. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 400 450 500 250 550 fed 600 (c) (d). 200 -80 400 600 Figure 2. (a) Pressure-time trace for an unfed urchin during the first 200 s of the experiment. The large negative pressure pulse, characteristic of unfed urchins, occurred just after the needle was inserted through the peristomial membrane, (b) Pressure-time trace for an unfed urchin 400- 600 s after the start of the experiment. This trace shows the characteristic, rhythmic fluctuations of pressure associated with movements of the lan- tern, (c) Pressure-time trace for a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 400 450 500 250 550 fed 600 (c) (d). 200 -80 400 600 Figure 2. (a) Pressure-time trace for an unfed urchin during the first 200 s of the experiment. The large negative pressure pulse, characteristic of unfed urchins, occurred just after the needle was inserted through the peristomial membrane, (b) Pressure-time trace for an unfed urchin 400- 600 s after the start of the experiment. This trace shows the characteristic, rhythmic fluctuations of pressure associated with movements of the lan- tern, (c) Pressure-time trace for a fed urchin during the first 200 s of the experiment, showing the characteristic, positive pressure pulse as the needle was inserted through the peristomial membrane, (d) Pressure- time trace for a fed urchin 400-600 s after the start of the experiment, showing rhythmical changes with lantern movements. Differences in the traces for starved and fed urchins (a and c) were statistically significant; during the third 200-s traces (b and d) the differences were not significant. where y is equal to -1 if an urchin is fed, and is equal to + 1 if an urchin is unfed. The nine variables descriptive of the pressure traces are x, to x9. The fitted slopes are a, to a9 and b is the intercept. For L. variegatus the average level of pressure was measured for each 2-min segment except the first, which was assumed to be a settling-down period. A paired /-test was done on the average pressures to compare the lights- off periods with the immediately ensuing lights-on periods. Results Description of the pressure traces Pressure traces for S. purpiiratus characteristically fluc- tuated at a frequency of Hz with a of Hz (n = 167 traces). This corresponds to an average period of 18 s, and the range of periods corresponding to the above is 13-29 s. When the needle was inserted through the peristomial membrane, there was usually a negative or positive pres- sure peak (Fig. 2) that
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
