Effects of formalin on haematological and blood chemistry in olive flounder,Paralichthys olivaceus(Temminck et Schlegel)

Erythrocytes of olive flounder, Paralichthys olivaceus (Temminck et Schlegel), were treated with serial concentrations of formalin (37% formaldehyde) to investigate in vitro haemolysis and methaemoglobin formation. In addition, the short-term toxicity of formalin concentrations of 0, 100, 212 and 300 ppm was also studied by clinical tests in which fish were subjected to 3-h bath exposure. There was no haemolysis of fish erythrocytes exposed to formalin concentrations ranging from 31.3 to 2000 ppm. Methaemoglobin formation, however, was induced at concentrations greater than 500 ppm. Red blood cell count, haemoglobin, haematocrit, mean corpuscular haemoglobin concentration and percentage of immature erythrocytes were also markedly elevated in all formalin-exposed groups (P<0.05). Formalin exposure also caused significant increases in alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, potassium, chloride, magnesium and inorganic phosphorus (P<0.05). However, total protein decreased significantly in the formalin-exposed groups (P<0.05). No significant differences in white blood cell count, mean corpuscular volume, mean corpuscular haemoglobin, albumin, glucose, total cholesterol, high-density lipoprotein cholesterol, free cholesterol, alanine aminotransferase, calcium, creatinine and total bilirubin were observed in the formalin-exposed groups (P>0.05).