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Resumo Objetivo A capacidade de acesso anterior à região cervicotorácica com base na idade e gênero do paciente e a possibilidade de variações anatômicas em diferentes populações geográficas ainda não foram investigadas. O objetivo deste trabalho foi realizar uma análise radiográfica de pacientes brasileiros para avaliar a acessibilidade anterior da junção cervicotorácica conforme idade e gênero. Métodos Análise radiográfica retrospectiva de 300 tomografias computadorizadas. Os pacientes foram separados por idade e gênero. Os parâmetros radiográficos estudados foram: nível horizontal acima do esterno (HLS, na sigla em inglês), angulação do corpo vertebral (VBA, na sigla em inglês), linha do disco intervertebral (IDL, na sigla em inglês) e angulação da linha do disco intervertebral (IDLA, na sigla em inglês). Resultados Os HLS e IDL mais frequentes foram T2 (34,3%) e C7–T1 (46%), respectivamente. Os valores médios de VBA e IDLA foram de 18 ± 8,94 e 19 ± 7,9 graus, respectivamente. Os homens apresentaram valores maiores de IDLA (p = 0,003) e VBA (p = 0,02). Os grupos de maior idade apresentaram valores maiores de IDLA (p = 0,01) e VBA (p = 0,001). Não houve diferenças de HLS entre os gêneros masculino e feminino (p = 0,3) ou faixas etárias (p = 0,79). Não foram observadas diferenças na IDL entre os gêneros masculino e feminino (p = 0,3); entretanto, o grupo mais velho apresentou nível mais caudal do que os grupos mais jovens (p = 0,12). Conclusões Em comparação a outras populações, nossa amostra apresentou IDL e HLS mais cefálicos. AVBA e a IDLA foram maiores no gênero masculino, enquanto VBA e IDLA foram maiores em grupos mais velhos. A IDL era mais caudal em pacientes idosos.

Made available in DSpace on 2022-04-29T08:29:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) We evaluated the spatiotemporal distribution of Limnoperna fortunei larvae, its abundance in relation to other zooplanktonic organisms (copepoda and cladocerans), and its macrofouling on net cages in the Chavantes Reservoir, Brazil. We also estimated its growth rate under this condition and limnological variables in the water column. Zooplankton densities were positively related to water temperature, and copepoda was the most abundant group. L. fortunei showed the highest density in November and March (18.565 to 30.014 larvae/m3) and the lowest from June to August (1.587 to 876 larvae/m3). Population parameters of L. fortunei, as derived from von Bertalanffy seasonal growth function, indicated fast annual growth (K = 1.22) in length in the first, second and third years of life at 21, 28, and 30 mm, respectively. We estimate that 62.920 juveniles/m2 will be recruited annually in fish farming, mainly in the reproductive period, which should be the focus of prevention methods. Our work is the first report to associate the abundance of L. fortunei larvae in the water column with the recruitment of juveniles. Instituto de Pesca Agência Paulista de Tecnologia dos Agronegócios Postgraduate Program Centro de Aquicultura Universidade Estadual Paulista Postgraduate Program Instituto de Pesca Agência Paulista de Tecnologia dos Agronegócios Instituto de Biofísica Carlos Chagas Filho Universidade Federal do Rio de Janeiro Departamento de Ecología Genética y Evolución Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires Postgraduate Program Centro de Aquicultura Universidade Estadual Paulista

Validation of classification system. To externally validate the Proximal Humerus Ossification System (PHOS) as a reliable skeletal maturity scoring system and to assess the learning curve associated with teaching the procedure to individuals of varying levels of experience. Assessment of skeletal maturity is essential for treatment decisions in Adolescent Idiopathic Scoliosis (AIS). PHOS is a five-stage system that uses the proximal humeral physis in assessing skeletal maturity and has been shown to reliably grade skeletal age leading up to and beyond peak growth age (PGA). This system is advantageous in the AIS patient, as it is often captured in standard scoliosis films. A medical student, an orthopedic surgery resident (PGY-2), spine fellow, and experienced scoliosis surgeon in his 25th year in practice were given a three-slide PHOS learning module. Each participant rated 100 X-rays on two separate occasions, separated by 1 week. Intra- and inter-observer reliability, as well as cross-institutional reliability, were calculated using intraclass correlation coefficients (ICC) with 95% confidence intervals [CI95]. Average intra-observer reliability ICC between scoring sessions was 0.94 [0.92, 0.96] and inter-observer reliability by level of training were 0.94 [0.91, 0.96], 0.93 [0.9, 0.95], 0.94 [0.91, 0.96], 0.96 [0.94, 0.97] for the medical student, PGY-2, fellow, and attending, respectively. Reliability across institutions was 0.99 [0.98, 0.99]. Combined rating observations (n = 400) showed 82% exact matches, as well as 17% and 1% mismatches by 1 and 2 stages, respectively. Similar to the PHOS developers, we found PHOS stage 3 to occur immediately after PGA. PHOS is easily learned and employed by raters with varying levels of training. It comprises a five-stage system to reliably measure bone age leading up to PGA and thereafter. This new system relies on visualization of the proximal humerus, which is readily available on standard scoliosis X-rays. Level III.

The intensive use of glyphosate in industrial agriculture may lead to freshwater contamination, encouraging studies of its toxic effect on non-target aquatic organisms. Glyphosate-based commercial formulations contain adjuvants, making them even more toxic than the active ingredient (a.i.) itself. The golden mussel Limnoperna fortunei is a freshwater invasive species which has been found to increase glyphosate dissipation in water and to accelerate eutrophication. The aim of this study is to evaluate the capability of L. fortunei to reduce the concentration of glyphosate in two commercial formulations, Roundup Max® and Glifosato Atanor®. Results were compared with the decay of the a.i. alone and in presence of mussels. Evasive response and toxicity tests were performed in a first set of trials to analyze the response of L. fortunei exposed to Roundup Max® and Glifosato Atanor®. Subsequently, we conducted a 21-day degradation experiment in 2.6-L microcosms applying the following treatments: 6 mg L−1 of technical-grade glyphosate (G), Glifosato Atanor® (A), Roundup Max® (R), 20 mussels in dechlorinated tap water (M), and the combination of mussels and herbicide either in the technical-grade (MG) or formulated form (MA and MR) (all by triplicate). Samples were collected at days 0, 1, 7, 14 and 21. No significant differences in glyphosate decay were found between treatments with mussels (MG: 2.03 ± 0.40 mg L−1; MA: 1.60 ± 0.32 mg L−1; MR: 1.81 ± 0.21 mg L−1), between glyphosate as a.i. and the commercial formulations, and between the commercial formulations, suggesting that the adjuvants did not affect the degrading potential of L. fortunei. In addition to the acceleration of glyphosate dissipation in water, there was an increase in the concentration of dissolved nutrients in water (N–NH4+ and P-PO43-) even higher than that caused by the filtering activity of the mussels, probably resulting from stress or from the degradation of glyphosate and adjuvants. We believe that a larger bioavailability of these nutrients due to glyphosate metabolization mediated by mussels would accelerate eutrophication processes in natural water bodies. The approach used here, where L. fortunei was exposed to two commercial formulations actually used in agricultural practices, sheds light on the potential impact of glyphosate decay on water bodies invaded by this species.

Carbon fiber reinforced polymers (CFRP) reduce weight in aerospace and automotive applications while maintaining or improving structural performance. Additional performance gains can be realized with composites if adhesive bonding is used in place of mechanical fasteners for structural assemblies. Surface preparation for adhesive bonding plays a critical role in the assembly process. Effective techniques for monitoring the pre-bonding surface conditions are crucial to obtain surfaces free from bond-degrading contaminants, e.g. mold release agents, which are widely used in CFRP manufacturing. In this work, optically stimulated electron emission (OSEE) was used prior to and after laser ablation to measure deposited levels of polydimethylsiloxane (PDMS) on CFRP (Torayca P2302-19). OSEE was also used to model the contamination layer thickness. After the specimens were adhesively bonded with a modified epoxy film adhesive (Loctite EA 9696 Aero), they were subjected to double cantilever beam (DCB) tests to investigate the hypothesis that surface contamination species and levels affect the fracture characteristics of adhesively bonded joints. This study relates OSEE photocurrent and the classification of the bond failure modes to their PDMS surface contamination levels prior to adhesive bonding. DCB test results show that (1) the region under the traces within the load and unloading boundaries consistently correlates with the bond strength and the probability of different failure modes, and (2) bond performance at fracture depends on the surface PDMS film thickness coating prior to laser surface treatment. The decrement in bond performance in this study correlates to the OSEE readings of contaminant levels on the adherent surfaces.

Although contamination and invasive species are two of the most relevant anthropogenic drivers affecting ecosystems, their joint impact on the environment has been poorly investigated. Glyphosate, directly or indirectly, contaminates freshwater systems which in turn may be invaded by the golden mussel Limnoperna fortunei. Under laboratory conditions, we studied the combined effect of technical-grade glyphosate, Roundup Max® and Glifosato Atanor®, in scenarios with and without L. fortunei, on phytoplankton from Salto Grande Reservoir (Uruguay River, Argentina). We expected that the effects of the interaction on phytoplankton and water quality would vary with the form of herbicide applied. The assay was conducted for 14 days (Tf) using 3-L bottles as experimental units. Eight treatments were performed in triplicate: C: Control; M: mussel; G: technical-grade glyphosate acid; R: Roundup Max®; A: Glifosato Atanor®; MG: mussel + technical-grade glyphosate acid, MA: mussel + Glifosato Atanor® and MR: mussel + Roundup Max®. The active ingredient was applied at 6 ppm. The dissipation of glyphosate in water was 1.5–2.6 times higher in presence of mussels. Treatments G and A showed an increase in phytoplankton abundance, mainly the cyanobacteria Microcystis spp. wich rised to 289% and 639% at Tf, respectively, relative to their values at Ti. Roundup Max® limited the growth of Microcystis spp., as its abundance decreased 59% relative to Ti. L. fortunei reduced phytoplankton abundances at Tf. Evenness increased significantly in M, MG, MR and MA, while it decreased in G, R and A relative to C. The interaction of factors produced a significant synergistic increase in periphyton; periphytic chlorophyll a concentration was 0.81 ± 0.02 μg cm−2 for MR; 0.09 ± 0.02 μg cm−2 for MA and 0.02 ± 0.01 μg cm−2 for MG. Limnoperna fortunei appeared as the driving force in the interaction. The assay described here allows for the rapid assessment of the impact of these types of agents on freshwater. Fil: de Stefano, Lucia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Gattás, Florencia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Vinocur, Alicia Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Cristos, Diego Sebastián. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; Argentina Fil: Rojas, D.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Pizarro, Haydee Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina

Contamination and biological invasions are important factors that alter the functioning of freshwater systems. We carried out two experiments involving daily measurements of dissolved oxygen (DO) and Limnoperna fortunei mortality: 1) the impact of DO on mussel survival mediated by glyphosate, 2,4-D and their mixture was analysed in a 22-day indoor experiment (IE) under controlled conditions using microcosms with L. fortunei, with and without air supply; and 2) the effect of each herbicide and their mixture on mussel accumulated mortality was compared in a 18-day outdoor experiment (OE) using mesocosms without air supply, with and without L. fortunei. Results showed that glyphosate, alone or mixed affected L. fortunei survival both directly and indirectly. In IE we observed direct toxicity of glyphosate in treatments with air supply, with accumulated mortality of 20.0% for glyphosate and 10.0% for the mixture. In OE, L. fortunei deepened the changes in the patterns of DO fluctuations driven by the herbicides, which led to hypoxia in the system. The accumulated mortality was 46.7, 8.6 and 48.2% for glyphosate, 2,4-D and the mixture, respectively. This study contributes to the understanding of the mechanisms that control the invasion of L. fortunei in freshwater systems influenced by agrochemicals.

Glyphosate is currently the most widely used herbicide in agricultural production. It generally enters aquatic ecosystems through surface water runoff and aerial drift. We evaluated the effect of glyphosate acid on biochemical parameters of periphyton exposed to concentrations of 1, 3, and 6 mg/L in outdoor mesocosms in the presence and absence of the mussel Limnoperna fortunei. Periphyton ash-free dry weight, chlorophyll a content, carotene/chlorophyll a ratio, lipid peroxidation levels, and superoxide dismutase and catalase activities were determined at days 0, 1, 7, 14, and 26 of the experimental period. Ash-free dry weight was similar between control and glyphosate-treated periphyton in the absence of L. fortunei. The latter had significantly lower carotene to chlorophyll a ratios and enzyme activities, and higher lipid peroxidation levels and chlorophyll a content than the former. These results show an adverse effect of glyphosate on the metabolism of periphyton community organisms, possibly inducing oxidative stress. On the contrary, no differences were observed in any of these variables between control and glyphosate-treated periphyton in the presence of L. fortunei. Mussels probably attenuated the herbicide effects by contributing to glyphosate dissipation. The results also demonstrate that biochemical markers provide useful information that may warn of herbicide impact on periphyton communities. Environ Toxicol Chem 2017;36:1775-1784. © 2016 SETAC.

The joint impact of the glyphosate-based commercial formulation Roundup Max® and the invasive mussel Limnoperna fortunei on phytoplankton and water quality was assessed in Salto Grande reservoir, a scenario were both stressors coexist. We performed an in situ mesocosm approach, through a 7-day experiment using 400-L enclosures. The following treatments were applied by triplicate: addition of 250 mussels (M); addition of 5 mg L−1 of active ingredient (a.i.) in Roundup Max® (R); addition of 250 mussels and 5 mg L−1 of a.i. in Roundup Max® (MR), and controls, without any addition (C). R showed higher total phosphorus (TP) and ammonium nitrogen (N–NH4 +) concentrations due to the herbicide input, and a significant increase in algal abundance, biovolume and chlorophyll a levels (Chl-a). In M mussels grazed on phytoplankton, which resulted in subsequent phosphates (SRP) release. A decrease in species diversity was observed in R and M with respect to C. In MR, there were higher TP and N–NH4 + concentrations, a decrease in biovolume, an antagonistic effect on Chl-a and a synergistic effect on phytoplankton abundance. Species diversity and evenness showed a significant decrease due to the explosive growth of a small and opportunistic Chlorophyta, Spermatozopsis exsultans. The dominance of this species may be due to negative selectivity for S. exsultans and/or release of potential competitors by L. fortunei, and to the input of nutrients by Roundup Max® and/or removal of competitors by its toxicity. Fil: Gattás, Florencia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: de Stefano, Lucia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Vinocur, Alicia Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina Fil: Bordet, Hugo Facundo. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Comisión Técnica Mixta de Salto Grande; Argentina Fil: Espinosa, Mariela Soledad. Comisión Nacional de Energía Atómica; Argentina Fil: Pizarro, Haydee Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Since its introduction into South America around 1990, the freshwater bivalve Limnoperna fortunei (the golden mussel) has spread rapidly and is now a dominant component of the benthic and periphytic fauna in many rivers, lakes, and reservoirs. Sizable impacts of this nonindigenous species on nutrient recycling, plankton abundance and composition, and trophic relationships with fishes have been reported, but its effects on the sediments have received little attention. In this work, we use eighteen 20-L flow-through experimental units with and without mussels where changes in the mass and characteristics of the sediments accumulated throughout a yearly cycle in monthly, biannual, and annual intervals are analyzed. Experimental units with mussels yielded almost 2 times more sediments than units without mussels and contained significantly higher loads of organic matter and total N. Total P was not affected by the presence of mussels. Sediments accumulated in the biannual and annual experimental units agreed well with the yields of the monthly units, but the vertical stratification of organic matter, N, and P was unpatterned. Seasonal changes in the volume of total sediments, biodeposits, and their organic matter and N contents were positively associated with ambient water temperature and with intermediate (~150–250 NTU, nephelometric turbidity units) turbidity. Our results suggest that ecosystem-wide modifications in the living conditions of the benthic epifaunal and infaunal organisms in waterbodies invaded by the mussel are likely significant, although variable locally, regionally, and across taxa. Fil: Tokumon, Romina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Boltovskoy, Demetrio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

The joint impact of the glyphosate-based commercial formulation Roundup Max

Larval fish development depends largely on their ability to capture and ingest food items, and on food availability. In this context, invasive species, eutrophication and river impoundments have complex impacts on fish larvae. Using samples collected in 2005–2009 in the Salto Grande reservoir (Argentina–Uruguay), periodically affected by cyanobacterial blooms, we studied the impact of the larvae of the exotic bivalve Limnoperna fortunei (Dunker, 1857) (Bivalvia) on larval fish diets. Compared with other nearby waterbodies, the abundance of fish larvae was scarcer in the reservoir, especially during algal bloom periods. Only 20% of the larval fish with gut contents fed on L. fortunei veligers. Seven fish taxa (of a total of 12) consumed veligers of L. fortunei, but only two showed a preference for this prey. Taxonomic changes in the larval fish assemblages due to the river's impoundment, and temporal uncoupling between veliger densities (affected by the toxigenic effects of Microcystis spp.) and ichthyoplankton could account for the comparatively low trophic importance of the invasive bivalve's veligers. These results reflect the complexity of interactions brought about when the same invasive species invades different environments, underscoring that the impacts involved depend as much on the invader, as on the regional and ecological settings of the area invaded. Fil: Paolucci, Esteban Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Leites, Valentín. Comisión Técnica Mixta Embalse; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina Fil: Boltovskoy, Demetrio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Previous work has shown that the invasive bivalve Limnoperna fortunei has had a measurable impact on local food webs, but knowledge of the trophic interactions involved is still very limited. On the basis of samples collected along the lower Paraguay-middle Parana´ rivers, we studied the feeding behavior and selectivity of larval fish, with emphasis on veligers of the introduced bivalve L. fortunei. Among feeding larvae (i.e., without a yolk sac), 16.5% had only Limnoperna veligers in their guts, while 15.6% had veligers and some other prey. Half of the fish taxa recorded (8 out of a total of 16) consumed Limnoperna veligers. The Paraguay and Parana´ rivers differed strongly in the proportions of fish larvae that consumed veligers: 14 and 68%, respectively. This difference paralleled the availability of veligers in the water column, which was significantly lower in the Paraguay (0.8 ± 0.5 ind. l-1 ) than in the Parana´ River (5.5 ± 2.3 ind. l-1 ). Conversely, cladocerans, originally the staple food of fish larvae, were more abundant in the Paraguay (consumed by 48% of the individuals) than in the Parana´ River (26%). These results indicate that, when widely available, Limnoperna veligers largely replace the original prey of fish larvae, especially in their younger stages (protolarvae). Fil: Paolucci, Esteban Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Almada, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Ministerio de Seguridad. Prefectura Naval Argentina; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Boltovskoy, Demetrio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Fish predation on microcrustaceans is of key importance for dominance of small zooplankters in warm shallow lakes, yet its role in floodplain environments remains poorly explored. We studied seasonal and spatial variations of the abundance, diet composition and feeding selectivity of small omnivorous–planktivorous fish in relation to zooplankton at different habitats in a floodplain lake of the Lower Paraná River. Fish catches were very high in spring and summer and scarce in autumn and winter, and their distribution varied among habitats in response to changes in refuge provision and oxygen concentration. Fish diet comprised zooplankton, phytoplankton and detritus, except in summer when Cyanobacteria prevailed; in general, cyclopoid copepods and cladocerans were positively selected. Macrozooplankton biomass was the highest in spring when calanoid copepods dominated, probably because their fast swimming velocity enabled their escape from predators. Lower macrozooplankton biomass in summer with low waters, was likely caused by harmful effects of Cyanobacteria or elevated salinity, while washing-out or dilution processes may explain macrozooplankton scarcity during cold seasons under low fish predation pressure. Our results indicate that in floodplain lakes, factors affected by or related to hydrology (salinity, Cyanobacteria development, dilution and washing-out processes) may have stronger influence than predation on zooplankton structure. Fil: Chaparro, Griselda Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Fontanarrosa, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: O'farrell, Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Glyphosate is currently the most widely used herbicide in agricultural production. It generally enters aquatic ecosystems through surface water runoff and aerial drift. We evaluated the effect of glyphosate acid on biochemical parameters of periphyton exposed to concentrations of 1, 3, and 6 mg/L in outdoor mesocosms in the presence and absence of the mussel Limnoperna fortunei. Periphyton ash-free dry weight, chlorophyll a content, carotene/chlorophyll a ratio, lipid peroxidation levels, and superoxide dismutase and catalase activities were determined at days 0, 1, 7, 14, and 26 of the experimental period. Ash-free dry weight was similar between control and glyphosate-treated periphyton in the absence of L. fortunei. The latter had significantly lower carotene to chlorophyll a ratios and enzyme activities, and higher lipid peroxidation levels and chlorophyll a content than the former. These results show an adverse effect of glyphosate on the metabolism of periphyton community organisms, possibly inducing oxidative stress. On the contrary, no differences were observed in any of these variables between control and glyphosate-treated periphyton in the presence of L. fortunei. Mussels probably attenuated the herbicide effects by contributing to glyphosate dissipation. The results also demonstrate that biochemical markers provide useful information that may warn of herbicide impact on periphyton communities. Environ Toxicol Chem 2017;36:1775-1784. © 2016 SETAC.

Multiple anthropogenic stressors act simultaneously on the environment, with consequences different from those caused by single-stressor exposure. We investigated how the combination of the invasive mussel Limnoperna fortunei and a widely applied herbicide, Roundup Max®, affected freshwater microscopic communities and water quality. Further, we compared these results with those induced by the combination of the mussel and technical-grade glyphosate. We carried out a 34-day experiment in outdoor mesocosms, applying the following six treatments: 6 mg L−1 of technical-grade glyphosate (G), the equivalent concentration of glyphosate in Roundup Max® (R), 100 mussels (M), the combination of mussels and herbicide either in the technical-grade or formulated form (MG and MR, respectively), and control (C). Herbicides significantly increased total phosphorus in water; R and MR showed greater initial total nitrogen and ammonium. R increased picoplankton abundance and caused an eightfold increase in phytoplankton, with high turbidity values; G had a lower effect on these variables. Herbicide-mussel combination induced an accelerated dissipation of glyphosate in water (MG 6.36 ± 0.83 mg G g DW−1 day−1 and MR 5.16 ± 1.26 mg G g DW−1 day−1). A synergistic effect on ammonium was observed in MR but not in MG. MR and MG had an antagonistic effect on phytoplankton, which showed a drastic reduction due to grazing, as revealed by M. We provide evidence of differential effects of Roundup Max® and technical-grade glyphosate over water quality and microscopic communities, and in combination with mussels. However, in the combination of mussels and herbicides, mussels seem to play a leading role. In the presence of L. fortunei, the effects of higher nutrient availability provided by herbicides addition were counteracted by the filtration activity of mussels, which released nutrients, grazed on picoplankton and phytoplankton, and boosted the development of other primary producers, periphyton and metaphyton. Fil: Gattás, Florencia María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Vinocur, Alicia Liliana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Graziano, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Dos Santos Afonso, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Pizarro, Haydee Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

The Asian mytiloid Limnoperna fortunei (Dunker, 1857) was first recorded in South America along the coast of the Rio de la Plata estuary in 1991 (Pastorino et al., 1993). Since then the mussel has expanded its range, colonizing most of the Rio de la Plata basin, as well as several minor watersheds. Because of its wide distribution, high densities and significant ecosystem engineering capabilities, L. fortunei has had sizeable impacts on the waterbodies colonized, including modification of nutrient concentrations and ratios, enhancement of water transparency, macrophyte growth and effects on cyanobacterial blooms, the abundance and diversity of benthic invertebrates, sedimentation rates and food availability for fishes (Sylvester, Boltovskoy & Cataldo, 2007; Boltovskoy et al., 2009, 2013; Cataldo et al., 2012a, b; Boltovskoy & Correa, 2015; Paolucci & Thuesen, 2015). Impacts on human activities have been especially marked: L. fortunei larvae enter raw water conduits of open cooling systems and develop large beds in pipes and other components, clogging them and causing pressure loss, overheating and corrosion (Boltovskoy, Xu & Nakano, 2015). Northward expansion of L. fortunei is expected to continue beyond South America and into Central and North America (Karatayev et al., 2015). Available data indicate that potentially colonizable areas include all continents except Antarctica (Kluza & McNyset, 2005; Karatayev et al., 2015), but the fact that water bodies lacking mussels exist in watersheds where L. fortunei has been present for decades suggests that some environmental conditions may limit the expansion of this invader (Darrigran et al., 2011). Among these, the concentration of suspended solids is of particular interest. Suspended matter can affect respiration, growth, parasite infestation and reproduction of the organisms (Robinson, Wehling & Morse, 1984; Alexander, Thorp & Fell, 1994; Rosewarne et al., 2013), thereby restricting their geographic spread, but this constraint has not been explicitly addressed in models of the potential distribution of L. fortunei (Kluza & McNyset, 2005;Oliveira, Hamilton & Jacobi, 2010). In order to estimate the tolerance of L. fortunei of inorganic suspended solids, thus providing data for analysis of its potential distribution worldwide, we assessed the species’ capability of filtering water and retaining phytoplankton at different clay concentrations. Individuals of L. fortunei were collected from Buenos Aires (348320S; 588250W) and stored in aerated aquaria filled with dechlorinated tap water at 23–25 8C. They were fed ad libitum on cultured algae (.95% Scenedesmus spp., mean biovolume 1300–1600 mm) known to be actively consumed by the mussel (Cataldo et al., 2012a). Individuals 15–20 mm (mean 17.3 mm) in shell length were isolated from the clumps and placed in flat trays in order to verify their vitality. Actively filtering individuals were transferred from the trays to acclimation vessels at 27 8C for 48 h. All individuals were starved for 24 h and then stocked in cylindrical plastic netting cages (10 cm high, 6 cm in diameter) placed at mid-depth in the experimental 2-l containers (Fig. 1). In the latter, an air hose was attached laterally to a tube located vertically on the bottom, thereby suctioning settling sediment particles and returning them to the water column (Fig. 1). Algal concentrations in the experimental containers ranged from 30 to 60 (mean 43.5+6.3 SE) mg Chl a l, mimicking usual values for eutrophic water bodies (Jones & Lee, 1982). Bentonite clay with a mean particle diameter of 9.45 mm, within the range of .90% of the inorganic suspended solids in the South American water bodies colonized by L. fortunei (Carignan, 1999; Sarubbi, Pittau & Menendez, 2004), was used at different concentrations: 0 g l (controls), 0.1, 0.5, 1, 2, 4, 6, and 8 g l. All experiments were performed at 27 8C (typical of the lower Parana River and Rio de la Plata estuary during the summer) in a controlled temperature chamber. For each sediment concentration, three replicates without (controls) and three with 60 individuals of L. fortunei were used. Upon termination of each experiment (120 min) all individuals were measured to the nearest 0.01 mm with digital calipers, and their tissues extracted and dried at 60 8C to constant weight (DTW). Immediately before start and after termination, each experimental container was sampled (40–150 ml) to estimate chlorophyll a concentrations. Samples were filtered through fibreglass filters (Whatman GF/F) and pigment extraction was performed with hot (60–70 8C) ethanol in darkness two or three times in order to avoid underestimations due to chlorophyll adsorption upon sediment particles (Koyama, Shimomura & Yanagi, 1968). The extracts were clarified by centrifugation, their volume adjusted and the absorbance at 665 and 750 nm measured with a spectrophotometer before and after acidification with HCl (1 N). Pigment concentrations were calculated according to Marker et al. (1980).

The use of glyphosate has increased dramatically during the past years around the world. Microbial communities are altered when glyphosate reaches water bodies. The freshwater golden mussel Limnoperna fortunei is an invasive species that has rapidly dispersed since it was introduced in Argentina two decades ago. Mussels alter aquatic conditions through their filtrating activity by increasing water clarity and nutrient recycling. We aim to evaluate the potential capacity of the golden mussel to reduce glyphosate concentration in water, in laboratory conditions. Firstly, the evasive response of mussels to glyphosate (10, 20, and 40mgl-1) was evaluated and a toxicity test was carried out for these concentrations. A three-week experiment was then performed to assess glyphosate variation under mussel presence for two mussel sizes. Finally, mussels' role on glyphosate concentration was evaluated considering different mussel parts (living organisms and empty shells) through another three-week experiment. Laboratory experiments were performed in triplicate using 2-l microcosms. An initial glyphosate concentration between 16 and 19mgl-1 was used, and when mussels or valvae were added, 20 organisms per aquaria were used. Samples were obtained at days 0, 1, 2, 4, 8, 14, and 21. Glyphosate decreased by 40% under large mussel presence in both experiments, and was reduced by 25% in empty shell treatments. We believe that part of the herbicide that disappears from the water column is adsorbed in valvae surface, while another proportion is being mineralized by microbial communities in shells' biofilm. The mechanisms by which living mussels increase glyphosate dissipation would be degradation, possibly mediated by bacteria associated to mussel's metabolism. Glyphosate half-life depended on mussel and valvae presence and varied with mussel size. L. fortunei presence (either alive or as empty valvae) alters glyphosate concentration in water. We provide preliminary observations from laboratory experiments, with strong potential ecological consequences, about two stressors that could be acting jointly on the environment. Fil: Di Fiori, Eugenia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pizarro, Haydee Norma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Dos Santos Afonso, María. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cataldo, Daniel Hugo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

In order to evaluate the effects of the golden mussel Limnoperna fortunei on phytoplankton density and composition and nutrient recycling we conducted a 24 h filtration experiment in Rio Tercero Reservoir (Argentina) using four 400 L mesocosms, two of them stocked with 1700-1800 adult mussels each, and two controls (without mussels). Nutrient concentrations and phytoplankton composition and density were evaluated at 0, 3, 6, 12, and 24 h. Estimated filtration rates were 1.48-3.14 mL mg DW -1 h -1 . Grazing pressure by the mussel was not associated with algal taxonomy or cell size. After 24 h, L. fortunei removed 84% of the particulate nitrogen, and 49% of the particulate phosphorus. Nutrient regeneration was very significant as well: ammonium was produced at a rate of 3 μM NH3g DW -1 h -1 , whereas production of phosphates was 0.42 μM PO4g DW -1 h -1 . It is concluded that the impact of L. fortunei on phytoplankton and nutrient cycling can be as significant as that reported for another invasive bivalve - the zebra mussel Dreissena polymorpha in Europe and North America, but the overall effect of this impact on the biota may differ strongly under different environmental settings.

In order to assess the effects of the introduced bivalve Limnoperna fortunei on water-column properties of Salto Grande reservoir, experiments were conducted using six 400 L mesocosms: 2 with 100 mussels, 2 with 300 mussels, and 2 controls (without mussels). At 0, 1, 2, 3, 7, 14, 21, 28, and 35 days we measured nutrient and chlorophyll a concentrations, counted and identified the phytoplankton, and estimated the density, size, and number of cells of the colonies of Microcystis spp. Cumulative periphyton growth and total accumulated sediments were assessed in all enclosures at the end of the experiment. Throughout the experiment, in the controls ammonia and phosphates dropped to near zero, whereas in the mesocosms with L. fortunei they increased two- to tenfold. Nitrates decreased in all mesocosms. In the presence of the mussel, chlorophyll a and algal cells dropped until day 3 increasing thereafter, whereas in the controls they increased from day 0. Periphyton growth and sediment accumulation were significantly higher in the mesocosms with mussels that in the controls. Cell density, proportion of colonial cells and colony size of Microcystis spp. increased in all enclosures, but these increases were dramatically (and very significantly) higher in enclosures with 100 and, especially, with 300 mussels, than in the controls. Our results indicate that L. fortunei modifies nutrient concentrations and proportions, and promotes aggregation of solitary Microcystis spp. cells into colonies; both these effects can favor blooms of this often noxious cyanobacteria.

Limnoperna fortunei (Dunker, 1857) (Bivalvia) invaded Argentina through the Rio de la Plata estuary around 1990 and is presently established throughout five South American countries as a dominant component of the benthic fauna and a major nuisance for industry and power plants. Between 1997 and 2006 we monitored the reproductive activity of L. fortunei through weekly measurements of planktonic larvae in six South American water bodies: Rio de la Plata estuary, Parana and Carapachay rivers, Salto Grande, Itaipu and Embalse de Rio Tercero reservoirs. Mean larval densities varied between 4000 and 7000 individuals m⁻³; except in the reservoirs of Itaipu (450 ind. m⁻³) and Salto Grande (869 ind. m⁻³), where the mussel was first recorded shortly before our surveys, and upstream dispersal is limited (Salto Grande). In all cases, reproductive output decreases during the winter. At four of the six sites surveyed larval densities were comparatively high for 8.8-10.2 months per year. A lower food supply is possibly responsible for the shorter reproductive period of 5.9 months at Embalse. At Salto Grande, there is a well-defined mid-summer drop in larval numbers, coinciding with blooms of cyanobacteria. We propose that, in addition to temperature, two major factors may regulate the reproductive activity of L. fortunei: (i) the availability of food; and (ii) blooms of toxic cyanobacteria, significantly shortening the otherwise very long reproductive period. This information is important for the design of antifouling programmes involving the use of molluscicides, and has potential for reduced biocide use. These results provide supporting evidence for some fundamental ecological theories of invasions discussed here.

Since its introduction in South America around 1990, the freshwater Asian mussel Limnoperna fortunei has been shown to strongly interact with several components of the local biota. However, investigation of its ecosystem-wide effects was hindered by (1) difficulties associated with evaluation of its densities over large spatial scales and (2) scarcity of pre-invasion environmental data. The present survey overcomes these shortcomings and addresses the question whether Limnoperna’s impact on the ecosystem-wide scale is measurable and significant. On the basis of diver-collected bottom samples, we estimated the overall density of this mussel in a reservoir (Embalse de Rio Tercero, Argentina), where Limnoperna is present since 1998 and analyzed changes in several water-column properties before and after the invasion. The 47 km2 reservoir hosts around 45 billion mussels; at these densities, a volume equivalent to that of this water body can potentially be filtered by the bivalves every 2–3 days. Data collected regularly since 1996 indicate that after the invasion water transparency increased, and suspended matter, chlorophyll a, and primary production decreased significantly, with strong changes occurring in the area with highest mussel densities. Our results indicate that the ecosystem-wide impacts of Limnoperna are generally comparable to those described in Europe and North America for another invasive mussel—Dreissena polymorpha. However, given Limnoperna’s wider tolerance limits, its influence on newly invaded water bodies, potentially including Europe and North America, will probably be stronger.

We conducted a field experiment to assess the influence of conspecific adults on recruitment success of the golden mussel Limnoperna fortunei. Tiles of 225 cm2 in surface were used as artificial substrates in four treatments: control (blank tiles), low (800 mussels m-2), medium (4000 mussels m-2) and high (12 000 mussels m-2) density treatments. Results obtained indicate that recruitment is strongly affected by the presence and density of conspecifics: after one and three months of exposure numbers of recruits were significantly higher on tiles with conspecific adults than on blank tiles, and there was a positive and significant relationship between the number of recruits and the number of adults in the three treatments assayed. Also, after three months of exposure recruits in all treatments with adults present were larger than recruits in the control treatment. Our results suggest that conspecific adults have a positive effect on recruitment success and growth of the newly settled juveniles through factors that enhance larval settling and/or that contribute to the survival of settlers in areas colonized by adult conspecifics. Fil: Sardiña, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Boltovskoy, Demetrio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

We studied experimentally the feeding selectivity of larvae of Prochilodus lineatus (Pisces), with particular emphasis on the role of veligers of the exotic bivalve Limnoperna fortunei. Three concen- trations of veligers were offered to three develop- mental stages of P. lineatus. Veliger concentrations were: (1) higher than in the field (''enriched'', 0.09 ind. ml -1 ), (2) unmodified from field conditions (''normal'', 0.06 ind. ml -1 ), and (3) lower than in the field (''low'', 0.02 ind. ml -1 ). Fish developmental stages were protolarvae (approx. 10 days old), me- solarvae (17 days), and metalarvae (25 days). Pro- portions (in terms of numbers and biomass) and selectivity values were calculated for each prey item evaluated: veligers, small cladocerans ? nauplii, medium-sized cladocerans, copepodits, and large cladocerans ? copepods. Protolarvae and mesolarvae consumed veligers almost exclusively (88-90%, both in numbers and in biomass) when offered prey enriched in veligers, whereas for metalarvae veligers represented only 16.0% of the food consumed. At lower veliger concentrations, only protolarvae pre- ferred Limnoperna veligers, whereas older fishes switched gradually to crustacean plankton. We con- clude that veligers are preferred by the early fish developmental stages, and we speculate that this may be because their slower swimming makes them easier to capture than planktonic crustaceans. However, as fish larvae grow larger, veligers become too small a prey for their energetic needs, and they switch to larger items like cladocerans and copepods. We anticipate that this new and abundant food resource has an important impact on the survival and growth of P. lineatus.

We examined the importance of the introduced Asian golden mussel (Limnoperna fortunei) in structuring invertebrate communities in South American rresnwaters. An experiment using artificial substrata (i.e., concrete tiles with either a layer of living mussels, a layer of intact empty shells that mimicked living mussels, or blank tiles) showed that, when considered in bulk, invertebrates (density and biomass) are enhanced significantly in the presence of live mussels (as compared with shells only and blank tiles). On a taxon-by-taxon basis, however, significantly higher densities and biomass on live mussel tiles than on blank and/or shells-only tiles were found only for Oligochaeta, which would especially benefit from the feces and pseudofeces produced by the living mussel beds. At the end of the experiment, the amount of accumulated sediment on the tiles differed greatly among treatments, with values up to three times higher on shells-only tiles than on live-mussel and blank tiles. Dead mussels act as a sediment trap, whereas the activity of live mussels helps keep the tiles less clogged with sediments. On the other hand, proportions of organic matter were two times higher in the presence of live mussels than in the other two treatments. Although the physical structure created by mussel shells plays a significant role, we conclude that the activity of living mussels is of major importance for controlling invertebrate numbers, biomass and diversity.

To assess the trophic impact of the planktonic larvae of the invasive Asian bivalve Limnoperna fortunei, introduced in South America around 1990, we investigated the gut contents of fish larvae collected at monthly intervals between October 2000 and March 2001 at three locations along a 600 km stretch of the Parana River, and during November 2004 in two areas of marginal lagoons connected to the river near the city of San Nicolas, Argentina. Zooplankton was also collected in the lagoons in 2004. In total, 11,956 fish larvae were retrieved, of which 1,511 were used for detailed analyses. Of the 15 fish taxa collected, 11 had veligers of L. fortunei in their gut. Fish larvae with empty guts represented 60% (San Nicolas) to 72% (Parana River) of the total number of fish. Proportions of feeding fish larvae with L. fortunei veligers in their guts varied between 20% (San Nicolas) and 56% (Parana River); in 15% of the guts analyzed, L. fortunei was the only food item recorded. For those specimens that had consumed L. fortunei larvae and any other food item, L. fortunei was the most important item in 55% (Parana River) to 71% (San Nicolas) of the animals in terms of biomass. No major temporal or spatial changes in the diet were observed along the Parana River, but the relative biomass contribution of L. fortunei larvae differed strongly in fishes of different developmental stage. In protolarvae and mesolarvae, veligers accounted for 30–35% of the gut contents. In metalarvae, veligers accounted for only 3%, indicating enhanced food supply for the earliest fish life stages. Comparison of the relative proportions of the three main zooplankton types (L. fortunei veligers, cladocerans, and copepods) in the water and in larval fish guts indicates that L. fortunei is always selected positively over the other two prey types. While our results strongly suggest that the expansion of L. fortunei results in an enhanced food supply for local fish populations, they do not necessarily imply that the overall effect on the ecosystem in general, and on the fish fauna in particular is beneficial.

We assessed the effects of the introduced bivalve L. fortunei on the abundance and biomass of associated benthic invertebrates in South American large floodplain rivers. The survey was based on comparisons of L. fortunei-covered and L. fortunei-barren areas in five artificial cages from where large predators were excluded, exposed to colonization by the mussel for a total of 17 months in the lower Parana river delta. Accompanying invertebrates were dominated by Oligochaeta, Nematoda, Rotifera, Copepoda, Gastropoda, Hirudinea, Chironomidae and nauplii. Also present in minor numbers were Tardigrada, Turbellaria, Cladocera, Ostracoda, Insecta, Hydracarina and Decapoda. Dominant invertebrates were 27–100% more numerous (and hosted 43–100% more biomass) in areas with L. fortunei than in areas barren of the mussel. In areas with L. fortunei, total invertebrate biomass (excluding the bivalve) was positively correlated with mussel biomass, and increased with time of exposure under water. No such trend was observed in areas barren of L. fortunei. It is suggested that higher invertebrate growth is associated with enhanced substrate complexity and, probably, the transfer of organic matter from the plankton to the sediments due to the mussels’ feces and pseudofeces. Some of the adverse ecosystem-wide effects of filter-feeding invasive mussels observed in European and North American water bodies may be offset in the Parana by the extremely high loads of organic matter in these turbid waters.

Comparison of Limnoperna fortunei numbers and biomass in screened (5, 15 and 40 mm) and unscreened cages deployed for 18 months in the lower Parana delta indicates that predators harvest 26-79% (numbers), or 20-85% (biomass) of the mussel population. Predation impact decreases with mussel size. On average, 6 kg of whole live mussel ¥ m -2 ¥ year -1 (0.36 g of dry mussel tissue ¥ m -2 ¥ day -1 ) were eliminated from the unscreened cages. Cages with 15 and 40 mm screens lost between 1 and 2 kg ¥ m -2 ¥ year -1 . Aquatic mammals, birds, and especially fish, are probably the main consumers of large mussels. Small L. fortunei are most probably eaten by fish and also by several invertebrates, including crustaceans, leeches and gastropods. It is suggested that L. fortunei intercepts a significant fraction of the organic carbon that the Parana-Uruguay rivers flush into the ocean, locally boosting numbers of benthophagous animals, deposit feeders and, indirectly, higher level predators. Our results indicate that only 15 years after its first introduction in South America this invasive species is very actively consumed by local predators, but predatory suppression of the mussel seems very unlikely. Comparisons with the effects reported for the zebra mussel (Dreissena polymorpha) in Europe and North America suggest that L. fortunei is consumed more actively and that its negative impact on the local fauna is more restricted. These differences are attributed to the fact that while D. polymorpha feeds chiefly on plankton, a limited resource, L. fortunei feeds on detrital particulate organic matter, whose supply in these large South American rivers largely exceeds consumption.

In South America, the inventory of species that feed on Limnoperna fortunei has increased steadily; in 2006, 18 fish species had been identified as predators of L. fortunei, whereas 7 years later, the list had grown to almost 50 species. In some areas, fishes that consume L. fortunei represent > 50 % of the species regularly present in commercial fisheries, including traditionally omnivorous, iliophagous, and ichthyophagous forms. Several economically important species have significantly changed their feeding habits since the mussel’s introduction, shifting from a diet based on plants and detritus to one dominated by adult mussels. Consumption of golden mussels is not restricted to fishes provided with teeth that can crush and grind the shells; many toothless species swallow whole specimens or nibble on the exposed siphons and mantle edges of the bivalve. Golden mussels can account for up to 100 % of the gut contents of some fish species, especially during the summer. Feeding of fishes on L. fortunei often involves the selective consumption of the smaller mussel size classes. Fish predation pressure on the mussel is likely high and it probably represents the most significant mechanism that modulates L. fortunei populations, but it is very unlikely to eradicate the mussel altogether. No comprehensive, large-scale studies are yet available on the effects of this new food supply on local fish stocks, but ancillary information suggests that these effects are likely very significant. Impacts are not restricted to species that consume the mollusc, but also affect species that benefit from this new food resource indirectly, including large ichthyophagous species feeding on molluscivorous forms, as well as on those that consume the organic matter-enriched sediments by the mussel’s feces and pseudofeces.

Young Limnoperna fortunei mature sexually from 5–6 to ~15 mm. The species is generally dioecious, with approximately equal numbers of males and females and very small (< 0.6 %) proportions of hermaphrodites. The gametogenic cycle has been described for both Asian and South American populations, recognizing between four and five reproductive phases. Gonadal cycles based on histological sections yielded somewhat dissimilar results for different areas. In Hong Kong, two yearly peaks in reproductive output were detected. In South America, mature sperm and ova have been recorded year round and several irregularly spaced spawning events have been observed, as well as more or less continuous breeding punctuated by peaks in spring and at the end of the summer. Reproductive studies based on changes in the abundance of larvae in the water column have been carried out in South America and in Japan. In tropical and subtropical South America, larval output is more or less continuous for 6–10 months of the year, often with a major peak in spring–early summer, and a smaller one in the late summer–autumn. In Japan, at considerably lower water temperatures, larval production is limited to 1–2 months centered around summer. Apparent disagreements between results based on histological data and on larval counts stem from the fact that while the latter integrate the reproductive output of extensive mussel beds dispersed over large areas, histological evidence pinpoints with high precision the ripening and spawning of isolated mussel clusters. Aside from water temperature, several other factors (pH, salinity, dissolved oxygen, suspended solids, chlorophyll a, flood–drought cycles) have been proposed as reproductive triggers, but actual associations have not been demonstrated. Peak larval densities can exceed 20,000 ind./m3, but, normally, values range around 6000 ind./m3, showing major fluctuations within short periods, as well as changes as a function of time elapsed post colonization, and availability of substrata suitable for adult occupation. Microcystin-producing cyanobacterial blooms can kill L. fortunei larvae. Facultad de Ciencias Naturales y Museo

Laboratory and field experiments indicate that the presence of Limnoperna fortunei decreases concentrations of particulate organic matter and increases ammonia, nitrate, and especially phosphate. Long-term series of field data partially confirm these results. After having been colonized by the mussel, a 47 km2 reservoir developed higher concentrations of ammonia and phosphates, a higher P:N ratio, more transparency, less seston, and less phytoplankton and primary production. Phytoplankton clearance rates by the mussel vary widely, suggesting that “normal” values for adult organisms are around 100 mL/ind./h, or ca. 2–4 mL/mg DW/h. Data on grazing selectivity are inconclusive, but seem to indicate highest impacts on small (< 1 mm) particles. Large plankton are negatively selected, but they may account for greater proportions of total biomass in the diet. Studies on consumption of toxic cyanobacteria yield conflicting results, but large golden mussel populations significantly enhance blooms of colonial Microcystis spp. through changes in nutrient availability, size-selective grazing, promotion of colony formation, and reduced grazing of toxic cells. These toxic blooms, in turn, suppress reproduction of the mussel, most probably killing the larvae. Growth of periphyton and aquatic macrophytes are enhanced significantly by the golden mussel.

Mature sperm cells of Limnoperna fortunei measure about 4 µm, and ova are typically spherical, 80–100 µm in diameter. Forty minutes after spawning, the first polar lobe appears, and the first division occurs 14 min later. Slightly over an hour after spawning, the second polar lobe appears and the second division yields a 4-cell stage. The third division occurs 90 min after spawning, and the fourth 115 min after spawning. Approximately 3.5 h after spawning (at 26 °C) the morula stage is reached. Six hours after spawning, the first trochophores appear (95–110 µm in length) at 28 °C. Subsequently, the prodissoconch I starts developing, initially as small rosette-shaped structures on the dorsal side of the trochophore. Straight-hinged veligers (115–160 µm) start appearing 24 h after spawning. These larvae start feeding externally and secrete the prodissoconch II. Umboned veligers (156–220 µm) are reached 287 (at 28 °C), 165 (25 °C) and 118 (20 °C) h after spawning. From there on, the larva reabsorbs its velum and develops a muscular, adhesive foot, yielding a plantigrade larva (250–405 µm), which shortly thereafter settles and attaches to the substrate. Development times are therefore strongly influenced by water temperature.

Limnoperna fortunei is a freshwater bivalve that invaded South America through Rio de la Plata estuary in 1989 and has since become a major macrofouling pest. Along the Parana-Paraguay waterway, which hosts intense boat traffic, L. fortunei has moved upstream at an average rate of of 250 km per year. In contrast, along the Uruguay river, where boat traffic is restricted to the lowermost 200 km section, upstream colonization is almost 10-times slower. This suggests that attachment to vessels is by far the most important dispersion mechanism. It is suggested that the Amazon, Orinoco and Magdalena basins are under high risk of invasion by this mussel, especially through their estuarine gateways. All South American basins host innumerable water bodies with favorable conditions for L. fortunei’s colonization. Known ecological tolerance limits of the mussel also suggest that it may colonize much of the area from Central America to Canada, including waters that due to their low calcium contents, high temperature and pollution levels, and low oxygen are inadequate for the survival of Dreissena polymorpha. Despite it’s remarkable geographic expansion and its extremely high population densities, L. fortunei’s ecological effects have received very little attention so far. It is suggested that the 2.4-fold increase in Argentine landings of freshwater fish between 1992–1993 and 2000–2001 may be associated with the introduction of this prey species.

Laboratory-reared larvae of Limnoperna fortunei (Dunker) were monitored until the morula stage at 26°C, and from there on until settlement at 20, 25 and 28°C. The first polar lobe is produced c. 40 min after spawning, and the first division occurs 14 min later. Slightly over an hour after spawning, the second polar lobe appears and the second division yields a 4-cell stage. The third division occurs 90 min after spawning, and the fourth 115 min after spawning. The morula stage is reached 3.5 h after spawning. The trochophore stage (size: 95-110 μm) is reached 20, 6.3 and 6 h after spawning at 20, 25 and 28°C, respectively. Straight-hinged veligers (115-175 μm) start appearing at 45, 26, and 24 h after spawning; umboned veligers (156-220 μm) at 287, 165 and 118 h after spawning; and pediveligers (>200 μm) at 480, 313 and 265 h after spawning. Implications of these findings for the dispersion of the species and for its fouling impact are discussed. © The Malacological Society of London 2005, all rights reserved. Fil:Cataldo, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Boltovskoy, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Clearance rates of Limnoperna fortunei (Bivalvia) were investigated in laboratory experiments using monocultures of the alga Chlorella vulgaris. Experimental conditions included two mollusc sizes (15 and 23 mm), and three water temperatures (15, 20 and 25 °C) covering the normal seasonal range in the lower Parana river and Rio de la Plata estuary. Filtration rates obtained were, for the larger mussels: 9.9, 13.1 and 17.7 ml mg tissue dry weight−1 h−1 at 15, 20 and 25 °C, respectively; and for the smaller ones: 17.7, 20.8 and 29.5 ml mg−1 h−1. Differences between sizes and between temperatures (except 15 vs. 20 °C) were statistically significant. In absolute terms larger animals have higher clearance rates, but as a function of body mass smaller individuals feed more actively. Within the range of experimental values used, filtration rates were positively associated with water temperature. These clearance rates (125–350 ml individual−1 h−1) are among the highest reported for suspension feeding bivalves, including the invasive species Dreissena polymorpha, D. bugensis and Corbicula fluminea. High filtration rates, associated with the very high densities of this mollusc in the Parana watershed (up to over 200,000 ind m−2) suggest that its environmental impact may be swiftly changing ecological conditions in the areas colonized.

In 1995-1996, Corbicula fluminea was collected at monthly intervals at two sites in the delta of the lower Paraná river (Argentina), at the confluence of the San Antonio and Vinculación rivers, and from the Paraná de las Palmas river close to its outlet into the Río de la Plata estuary. The San Antonio site is located in the vicinity of sources of industrial and sewage effluents, whereas the more remote Paraná de las Palmas river sampling location is considerably less polluted. Growth rates of caged individuals at the two sites also monitored during the same period, and Cu, Cd, Pb and Zn were measured monthly in the water and in tissue of animals. Throughout the year concentrations of all metals in water, as well as Pb and Zn in tissue, varied irregularly and their levels at the two sites were roughly similar; on the other hand, Cu and Cd in tissue of animals from the polluted site were consistently and significantly higher than in those from the remote site. Changes in the size-frequency of clams from Paraná de las Palmas river throughout the period surveyed clearly indicated a highly structured population with a single well defined reproduction period in October-November. In contrast, shell lengths at San Antonio changed very little throughout the 13 month period, with over 88% of the clams varying between 18 and 20 mm in length; no discernible cohorts were recorded. Growth rates of caged clams were very significantly lower at the polluted site, with the remote site latter yielding comparable values to those obtained from the remote site cohort analysis data. Highest growth rates (around 10 mm) were attained by the smallest (about 7-8 mm) clams reared in Paraná de las Palmas river waters, whereas 23 to 25 mm organisms maintained in San Antonio waters grew only 2 to 3 mm in the same period. Of the 57 animals which survived throughout the caging experiment, those below 10 mm at the outset increased, on average, 8.2 mm in length after 13 months, whereas clams less than10 mm in length grew only 4.2 mm. The condition index (i.e., dry tissue weight divided by shell length) of clams from San Antonio was consistently about 50% lower than that of clams from the Paraná de las Palmas river.It is concluded that delayed growth, poorer condition index, and the abnormal population structure at San Antonio are due to enhanced pollution in this area as compared with the Paraná de las Palmas river, and that all three traits constitute a more useful biomarker of contaminants.

Densities of planktonic larvae of the Asian freshwater invasive pest bivalve Limnoperna fortunei (Dunker) were monitored weekly between 19 September 1997 and 22 January 1999 at two sites: the Parana de las Palmas river, ca. 130 km north of Buenos Aires (33°57.5′ S, 59°12.5′ W), and a coastal station on the Rio de la Plata estuary, in Buenos Aires (34°33.5′ S, 58°24.5′ W). Very variable but generally high (up to 25 000–35 000 ind. m−3) concentrations were recorded at both sites in September 1997-April 1998, and again in August 1998–January 1999, suggesting continuous reproduction during these months. In May through July 1998 larval densities were generally below 100-200 ind. m−3. The threshold temperature level associated with the onset and termination of reproduction was ca. 16–17 °C. With the exception of August-September 1998, when Rio de la Plata temperatures were below 16.7 °C and larval concentrations less than 1000 ind. m−3, whereas those of the Parana were above 16.7 °C, with 1300–13 000 larvae m−3, coupling between the two sites investigated was generally good. Since its invasion in Argentina around 1990, L. fortunei has rapidly become a major nuisance for industrial and power plants located along the lower Parana and Rio de la Plata. The fact that the mollusc produces larvae during 9 months per year greatly hinders its control.

Settling and growth of the Asian freshwater mussel Limnoperna fortunei on experimental PVC frames in the Parana de las Palmas river, ca 130 km north of Buenos Aires was monitored at monthly intervals in 1998. Frames were deployed in January. In February and March colonization reached 3800044000 mussels m-*, with early juveniles ( 2 mm) mussels. In September through December densities grew steadily again, with early juveniles (< 2 mm) accounting for over 95% of the mussels recorded. During their first month, animals born in January grew to ca 34 mm in length; in March they reached 7-8 mm, and by mid April 11-12 mm. In late April through July the growth rate decreased to < 2 mm per month, and in August it stopped almost completely, resuming again in late September. During the first year animals born in January reached 20mm in length; by the end of the second year the estimated length was 30mm, with a maximum theoretical length of 35mm being reached after 3 years. The data agree with the reported population dynamics of L. fortunei in Hong Kong in that both populations are characterized by extended reproduction periods lasting ca 9 months, and that the spring onset of breeding is triggered by a rise in temperature above approximately 16-17°C. On the other hand, in the Parana river reproduction was found to be continuous between September and March, and the period of lowest yearly temperatures was characterized by a very strong breeding decline, whereas for the Chinese populations 2-3 yearly spatfalls and breeding pulses roughly coinciding with the lowest and highest water temperatures were described.

Benthic individuals and drifting planktonic juveniles of Corbicula fluminea were sampled in the Lower Delta of the Parana River (Argentina) at monthly intervals between October 1995 and October 1996. Densities of settled clams above 1 mm, around 300–1000 ind. m-2, varied little throughout the year. Below 1 mm benthic juveniles, on the other hand, showed a single conspicuous abundance peak in October-November (up to 1722 ind. m-2), and were practically absent during the rest of the year (overall annual mean: 1070 ± 797 ind. m-2). Drifting juveniles showed one major peak in December 1995 (160 ind. m-3), and a minor one at the end of March (24 ind. m-3). Length-frequency analyses of the monthly field data clearly indicate a highly structured population with a single well defined reproduction period centered on October–November. Population parameters derived from the seasonally oscillating version of von Bertalanffy's growth formula were as follows: maximum shell length: 32 mm (maximum observed shell length: 33 mm); growth constant: 0.65; growth seasonality (i.e., span of summer-to-winter growth-rate difference): 0.7; winter point (i.e., time of the year when growth is minimum): 0.5 (June–July); estimated size range for one year-old individuals: 15.3–22.4 mm; for two years: 23.5–27 mm, and three years: 27.5–29.3 mm. Comparison with previous data confirm the influence of water temperature on the clam's reproduction and growth and furnish additional evidence suggesting that food availability may be as important for recruitment as thermic regimes. Contrasts between traits of the population analyzed herein with those described previously from a nearby (ca. 10 km) site more influenced by industrial pollution point at the influence of water quality on Corbicula's recruitment and growth.

Corbicula jZuminea was collected at monthly intervals in November 1991-June 1993, and in March, April 1995 at a site located in the vicinity of strong sources of industrial and sewage effluents (confluence of the Rivers San Antonio and Vinculacibn, SaV); and in November 1994 and March, April 1995 at a presumably less polluted one (Parana de las Palmas River, PP), in the lower delta of the Parana River (Argentina). Abundances at SaV ranged between 430 and 10,300 ind. me2, being noticeably higher than those at PP, as well as those at 19 stations between and around these two locales. Shell lengths at SaV were monotonous throughout the 19-months period, over 90 % of the clams varying between 16 and 22.5 mm in length; no discer- nible cohorts were recorded. At PP, on the other hand, juveniles below 5 mm were largely dominant, and shells above 25-30mm in length were very common. Larvae retrieved from the gills of gravid clams showed much greater mortality rates in waters from SaV (up to 75 % after 120 hr), than in those from PP and in the control (approx- imately 10 % after 192 hr). The first internal growth-related mark in clams from SaV was closer to the umbo (mean: 14.2mm), than that in clams from PP (mean: 24mm). It is concluded that inadequate water quality at SaV is responsible for 100 % mortal- ities of newborns, for dwarfed adult clams, and for the lack of discernible cohorts.

Toxic cyanobacterial blooms and biological invasions are major threats to freshwater systems worldwide. While usually dealt with independently, the two threats can interact to produce synergistic or antagonistic outcomes. The aim of this survey is to analyse interactions between the cyanobacterium Microcystis spp. and the Asian invasive mussel Limnoperna fortunei. On the basis of 9 years of observational data in a large subtropical reservoir (Salto Grande, Argentina-Uruguay), we analyse causal relationships between recurring summer-early autumn blooms of Microcystis spp. and recruitment by L. fortunei. Reproduction of the mussel was interrupted during dry summers (January-April), coinciding with periods of peak Microcystis spp. growth and low water discharge (which favours build-up of algal biomass). On the other hand, wet summers with high discharge rates were characterised by low Microcystis spp. densities and high numbers of L. fortunei larvae in the water column. Of the seven South American waterbodies investigated, Salto Grande was the only one with very marked cyanobacterial blooms and where larval numbers decrease to near zero during January-April; in all others, reproduction peaks in January-April. The assumption that microcystin-producing algae are responsible for these troughs during periods when elsewhere larvae are very abundant was reinforced by experimental results indicating that microcystin-LR is highly toxic to the mussel's larvae, eliminating 58-100% of animals in 48 h at 10-20 μg L-1. Paradoxically, high concentrations of microcystin in water are probably partly due to L. fortunei's own activity, which enhances growth of Microcystis spp. through modification of nutrient concentrations, selective grazing of solitary Microcystis spp. cells over colonial ones and production of chemical cues that trigger the formation of colonies. These interactions have important implications for the management of biofouling of industrial raw cooling water facilities by the byssate mussels, as well as policies oriented at curtailing the spread of the invasive bivalve. Fil: Boltovskoy, Demetrio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Correa, Nancy Myriam. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina Fil: Bordet, Hugo Facundo. Comisión Técnica Mixta de Salto Grande; Argentina. Universidad Nacional de Entre Ríos; Argentina Fil: Leites, Valentín. Comisión Técnica Mixta de Salto Grande; Argentina Fil: Cataldo, Daniel Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

In order to evaluate the resilience to salinity as a factor enhancing freshwater invasiveness, we assessed the tolerance of the mussel Limnoperna fortunei to salinity conditions mimicking changes in an estuary. We tested mussel mortality in 30-day exposures to constant and fluctuating salinities at different temperatures in the laboratory. Test conditions simulated different seasons of the year and locations with increasing influence of marine waters in Río de la Plata, Argentina. Significant mortality (31% after 30 d) was observed at a constant salinity of 2?, increasing to 45% and 57% at 5? and 10?, respectively. In contrast, considerably greater tolerances were observed when conditions in the experimental chamber fluctuated between salt- and fresh water. No significant mortality was observed in mussels exposed to a salinity cycle with abrupt salinity changes ranging 1-23? (mean 2.68?) over a month. Tolerance to this type of regime was unaffected by different temperatures within ambient ranges. Tests at constant salinity underestimate the tolerance of this and probably other freshwater nonindigenous species (NIS) to short term saltwater exposures. Estuarine ports account for ca ⅔ of non-marine ports globally, thus constituting hotspots for NIS propagule pickup and delivery into continental aquatic ecosystems via shipping vectors. The tolerance of L. fortunei to estuarine conditions likely contributes to the species? remarkable invasive success. These results highlight the need to determine causes of invasiveness, and study NIS traits not alone but in combination with transport network properties. Fil: Sylvester, Francisco. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Fil: Notaro, Carolina. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Fil: Cataldo, Daniel. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Museo Arg.de Cs.nat; Fil: Boltovskoy, Demetrio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Museo Arg.de Cs.nat

Engineered domains of human fibronectin (Adnectins™) were used to generate a bispecific Adnectin targeting epidermal growth factor receptor (EGFR) and insulin-like growth factor-I receptor (IGF-IR), two transmembrane receptors that mediate proliferative and survival cell signaling in cancer. Single-domain Adnectins that specifically bind EGFR or IGF-IR were generated using mRNA display with a library containing as many as 10 ( 13) Adnectin variants. mRNA display was also used to optimize lead Adnectin affinities, resulting in clones that inhibited EGFR phosphorylation at 7 to 38 nM compared to 2.6 μM for the parental clone. Individual, optimized, Adnectins specific for blocking either EGFR or IGF-IR signaling were engineered into a single protein (EI-Tandem Adnectin). The EI-Tandems inhibited phosphorylation of EGFR and IGF-IR, induced receptor degradation, and inhibited down-stream cell signaling and proliferation of human cancer cell lines (A431, H292, BxPC3 and RH41) with IC 50 values ranging from 0.1 to 113 nM. Although Adnectins bound to EGFR at a site distinct from those of anti-EGFR antibodies cetuximab, panitumumab and nimotuzumab, like the antibodies, the anti-EGFR Adnectins blocked the binding of EGF to EGFR. PEGylated EI-Tandem inhibited the growth of both EGFR and IGF-IR driven human tumor xenografts, induced degradation of EGFR, and reduced EGFR phosphorylation in tumors. These results demonstrate efficient engineering of bispecific Adnectins with high potency and desired specificity. The bispecificity may improve biological activity compared to monospecific biologics as tumor growth is driven by multiple growth factors. Our results illustrate a technological advancement for constructing multi-specific biologics in cancer therapy.