Alois Schäfer

Type 1 ribosome-inactivating proteins - entomotoxic, oxidative and genotoxic action on Anticarsia gemmatalis (Hübner) and Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).

Ribosome-inactivating proteins (RIPs) from plants inhibit protein synthesis by inactivating ribosomes. Some two-chain (type 2) RIPs are highly toxic and may play a role in plant defense. The lower toxicity of single-chain (type 1) RIPs reflects the lack of a protein domain able to bind to, and translocate the toxin across cell membranes. We studied the effect of single-chain RIPs, lychnin, momordin, gelonin, PAP-S and saporin S-6, in larvae of Anticarsia gemmatalis and Spodoptera frugiperda. After ingesting a total dose of 20 or 40 microg of the toxins, weight gain, survival rate, lesions in DNA and oxidative status (catalase and superoxide dismutase activities and lipidic peroxidation) of RIP-treated insects were assayed. Momordin was the less toxic in the biossays. S. frugiperda had a more pronounced weight loss on the 4th day of treatment and A. gemmatalis on the 10th day. RIP-induced mortality reached 57.13% for A. gemmatalis and 29.45% for S. frugiperda. RIP-treated insects showed a 2-3-fold increase in DNA lesions as assessed by the comet assay, but there were no correlations between stress markers and DNA damage. We conclude that single-chain RIPs are entomotoxic to lepidopteran insects causing extensive DNA lesions.

Mosses as indicators of atmospheric metal deposition in an industrial area of southern Brazil

Caxias do Sul hosts the second largest metal-mechanic pole in Brazil, which increases the risk of atmospheric contamination. With the aim of identifying species that might be useful as indicators of atmospheric deposition of metals, 15 species of mosses from an urban and a rural setting were analyzed and compared with specimens deposited at the Herbarium of the Universidade de Caxias do Sul. Metal concentrations (Zn, Ni, Cd, Cr, Cu and Pb) were determined using Atomic Absorption Spectrometry (AAS). The Mann-Whitney test indicated concentrations of Zn, Cu, Pb and Cr that were significantly different between the urban and rural areas. Additionally, Concentrations of Zn, Cd, Cu and Pb were significantly higher in recently collected samples. The species Thuidium tomentosum Besch., Sematophyllum subpinnatum (Brid.) E. Britton, Helicodontium capillare (Hedw.) A. Jaeger, Schlotheimia jamesonii (W.-Arnott) Brid. and Meteorium deppei (Hornsch. ex Mull. Hal.) Mitt. are potential biomonitors of atmospheric metal deposition.

Tolerance of benthic macroinvertebrates to organic enrichment in highland streams of northeastern Rio Grande do Sul, Brazil

AIM: the aim of this study was to determine the ecological valence of benthic macroinvertebrates at different pollution levels in highland rivers and streams of Rio Grande do Sul; METHODS: the dataset proceeds from samplings performed between 2002-2011 in 35 lotic ecosystems. The Chemical Index was used to determine pollution levels. Indices of richness and Shannon diversity were applied to characterize the structure of benthic communities. The descriptors used to determine taxas ecological valence were selected according to Coefficient of Variation and regression analyses. Groups of tolerance were identified using Interquartile range and cluster analysis; RESULTS: Conductivity and Chemical Index were the descriptors best related with diversity of benthic macroinvertebrate community. These metrics were used to determine the tolerance range of 38 taxa. Interquartile range and cluster analysis revealed three groups of taxa, according to their occurrence in different levels of pollution: taxa with narrow amplitudes, present at sites with very low or very high load of organic enrichment; taxa with moderate amplitude, found until moderately polluted sites; and taxa with occurrence in widespread environmental conditions. The results, when compared to other studies in Brazil, showed differences in some taxas tolerance. This observation indicates the need to assess the bioindication potential of these taxa in genus and species level; CONCLUSION: the present study contributes to increase knowledge about the bioindicator potential of benthic macroinvertebrates. Therefore, the study supports an advanced biomonitoring of ecological quality in mountain streams of southern Brazil.

Morphological characterization of eighteen lakes of the north and middle coast of Rio Grande do Sul, Brazil

AIMS: The present study aimed at a morphological characterization of 18 lakes of the municipalities of Cidreira, Balneario Pinhal and Palmares do Sul, situated in the northern and middle coastal plain of Rio Grande do Sul, Brazil. METHODS: The morphometric survey was conducted in the summer of 2011/2012, based on echo sounder coupled with GPS and the application of remote sensing and GIS procedures. The morphometric parameters used for the characterization were: surface area, perimeter, perimeter development, volume, relative fetch, maximum depth, average depth, relative depth, median depth of volume, length and width. The statistical interpretation included Test of Normality, Coefficient of Variation, Correlation and Regression Analysis, Cluster Analysis, Discriminant Analysis and Principal Component Analysis. RESULTS: Eighteen lakes were described and five of them are presented by aerial photo and bathymetric map. They represent the proposed morphological lake types. The calculation of the coefficient of variation revealed larger amplitudes of parameters related to lake size than to depth. The application and interpretation of cluster analysis, confirmed by discriminant analysis, distinguished those lakes in five morphological groups, which differ mainly by size and subsequently by depth. The Principal Component Analysis identified the first component with positively charged variables of size and negatively charged relative depth, and a second component with positive charge of maximum and average depths. CONCLUSIONS: The low relative depths and the exposure to constant northeastern winds reduce the transparency of the lakes. Consequently, they are light limited by suspension of inorganic and organic matter. A property that limits the application of trophic state indices. The high dynamic of the water bodies produces an oxygenated sediment surface that facilitates the settlement by aerobic organisms all over the bottom area. The shallowness and the low median depths of volume are limiting factors for sustainable water supply management. The morphological characteristics of the coastal lakes make very difficult an accurate ecological assessment based on usual trophic state criterions and a sustainable water resource management using general guidelines.