Friday Jul 20, 2012

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SO ...finishing up my biological investigation class. Together with two guys and help from the TA (mostly with stats issues) I completed my very first independent biological experiment biggrin



Tested color preference in L. Lymneae Stagnalis (medium large pond snails that are a host for the parasite the causes "swimmers itch") We thought that they would prefer green because their food source is green. Turns out that they prefer purple and hate black. we tested all possible color combinations for red, black, purple, yellow, white, green and blue. 5 snails per container and 7 containers. (that's 35 data points x 21 trials) We left them in the containers to go to their preferred side for 45 minutes and it took us about 15 to get ready for the next trial. SO all in all we spent roughly 30 hours working on this experiment.

here are our results....

Color #1 Color #2 P-value
Black Blue 0.0053428636
Black yellow 0.0121428719
Black white 0.0001957093
Black purple 0.0242857437
Black red 0.0121428719
Black green 1.90E-07
Blue yellow 0.1320605996
Blue white 0.067519705
Blue purple 0.0242857437
Blue red 0.067519705
Blue green 0.0121428719
Yellow white 0.1181594838
Yellow purple 0.042967085
Yellow red 0.0945275871
Yellow green 0.0121428719
White purple 0.067519705
White red 0.0001957093
White green 0.0242857437
Purple red 0.1181594838
Purple green 0.0006849825
Red green 0.1181594838
Bold text indicated a statistically significant P value





And for those of you that are used to reading and translating scientific papers here are our results with error bars


Super excited about our results!eeek Hoping to maybe present that at an undergraduate research conference. Might have to run it again with light-bulbs instead of plastic covers though.
tubaart:
Out of curiosity, did you consider the differences in color vision between the snails and people? It's important to consider both what the actual (spectroscopic) color you were presenting was (as opposed to the color we see with our tri-colored cones), and also what the color-response the target animal sees with their, presumably, different color receptors. If I remember right, most invertebrates (excepting cephalopods) are either one- or two-color viewers, and the absorption ranges are not the same as any of the human ones.

It may be that rather than being color-specific, you were finding that the snails were just luminance phototaxic - preferring whatever is brightest to them, given their specific frequency/wavelength response.

Just a thought because, hey, I'm a nerd, too. ;-)

tongue
higgs:
That's a really good point. We didn't find much in the literature about gastropod vision (because everything we cited had to be a primary source) so we didn't think to try and figure that out. We did test the lux levels under the plastic and then averaged them for each color. I have the lux on the bar graph which didn't show up when I pasted it into this blog for some reason. thanks for the idea!kiss

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