Effects of starvation on kidney melano-macrophage centre in olive flounder, Paralichthys olivaceus (Temminck and Schlegel)

We investigated the influence of nutritional conditions on histological changes in melano‐macrophage (MM) accumulation in the kidney caused by long‐term starvation. These data were used to determine nutritional indices for olive flounder, Paralichthys olivaceus (Temminck and Schlegel). Experimental groups were established: control, fed and starved. All fish were fed daily with commercial feed at 1–3% of their total body weight for 2 weeks before the start of the experiment (initial control). The control group received feed at 1–3% of their total body weight and the fed group received feed ad libitum, while the starved group fasted throughout the experiment. Ten fish were removed from the initial control at the start of the experiment and each of the three groups every 4 weeks during the 12 weeks of the experiment to examine to investigate kidney MM accumulation. Kidney MMs with dark brown pigment were randomly distributed in the kidneys of starved fish, increasing rapidly after week 4, while deposition levels remained low throughout the experiment in the control and fed groups. These results suggest that catabolic tissue breakdown is a major factor contributing to the formation of pigments within MMs. These results suggest that the degree of MMs deposition in the kidney can be used as alternative indicators to identify starvation in wild and cultured olive flounder.