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First published online September 9, 2005
Journal of Experimental Biology 208, 3441-3450 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01766

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Sensitivity of the anterior lateral line to natural stimuli in the oyster toadfish, Opsanus tau (Linnaeus)

Lucy M. Palmer^1,2, Max Deffenbaugh^2,3 and Allen F. Mensinger^1,2,*

¹ Biology Department, University of Minnesota Duluth, Duluth, MN 55812, USA
² Marine Biological Laboratory, Woods Hole, MA 02543, USA
³ ExxonMobil Upstream Research Company, PO Box 2189, Houston, TX 77252, USA

View larger version (29K): [in a new window]   Fig. 1. Dorsal view of the experimental arena. The recharging habitat and stage (RECHABS) consists of the cylindrical habitat (H) and octagonal stage (S). Neural telemetry and tag recharging could transpire when the fish was in the habitat or over the stage. The black circle (arrow) represents an opaque barricade that restricted the prey and the toadfish to the stage area. Fish movements were recorded with an overhead video camera (C). Drawing is not to scale.

View larger version (15K): [in a new window]   Fig. 2. The mean normalized neural firing rates of (A) silent (N=4) and (B) spontaneously active afferent fibers (N=5) of the anterior lateral line are plotted versus the distance of the innervated neuromasts to the prey. All firing rates were normalized according to the maximum firing rate recorded during each trial. Neural activity was analyzed only when the prey fish was at the same location for greater than 500 ms. All distances were measured from the insertion point of the nearside prey pectoral fin to the neuromast that was innervated by the recording. Asterisks indicate significantly different means from controls (ANOVA). The broken horizontal line in B represents the mean normalized spontaneous firing rate from spontaneously active fibers.

View larger version (10K): [in a new window]   Fig. 3. The probability of a silent fiber (triangles) firing during a prey encounter and the probability of a spontaneously active fiber increasing its discharge rate one (filled circle) or two (open circle) standard deviations above its spontaneous discharge rate during a prey encounter is plotted versus prey distance. If the silent fiber fired during the event, it was considered stimulated, and the probability of the silent fibers firing was calculated as: (stimulated encounters/total encounters)x100. If the firing activity of the spontaneously active fibers firing increased one and/or two standard deviations above its mean resting discharge rate it was considered stimulated and the probability was calculated as: (stimulated encounters >1 S.D./total encounters)x100 and (stimulated encounters >2 S.D./total encounters)x100. The data represent the summary of all trials for each fiber class, and each point represents a minimum of 15 trials at each distance. Prey distance was binned into 2 cm segments.

View larger version (21K): [in a new window]   Fig. 4. The activity of a silent, afferent fiber innervating a superficial neuromast on the infraorbital lateral line, as monitored during prey movement. (A) The distance (cm) of the prey fish from the recorded neuromast. (B) The full neural waveform from the anterior lateral line nerve that was transmitted via inductive telemetry. Although multiunit activity is visible in the trace, only the fiber with the greatest amplitude of action potential was used for data analysis. The fiber had no spontaneous activity and exhibited maximum firing (10 Hz) when the prey fish was within 1 cm of the neuromast.

View larger version (27K): [in a new window]   Fig. 5. Neural activity during the approach of a single prey fish. The diagram depicts the head of the toadfish projecting out of its habitat and the sequential positions of the approaching prey: (A) 10 cm; (B) 3.5 cm; (C) 1.0 cm. Images were reconstructed from single video frames. The letter next to the prey fish corresponds to neural activity from a superficial neuromast on the suborbital portion of the infraorbital lateral line. Although multiunit activity is visible in the trace, data analysis was restricted to the fiber with the greatest amplitude of action potential.

View larger version (14K): [in a new window]   Fig. 6. Firing rates of (A) a spontaneously active afferent fiber and (B) a silent fiber in response to a prey fish located at variable distances from the neuromast. Both fibers innervated superficial neuromasts. All distances were measured from the insertion point of the nearside prey pectoral fin to the neuromast that was innervated by the recording. The broken horizontal line in A represents the mean spontaneous activity. All firing rates were normalized according to the maximum firing rate elicited by prey movements during each trial. Neural activity was analyzed only when the prey fish was at the same location for greater than 500 ms.

View larger version (10K): [in a new window]   Fig. 7. Mean firing rate (± 1 S.E.M.) of four anterior lateral line afferents fibers [three spontaneous (SP) and one silent (SL)] immediately before (open) and during (filled) a toadfish prey strike. Numbers above the bars represent the number of prey strikes that were averaged for each fiber.

View larger version (8K): [in a new window]   Fig. 8. Neural activity from an afferent anterior lateral line fiber before, during and after a prey strike. Vertical lines on the trace indicate individual action potentials from a single fiber that were discriminated based on spike amplitude. The arrows indicate initiation of opercular contraction for each ventilation cycle. The time during the strike, capture and subsequent expulsion of the prey is boxed in A, and this interval is expanded in B. The prey was retained in the mouth of the toadfish for approximately 1 s before being expelled.

View larger version (110K): [in a new window]   Fig. 9. The picture shows the water movements produced by an 8 cm SL Fundulus heteroclitus taken with a digital video camera at 1000x1000 pixel resolution. Each velocity vector represents the average of a 32 pixelx32 pixel window, and the center of each window is spaced 16 pixels apart. Velocities are presented by pseudo color images. Scale bar, 2 cm.

View larger version (9K): [in a new window]   Fig. 10. The frequency of attacks by 8 cm SL toadfish at 2 cm SL guppies is plotted versus the distance between the two fish at the time the toadfish launched its attack. The total number of attacks analyzed was 78. Modified from Price and Mensinger (1999).