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Vol. 51 No. 7, 2012
Effects of Sublethal and Lethal Copper Concentrations on the Gill Epithelium Ultrastructure of Nile Tilapia, Oreochromis niloticus
Sandra Mariza Monteiro1,*, Elsa Oliveira2, António Fontaínhas-Fernandes1, and Mário Sousa2,3
1Department
of Biology and Environment and Center for Research and Technology for
Agro-Environmental and Biological Sciences, University of
Trás-os-Montes and Alto Douro, Apartado 1013, Vila Real 5001-801,
Portugal
2Lab Cell Biology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto 4099-003, Portugal
3Center for Reproductive Genetics Alberto Barros, Porto 4100-009, Portugal
Sandra Mariza Monteiro, Elsa Oliveira, António Fontaínhas-Fernandes, and Mário Sousa (2012) Histopathology
is currently being used as a screening method to detect copper toxicity
in fish. However, a knowledge gap exists regarding copper’s
effects on the gill epithelial ultrastructure. To fill in this
gap, Nile tilapia Oreochromis niloticus
were acutely exposed to sublethal and lethal waterborne copper
concentrations. Results showed that in the basal region of gill
lamellae, a sublethal concentration caused edema, stretching of pillar
cells (PLCs), and the disappearance of pericytes (PCTs), whereas in the
apical region PLCs remained intact, and PCTs and pavement cells (PVCs)
were activated. In the filament epithelium, PVCs showed
structural signs of high functional activity, while mitochondrion-rich
and mucous cells were degenerated. In the deep filament region,
there were edema, loss of neuroepithelial cells, proliferation of
undifferentiated cells (UDCs), and transformation of leukocyte-like
cells into macrophages. Acclimation was characterized by
vasodilatation of the entire lamellar axis and a decrease in the
filament epithelial thickness. The protruding lamellae showed PCT
proliferation, whereas the superficial filament epithelium became
denser due to UDC attachment. All fish exposed to the lethal dose
died within 24 h. Gills showed vasodilatation and edema that had
lifted the PVCs, and necrosis was evident. In conclusion, our
findings contribute to clarification of gill epithelial cell dynamics,
and also revealed that apical and basal regions of the lamellae showed
different responses, with the apical region exhibiting higher
resistance to the toxic actions of copper. Also, superficial and
deep regions of the filament epithelium showed dissimilar responses to
copper, with the deep epithelium playing important roles in
regeneration and protection.
Key words: Teleostei, Branchial epithelium, Ultrastructure, Copper, Acute toxicity.
*Correspondence: Tel: 351-259-350108. Fax: 351-259-350266. E-mail:smonteir@utad.pt
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