Effects of glyphosate herbicide on Cnesterodon decemmaculatus

R.J. MENÉNDEZ-HELMAN; G.V. FERREYROA; M. DOS SANTOS AFONSO; A. SALIBIÁN

Seville, Spain

Congreso; SETAC Europe 20th Annual Meeting; 2010

SETAC Europe

Abstract: Glyphosate, N-phosphonomethylglycine, PMG, is the active component of non-selective, postemergent and broad spectrum commercial herbicides widely used in agriculture. PMG could cause environmental problems with a negative impact on wildlife, particularly in an aquatic environment where chemicals may persist for a long time. The toxicity of glyphosate to juvenile specimens of Cnesterodon decemmaculatus (mean body weight, 0.14 g; mean total length 2.7 cm) was evaluated. This endemic teleost is widely distributed in Neotropical America. The specimens were captured in an unpolluted watercourse of the Humid Pampa Region, and acclimated at constant temperature (22-24 ºC) and photoperiod (12L:12D). Semi-static bioassays were conducted to determine the 96h-LC50 under concentrations range of 1-140 mg.L-1; USEPA moderately hard water as assay medium and the same conditions of the acclimation.No mortality was recorded at 1 mg PMG.L-1, this concentration is close to that found environmentally in farming areas of the Buenos Aires Province. On the other hand, the highest concentration (140 mg.L-1) provoked almost 100% mortality after 48 h of exposure. The analytical determination of the herbicide in the test media showed that PMG concentration remained virtually unchanged during the bioassays.The effect of the herbicide on two toxicity biomarkers was also investigated. Homogenates of anterior, middle and posterior parts of the fish were prepared and the acetylcholinesterase (AChE) and catalase activities in each one of those fractions was determined; PMG significantly affected the activity of AChE at concentrations lower than the LC50. In addition, the content of glycogen and total protein in the homogenates were also measured.