. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CUES FOR ENCYSTMENT IN H. NUNNl 113 females in cysts in all treatments (Fig. 3); mean male/ female ratio = Field population study A. Number of free-living H. nunni/numher of cysts over 12 months. There was a significant difference (P = <) between mean copepod abundance by month (Fig. 4). January and February had significantly more free-living H. nunni than other months (April-November); March was not significantly different from Jan-Feb or Apr-Nov (Tukey's multiple comparison procedure). Free-living H. nunni r
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CUES FOR ENCYSTMENT IN H. NUNNl 113 females in cysts in all treatments (Fig. 3); mean male/ female ratio = Field population study A. Number of free-living H. nunni/numher of cysts over 12 months. There was a significant difference (P = <) between mean copepod abundance by month (Fig. 4). January and February had significantly more free-living H. nunni than other months (April-November); March was not significantly different from Jan-Feb or Apr-Nov (Tukey's multiple comparison procedure). Free-living H. nunni reached maximum abundance in winter and were low in number, then absent as summer progressed. The mean number of full cysts throughout the year was not significantly different between months, because the num- ber of cysts in the cores was extremely low (Fig. 4). Cysts were most abundant in summer, when free-living //. nunni were absent from the core samples (Fig. 4). B. Free-living males and females over 12-month study. The mean number of males compared to females was significantly different over the one-year sampling period (males and females both with P = <) (Fig. 5). The number of males was slightly greater than females in Oc- tober and November (time of emergence from cysts). The population was dominated by females from December to April, the period of peak egg production (Fig. 5). Free- living males and females disappeared in summer during peak encystment time (May, June, July). Discussion In the field, H. nunni encysts in early summer (day- length 14 h, temperature 15-18°C). In the laboratory, therefore, we expected H. nunni not to encyst under winter ( cold-short day) conditions. Nevertheless, encystment occurred in all treatment conditions and was not inhibited cc HI m 5 < LLJ. HOT-SD COLD-LD TREATMENT COLD-SD Figure 3. The effect of temperature and photopenod regimes on the mean number of male compared to female copepods after removal from the full cyst
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
