Total leukocyte counts methods in fish, Oreochromis niloticus

Haematological investigation is animportant part of disease diagnosis. The techniquesused for mammals are generally applicable forfishes with slight modification. The presence ofnucleated erythrocytes and thrombocytes in fishmay cause some confusion in the identification ofblood cells, mainly in total leukocytes count. Thiswork evaluated two different methods (direct andindirect) of leukocytes counting. Specimens oftilapia were divided randomly into four groups of 48fish each. Each group was further randomized intothree replicate experiments of 16 fish per replicatein 40 L aquarium and maintained for 10 days. Counting of leukocytes in peripheral blood wasdetermined in six fishes per group at the times: 0,3, 7 and 10 days. The direct method in Neubauerchamber showed a large dispersion of data inregard to the average, the opposite was observedin indirect method determined in blood smears thatshowed more homogeneity among groups. Due tothis factor the indirect method can be consideredmore accurate than the direct method for countingleukocytes in fishes.O estudo da hematologia é consideradouma importante ferramenta para o processode diagnóstico de doenças. As técnicas usadas emmamíferos são amplamente aplicadas em peixes,no entanto com algumas modificações. A presençade eritrócitos nucleados e trombócitos em peixespode causar dificuldade na identificação das célulassangüíneas, principalmente na contagem deleucócitos totais. A presente pesquisa foi realizadacom o objetivo de avaliar duas metodologias (diretae indireta) de quantificação de leucócitos. Espécimesde tilápia foram divididos ao acaso em quatrogrupos de 48 peixes cada. Cada grupo foi divididoem três réplicas experimentais com 16 animais porréplica em aquários de 40 L e mantidos por 10 dias.A quantificação dos leucócitos foi determinada em6 animais por grupo nos tempos: 0, 3, 7 e 10 dias. Ametodologia direta em câmara de Neubauer apresentougrande oscilação dos dados com relação àmédia, o oposto tendo sido observado na metodologiaindireta realizada em extensões sanguíneas,que apresentou maior homogeneidade entre osgrupos. Devido a este fator a metodologia indiretapode ser considerada mais confiável que a metodologiadireta para quantificação de leucócitos empeixes

Cytogenotoxicity biomarkers in fat snook Centropomus parallelus from Cananéia and São Vicente estuaries, SP, Brazil

The aquatic environment receives many contaminants that can induce damages at the molecular, biochemical, cellular and physiological levels. Centropomus parallelus, an important food resource for local populations, is a predator fish that feeds on small fishes and benthic invertebrates, thus being vulnerable to the bioconcentration and biomagnification processes. This study aimed to evaluate cytogenotoxic responses in erythrocytes from C. parallelus juveniles collected in the Cananéia and São Vicente estuaries, both in winter and in summer. After anesthesia, blood samples were collected by caudal puncture. Blood smears were prepared on glass slides and stained with May-Grünwald-Giemsa dye. Two thousand cells were analyzed per slide (1000x), and nuclear abnormalities (NA) and micronuclei (MN) were scored. The São Vicente sample showed MN and NA frequencies (%/1000 cells) of 0.325 and 3.575, in winter, and of 0.125 and 2.935 in summer respectively; the Cananéia sample showed frequencies of 0.0325 and 0.03, in winter, and of 0.065 and 0.355 in summer, respectively. The rates found in São Vicente were significantly higher than those found in Cananéia, evidencing that the levels of pollution in that estuary were high enough to induce genetic damages