In freshwater environments, one of the challenges aquatic grazers face
are periods of suboptimal food quantity and quality. In a life table
experiment, the effect of food quantity (a gradient of algae
concentration) and quality (a diet of cyanobacteria) on the life history
and resource allocation strategy in Daphnia magna was tested.
Growth-related traits were similarly affected by both low food quantity
and quality, and the reproductive strategies differed. The per-clutch
investment (clutch volume) did not differ between Daphnia fed with
cyanobacteria and underfed mothers, but resources were differently
allocated; underfed mothers increased their per-offspring investment by
producing fewer, but larger eggs, whereas cyanobacteria-fed mothers
invested in a greater number of eggs of smaller size. I argue that both
strategies of resource allocation (number vs. size of eggs) may be
adaptive under the given food regime. The cyanobacteria diet-driven
fitness losses are comparable to losses caused by low food quantity.