. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VISUAL ORIENTATION BY ZENARCHOPTERUS 115 60-240°, 90-270°, 120-300°, 150-330°), only half were used with an individual fish. For each condition, 10 consecutive photographs of the fish's headings were made at 10 sec intervals timed and counted by the intervalometer. The filter was then changed manually to its next position or removed for the NF condition. After a 10 sec pause to let the fish settle down, another 10 frame sequence was made, etc. The order of presentation of the conditions, as well as the angle of the polarizer
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. VISUAL ORIENTATION BY ZENARCHOPTERUS 115 60-240°, 90-270°, 120-300°, 150-330°), only half were used with an individual fish. For each condition, 10 consecutive photographs of the fish's headings were made at 10 sec intervals timed and counted by the intervalometer. The filter was then changed manually to its next position or removed for the NF condition. After a 10 sec pause to let the fish settle down, another 10 frame sequence was made, etc. The order of presentation of the conditions, as well as the angle of the polarizer were randomly selected with the constraints that no condition was used twice with a given fish, and all conditions were tested an equal number of times. The angle between the fish's longitudinal axis and the sun's bearing taken as 0° reference was measured to the nearest 10° from the photographs. For analysis these headings were grouped into 30° sectors centered to coincide with the six 120 CD 60 Z tr LU CD 0 CO 300' 240 i i r l r i i. •w _L l 90C 60' CO CO so0 : 0" o m to AM 12 PM LOCAL 14 T 16 18 M E FIGURE 2. Sun's hearing and altitude during the experimental periods. Note that for August 28th the solar bearing \vas constant near W by WNW during the full period. On the 29th the bearing was stable for the first hours, then it shifted very rapidly. For this reason measurements made during the last 30 min (4 of the 12 fish) were excluded from the main analysis. polarization planes tested. Obviously the positions and angular extent of these sectors are fixed and the response variable is the number or percentage of observed orientations which falls within each. The experimental design permits the overall data to be analyzed in several ways to test for various significant stimulus components. Thus the total distribution as recorded has the sun's bearing at 0° and the imposed ('-vector randomized (Fig. 3). When transposed to geographical coordinates (0° -North)
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
