Biomarcadores histológicos para monitoramento da sanidade de duas espécies de peixes neotropicais em área lacustre maranhense, Brasil

Abstract

Fish are susceptible to the action of environmental stressors (chemical, physical and biological) that can have negative effects on this class of vertebrates. In these animals, some organs can be affected, such as the gills and the liver, and histology is an important tool for the evaluation of the impacts caused in these organs. Therefore, the aim of the study was to monitor the health of two species of neotropical fish in a lake area in Maranhão with the use of histological biomarkers. For this, 42 specimens of adult fish were captured, 21 of Hoplerythrinus unitaeniatus and 21 of Cichlasoma bimaculatum, which were transported alive in source water to the laboratory for euthanasia, removal of gill and liver fragments and subsequent histological analysis in the Multiuser Laboratory. Graduate Program (LAMP) at UEMA. Right after, the organ fragments were submitted to histological processing steps and, finally, stained with hematoxylin - eosin (HE). Branchial and hepatic histological alterations were evaluated in a semi-quantitative mode, by calculating the histological alteration index (AHI), based on the severity of each lesion, as follows: (i) stage I alterations - they do not compromise organ function; (ii) stage II - more severe injuries that impair the normal functioning of the organs; and, (iii) stage III - very severe and irreversible injuries. The results were presented together for the two species in which it was found that the most frequent gill alterations were complete (85.71 %) and incomplete (85.71 %) fusion of several lamellae, lifting of the epithelium (80.95% ), blood vessel congestion (76.19 %), lamellar disorganization (76.19 %) and lamellar epithelium hyperplasia (76.19 %), all stage I. Stage II alterations (hemorrhage and rupture of the lamellar epithelium , mucus cell hyperplasia and hypertrophy, chlorine cell hyperplasia and hypertrophy, complete fusion of all lamellae, uncontrolled proliferative tissue thickening, pillar cell disruption) and III (cell necrosis and degeneration and, lamellar aneurysm) were also observed, but less frequently. The most frequent hepatic alterations were vacuolization (90.47 %), melanomacrophage center (78.57 %), cell contour deformation (66.67 %) and nucleus in the cell periphery (52.38 %), stage alterations I and hyperemia (45.24 %) and cytoplasmic degeneration (40.48 %), stage II alterations. In a lower percentage, necrosis (9.52 %), stage III alteration was also observed. It is concluded that the two species of neotropical fish evaluated had their sanity compromised, which may be the result of interactions with stressors of different natures, including irreversible injuries that were possibly compromising the functioning of the evaluated organs.