Effects of Glyphosate and Roundup® Ultramax formulation on liver histology of Leptodactylus latrans tadpoles (Amphibia: Anura)

BACH N.; LOPEZ, G.C.; NATALE G.S.; RONCO A.E.; SOMOZA M.G.

Buenos Aires

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

Society of Environmental Toxicology and Chemistry (SETAC)

In the last years, the agricultural expansionhas led to the increased use of pesticides, with glyphosate as the most widelyused herbicide worldwide. This is also true in Argentina, where glyphosateformulations are the most commercialized herbicide. It is known that glyphosateformulations are much more toxic than the active chemical (glyphosate technicalgrade), and these differences in toxicity can be attributed to the adjuvants.In this context, the aim of the present study was to evaluate sublethal histologicaleffects of the glyphosate formulation Roundup Ultramax and technical gradeglyphosate on Gosner-stage 36 Leptodactylus latrans tadpoles. Semi-staticbioassays were performed using 96 h of exposure with Roundup Ultramaxformulation (Monsanto) (0.37-9.62 mg a.e./L) and technical grade glyphosate95.1% (Gleba) (10-1000 mg/L). A control group was included using filtrated andde-chlorinated tap water. The bioassays were conducted with 4 replicates byconcentration in glass chambers with 500 ml of solution and 5 larvae each.Mortality was registered every 24 h, prior to the media replacement, and deadindividuals were removed. At 96 h, all living tadpoles were euthanized bybenzocaine solution, fixed in Bouin´s solution and preserved in ethanol 70%.Larval body were embedded in paraffin, serially sectionedat 6μm and stainedwith hematoxylin and eosin.Tentransverse sections, taken every 12 μm,wereobservedfor each individual under microscope in order to detect anomaliescaused by exposure to the herbicide. Heart, digestive tract and liver wereobserved, and special attention was taken on the liver, due to its knowndetoxifying activity. The number of liver melanomacrophagic cells (MMc) and ofmelanomacrophagic centers per liver area, were determined using Image-Pro Plusprogram. Data were analyzed by Kruskall-Wallis test followed by Dunn´s post hoctest in order to detect differences compared to control group. No anomalieswere detected either in the heart or in the digestive tract of treated tadpolescompared to control ones. However, livers of tadpoles exposed to Roundup (5.18mg a.e./L) and to glyphosate technical grade (1000 mg/L), presented an increaseof MMc (p< 0.0001) and of MMc centers (p< 0.0001) and then more melaninpigmentation in the liver. These results indicates that MMc, MMc centers andmelanin contained in MMc, could be protecting the tissue from some kind ofdamage induced by Roundup formulation and glyphosate technical grade.