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The contamination and risk assessment of heavy metals in the bottom sediments of the Lake Valencia, Venezuela, was performed by determining the Enrichment Factor (EF), the Geoaccumulation Factor (Igeo), the availability of metals and the Risk Index Code (RAC). The sediments were anthropogenic ally enriched with Pb, Zn, Cu and Cr and classified as uncontaminated to moderately contaminated, with a medium risk of Zn, Co, Ni and Cr, and low risk of Cu, Pb and Cd. Analysis of correlations and PCA showed temporal variations in the concentration of metals in the sediments during the rainy season, and spatial variations, where the depth and anthropogenic inputs are the main variables. The contamination of sediments was located on the axis connecting the mouths of the river Guayos, which crosses the city of Valencia, and the river Güey which crosses the city of Maracay, both highly industrialized. Although the concentration of dissolved heavy metals into the waters was within the regulations, important concentrations of Pb and Hg and the bioaccumulation of Hg and Cr, determined by the Bioconcentration Factor (BCF), were found in the fish tissues which indicate that the metal enrichment of the lake sediments is affecting the biota.

The nematode Caenorhabditis elegans has evolved as a powerful invertebrate model to study innate immunity to pathogens. C. elegans possesses inducible defence mechanisms to protect itself from pathogenic attack, mainly by the production of antimicrobial effector molecules. Its innate immune system is under the control of a surprisingly complex network of evolutionary conserved signalling pathways, which are activated depending on the pathogen, suggesting that C. elegans is able to mount a specific defence response to different pathogens. In this review we will introduce the worm's immune system and discuss the different signalling pathways that regulate its response to bacterial pathogens which mainly infect C. elegans by an oral route and by invading its intestine, before focusing our attention on the resistance of C. elegans to a natural occurring fungal -pathogen that infects the worm by invading its -epidermis.