Food availability effects on reproductive strategy: the case of Acartia tonsa (Copepoda: Calanoida)

Food availability has been linked to changes in the biochemical composition of zooplankton eggs. However, a number of species are capable of resource storage and are thereby able to use accumulated reserves for reproduction during periods of poor food conditions. Conversely, in species such as Acartia tonsa with limited storage capacities, there can be a strong dependence of egg composition on ambient food conditions. The aim of this study was to determine the effect of food availability on the carbohydrate, protein and fatty acid composition of A. tonsa females and their eggs after being fed with different concentrations of the cryptophyte Rhodomonas baltica. During the experiments, no significant differences in the biochemical composition of females were observed, although egg protein composition was higher in food-limited females. We propose that the production of protein-rich eggs by food-limited copepods is a reproductive strategy for ensuring the survival of offspring during poor feeding conditions. In terms of their relative biochemical makeup, there were no significant differences between both adults and eggs of A. tonsa and their prey R. baltica. However, these biochemical similarities did not influence egg production. Rather, higher biochemical similarities were observed between R. baltica and eggs when females were food limited. These findings suggest that food-limited females may moderate the cost of reproduction by producing eggs without much modification to the substrates they ingest.