. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 114 J. WILLIAMS-HOWZE AND B. C. COULL O o 6 30 25 20 15 10. SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS Figure 5. Mean number of free-living male and female copepods taken from the cores during the field study. Core samples were taken once a month for twelve months. Number per 10 cnr is the unit of density for meiobenthos, in contrast to number per rrr used for macrobenthos. Error bars are one standard deviation of mean. opment than the hot treatment regime. Copepodites nor- mally reach adulthood in early summer (
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 114 J. WILLIAMS-HOWZE AND B. C. COULL O o 6 30 25 20 15 10. SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS Figure 5. Mean number of free-living male and female copepods taken from the cores during the field study. Core samples were taken once a month for twelve months. Number per 10 cnr is the unit of density for meiobenthos, in contrast to number per rrr used for macrobenthos. Error bars are one standard deviation of mean. opment than the hot treatment regime. Copepodites nor- mally reach adulthood in early summer (April-May) in the field, and encyst during summer months only (Fig. 4). Greater total number of cysts in the hot treatments (81 Hot-LD, 117 Hot-SD) versus the cold treatments (48 Cold-LD, 51 Cold-SD) were probably due to increased rates of development. The high number of encystment events in the hot-short day was unexpected, particularly because longer photoperiod has been implicated as the main cue triggering summer dormancy in other copepods (Watson and Smallman, 197la, b; Sarvala, 1979). Not all of the sexually immature adult H. nunni en- cysted. In most treatment dishes there were mating and reproducing free-living copepods throughout the entire 23 weeks, along with encysted individuals; this was un- expected, because no free-living forms have been found in the summer (Coull and Grant, 1981, and Fig. 5). Coull and Grant (1981) hypothesized that the free-living pop- ulation either moved to another area, or all members en- cysted. The calanoid copepod Diaptomus sangiiineus produces diapausing and subitaneous eggs sequentially during the same reproductive period, and Hairston and Munns (1984) suggested that it was using a bet-hedging strategy (sensu Stearns, 1976), anticipating that an envi- ronmental catastrophe would not occur or would be less severe than expected. Reproductive success could then be insured in either situation. In harpacticoid and cyclopoid copepods, such a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
