First hematologic and serum biochemistry record of black drum Pogonias cromis (Linnaeus, 1766) in a Neotropical hypersaline Lagoon

This study is a pioneer in describing the first hematological parameters and serum biochemistry record of black drum, Pogonias cromis (Linnaeus, 1766) in a Neotropical hypersaline Lagoon.  We collected a total of 32 individuals of P. cromis, with a total length (TL) ranging between 160 and 710mm, and total weight (TW) ranging between 24 and 39.8g. Blood samples were taken and the presence of granulocytes, lymphocytes, and monocytes indicated that P. cromis had developed an immune system. Increased levels of thrombocytes with decreased levels of the lymphocytes, may be due to an increased frequency of lymphocytes among the leukocytes, which is also seen in the trend of higher levels of lymphocytes associated with an increased leukocyte count. The mean count of red blood cells (1.97 ± 0.07 106 mm³) was relatively low, whilst the hematocrit (37.4 ± 0.9%) and mean corpuscular volume (195.8 ± 1.9 fL) were higher when compared with those of other species of marine fish. High total plasma protein values (6.3 ± 0.1 g/dL) suggest an osmotic imbalance, which could be due to the stress of the environment. The relatively high values of ALT and AST (90 ± 0.7 and 229 ± 4.5 U/L, respectively) and urea (24.7 ± 0.6 mg/dL), and the low levels of creatinine (0.10 ± 0.02 mg/dL), suggest possible liver dysfunction in this species in this ecosystem. This work indicates the use of hematological analysis of P. cromis could be used as an effective biomarker for environmental risk assessments.