Morphological abnormalities in natural populations of the common South American toad Rhinella arenarum inhabiting fluoride-rich environments.

Morphological abnormalities in amphibians may be attributed to contaminants, ultraviolet radiation and trematode parasites, or a synergistic effect between them. In the present study, morphological abnormalities in Rhinella arenarum adults from natural and artificial fluoride-rich environments were identified and evaluated. Three sites were sampled in central Argentina: Los Vallecitos stream (LF-LV), Los Cerros Negros stream (MF-CN), and Decantation ponds (HF-DP), with low (0.33 mg/L), middle (2.03 mg/L) and high (14.0 mg/L) fluoride levels respectively; the latter site is associated with a fluoride mine. Abnormal individuals were photographed and then standard radiographs were taken. Abnormality frequencies and relative percentage of abnormal individuals were calculated for each site. In addition, skeletochronology was used to estimate toad's age. Five abnormality types were identified: syndactyly, ectrodactyly, polydactyly, microphthalmia and ectromelia. Percentages of abnormal individuals per site were: LF-LV = 4%, MF-CN = 21.2% and HF-DP = 6.4%. The MF-CN and HF-DP populations had morphological abnormality frequencies that exceeded the reference value (5%) reported in the literature. The average age did not differ between sites. The results of this study indicate that there is an association between frequency of morphological abnormalities and high fluoride levels.

Evaluation in situ of genotoxic and cytotoxic response in the diploid/polyploid complex Odontophrynus (Anura: Odontophrynidae) inhabiting agroecosystems.

Polyploidization has been documented across a wide range of vertebrates. Gene duplication could promote better adaptation to environmental changes and to chronic injury or stress. We investigated if genotoxic and cytotoxic responses to agricultural impact are affected by ploidy. We evaluate syntopic populations of the cryptic diploid/polyploid complex Odontophrynus cordobae/O. americanus breeding in an agroecosystem from Central Argentina. The blood of 72 adult anurans was analysed. We used erythrometry to distinguish Odontophrynus individuals with different ploidy levels. We calculated micronucleus frequencies (Mn) and erythrocytic nuclear abnormalities (ENAs) as genotoxic effects and enucleated, mitotic, pyknotic and immature erythrocytes as cytotoxic endpoints (CYT). Mn, ENAs and CYT frequencies were significantly different between diploid and polyploid organisms. The higher frequencies of Mn and CYT were recorded in polyploid organisms, and the higher frequency of ENAs was recorded in diploids. These results indicate that stress response, as indicated by most genotoxic and cytotoxic endpoints, was higher in polyploids respect to diploids. Polyploidy could provide greater genetic flexibility increasing buffering against exogenous DNA-damaging agents and thus confer an advantage over diploids under certain environmental conditions.