Efeitos do Roundup™ e do Thiodan em adultos de Astyanax bimaculatus (Characidae: Teleostei): Valores de CL50 e morfologia testicular / Effects of Roundup™ and the Thiodan in adults of Astyanax bimaculatus (Characidae: Teleostei): Values of CL50 and testicular morphology

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

22/07/2010

RESUMO

The indiscriminated use of agrochemicals in modern agriculture is unleashing a series of damages to the environment posing serious threats to the survival of important ecosystems. The main objectives of the present study was to determine the LC50-96h and investigate the effects of Roundup™ (Monsanto) and Thiodan (Bayer) in testicular morphology of the fish species Astyanax bimaculatus adult males. For this purpose we selected adult males of this species in homogeneous lots with 4.0 to 6.0cm of standard-length, to determine the LC50 and evaluate the toxicity by morphological and morphometrical studies. Fragments of testes were collected, fixed, embedded in historesin, sectioned and stained for histological analysis. The LC50 of Roundup™ was 14mg.L-1 with confidence interval 9.3 to 22.6 mg.L-1 (P<0.05). The acute toxicity test showed abnormal behaviour such as attempted to escape, erratic swimming and searching for oxygen on the surface at concentration 5.2mg.L-1 immediately after adding the product in aquariums. Histological analysis showed morphological changes when compared to the control group such as the discontinuity or even lack of the mesothelium; tissue disruption characterized by the presence of spermatids in the testicular parenchyma; presence of spermatocytes in the lumen of tubule; presence of erythrocytes outside the capillaries blood (hemorrhage); and vacuoles in intertubular space cells. The morphometric analysis showed a reduction in the measurement of the average nuclei diameter of secondary spermatocytes at the concentration of 1.3mg.L-1; and increase in number of secondary spermatogonia at concentrations 1.3 and 2.6 mg.L-1. The conclusion is that A. bimaculatus adult can be used as bioindicators organisms of aquatic environment and their testes as bioindicator organ. The LC50 of Thiodan was 17.7μg.L-1 with xii confidence interval 11.1 to 29.6 μg.L-1 (P<0.05). In the treated groups it had been observed the behaviour of attempt to escape and 40% mortality at the highest concentration, severe agitation, erratic swimming, and hyperventilation at all concentrations. Histological analysis had shown morphological changes compared to the control group as mesothelium detachment with discontinuity or even lack thereof; degeneration of mesothelium cells; hemorrhage; vacuoles in intertubular space cells; break of cysts, and spermatids located out in the intertubular space; red blood cells within cysts of spermatocytes; spermatocytes in the lumen of the tubule; as well as the presence of oocyte in the tubular compartment. Morphometric analysis indicated a decrease in the secondary spermatocytes cysts diameter at concentrations 1.15 e 2.3 μg.L-1 (P<0.05); increase in the primary spermatocytes nucleus diameter at all concentrations (P<0.05); reduction in the secondary spermatocytes nucleus diameter at lower concentration (P<0.05); increase in the primary spermatogonia nucleus diameter in groups 2.3 and 5.6 μg.L-1 (P<0.05); reduction on the count of primary spermatocytes at concentrations 1.15 and 2.3 μg.L-1 (P<0.05); increase of both spermatogonia cell types at concentration 1.15μg.L-1 and decrease in concentration 5.6μg.L-1 (P<0.05). These findindings indicate that A. bimaculatus adult should not be used as bioindicator organism, because it has low sensibility to this product, but testes can be used as bioindicator organ.

ASSUNTO(S)

peixe astyanax bimaculatus agrotóxicos recursos pesqueiros de aguas interiores fish astyanax bimaculatus pesticides

ACESSO AO ARTIGO

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