The giant toad (Rhinella marina) as a biomonitor of different polluted scenarios in Mexico Chapter uri icon


  • The giant toad (Rhinella marina) is an anuran amphibian, omnivorous and opportunistic. Its life cycle, as well as its somatic and hepatosomatic index, voracious appetite and highly permeable skin make it a susceptible species to the bioaccumulation of organic and inorganic pollutants and their toxicological effects. Due to these characteristics R. marina is considered a good biomonitor of environmental pollution. This chapter presents three case studies that demonstrate the above. As a first case, toads were collected from sampling stations in the Río Verde (rural-reference) and Río Santiago (urban-impacted) of Jalisco. As exposure biomarkers were determined lead (Pb) and persistent organic pollutants (POPs) in muscle and liver tissue, respectively, and as effect biomarker: DNA damage (comet assay) in complete blood. A major presence of Pb was found in muscle tissue of the organisms that inhabiting the urban area (181.8 ng/g tissue) compared to those in the rural area (108.6 ng/g tissue); dichlorodiphenyltrichloroethane (DDT) and its metabolites; also, endosulfan, atrazine, hexachlorocyclohexane (HCH) isomers and hexachlorobenzene (HCB) was found in liver tissue of toads from urban areas. DNA damage in urban toads compared with laboratory toads were found. This shows the exposure and possible effects of pollutants in that area. In the second case of study, the objective of the research was to evaluate the persistent organic pollutants in the liver tissue as well as DNA damage in the blood of R. marina of two indigenous areas (Cuatlamayan and Tocoy, San Luis Potosí, México). The results of exposure to toads indicate the presence of atrazine, HCB, HCH and isomers, DDT and metabolites. The percentage of presence of micronuclei for Cuatlamayan and Tocoy was 77.7%25 and 80%25, respectively, compared with the laboratory toads (42.8%25). This study provides a baseline of exposure to POPs and genotoxic effect in different indigenous and rural areas of the Huasteca region of Mexico. Finally, in the third case of study the activity of non-destructive biomarkers (aminolevulinic acid dehydratase -d- ALAD-, median corpuscular hemoglobin content -MCHC-, butyrylcholinesterase -BChE-, condition factor) were determined in blood sample of giant toad from the basin of the Coatzacoalcos River (Veracruz) and compared with the organisms of reference (laboratory toads). Toads of the Coatzacoalcos River showed an increase in BChE 1.4-1.5 times and in MCHC 1.3-1.5 times compared to laboratory organisms. A percentage of d-ALAD inhibition of 60-65%25 was found in Coatzacoalcos amphibians compared to the laboratory. These studies demonstrate the useful of R. marina as a biomonitor of polluted sites. © 2018 Nova Science Publishers, Inc.

publication date

  • 2018-01-01