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The effects of different coloured visual stimuli on Paracheirodon innesi in a fixed
environment
Taylor Brooks, James Holobow & Allyson MacDougall
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Paracheirodon innesi
• Fresh water fish● Native to streams in Colombia,
Peru and Brazil● Iridescent blue with red stripe ● Approximately 3 cm long
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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
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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
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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
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Materials & Methods
• Experimental design was simpleo Limited external variables
• Modelled fish blobs constructed of silicon sealant painted with nail polisho 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
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Materials & Methods
• Models were ~3 cm o intended to vaguely
resemble real fish
• The aquarium was split into three sectionso Control o Middleo Coloured Model
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Materials & Methods
• 15 minute trialso Position recorded at 30 second
intervalso Trials repeated with
orientation of aquarium reversed
o Repeated test 3 times 6 trials/colour
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Results
• P. innesi preferred Green and Aqua systems mosto Time spent next to model
o Green (50.6%, SE ± 0.050)o Aqua (65.6%, SE ± 0.023)
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Results
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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)
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Discussion Sources of error:
● Background stimuli● Fish inconsistency/ Overuse● Issues with our coloured model fish
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Why is this Important?Knowing the most stimulating visual in P. innesi is important
because it can give insight towards● Schooling● Mating● Predator avoidance
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Future Studies
• Use iridescent nail polish o Stimulate iridophores
• Compare coloured models against each other• Use different fish species to compare light
absorbances