. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 294 R. B. FORWARD ET FIGURE 5. Number of crabs from estuary A releasing larvae (ordinate) at times (abscissa) relative to the end of the light phase. Crabs were placed on a 14:10 LD cycle in the laboratory for 5 days and then maintained under constant conditions. "Lights oft"" indicates the end of the light phase on the first night and "sunset" is the time of sunset in estuary A. Other symbols, as in Figure 1. No releases occurred at other times. were held at °C in 9 ppt sea water, subjected
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 294 R. B. FORWARD ET FIGURE 5. Number of crabs from estuary A releasing larvae (ordinate) at times (abscissa) relative to the end of the light phase. Crabs were placed on a 14:10 LD cycle in the laboratory for 5 days and then maintained under constant conditions. "Lights oft"" indicates the end of the light phase on the first night and "sunset" is the time of sunset in estuary A. Other symbols, as in Figure 1. No releases occurred at other times. were held at °C in 9 ppt sea water, subjected to a summer photoperiod (15:9 LD cycle; cool white fluorescent lamps positioned over the tank; intensity : W/m2) and fed with Purina cat chow. Females became ovigerous in January and breeding continued through the spring. The method for monitoring releasing was identical to that for the previous crabs on an altered LD cycle. However during constant conditions the crabs were placed in the environmental cabinet (tempera- ture, 26°C) having low intensity red light ( red incandescent lamp; wavelength output was greater than 600 nm; intensity about W/m2). Releasing was moni- tored for 3 days. Winter crabs also exhibited a rhythm in larval release that was entrained to the altered LD cycle (Fig. 6A). Only 4% of the crabs did not release larvae in the sampling time which indicates releasing was nonuniform over the solar day (P < ). On all 3 nights the release distribution was not uniform within the sampling interval (P < ). Again releasing began at the end of the light phase and continued for about the next h. Eleven percent of the crabs (n = 5) released larvae on con- secutive nights, with a mean time between releases of 23 h 30 min (SE = 15 min) when rounded off to the nearest 15-min interval. Estuary B: entrainment to a LD cycle in the laboratory To determine whether crabs from estuary B could change from an apparent circatidal to a circadian rhyt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
