Effect of diet on levels of amino acids during embryonic and naupliar development of the copepod Calanus helgolandicus

Abstract

The contents of free amino acid (FAA) and total amino acid (TAA) pools were determined in the eggs, embryos and N1 and N2 nauplii generated by Calanus helgolandicus females fed either the diatom Phaeodactylum tricornutum or the dinoflagellate Prorocentrum minimum for 3 and 10 d. With both diets, egg production rates increased by a factor of 5 to 10, and free amino acid (FAA) and total amino acid (TAA) contents were double those measured in eggs spawned by wild females. Higher levels were measured for almost all amino acids, except methionine, taurine, glutamine, glutamic acid, aspartic acid and ornithine. When embryos developed to live nauplii, 50 to 72% of the initial concentration of the FAA content was used. There was no preferential utilisation of essential over non-essential amino acids. The TAA pool also varied with development. The mean FAA:TAA ratio remained between 11 and 19. With the Prorocentrum minimum diet, hatching success remained constantly >85%, whereas it declined to 0% at the end of the 10 d incubation period with Phaeodactylum tricornutum. After 10 d of feeding on this alga, the FAA content of developing embryos increased significantly, indicating liberation of amino acids due to proteolysis. None of these embryos developed to hatching. Inhibition of hatching success related to the ingestion of P. tricornutum was not due to a lack of any amino acid. The results indicate that the chemical composition of freshly spawned copepod eggs is sensitive to the maternal diet.