The area centralis of the archer fish: from acuity and physiology to eye movements’ strategy
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1
Ben Gurion University, Life Sciences , Israel
Archer fish exhibit extreme visual behavior in shooting water jets at prey hanging on vegetation above water. Motivated by the archer fish capacity to knock down small prey, either static or moving, as high as two meters above water level, we studied the different factors that contribute to its excellent visual acuity. First, we studied the static visual acuity in the archer fish and found, behaviorally, that the fish minimum angle of resolution is ~0.1 o and that this resolution is facilitated by a specialized part in the fish retina – the area centralis. Then by combining anatomy of area centralis and physiology of retinal ganglion cells there, the only cells that project axons to the brain, we showed that retinal ganglion cells in the area centralis stream information to the brain at a comparable resolution with which it is sampled by the photoreceptors. Moreover, this resolution is approximately the same as that observed behaviorally in the visual acuity test. Moving to dynamic visual acuity, we studied how the archer fish employs its area centralis for the interception of moving targets. This study is unique since most research on eye-tracking of moving targets was focused on how foveated primates track targets with their fovea by employing a combination of saccadic and smooth pursuit eye movements. However, fish do not possess smooth pursuit eye movements, thus they can be used to examine how non-foveated vertebrates solve this problem with only saccadic eye movements. We tracked gaze direction of fish during interception of moving targets and found that they employ saccadic eye movements based on prediction of target position when it is hit. The fish fixates on the target’s initial position for ~0.2 sec from the onset of its motion, a time period used to predict if a shot can be made before the projection of the target exits the area centralis. If the prediction indicates otherwise, the fish performs a saccade that overshoots the center of gaze beyond the present target projection on the retina, such that after the saccade the moving target remains inside the area centralis long enough to prepare and perform a shot. Together these results not only explain the archer fish ability to exhibit its unique visual behavior, but they also make it an excellent animal model for studying how fine visual details are streamed to the brain by retinal output.
Keywords:
Acuity,
archer fish,
area centralis,
EYE MOVEMENT,
ganglion cells
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Sensory: Vision
Citation:
Ben Simon
A and
Segev
R
(2012). The area centralis of the archer fish: from acuity and physiology to eye movements’ strategy.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00198
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Received:
29 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Ronen Segev, Ben Gurion University, Life Sciences, Beer Sheva, 84105, Israel, ronensgv@bgu.ac.il