Winter quiescence and spring awakening of the Eastern oyster Crassostrea virginica at its northernmost distribution limit

摘要: To test the hypothesis that oysters, Crassostrea virginica, from northernmost part of species range in Gulf St. Lawrence (48°N) open their valves at lower temperatures than those reported for more southern Hall element sensors were used to monitor gaping behaviour. These observations made a flow-through system and temperature, salinity relative fluorescence unfiltered seawater monitored. Photoperiod was controlled (15 h dark:9 h light) light levels measured but not closely controlled. Gaping behaviour followed February June 2010 (113 days) April May 2011 (34 days) classified into three successive phases: quiescent, awakening active. Although either closed or slightly during quiescent phase (maximum gape angle = 0.49°, SE = 0.04), they abruptly opened maximum angles about 5.88° (SE = 0.29) phase. Moreover, there noticeable synchrony amongst individuals, since approximately one-half monitored population awoke within 6.6-h period both study years. Correlative analyses identified temperature as factor influencing valve movement, oysters awakened when 0.2–4.0 °C (mean = 2.2, SE = 0.2). Oysters exerted maximal angle soon reached 2.8–6.6 °C (mean = 4.8, During active phase, remained 68.6 % (2010) 79.7 % (2011) time. An unexpected result observation diurnal rhythm openness whereby greatest near end afternoon least early morning.