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

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

Ciudad Autónoma de Buenos Aires

Congreso; 11th Biennial Meeting; 2015

SETAC Latin America

In the last years, the agricultural expansion has led to the increased use of pesticides,with glyphosateas the most widely used herbicide worldwide.Thisis also true inArgentina, where glyphosate formulations are the most commercialized herbicide.It is known that glyphosate formulations are much more toxic than the activechemical (glyphosate technical grade), and these differences in toxicity can beattributed to the adjuvants. In this context, the aim of the present study wasto evaluate sublethal histological effects ofthe glyphosate formulation RoundupUltramax and technical grade glyphosate on Gosner-stage 36Leptodactyluslatrans tadpoles. Semi-static bioassays were performedusing 96 h of exposure with Roundup Ultramax formulation (Monsanto) (0.37-9.62mga.e./L) and technical grade glyphosate 95.1% (Gleba) (10-1000 mg/L). Acontrol group was included using filtrated and de-chlorinated tap water. Thebioassays were conducted with 4 replicates by concentration in glass chamberswith 500 ml of solution and 5 larvae each. Mortality was registered every 24 h,prior to the media replacement, and dead individuals were removed. At 96 h, allliving tadpoles were euthanized by benzocaine solution, fixed in Bouin´ssolution and preserved in ethanol 70%. Larval body were embedded in paraffin,serially sectionedat 6μm and stained with hematoxylin and eosin.Tentransverse sections,taken every 12 μm,were observedfor each individual under microscopein order to detect anomalies caused by exposure to the herbicide. Heart,digestive tract and liver were observed, and special attention was taken on theliver, due to its known detoxifying activity.The number of livermelanomacrophagic cells (MMc) and of melanomacrophagic centers per liver area,were determined using Image-Pro Plus program. Data were analyzedbyKruskall-Wallis test followed by Dunn´s post hoc test in order to detectdifferences compared to control group.No anomalies were detected either in the heart or in the digestive tract of treated tadpoles compared to control ones.However, livers of tadpoles exposed to Roundup (5.18 mga.e./L) and toglyphosate technical grade (1000 mg/L), presented an increase of MMc(p<0.0001) and of MMc centers (p<0.0001) and then more melanin pigmentation in the liver. These results indicates that MMc, MMc centers and melanin contained in MMc, could be protecting the tissue from some kind of damage induced by Roundup formulation and glyphosate technical grade.