Predatorinducerad fekunditet hos Daphnia pulex vid simulerade årstidsbundna temperaturvariationer
Female growth, number of eggs and egg growth of Daphnia pulex were studied at four temperatures, 12, 16, 18 and 20°C. I hypothesized that female growth and number of eggs would be lower and the size of the eggs larger in the presence of a predator (kairomones) than in its absence. This effect was expected to be more evident at lower temperatures. I could not find any effect of kairomones on female growth, number of eggs or egg size, although there was a weak tendency for an effect on number of eggs. There was, however, an effect of temperature, regardless of predator treatment (i. e. presence vs absence of kairomones), on number of eggs, where females produced fewer numbers of eggs with increasing temperature. The effect temperature on the number of eggs was not anticipated. Two of the temperatures, 12 and 18°C, were carried out in darkness due to malfunctioning equipment. In addition, for some unknown reason, a high ratio between the number of ephippia and eggs occurred at at16 and 18°C, regardless of predator treatment. These complicating factors (darkness and ephippia) can have had a negative effect on detecting a response by Daphnia to kairomones.