Toxidez aguda do zinco em lambaris Astyanax aff. bimaculatus (Linnaeus, 1758)

• Ano de defesa: 2009
• Autor(a) principal: Santos, Daiane Cristina Marques dos
• Orientador(a): Matta, Sérgio Luis Pinto da
• Banca de defesa: Zuanon, Jener Alexandre Sampaio , Ribeiro Filho, Oswaldo Pinto
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Biologia Animal
• Departamento: Biologia e Manejo animal
• País: BR
• Palavras-chave em Português: Metais pesados; Toxicologia; Testículos; Fígado; Brânquias; Zinco
• Palavras-chave em Inglês: Heavy metals; Toxicology; Testis; Liver; Gilss; Zinc
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::CLINICA E CIRURGIA ANIMAL::TOXICOLOGIA ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/2211

The increase of contamination levels in aquatic ecosystems causes morphological, physiological and biochemical alterations in aquatic organisms. In this context, this paper proposes to study the acute effects of different zinc (Zn) concentration levels on gills, liver and testis histology in Astyanax aff. bimaculatus. The experimental design involved seventy-two adult males separated in five treatments and a control group, with 12 replications was performed using 3, 5, 10, 15 e 20 mg/L of water. After an exposure of 96 hours, the animals were euthanized, measured and weighted, and fragments of liver, muscle, bone, gills, and testes were collected. Part of this material was used for standard histological techniques and the remaining tissues were dehydrated and digested for quantification of zinc absorption. During the experiment, all water abiotic parameters (dissolved oxygen, pH, toxic ammonia, electrical conductivity, hardness and temperature) varied within acceptable levels for this species. Lethal zinc concentration (CL) 50-96 hours of acute exposition was characterized as 10 mg/L. Zinc was considered as highly toxic in acute exposure, even at the Brazilian legal concentration, which is 5 mg/L in water to rearing animals. The histopathological changes found on the gills were hyperplasia, lamellar fusion, aneurism, destruction of lamellar epithelium, membrane rupture, and deletion of secondary lamella, and increase on mucus production were more remarkable in treatments exposed to higher zinc concentrations. The gills were an excellent indicator of the environmental contamination for Zn, because they are in direct contact with water, and the greater permeability allows realizing gas exchange with the environment. In the liver, histological alterations were characterized as vascular congestion, reduction of cellular volume, change of the position of the hepatocyte nucleus, necrosis, and disarrangement of cordonal structure, leukocyte infiltrate, and vacuolization, being more severe in treatments exposed to higher concentrations of zinc. The increased concentrations of zinc in water implicate the physiological functions of the liver. The number of hepatocytes may be a compensatory mechanism for the restoration of homeostasis against environmental pollutants. In the gonads, the main alterations were characterized as cyst rupture, delayed development of germ cell line, pyknotic nuclei, cellular conglomerate, detachment of cyst walls and vacuole formation. Zinc affected the reproductive functions of the species under study, being more severe in treatments exposed to higher concentrations of this metal, especially in delayed development of cysts, rising to reduction in the production of sperm and may impair the fertility rate and consequently the maintenance population stocks.