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First published online January 17, 2007
Journal of Experimental Biology 210, 505-511 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02677
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The directional hearing abilities of two species of bamboo sharks

Brandon M. Casper* and David A. Mann

College of Marine Science, University of South Florida, 140 7th Avenue South, St Petersburg, FL 33701, USA


Figure 1
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  		Fig. 1. Diagram of the directional shaker table setup. The fifth, mechanical shaker, which produces the up/down motion (Z-axis) of the dish, is located under the dish and not visible in this picture. Drawing not to scale.

 

Figure 2
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  		Fig. 2. (A) Acceleration raw signals for a stimulus directed in the Z direction (up/down) as recorded from the three-dimensional accelerometer. (B) Auditory evoked potentials (AEPs) from the white-spotted bamboo shark Chiloscyllium plagiosum, in response to a 100 Hz signal at six signal levels. As the signal is decreased in acceleration level (m s–2) the AEP signal also decreases until it is lost in the noise at 6.0–3 m s–2. (C) 2048-point Fast Fourier Transform (FFT) of the same AEP for the shark in response to a 100 Hz sound. The arrow indicates the frequency doubling peak, which occurs at 200 Hz.

 

Figure 3
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  		Fig. 3. Directional hearing thresholds for the white-spotted bamboo shark Chiloscyllium plagiosum (N=4) and the brown-banded bamboo shark Chiloscyllium punctatum (N=2), for each of the seven directions (see text) measured at (A) 20 Hz, (B) 50 Hz, (C) 100 Hz and (D) 200 Hz. Values are means ± s.e.m. There was no significant difference between any of the directions at any of the frequencies except at 50 Hz for interactions between the Z and 30° directions and the Z and 90° directions.

 

Figure 4
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  		Fig. 4. Composite directional shaker audiograms of the white-spotted bamboo shark Chiloscyllium plagiosum (N=4), the brown-banded bamboo shark Chiloscyllium punctatum (N=2), and the goldfish Carassius auratus (N=2). These audiograms are compiled from the average of all of the thresholds at each of the directions for each frequency tested. Values are means ± s.e.m. Also plotted is the dipole audiogram for C. plagiosum (N=4) to compare responses from different stimuli. The dipole thresholds were significantly lower than the directional shaker thresholds at 50 and 200 Hz for C. plagiosum.

 

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© The Company of Biologists Ltd 2007