A karyotype comparison between two species of bordered plant bugs (Hemiptera, Heteroptera, Largidae) by conventional chromosome staining, C-banding and rDNA-FISH.

A cytogenetic characterization, including heterochromatin content, and the analysis of the location of rDNA genes, was performed in Largus fasciatus Blanchard, 1843 and L. rufipennis Laporte, 1832. Mitotic and meiotic analyses revealed the same diploid chromosome number 2n = 12 + X0/XX (male/female). Heterochromatin content, very scarce in both species, revealed C-blocks at both ends of autosomes and X chromosome. The most remarkable cytological feature observed between both species was the different chromosome position of the NORs. This analysis allowed us to use the NORs as a cytological marker because two clusters of rDNA genes are located at one end of one pair of autosomes in L. fasciatus, whereas a single rDNA cluster is located at one terminal region of the X chromosome in L. rufipennis. Taking into account our results and previous data obtained in other heteropteran species, the conventional staining, chromosome bandings, and rDNA-FISH provide important chromosome markers for cytotaxonomy, karyotype evolution, and chromosome structure and organization studies.

Genotoxic effects of Roundup Full II® on lymphocytes of Chaetophractus villosus (Xenarthra, Mammalia): In vitro studies.

In Argentina, Chaetophractus villosus has a wide distribution that overlaps with agricultural areas where soybean is the predominant crop. In such areas the pesticide Roundup Full II® (RU) is widely applied. The genotoxic effect of its active ingredient glyphosate (RU is 66.2% glyphosate) on the peripheral blood lymphocytes of C. villosus was tested over a range of concentrations (280, 420, 560, 1120 µmol/L). Culture medium without glyphosate served as negative control, while medium containing mitomycin C served as positive control. Genetic damage was characterized in terms of the percentage of cells with chromosome aberrations (CA), the mean number of sister chromatid exchanges (SCE) per cell, and the modification of cell proliferation kinetics via the calculation of the replication index. Significant increases (p < 0.0001) were seen in the CA frequency and the mean number of SCEs per cell compared to negative controls at all the RU concentrations tested. Chromatid breaks, the only form of CA observed, under the 560 µmol/L RU conditions and in presence of mitomycin C were four to five times more common than at lower concentrations, while no viable cells were seen in the 1120 µmol/L treatment. The mean number of SCEs per cell was significantly higher under the 280 µmol/L RU conditions than the 420 or 560 µmol/L RU conditions; cells cultivated in the presence of MMC also showed significantly more SCEs. All the RU concentrations tested (except in the 1120 µmol/L RU treatment [no viable cells]) induced a significant reduction in the replication index (p < 0.0001). The present results confirm the genotoxic effects of RU on C. villosus lymphocytes in vitro, strongly suggesting that exposure to RU could induce DNA damage in C. villosus wildlife.

Chaetophractus villosus as a sentinel organism: Baseline values of mitotic index, chromosome aberrations and sister chromatid exchanges.

Sentinel species are useful tools for studying the deleterious effects of xenobiotics on wildlife. The large hairy armadillo (Chaetophractus villosus) is the most abundant and widely distributed mammal in Argentina. It is a long-lived, omnivorous, burrowing species, with fairly restricted home ranges. To evaluate the level of spontaneous genetic damage in this mammal, we determined the baseline values of several genotoxicity biomarkers. The study included 20 C. villosus adults of both sexes from eight pristine localities within its geographic distribution range. Genotoxicity analysis was performed on 72-h lymphocyte cultures, using mitomycin C as positive control. We obtained the baseline values of mitotic index (MI=10.52±0.30 metaphases/total cells, n=20), chromosome aberrations (CA=0.13±0.22, n=20), sister chromatid exchanges (SCE)=6.55±0.26, n=6) and replication index (RI=1.66, n=6). MI and CA did not show significant differences (P>0.05) among localities or between sexes. No significant differences in MI, CA, SCE, and RI (P>0.05) were found between values from the pristine localities and historical data. There were significant differences in CA, SCE, and RI (P<0.05) between lymphocyte cultures from pristine localities and those exposed to mitomycin C. We propose the large hairy armadillo as a sentinel organism for environmental biomonitoring of genotoxic chemicals due to its abundance, easy manipulation, well-known biology, the fact that it is usually exposed to different mixtures and concentrations of environmental contaminants, and the baseline values of genetic damage characterized by MI, CA, SCE and RI as biomarkers.