1. From: Visual acuity in the archerfish: Behavior, anatomy, and neurophysiology
Journal of Vision. 2012;12(12):18. doi: /
Figure Legend:
The fish monitors a target above water level using a small area on its retina. A. Left panel, drawing of x- and y-axes of the frame of the eye model on a segment containing a front view image of the iris of the fish eye (taken parallel to the iris plane). Right panel, diagram of the axes of the eye coordinate system, the fish, and the experimental set-up. To extract the fish eye orientation after it shifted its gaze toward the target, we employed a model of the eye that consisted of a frame with three perpendicular axes surrounded by a sphere. We measured the rotation of the frame from a reference orientation, in which it is aligned with the coordinate system to its postsaccadic orientation. B. A diagram of the frame in the reference orientation and the postsaccadic one. Here we refer to the rotations of the reference frame around the x-, y-, and z-axes as pitch, yaw, and roll, respectively. C. Upper and lower left panels: two segments containing images of the eye in the reference orientation and in the postsaccadic one, respectively. Upper and lower right panels: the contour of the stripe on the iris in the two segments relative to the x-y plane of the coordinate system. To measure the roll angle of the frame we rotated the contour of the segment of the front view image around the z-axis of the coordinate system to match it with the one of the postsaccadic segment, and the angle we extracted for this rotation is the roll angle. D. Upper and lower left panels: the two segments and on top, sketches of ellipses that were fitted to the contour of the images of the pupils in the segments. The front view image segment was rotated around the z-axis according to the roll angle. Upper and lower right panels: the two ellipses from the two segments relative to the x-y plane of the coordinate system. To measure the pitch and yaw, we rotated the ellipse of the front view segment around the x- and y-axes of the coordinate system to match it with the postsaccadic one. The rotation angles that we extracted for this match are the pitch and yaw. E. The mean values of the pitch, yaw, and roll of the frame in its post saccadic orientation were −8.6°, 5.8°, and 36.2°, respectively, and their standard deviations were <1°. The convergence of these measurements to a small region in the pitch, yaw, and roll space indicates that in all trials the fish employs a small and singular region on its retina to monitor the targets after the saccade.
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