First published online August 4, 2005
Journal of Experimental Biology 208, 3037-3046 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01750
Behavioural discrimination of polarized light in the damselfish Chromis viridis (family Pomacentridae)
Martina Mussi,
Theodore J. Haimberger and
Craig W. Hawryshyn*
Department of Biology, University of Victoria, PO Box 3020 Stn. CSC,
Victoria, British Columbia, Canada V8W 3N5
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Fig. 1. Optical system. Light from the 150 W xenon lamp was projected though two
UV-transmissive biconvex lenses before hitting a beam-splitter, which
transmitted 50% of the light to the right optical window of the behavioural
chamber and 50% to a front-surface mirror, which hit the left optical window
of the behavioural chamber.
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Fig. 2. Spectroradiometer measurements (Ocean Optics; USB2000) of the light
entering the two windows in the test tank (orange line). Spectral background
of the light entering the test tank when the UV light content was filtered
using a 450 nm long-pass filter (black line).
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Fig. 3. (A) Each session (S1–S10) of training, which included 20 trials, is
shown on the x-axis, plotted against choice frequency. Fish A
(diamond) required four sessions before discriminating the reference e-vector.
Fish B (square) required seven sessions, whereas fish C (triangle) required
three, and fish D (circle) required six sessions. Positive response was a
correct choice frequency of 70% or above. (B) Time to respond. The time to
respond was recorded from the opening of the gate until fish chose an e-vector
within the choice area. The time to respond (mean ±
S.E.M.) diminished with the training sessions
for each fish.
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Fig. 4. C. viridis could discriminate between 0° and 90° e-vector
orientations (P<10–4 in each case). Each point
represents the percentage of correct choice frequency (mean ±
S.E.M.) when 0° and 90° e-vector
orientations were presented. The horizontal line represents the choice
frequency value for a significance level of P=0.001 x for
40 Bernoulli trials calculated using the binomial probability function. Fish A
and C were trained to swim towards 90° e-vector orientation (85% and 80%
correct choice frequency, respectively). Fish B and D were trained to select
0° e-vector orientation (80% correct choice frequency in both fish).
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Fig. 6. Eliminating the UV part of the spectrum in the polarization stimuli impairs
e-vector discrimination. The UV part of the spectrum in both stimuli was
removed using a 450 nm long-pass filter (40 trials per fish, N=2).
Each point represents the percentage of correct choice frequency (mean
± S.E.M.) between the reference and
comparison e-vectors. The horizontal dashed line indicates 50% choice, i.e.
random choice between the two stimuli.
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© The Company of Biologists Ltd 2005
e-vector) is plotted against the percentage of choice
frequency for each fish. Each point represents the percentage of correct
choice frequency (mean ± S.E.M.)
between the reference e-vector and the comparison e-vector (40 trials per
fish, N=4). The horizontal shaded bands represent the range of choice
frequency values that correspond to significance levels of
P=0.001