Total leukocyte counts methods in fish, Oreochromis niloticus

Abstract

Haematological investigation is an
important part of disease diagnosis. The techniques
used for mammals are generally applicable for
fishes with slight modification. The presence of
nucleated erythrocytes and thrombocytes in fish
may cause some confusion in the identification of
blood cells, mainly in total leukocytes count. This
work evaluated two different methods (direct and
indirect) of leukocytes counting. Specimens of
tilapia were divided randomly into four groups of 48
fish each. Each group was further randomized into
three replicate experiments of 16 fish per replicate
in 40 L aquarium and maintained for 10 days. Counting of leukocytes in peripheral blood was
determined in six fishes per group at the times: 0,
3, 7 and 10 days. The direct method in Neubauer
chamber showed a large dispersion of data in
regard to the average, the opposite was observed
in indirect method determined in blood smears that
showed more homogeneity among groups. Due to
this factor the indirect method can be considered
more accurate than the direct method for counting
leukocytes in fishes.