Changes in the plasma free amino acid profile of the Norway lobster Nephrops norvegicus at different stages of infection by a parasitic dinoflagellate (genus Hematodinium)

Abstract

The haemolymph free amino acid (FAA) composition of Norway lobsters Nephrops norvegicus from the Clyde estuary, Scotland, UK, at different stages of infection by the parasitic dinoflagellate Hematodinium sp. was determined by reverse phase high performance liquid chromatography (HPLC). In uninfected lobsters the total detected haemolymph FAA concentration was 3.79 μmol ml-1. Collectively, glycine, histidine/glutamine, alanine, serine, taurine and asparagine constituted 80 % of the total. The concentrations of several FAAs, notably serine, were reduced in early infections (Stage 1), while at later stages (2-4) several FAAs were increased in concentration. The most significant change was in taurine, which had increased 13-fold (from 0.22 to 2.56 μmol ml-1) in the final infection stage, when its relative contribution to the total FAA was 41.6%. Possible causes of these changes in the lobster haemolymph FAAs are the breakdown of host tissues including the hepatopancreas and muscle, haemocyte lysis, a host stress response and release of FAAs from the parasite cells. Results indicate that the taurine:serine ratio in the haemolymph provides a sensitive diagnostic measure of patent Hematodinium infections. Implications of these FAA alterations for Hematodinium-infected IV. norvegicus are discussed.