Guppy's favorite color

What is guppy favorite Color ?

 An article made on February 2017, by FindingGuppy team.

Perception of color is a major innovation in the evolution of life. Thanks to their eyes, Homo sapiens can perceive a wide range of colors between red and blue but it's only a small part of the visible spectrum. Other animals perceive different colors than us: cats can’t perceive red light, while bees can sense ultraviolet light. During this final project of Biosensors, we asked ourselves what color was perceived by the Poecilia reticulata fish, also known as guppy. We decided to design an experiment in order to determine to which color the guppies are most responsive to.

But... Who is the guppy?

Guppies (Poecilia reticulata) are small tropical fishes (3 to 4 cm) that can live in water going from 18 to 30°C. It is very common in aquariums and houses, maybe you have some in your house. We know that guppies have 6 opsins. Opsins are proteins present in the retina that allow perception of color. In human eyes, there is 3 opsins: for short wavelength (blue), medium wavelength (green), and long wavelength (red). Guppies are more sensitive than human to infrared and ultraviolet light, what allow them to efficiently find food or select their mating partner.

Make How did we test guppy's response to light?

There was nothing complicated in our protocol! We prepared an aquarium in which we ran our experiment. We put one guppy in it, and we let it discover his new environment during 5 minutes, in order to let it calm down. Then, we began a 2min recording of the fish behavior while the light was torn off, we were measuring how many times did he spent in each of the 4 area of the aquarium. After this, we turned on the LED, and each area was illuminated with a specific color. We recorded guppy's movement during 2 minutes and took the measurements of the fish position. We repeated these steps 3 times per fish, in order to have enough data to have significant results.

This experiment had been made 3 times on the 4 fishes.
 

And what results did we get?

After this experiment, we had to treat and analyze data. In order to do so, we make the difference between the time spent while the light was on and while the light was off, for each area. Each block corresponds to 1 guppy. The color of the bar corresponds to the color area: green, blue, red and white. When the bar is greater than zero, it means that the fish spend more time in the area after we turned on the light. 

This graph shows that the first guppy spent less time in the red area, but more in the white area. The second spent less time in the red area, but more in the green. The third spent less time in the red and in the white, and a much more in the blue one. And the last fish just didn’t move and stayed in the same area.

As you can see here, the results are quite different. The first and the second guppy had spent more time the red area, while the  other spent most of their time in the blue area. It’s quite hard to interpret.

And these are our last results, after we had fed the fishes. The tendency is still different from the two other experiments: it seems that they prefer green and blue area.

Make a conclusion is a big challenge!

We have such various results that we cannot conclude a specific attraction for any light. Fishes seems to have random movements, even if they are more active after being fed. It would be interesting to repeat the experiments, but avoiding some bias, like the water leak of our aquarium, the noise, the enlightening of the room… And most of all, studying more fishes than 4 !

Going further! 

If you want to know more about this experiment, here are links that can be helpful :

• Contact us:  finding.guppy@gmail.com
• Learn more about guppies while watching this video (in french).
• Understand how guppy sees with this paper.
• Follow our twitter account.
• Discover our Storify.
• Explore our Github, and find all the documentation you need to repeat our experiment.

Special acknowledgement to Tamara, who made this project possible, and all the teaching team that supported and helped us.

By FindingGuppy Team: Nina Guérin, Daphné Guénée & Nicolas Larrouy

All the images belong to the member of the FindingGuppy Team except the second one that comes from commons.wikimedia.org.