Change in metabolism and nitrogen isotopic composition of amino acids through egg production of the calanoid copepod Acartia steueri

Abstract

Organisms have complex metabolic networks, and their fluxes could be sensitive depending on various physiological and environmental conditions. As one of these factors, reproduction (e.g., egg production) is a common and essential process to create new individuals. However, little is known about the effect of reproduction in metabolic fluxes of organisms. In this study, we cultured the calanoid copepod Acartia steueri, and measured the stable nitrogen isotopic composition (δ¹⁵N) of amino acids in adult males and females and their eggs in order to demonstrate the effect of reproduction in amino acid metabolic fluxes of this species. The δ¹⁵N values of glutamic acid and phenylalanine and the estimated trophic position were 6.3‰, -2.6‰ and 1.73 for male adults; 7.0‰, -2.6‰ and 1.78 for female adults; and 7.3‰, -2.3‰ and 1.82 for eggs, respectively. These results demonstrate no substantial change in the isotopic signature of amino acids among the examined samples, implying that the balance in the amino acid metabolism between assimilation (i.e., absorbing input and biomass construction) and dissimilation (i.e., amino acid deamination) may not change with egg production in this copepod.