First published online June 27, 2008
Journal of Experimental Biology 211, 2252-2262 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.011130
Complex sexual courtship displays by luminescent male marine ostracods
Trevor J. Rivers* and
James G. Morin
Department of Ecology and Evolutionary Biology, Cornell University,
Ithaca, New York, NY 85201, USA
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Fig. 1. Setup for three-dimensional video analysis. For close viewing, two
low-light CCD cameras were positioned to cover (with overlap) the front of the
tank (TF, top front; BF, bottom front), and one CCD camera (CCD=SIDE) and a
video camera with night-vision device (NVD) and infrared barrier filter in
tandem recorded movement and luminescence, respectively, from the side. The
image panel box at the lower right indicates the image partitioning of the
recordings.
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Fig. 2. Two three-dimensional examples of male ostracod displays, showing
luminescence, swimming patterns and speeds. (A) Close-up of the first seven
pulses of a display. (B) Example of an entire display. In the stationary phase
males swim slower than when in the helical phase (see also
Table 2,
Fig. 4D and
Fig. 5). Data points are every
67 ms. Large blue circles indicate the location of each luminescent pulse. The
color of the small spheres indicates the swimming speed of the ostracod at
that given point in time. The z-axis is in centimeters from the top of the
tank, the x-axis is the distance from the left side of the tank, and the
y-axis is the distance in depth from the first data point.
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Fig. 3. Typical photometric waveforms of a single display train. The first three to
four bright pulses are typical of the stationary phase and the remaining
pulses are typical of the helical phase. The mean duration of each pulse
decreases during the stationary phase, but becomes more consistent during the
helical phase (see also Fig.
4).
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Fig. 4. Characteristics of a luminescent display train during stationary (shaded)
and helical (nonshaded) phases. (A) Mean pulse intensity (as a percentage of
first pulse). Helical phase pulse intensities are approximately 10% of the
initial stationary pulse (N=16). (B) Mean pulse duration: pulse
duration decreases rapidly during the stationary phase, then only slowly
during the helical phase (N=16). (C) Mean interpulse interval.
Interpulse intervals decrease rapidly during the stationary phase, but are
highly conserved during the helical phase (N=85 pulse 1, see
Table 2 for remainder). (D)
Mean interpulse distances. Vertical distance increases during the stationary
phase, then levels off during the helical phase, but there is no trend for
horizontal movement during the course of a display (N=85 pulse 1, see
Table 2 for remainder). Bars
indicate standard errors. For C and D the points are interpulse
values so points occur between pulse numbers.
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Fig. 5. Time–distance relationships of luminescent courtship display trains
in Vargula annecohenae (from Table
2). Data points represent vertical distance traveled after each
flash: filled diamonds indicate the stationary phase (shaded area) and open
squares indicate the helical phase of the display. Horizontal solid lines
correspond to pulse duration. The vertical swimming speed (5.41 cm
s–1) was calculated from the regression line (dotted line)
during the helical phase, which is consistent over the course of a display.
Since we used the mean time and distances
(Table 2), there are no error
bars.
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Fig. 6. Mean swimming speeds of luminescing males before, at and after a
luminescent pulse. The inset graph shows a representative male releasing three
pulses during a 2 s period. Males swim slowest when starting a luminescent
pulse (black dots), and fastest immediately after releasing a pulse
(N=50).
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Fig. 7. Model of four luminescent display trains produced by a single Vargula
annecohenae, based on the interpulse intervals, interpulse distances,
pulse intensities, and swimming patterns of males displaying in the lab
(Tables 1 and
2). The first three pulses in
each train are the stationary phase; the remaining pulses are the helical
phase. Black dots indicate the location of the light pulses (their size
corresponds to relative intensity) and the faint lines indicate swimming
trajectory (only the third display train shows the stationary phase swimming
pattern). Once a male reaches the top of the train, it swims rapidly downward
without spiraling, and then commences displaying again.
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© The Company of Biologists Ltd 2008
