eyes (i.e. size of the eye, number of ommatidia,...).
We had no problem with bigger crabs but we were not able to discern the ommatidia of Dyssodactylus primitivus. It looks like the surface is smooth and there are no ommatidia.
What is the typical size of an ommatidium? the smallest? Have you ever eard of simple eyes in crabs (sounds strange to me but...)? Also, would it be possible that gold coating (5 minutes) hide the boundaries between ommatidia?
Guillaume
Just using a light microscope may not give you the resolution to see the individual ommatidia. Have you tried any histology? I have some blue crab eyes that I've done some histology (and tons of lobster eyes), and at least for the blue crab megalopae and juveniles the ommatidia are quite obvious in histology.
Thank you for your answer!
What kind of histology method did you use? Any coloration?
I use standard H&E histology but decalc using the decalcifying solution in Luna (1968). See below for examples. I'm not sure this method applies to your research question.
http://www.vims.edu/~jeff/biology/Atlas_of_lobster_histology.pdf
http://www.vims.edu/~jeff/biology/2009%20Magel%20et%20al.%20Biol%20Bull%20idopathic%20lesions%20in%20lobsters.pdf
http://www.vims.edu/~jeff/biology/2006%20maniscalco%20&%20shields%20JIP%20idiopathic%20lesions%20in%20lobster%20eyes.pdf
I am also not sure but anyway we can consider those methods if needed so thank you! We will maybe try with an environmental SEM to view uncoated samples.
You might try something simple first such as a vital stain or contrast stain. There is an old method using silver nitrate to stain exterior details. I haven't done this, but you could even try something simple such as epifluorescence to see if there are small ridges on the surface that define each cornea. Doubt if it will work, but you never know.
Ok thank you!
It seems like we had to extract the eyes from the body...the ommatidia were observed on the hidden part of the eye! We think that these crabs might hide their eyes when stressed in order to protect them and thus it would be normal not observing ommatidia on the dead individuals. But we definitely need to read more bibliography about it.
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