OFFSPRING SIZE IN DAPHNIA - DOES IT PAY TO BE OVERWEIGHT

Variation in offspring size and number has been described for a wide r ange of organisms. In this study I investigated the relationship betwe en resource level of the mother and size of her offspring in the clado ceran Daphnia magna, in order to assess whether offspring produced at different food levels are optimal in size for these food levels. Optim al offspring size was defined as the size of offspring that yields the highest parental fitness (i.e. offspring of optimal size have the hig hest juvenile fitness per unit maternal effort invested in them). I ob served that especially at the higher food levels, daphnids produced of fspring that are larger than the computed optimal offspring size at th ese food levels. I interpret this as a mechanism to avoid starvation o f neonates in the case of suddenly deteriorating food conditions.