Science Buddies: "Ask an Expert"

I am a 9th grade Biology student and am doing a science fair experiment on the whether snails can see in color. I have done the the experiment, and your opinion is required as 25% of the grade, so please respond as soon as you can. I would like to know how you would have gone about the experiment, whether you think snails see in color, and what changes you would make to how I did the experiment.
It is as follows: I have 10 snails, and for the control I have placed 2 sheets of plain white printer paper 2 inches apart, and I had placed 1 snail between the two and about a centimeter in front of them. the snail would go one way or the other, and the results would be recorded, once per snail. I then placed them between red sheet and green sheet and recorded the results, and green and yellow and recorded THOSE results. I have my graphs and things all done, but I still need an expert opinion.

Hi,

As far as I can tell it seems unlikely that snails have eyes that can detect color. In two papers I have seen there have been two types of photoreceptors found in snail eyes, both having the same spectral sensitivity spectrum. This implies seeing only black and white(ot shades of brightness if you prefer). Here is the full text of one paper:

http://www.ucm.es/info/Psi/docs/journal ... /art18.pdf

And an abstract& first page of the second paper:

http://www.springerlink.com/content/e4tp2554087n8271/

Some people have found evidence that snails can detect color:

http://www.usc.edu/CSSF/History/2004/Projects/J1923.pdf

Here is a more readable describition of the vision of apple snails:

http://www.applesnail.net/content/anatomy/senses.php

So the preponderant opinion is that snails do not have color vision, at least not the kind of color vision that works like human color vision.

Based on what I found in my searching, the thing you would need to control for in your color choice experiment is the brightness of your comparison colors at about 490 milli microns, the center of the snail eye sensitivity spectrum(I.e. if the snail saw only shades of gray, would it see the same shade of gray in both choices). You might also test to see the differences between a light and dark shade of the same color. The first link in the answer above is to a paper that describes how they attempted to answer your question.

Good luck with your project!

Best regards,

Barrett L Tomlinson

Thanks for your help, I really appreciate it.