Homeostasis in the essential amino acid composition of the marine copepod Euterpina acutifrons

The essential amino acid composition (EAA) of females and eggs of Euterpina acutifrons and their food was analyzed on copepods fed with different micr oalgae and collected from the field. There were not significant differences in the EAA of females, but the EAA of eggs varied according to food source . As predicted by homeostasis theory, a higher reproductive success was obs erved as the EAA of females and food became more similar. This chemical hom eostasis explains the selective retention of amino acids observed in copepo ds, tells why conversion efficiencies of ingested nitrogen may vary accordi ng to the food source, and shows the importance of food quality on reproduc tive success in copepods.