Ultramax formulation on liver histology of Leptodactylus latrans tadpoles (Amphibia: Anura).

NADIA C. BACH; GABRIELA C. LÓPEZ; GUILLERMO S. NATALE; ALICIA RONCO; GUSTAVO M. SOMOZA

Buenos Aires

Congreso; SETAC Latin America 11th Biennial Meeting.; 2015

SETAC LA

In the last years, the agricultural expansion has led to the increased use ofpesticides, with glyphosate as the most widely used herbicide worldwide. Thisis also true in Argentina, where glyphosate formulations are the mostcommercialized herbicide. It is known that glyphosate formulations are muchmore toxic than the active chemical (glyphosate technical grade), and thesedifferences in toxicity can be attributed to the adjuvants. In this context, the aimof the present study was to evaluate sublethal histological effects of theglyphosate formulation Roundup Ultramax and technical grade glyphosate onGosner-stage 36 Leptodactylus latrans tadpoles. Semi-static bioassays wereperformed using 96 h of exposure with Roundup Ultramax formulation(Monsanto) (0.37-9.62 mg a.e./L) and technical grade glyphosate 95.1%(Gleba) (10-1000 mg/L). A control group was included using filtrated and dechlorinatedtap 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 sectioned at 6 μm and stainedwith hematoxylin and eosin. Ten transverse sections, taken every 12 μm, wereobserved for 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) andof melanomacrophagic centers per liver area, were determined using Image-ProPlus program. Data were analyzed by Kruskall-Wallis test followed by Dunn´spost hoc test in order to detect differences compared to control group. Noanomalies were detected either in the heart or in the digestive tract of treatedtadpoles compared to control ones. However, livers of tadpoles exposed toRoundup (5.18 mg a.e./L) and to glyphosate technical grade (1000 mg/L),presented an increase of MMc (p< 0.0001) and of MMc centers (p< 0.0001) andthen more melanin pigmentation in the liver. These results indicates that MMc,MMc centers and melanin contained in MMc, could be protecting the tissuefrom some kind of damage induced by Roundup formulation and glyphosate