Evaluacion de los efectos del herbicida glifosato en el pez Prochilodus lineatus a traves del test de aberracion cromosomica.
Argentina produces and exports raw materials and agricultural inputs. Its' farming system, like most of the countries in the world, has undergone remarkable process of intensification in order to increase the hectare's productivity to satisfy nutritional needs.
This change turned crops more sensitive to disease causing organisms, so pesticides are used to control them. Waste and chemical substances resulting from this practice are dumped to watersheds and contaminating it, causing a serious impact on the environment (15,19).
Fishes are used as environmental toxicity bioindicators, because of their sensitiveness and usefulness in the evaluation of ecological risk by chemical contaminants (4,17,26). Currently, glyphosate is one of the pesti cides which use has been widespread. Glyphosate (N-phosphonomethyl glycine) is a systemic herbicide, that affects all the organs of a plant, is non-selective and of broad spectrum. It is applied to the foliage at the stage of post-emergence. According to the categorization of the USEPA (United States Environmental Protection Agency) it's a class II (moderately toxic) with acid character substance (2,25,28).
Many authors evaluated mutagenic and genotoxic effects of glyphosate in its Roundup[R] commercial formulation through micronuclei and comet trials in aquatics organisms (6,8,13,14,16). Nevertheless, there are sparse data about chromosomal aberrations induced by being in contact with this herbicide.
The aim of this study was to evaluate the mutagenicity of herbicide glyphosate (Roundup Full II[R]) by testing chromosomal aberrations in fish (Prochilodus lineatus).
MATERIAL AND METHODS
The methodological procedures used in this study were endorsed by the Committee of Ethics and Biosecurity of the Faculty of Veterinary Science, Northeast National University (UNNE), protocol 0033.
Animals. Eight young and healthy specimens of Prochilodus lineatus (Order Characiformes, Family Prochilodontidae), from the aquaculture center of the Institute of Ichthyology from the Northeast (INICNE) of the Veterinary Sciences Faculty, UNNE. They have a period of a week to get accustomed, being fed with an appropriate ration every 48 h, before the bioassay had started. Fish were kept in 300 liters tanks, with continuously aerated water, temperature around 20[degrees]C, ph 7.0 and a photoperiod of 12 h light.
Experimental design. After the adaptation period fishes were divided into two groups (treated and control), each one containing 4 animals. The animals were kept in aquariums of 7 liters, in a density of 1 g of fish by every liter of water. Control aquariums were loaded only with artesian water, while the treated tanks were filled with a solution of glyphosate in a concentration of 0,1 ug/l of water. The treated group received every 7 days a dose of herbicide with the renewal of the water and the water was also renewed in the control group. Food was provided every 48 h. Fish were kept in the aquariums in a chronic toxicity test for a period of 70 days.
Preparations of chromosomes. After the period of experimentation the fishes-were sacrificed with an overdose of the anesthetic drug Tricaine Methanesulfonato MS-222 (Finquel[R]) dissolved in water. The somatic chromosomes were prepared according to the conventional technique for the of mitotic's chromosomas (12), both in control and treated groups. A total of 50 metaphases per individual were analyzed.
Statistical analysis. The differences in the frequencies of chromosomal aberrations were determined by comparison of the treated group with the control one, through the U Mann-Whitney non-parametric test. The statistical program SPSS was used for the analysis.
Diploid number in P. lineatus is 54 chromosomes (metasubmetacentrics), fundamental number 108. There are not chromosomal differences between sexes.
We analyzed a total of 339 metaphases not being possible to find the 50 established in two specimens, belonging one to the control group and the other from the treated one. A total of 168 metaphases in control group were counted, of which 124 were normal and 44 had chromosomal aberrations (ACs). Whereas in the treated group, 171 metaphases were analyzed, identifying 30 normal and 141 ACs. These data showed an increase of the CAs in the treated group. The abnormalities found were breaks, stickiness, endomitosis, gaps, fragments and pulverization (Figure 1). Differences in aberration's frequencies between the treated and the controls groups were statiscally significant (p<0.05, Figure 2).
In previous studies, it was determined that the species Prochilodus lineatus presents 54 chromosomes (meta-sub-metacentrics), equal to 108 fundamental number, not observing sex chromosomal heteromorfism (5). The conservative nature of the karyotype structure is characteristically observed in all species of the genus Prochilodus (P. vimboides, P. lineatus, P. affinis, P. marggravii, P. cearensis, P. argenteus and P. nigricans), exhibiting a karyotype consisting of 54 bibraquials chromosomes (20,21).
The presence of 0-2 microchromosomes Bs was also observed, which varied in number not only between but also in the same karyotypic snap. The occurrence of supernumerary chromosomes or Bs in P. lineatus from different sampling points of the Parana River (Brazil) reached a number of 0-7 in certain populations (3,5,7,18,20,21).
There are scarce research considering pesticides in teleosts, including the chromosome aberration test. Being this one a valuable genetic biomarker of environmental pollution. Chromosomal aberrations found in specimens of P. lineatus exposed to glyphosate (Roundup Full II) were gaps, breaks, stickiness, endomitosis y pulverization. Similar CAs were observed in laboratory fish bioassays where other pesticides were used.
An experience carried out on specimens of Channa punctatus (23) subjected to a dose of 0.01 ppm of Dichlorvos (o,o-Dimethyl-2, 2-dichlorovinyl phosphate) in an acute assay, exhibited several alterations at chromosomal level, identified as gaps, breaks, fragments and stickiness. In Etroplus suratensis (10) exposed for 96 h to the action of methyl parathion in concentrations of 0.05, 0.1, and 0.2 ppm; and phosphamidon at a dose of 0.5, 1.0 and 2.0 ppm, had shown significant increase of different types of aberrations (gaps and fragmentations).
Intramuscular injections with azadirachtin (biological metabolite of the plant Azadirachta indica, which features insecticides) in Oreochromis mossambicus caused significant injuries at cytogenetic level, being the chromosomal breaks a frequent structural anomaly (9).
Experiences with individuals of Channa punctatus 11 subjected to the action of pentachlorophenol and 2,4-dichlorophenoxyacetic acid during 48, 72, and 96 hours revealed the occurrence of structural chromosomal aberration (breaks, stickiness and pulverization chromosomal). Specimens of Oreochromis niloticus (Nile tilapia) exposed to the action of the herbicide Butataf (N-Butoxymethyl-2-chloro-2,6-diethylacetanilide) (22) during a month at concentrations of 0.02, 0.002, 0.004 and 0.008 ppm, showed a notable increase of injuries at chromosomal level, such as fragmentation, breaks, stickiness and deletion.
Active substances of pesticides (27) induce lesions in the DNA (aberrations) and the type of problem found is subject to the nature of the pesticide concentration and the period of exposure. Such adverse effects could lead through different mechanisms, damage genetic material (1,24).
In conclusion, the results obtained in the present study showed that chronic exposure to the herbicide glyphosate (Roundup Full II), even at sublethal doses, can induce chromosomal damage in Prochilodus lineatus. These specimens are an excellent natural model for the detection of mutagenic agrochemicals effects.
Acknowledgements. Authors would like to express their sincere thanks to the staff of the Instituto de Ictiologia del Nordeste (INICNE) and the financial support of the Secretaria de Ciencia y Tecnica de la UNNE and the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET).
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Caramello, C.S. ; Jorge, M.J. ; Jorge, N.L. ; Jorge, L.C. 
 Facultad de Ciencias Veterinarias, Univ. Nac. Nordeste (UNNE), Sargento Cabral 2139, Corrientes, Argentina, Tel: 0379-4425753, int:152.  Facultad de Ciencias Exactas y Nat. y Agrim., UNNE. E-mail: firstname.lastname@example.org
Caption: Figure 1. Photomicrograph slide of kidney cells showing (a) normal metaphase without chromosome B; (b) normals metaphases with chromosome B; (c) chromosome stickiness; (d) endomitosis; (e) gaps; (f) breaks; (g) chromosome fragments, and (h) pulverization of P. lineatus.
Caption: Figure 2. Box plot showing number of chromosomal aberrations on each group, control and treated, in P. lineatus at each period of exposure (70 days). with significant differences between groups (p<0.05)
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|Author:||Caramello, C.S.; Jorge, M.J.; Jorge, N.L.; Jorge, L.C.|
|Date:||Jul 1, 2017|
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