DEVELOPMENT OF PSEUDOCALANUS-ELONGATUS (COPEPODA, CALANOIDA) CULTUREDAT DIFFERENT TEMPERATURE AND FOOD CONDITIONS

The pelagic copepod Pseudocalanus elongatus Boeck was bred 3 times fro m nauplius stages I and II to maturity at 5, 10, 15 and 20 degrees C a nd at 4 different rations of autotrophic and heterotrophic food. The r ate of development of the copepods increased with increasing temperatu re and food supply. The shortest generation times (from egg to adult) were 59 d at 5 degrees C and 19 d at 15 degrees C. The generation time nearly doubled when food concentration was very low. At 20 degrees C mortality rates were high and development did not proceed faster than at 15 degrees C. At all food levels the stage duration was generally c onstant (nearly isochronal), but the last 1 or 2 developmental stages took longer. The relationship between development time and temperature is described by Belehradek's functions al different food levels. This relationship predicts a generation time of approximately 45 d during spring bloom conditions in the North Sea and about 30 d during summer due to food limitation. Field estimates from the literature are too sc arce to evaluate the presumption of food limitation during summer cond itions. Some evidence of a low critical food level was found compared to other North Sea copepod species. Together with a fast development r ate at low temperatures, this may explain the numerical dominance of P . elongatus in the North Sea and the northeast Atlantic Ocean.