Determination of biogenic amines in the water flea, Daphnia magna (Cladocera, Crustacea) and their diurnal variations using ion-pair reversed phase hplc with electrochemical detection

Abstract

1. 1. Diurnal variations and basic whole tissue contents of biogenic amines (BA) and some metabolites; 3,4-dihydroxyphenylalanine ( l-dopa), dopamine (DA), noradrenaline (NA), adrenaline (ADR), tyramine (TYR), epinine (EPI), 3-methoxytyramine (3-MT), 3,4-dihydroxyphenylacetic acid (DOPAC), l-tryptophan (TRP), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), have been determined in the water flea, Daphnia magna, using ion-pair reversed phase HPLC with electrochemical detection. 2. 2. In water fleas sampled at 19:00 (offset and onset of light, 21:00 and 09:00, respectively), the amounts of BAs were: TRP 32.80; TYR 7.65; l-DOPA 3.86; DA 3.84; NA 0.60; DOPAC 0.52; ADR 0.08; 3-MT 0.09; 5-HTP 0.05; 5-HT 0.08; 5-HIAA 0.10 and EPI 0.01 ng/mg protein. 3. 3. Over a 24-hr period (light on from 09:00 to 21:00) the catechols l-dopa, DA and DOPAC peaked at 08:00. These peaks were also found in water fleas exposed to continuous light, but not in water fleas exposed to continuous darkness. The l-DOPA and DOPAC peaks were higher in continuous light. 4. 4. In continuous darkness, DOPAC showed a bimodal pattern with peaks at 15:00 and 08:00. The lowest concentrations of catechols were recorded between 15:00 and 21:00. 5. 5. Therefore, the concentrations given above are considered to represent basic levels of catechols. No BAs other than l-DOPA, DA and DOPAC were found to exhibit diurnal variations. 6. 6. The range of BAs in crustaceans with a possible role as neurotransmitters or neuromodulators and metabolites or precursors to these can thus be extended to include A, EPI, 3-MT, DOPAC, TRP, 5-HTP and 5-HIAA.