. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. I TS? Vi9 T9<? J|. 10 22 80 135 175 230 1450 -2 -I sec FIGURE 5. Distributions of 17 day old 5. vermicularis trochophores exposed to different intensities of light and following various periods of light adaptation. Histogram bars show the percentages of larvae in five regions of the experimental container. Each column of graphs represents a single experiment, monitored at progressive time intervals, so the effect of light adaptation can be seen by noting changes in distribution while reading down a column. Numbe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. I TS? Vi9 T9<? J|. 10 22 80 135 175 230 1450 -2 -I sec FIGURE 5. Distributions of 17 day old 5. vermicularis trochophores exposed to different intensities of light and following various periods of light adaptation. Histogram bars show the percentages of larvae in five regions of the experimental container. Each column of graphs represents a single experiment, monitored at progressive time intervals, so the effect of light adaptation can be seen by noting changes in distribution while reading down a column. Number of larvae sampled is indicated to the right of each graph together with a symbol showing significance level, as determined by Chi-Square test for goodness of fit to a uniform distribution. Open circle: P < Half-closed circle: P < Closed circle: P < No symbol: not significant. adapted one-eyed trochophores to horizonal light at approximately two-day inter- vals. Multiple light levels were used at 6, 11, and 17 days; qualitative observations were made on the other days at a single intensity. Since the basic response did not change throughout this period, we present data from a single typical experiment (Fig. 5). Following dark adaptation, larvae responded to light of low intensity by swimming toward it. After swarming against the light side of the chamber for several minutes, they were invariably light adapted and changed the sign of their response. The time required for light adaptation was an inverse function of intensity. Indeed, at very high intensities, no photopositive period was apparent at all, though this may be because the change from positive to negative phototaxis occurred faster than the time lag inherent in our counting procedure. The overall strength of the response, as measured by the percentage of larvae responding, was also influenced by intensity. At 10 ^E- m~2 • sec"1, only about 40% of the larvae occupied the darkest regio
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
