The histopathology and ultrastructure of steatitis affecting common dab Limanda limanda

This study presents a new description, based on histopathological and ultrastructural studies, of a disease affecting the common dab Limanda limanda (L.). The condition can be recognised by the presence of multiple orange or yellow lesions in the pterygophorial region of the fish. The principal histopathological features are necrosis of fat cells, extensive macrophage infiltration leading to the formation of granulomatous structures, and the accumulation of lipopigment by lipid peroxidation. Based on this description, the condition has been diagnosed as steatitis. Although pathology associated with lipid peroxidation is the dominant characteristic of the lesions examined, it is proposed that this process is secondary to necrosis of the adipose tissue. The aetiology is discussed in the light of these observations. In addition, the first record of this condition affecting long rough dab Hippoglossoides platessoides (Fabricius) is made.