. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ARROW WORM PHOTOTAXIS 423. FIGURE 5. Photograph taken by a 3 s continuous exposure, showing an arrow worm's pattern of target-aiming swimming. Light (50,000 lux) directed from the right was reduced by 90%. Note that the worm, which had been inclined toward the left, changed its body axis to the right almost instantaneously: No trail linking the left-oriented posture to the right appears on the photograph, indicating a very quick change sequence. Scale: 1 cm. In each experiment, a light-adapted worm was placed in a trough 20
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ARROW WORM PHOTOTAXIS 423. FIGURE 5. Photograph taken by a 3 s continuous exposure, showing an arrow worm's pattern of target-aiming swimming. Light (50,000 lux) directed from the right was reduced by 90%. Note that the worm, which had been inclined toward the left, changed its body axis to the right almost instantaneously: No trail linking the left-oriented posture to the right appears on the photograph, indicating a very quick change sequence. Scale: 1 cm. In each experiment, a light-adapted worm was placed in a trough 20 cm long, 4 cm wide, and 4 cm deep, which was illuminated from both ends, one end at 800 lux and the other varying from 160-2400 lux. After 5-10 min, the fixed-intensity light was turned off and whether the worm oriented and swam toward the remaining light was recorded (Fig. 6). The larger — AI, the more worms swam toward the light. The mechanisms involved in the response's two steps (steer and swim) differed in sensitivity, so that a majority only steered themselves upon small —AI's, whereas all the animals went on to the second step (swim) in response to the largest —AI. 100 in 0) O) as I o I 50 1 160 400 (83) (67) 800 (50) n 1200 16OO 2000 24OO (40) (33) (29) (25) Final light intensity in lux (Percentage reduction of total light intensity) FIGURE 6. Target-aiming response following intensity reduction by extinguishing a light of 800 lux from one end, showing percentages of worms (n = 20) that steered (white bars) or steered and swam (black bars) toward the remaining light at the opposite end of the trough (abscissa). The reduction in intensity is indicated in brackets along the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biologi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
