Cytogenetic analysis of nuclear abnormalities in the erythrocytes of gecko lizards (Phyllopezus periosus) collected in a semi-arid region of northeast Brazil: Possible effects of natural background radioactivity

Evidences of radioresistance in Drosophila melanogaster from Northeastern Brazil

BACKGROUND

Ionizing radiation can inflict cellular damage, the severity of which is determined by the dose, exposure duration, and its capacity to penetrate cells. Some studies have demonstrated that genetic and epigenetic mechanisms have enabled organisms to develop adaptive traits and enhance their ability to repair DNA damage. Northeastern Brazil, a region containing rocky outcrops rich in uranium and thorium, is an ideal scenario to study natural radiation and its effects on natural populations. This study presents evidence of radioresistance in the offspring of a natural strain of Drosophila melanogaster resident in the municipality of Cerro Corá (CC-res), an environment with high levels of radon-222.

MATERIAL AND METHODS

Genotoxicity was assessed using the comet assay in offspring of the CC-res and Oregon-R (OR), the control group, both reared under the same laboratory conditions for between 7 and 13 months. The adults and their offspring larvae were exposed to the Cerro Corá environment for 6 days during the dry and wet seasons. Low damage index and frequency were observed only in the CC-res. To confirm the radioresistance, the same strains were exposed after 16 months of cultivation to controlled doses of gamma radiation.

RESULTS AND CONCLUSIONS

CC-res exhibited significantly lower levels of damage compared to the OR strain, with a clear dose-response effect to the irradiation observed exclusively in the OR group. The results support the occurrence of radioresistance in the CC-res strain and underscore the need for further in vivo studies investigations into the impact of Brazil's natural environmental radiation.

Cytome analysis (micronuclei and nuclear anomalies) in bioindication of environmental pollution in animals with nuclear erythrocytes

Assessment of cytogenetic homeostasis of indicator animals is of great importance in ecological monitoring. The simplest method of its study is micronucleus analysis. Animals with nuclear erythrocytes are often used as indicator animals. In addition to the micronuclei usually recorded, a wide range of cytological nuclear and cellular abnormalities (cytomic analysis) is encountered when assessing the spontaneous level and under the influence of anthropogenic factors. Spontaneous frequency of cytogenetic disorders in 36 species of fish, amphibians, reptiles and birds was studied. Ecological monitoring of territories of Kazakhstan with different types of pollution (radiation, petrochemical, pesticide, heavy metals, due to rocket and space activities) was carried out with the help of separate species of animals. The results of the study include comparative descriptions, schematics and microphotographs clearly demonstrating a wide range of cytological anomalies of nuclear erythrocytes of animals of different classes. The greatest spectrum of nuclear anomalies in the studied animals was registered at petrochemical and pesticide contamination of territories. Depending on the tasks and climatic-geographical conditions, all investigated species can be used as bioindicators. Testudo horsfieldii is an exception for desert regions due to high spontaneous micronuclei level in this species. A review of the names of the main nuclear anomalies is carried out and variants of its ordering are proposed.

Eco-toxicological effects assessment: comparative characteristics of environmental conditions and status of vertebrate indicator species in the "Dnepr" launch vehicle accident zone

Space rockets are regularly launched from the Baikonur Cosmodrome in Kazakhstan. The ecological impact of territories affected by the consequences of space rocket activities on the environment is a significant concern. On July 27, 2006, the Dnepr rocket was launched from the Baikonur Cosmodrome, resulting in an abnormal situation and its emergency fall. The rocket fuel components, heptyl, and amyl, led to decontamination and reclamation activities. However, the self-restoration of soil and vegetation cover is currently in the earliest stages. Consequently, an assessment of the remote consequences of the accidental fall of the Dnepr launch vehicle for environmental objects was conducted. The study involved eco-toxicological characterization of habitat conditions, assessment of species diversity, determination of key morphophenetic indicators, and the genetic status of indicator species as the main parameters. The results revealed an increased level of genotoxicity in soils at the accident site. While there were deviations from the norm in some morphophenetic and cytogenetic parameters in indicator animals, they were not critical for their existence in this territory. Possibly, at the physiological level, they exhibit a high enough adaptation potential and compensatory mechanism.

DNA damage as indicator of the environmental vulnerability of bats in Brazil's Caatinga drylands

Brazil's Caatinga drylands is under extensive environmental deterioration, with 38% of its natural cover already lost. There is a need for a better understanding of the effects of such degradation on Caatinga's rich and singular biota. Bats form a large part of this biota, and are pointed as good bioindicators. Here, we used the micronucleus test -an easy-to-use, accessible and cost-effective in vivo approach- to detect DNA damage in cells from bats of different species and feeding habits in three protected areas in the Caatinga, comparing them with samples from an industrial sugarcane plantation. We hypothesized that environmental disturbance would reflect in DNA damage, with lower levels of damage in the less disturbed protected areas. The frequency of micronucleated cells differed significantly between sites and feeding habits (carnivores > insectivores > frugivores > nectarivores > hematophagous) but did not differ between sexes. Alarmingly, the highest levels of DNA damage were in two strictly protected areas (Seridó and Raso da Catarina Ecological Stations). Glossophaga and Anoura were the genera with more damaged cells, and had, respectively, 1.48 and 3.53 times more micronucleated cells (average of 19.33 and 22.67 cells, respectively) than individuals from the same genera from the area with least damaged cells (average of 7.80 and 5.00 cells, respectively). Our analysis is a warning call for an in-depth investigation on the effects of both genotoxic contamination and environmental stressors on bats and other species in Brazil's Caatinga, including the role that historical human-induced processes -like the intense use of agrochemicals- may have had in the region.