1. The effects of different coloured visual stimuli on Paracheirodon innesi in a fixed environment Taylor Brooks, James Holobow & Allyson MacDougall

2. Paracheirodon innesi Fresh water fish ●Native to streams in Colombia, Peru and Brazil ●Iridescent blue with red stripe ●Approximately 3 cm long

3. P. innesi Eyes ●Rod Pigments absorb λmax of 500-545 nm ●Melanosomes: organelles in pigment cells in eyes (melanins) ●Light response in the retina activates the migration of melanosomes and the elongation of cones (colour vision) ●Melanosomes and cones meld together to direct incoming light to the rods ●Spectral absorbance of melanosomes is ~ 480 nm

4. Iridophores ●Scales have alternating layers of guanine and cytosine ●Scatter light to a shine ●Minimal light exposure = ultraviolet/blue ●Great light exposure = green ●Respond to each other best in bright environments

5. Purpose ●Examine the response of different coloured stimuli in P. innesi ●P. innesi will stay in close proximity to colours that are within the wavelength range of 500-545 nm

6. Materials & Methods Experimental design was simple o Limited external variables Modelled fish blobs constructed of silicon sealant painted with nail polish o Red, yellow, green, blue, aqua Modelled fish were placed inside of a jar paired with an empty control jar at the opposing end of the aquarium

7. Materials & Methods Models were ~3 cm o intended to vaguely resemble real fish The aquarium was split into three sections o Control o Middle o Coloured Model

8. Materials & Methods 15 minute trials o Position recorded at 30 second intervals o Trials repeated with orientation of aquarium reversed o Repeated test 3 times  6 trials/colour

9. Results P. innesi preferred Green and Aqua systems most o Time spent next to model o Green (50.6%, SE ± 0.050) o Aqua (65.6%, SE ± 0.023)

10. Results

11. Discussion ●Aqua has a wavelength of ~ 480 nm, the same spectral absorbance as the melanosomes ●Blue and green were the second most popular and are on either side of the 480 nm on the wavelength spectrum ●Green was 2nd most popular and it’s on the higher end of the spectrum (500-545 nm)

12. Discussion Sources of error: ●Background stimuli ●Fish inconsistency/ Overuse ●Issues with our coloured model fish

13. Why is this Important? Knowing the most stimulating visual in P. innesi is important because it can give insight towards ●Schooling ●Mating ●Predator avoidance

14. Future Studies Use iridescent nail polish o Stimulate iridophores Compare coloured models against each other Use different fish species to compare light absorbances