. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 46 JOHN D. PALMER AND FRANK E. ROUND semi-darkness. This obviously tends to negate the desired effect of the overhead experimental light regime. The laboratory populations were also sampled with the lens-paper technique and the average of 3-6 samples used for each cell count. Because this technique unavoidably reduces the size of the sample populations, during long-term observations, sampling on some days was intentionally omitted. RESULTS Field observations The sampling station on the Barnstable Harbor sand-flats is uncover
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 46 JOHN D. PALMER AND FRANK E. ROUND semi-darkness. This obviously tends to negate the desired effect of the overhead experimental light regime. The laboratory populations were also sampled with the lens-paper technique and the average of 3-6 samples used for each cell count. Because this technique unavoidably reduces the size of the sample populations, during long-term observations, sampling on some days was intentionally omitted. RESULTS Field observations The sampling station on the Barnstable Harbor sand-flats is uncovered by the tide for an average duration of hours once every hours. Field observa- tions were made at intervals during the summers of 1965 and 1966 and were timed so that the presence of the cells on the surface during morning, midday, and eve- ning low tides could be described and compared. It was found that when low tide straddles the time of sunrise the cells do not appear on the surface until shortly after the time of sunrise. Once they begin to appear, their numbers rapidly increase to a maximum value which then remains relatively constant until about 30-60 minutes before the return of high tide, at which time the cells begin to re-burrow back into the substratum. A representa- tive curve is described in Figure 1. 400 • 300 : CM £ G 200 • O. 100 •:• o b. '• •;.-:'. *K: ,• •..: • 5 6 ~7 8 Time of Day FIGURE 1. Field observations of the vertical-migration rhythm in Hantzschia. Wavy lines (HT) represent the times of high tide. Straight line (LT) subtending and connecting consecu- tive wavy lines indicates time of low tide. The time of sunrise is represented by the boundary between stippled and unstippled areas. The shaded horizontal bars supported by dashed lines signify periods when the sands were covered by opaque canisters. See text for further Please note that these images are extracted from scanned page images that may have been
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
