. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 260 240 220 200 180 160. 140. 120. 100. 80. 60. 40. 20. A PROGRAMMED LIFE CYCLE IN XEANTHES Spearman Rank Correlation, r=-0 248, 295. 350 400 450 Days in culture Figure 5. Regression ot'numher of young on days in culture. Data are combined from all three experiments. pattern by which the animals could seasonally synchronize activities (Fig. 1). Parturition by most worms under fixed, neutral daylength was in April-June 1989 in experiment A, following increasing temperatures, and in April-May 1990 in experiments B
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 260 240 220 200 180 160. 140. 120. 100. 80. 60. 40. 20. A PROGRAMMED LIFE CYCLE IN XEANTHES Spearman Rank Correlation, r=-0 248, 295. 350 400 450 Days in culture Figure 5. Regression ot'numher of young on days in culture. Data are combined from all three experiments. pattern by which the animals could seasonally synchronize activities (Fig. 1). Parturition by most worms under fixed, neutral daylength was in April-June 1989 in experiment A, following increasing temperatures, and in April-May 1990 in experiments B and C, following a period of little temperature change. Previous experiments with Ar. lim- nicola (Fong and Pearse, 1992) showed that temperature had no effect on the timing of parturition in worms ex- posed to seasonally changing daylength from birth. Constant short (8:16) and long (16:8) daylength had no consistent effect on parturition synchrony but tended to desynchronize parturition especially when long day- length was combined (either before or after) with neutral daylength. Short and long daylengths also had a detri- mental effect on fecundity. However, the disruptive effect of long daylength on reproductive timing and fecundity was mitigated when followed by increasing daylengths. Decreasing daylengths did not synchronize parturition and no consistent trend was evident. Moreover, partu- rient synchronization was not as tight among worms in neutral -*• decreasing daylengths as it was in constant neutral daylengths (Fig. 3). Exposure to different photoperiodic regimes affected fecundity. The highest fecundity in any experimental treatment was found in fixed neutral daylength (experi- ment A), and the lowest in long daylength (experiment C). Nevertheless, fecundities in the present experiments, in general, were lower than those previously recorded in AT. limnicola exposed to seasonally changing daylengths continuously from birth (Fong and Pearse, 1992). Thus, a seasonal
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
