A key to identify the known mature larvae of the South American genera of the family Elmidae is provided. The key includesseven genera presently assigned to the subfamily Larainae and 15 genera assigned to the subfamily Elminae. New distributionaldata for all genera and a checklist of described larvae are also included. The mature larva of Macrelmis saltensis Manzo isdescribed and illustrated for the first time, and compared to other known larvae of the granigera species-group. Distributionalnotes for M. saltensis increase its known range to the north, this being the first citation of the species for Bolivia. Macrelmis isis(Hinton) is also cited for the first time for Bolivia.

Temporal and spatial variation in the concentrations of intra- and extra-cellular microcystins were studied in a hypertrophiclake with bloom of Planktothrix agardhii (Gomont) Anagnostidis et Komarek. Concomitantly with increase in watertemperature (from 2 to 20 °C) abundance of P. agardhii increased from 1.9 x 105 to 4.3 x 107 trichomes L-1. In autumn, in spiteof temperature lower (14°C) than in summer it was still very high. Mass development of P. agardhii (to 6 x 106 L-1 and higher)caused a severe decrease in water transparency (to 0.5 - 0.2 m in summer/autumn). The cyanobacterium density was relativelyuniform within water column; only in summer (July) it was significantly higher (by about 30%) in surface than in bottom layer.From spring to autumn microcystins (MCs) were mainly biomass-bound (up to 90 μg MC-LR equiv. L-1), whereas the level ofextra-cellular toxins was much lower (up to 2 μg L-1) and relatively stable. Only in winter, high amounts of MCs (11.3 μg L-1)were released from decaying biomass into water. The increasing concentrations of biomass-bound microcystins in the lake waterpositively correlated (R2 = 0.9863; y = -0.1285x2 + 7.14x ) with the abundance of P. agardhii and the highest concentrations ofthe intracellular MC fraction were found during the exponential phase of P. agardhii growth. In addition, the surface-sampledbiomass of P. agardhii contained in autumn 2-fold more MCs (2.75 μg MC-LR equiv. per 106 P. agardhii trichomes) than thebottom-sampled one (1.41 μg MC-LR equiv. per 106 trichomes). This is the first report showing that despite the homogenousdistribution of P. agardhii in water column of a shallow lake, various seasonal and spatial distributions of both extra-cellularand intracellular fractions of microcystins occur.

Seven new species of Glossosomatidae are described from Bolivia. The seven new Bolivian species are: Mexitrichia collegarumn. sp., M. eduardoi n. sp., M. marini n. sp, M. usseglioi n. sp, Protoptila alumnorum n. sp, P. goitiai n. sp and P. myriamae n.sp. 18 species are recorded at the moment from Bolivia and northwestern Argentina: Merionoptila wigodzinskyi, Mexitrichiaalbolineata, M. bolivica, M. pocita, M. punensis, M. simla, M. argentinica, M. paraenchrysa, M. wygodzinskii, Protoptiladubitans, P. misionensis and the seven new species. A list of species of Glossosomatidae from Bolivia and northwestern Argentinais provided with new distributional records.

Morphology of both the valves and limbs of several parthenogenetic populations of the widespread non-marine ostracodCryptocandona vavrai Kaufmann (sensu lato) living in groundwater habitats of western (France) and south-eastern Europe(Romania) was examined for the extent of intra- and interpopulational variation. Geometric morphometrics and multivariatestatistics were employed for the description of the valve morphological disparity whereas the discriminant analysis wasperformed for the comparative analysis of the limb chaetotaxy. The ranges of the most studied limb traits principally overlappedamong the populations, however considerable differences in the carapace shape and size, reflecting microevolutionary changes ata macro-scale (inter-population) level, allowed distinguishing quantitatively some Romanian populations which deserve aseparate specific status. Hence, a new species Cryptocandona racovitzai sp. nov. is described which differs from C. vavrai sensustricto mainly in larger size, in more triangular valve shape as seen laterally and in less developed inner lamella of the valves.Finally, after examination of more material from Romanian groundwaters, we hypothesised the presence of more new specieswithin the studied lineage and concluded that Cryptocandona vavrai sensu lato is a polymorphic lineage consisting of severalgeographically differentiated species rather than just only one widely dispersed species.

Chlorophyll-a concentration and physico-chemical water quality of water bodies surrounding Santa Fe City (Argentina) wereanalyzed at 20 sampling sites during different hydroclimatic periods (August-September 2005, March-April 2006). Areas withdifferent water quality were separated by Euclidean cluster analysis, and correlation among both environmental and chlorophylldistance matrices were found (p<0.01). The areas more affected by anthropogenic influence, Los Saladillos and Salado Rivers,reached the highest trophic level as regards to chlorophyll concentration. Acceleration in the eutrophication process wasregistered in comparison with previous studies, and chlorophyll-a concentrations are similar to those encountered in othereutrophicated rivers of the world. The oligo-mesotrophic level found at the Setúbal shallow lake was lower than expected due tothe nutrient contents and human activities of its basin. However, the incoming of pristine waters from the Paraná Systemproduces a sweeping effect and a semi-lotic lake behavior that impedes eutrophication enhancement. During high-waters thisriver also improved water quality of Santa Fe and Coronda Rivers. The chlorophyll-a diminution at Setúbal Lake and Santa FeRiver in comparison to earlier studies, may be also explained by the introduction in the last decade of the bivalve Limnopernafortunei that could be responsible of important losses of algal cells. Although trophic state according to chlorophyll-aconcentration was improved with discharge increments, nitrate and total phosphorus concentration augmented in most sites as aresult of the input from polluted flooded areas. The higher ranges encountered in the present study either of chlorophyll-a ornutrient content, indicate changes in water quality and a resultant eutrophication process over a period of decades. The health ofwater bodies is not yet in danger, but it is declining due to induced man-changes.