Time-dependent hematological responses of Nile tilapia Oreochromis niloticus exposed to an estuarine contaminated water

Aline Raquel Gomes Guerra,Fábio Cop Ferreira,José Reinaldo Oliveira Conceição,Olivia Menossi,Rafael Mendonça Duarte,Ursulla Pereira Souza

doi:10.33448/rsd-v10i6.15715

Abstract

We aimed to study hematological responses of Oreochromis niloticus experimentally exposed to the contaminated water of the Santos-São Vicente Estuary, testing hypotheses that exposure time to estuarine water promotes deleterious effects on hematological parameters and evaluating the use of erythrocytes and leukocytes alterations as environmental biomarkers. Estuarine water was collected from Largo da Pompeba. For the biological assay, 28 juveniles of O. niloticus (red strain) of both genders were randomly selected from commercial pisciculture. For the biological assay, 28 juveniles of O. niloticus of both sexes were randomly selected from commercial fish farms. The juveniles were kept in estuarine water for 72 and 120 hours and, after exposure, blood was collected by puncture of the caudal vein to determine total erythrocytes, hemoglobin concentration, hematocrit, hematimetric indices and total leukocytes, as lymphocyte, neutrophils, monocytes, eosinophils, and basophils were quantified by blood extensions. To test exposure overtime on hematological variables, we performed a two-factor Multivariate Analysis of Variance. Exposure for 72 hours resulted in immunosuppression as seen by the reduced counts of neutrophils, monocytes, and lymphocytes in the bloodstream, whereas after 120 hours the immune system was stimulated with the increase of all leukocyte cell types. Exposure to estuarine water resulted in marked changes in the leukocyte count of O. niloticus, demonstrating that alterations in white blood cells might be more sensitive biomarkers than red blood parameters.

Highlights

In aquatic ecosystems the water quality is strongly linked to fish health and, to the whole environment.Changes in physical and chemical properties of water, either due to natural events or to anthropogenic actions, might act as a stressor to aquatic organisms and disrupt animal homeostasis
During the first 72h, significant reductions of about 55%, 38%, and 35% in monocyte, neutrophil, and total leukocyte counts, respectively, were seen in fish exposed to estuarine water, compared to the control group
We demonstrated that the exposure time exerted a differential effect on hematological response of white series in O. niloticus exposed to the contaminated water of the Santos-São Vicente Estuary

Summary

Introduction

Changes in physical and chemical properties of water, either due to natural events or to anthropogenic actions, might act as a stressor to aquatic organisms and disrupt animal homeostasis These systemic disturbances might promote a series of physiological responses (Tort, 2011) that in turn can be used as biomarkers (van der Oost, Beyer, & Vermeulen, 2003). & Cossu-Leguile, 2003; Hamza-Chaffai, 2014) In this context, alterations in hematological parameters have been seen in several fish species exposed to a wide range of pollutants and were demonstrated to be sensitive biomarkers for environmental monitoring (Javed & Usmani, 2014; Authman, Zaki, Khallaf, & Abbas, 2015; Naqvi, Shaib, & Ali, 2016; Yaghoobi, Safahieh, Ronagh, Movahedinia, & Mousavi, 2017). Once blood parameters rapidly respond to xenobiotic exposure (Alwan et al 2009), even in reduced concentrations

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