. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 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 cysts. The duration of the experiment was 23 weeks, and treatment conditions are as listed in the legend to Figure I. Error bars are one standard deviation of SEPT OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS Figure 4. Mean number of encysted and free-living copepods taken from the cores during the field study. Core samples were taken once
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 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 cysts. The duration of the experiment was 23 weeks, and treatment conditions are as listed in the legend to Figure I. Error bars are one standard deviation of SEPT OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS Figure 4. Mean number of encysted and free-living copepods taken from the cores during the field study. Core samples were taken once a month for twelve months. Number per 10 cm- is the unit of density for meiobenthos, in contrast to number per m: used for macrobenthos. Error bars are one standard deviation of mean. by the dark, cold environment (9 h light at 10°C). En- cystment in H. nunni must be genetically induced, because sexually immature adults encysted regardless of the sur- rounding temperature or photoperiod regime. Our results are in direct contrast to those of previous research, which indicate that photoperiod and temperature are necessary mechanisms for inducing copepod diapause, for cal- anoids (Marcus. 1980, 1982a, b, 1987; Hairston et ai. 1990), cyclopoids (Watson and Smallman, 197la, b; Elg- mork and Nilssen, 1978). and freshwater harpacticoids (Sarvala, 1979). Additionally, no female H. nunni dis- sected from cysts had attached spermatophores, egg sacs, or maturing ova, nor did any males have developing sper- matophores. Because mated adults would show at least some of these characteristics, the encysted individuals must not have mated. In Canthocamptus staphylinm, however, females with attached spermatophores encyst (Sarvala, 1979), and fertilized, adult females of Cyclops strenuus diapause (Naess and Nilssen, 1991). Although temperature and photoperiod apparently did not specifically cue encystment, they did affect the de- velopmental rates of//, nunni. The most significant effect w
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