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The exposure to environmentally relevant chlorpyrifos concentrations (0.03, 0.06 and 0.12 µg chlorpyrifos L−1) causes increases in precopulatory guardian behavior time, amplexus reformulation after exposure and in the number of ovigerous females in the amphipod Hyalella curvispina. Effects in incubation period, effective hatching and median lethal concentration on the decapods Macrobrachium borellii and Aegla uruguayana, both in adults and embryos, were achieved at higher concentrations than those found in the environment. Environmentally relevant chlorpyrifos concentrations appear not to affect decapods but several effects in reproductive traits of amphipods were observed.

Global trends in pesticide use can increase aquatic pollution and affect resident fisheries. Crabs exposed to organophosphate pesticides, such as chlorpyrifos, may increase production of reactive oxygen species (ROS), affecting the pro-oxidant/antioxidant balance. Zichiopsis collastinensis crabs were exposed to environmentally relevant concentrations of chlorpyrifos (0.1 and 0.5 µg L−1). Effects on the oxidative stress enzymes catalase, superoxide dismutase, glutathione S-transferases, glutathione reductase, and on thiobarbituric acid reactive substances and hydrogen peroxide concentrations were evaluated at four intervals during 96 h exposures. Exposures caused decreased GST activity and increased H2O2 levels in gills. There were modifications of GST, CAT and SOD activities in the hepatopancreas after 12 h of exposure, and an increase of H2O2 levels at every exposure interval observed. The present study proved that chlorpyrifos lead to oxidative stress in Z. collastinensis. However other enzymatic/non-enzymatic responses should be further investigated in order to be included as part of a battery of biomarkers, together with H2O2 levels, which is a parameter highly recommended to be taken into account. Fil: Negro, Carlos Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Iturburu, Fernando Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Mendieta, Julieta Renee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; Argentina Fil: Menone, Mirta Lujan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina

Sublethal effects of the pesticide chlorpyrifos were evaluated in the crab Zilchiopsis collastinensis (Decapoda, Trichodactylidae). Crabs were exposed to high concentrations of chlorpyrifos at the beginning of the experiment and controlled dilution, under natural light and temperature conditions. A control and three concentrations (22.4, 41.25 and 61.4 µg chlorpyrifos L−1) were evaluated in triplicate. Nine crabs per concentration and day were used. The gills, hepatopancreas and ovaries were sampled before pesticide exposure (day 0) and 8, 15 and 22 days later, when concentrations were diluted and below the detection limits. The histopathological effects and their variations in time were observed and quantified. In gills, hyperplasias were observed in several cases, mainly in crabs exposed to chlorpyrifos. The number of collapsed lamellae and the number of affected lamellae quickly increased in exposed crabs, as effects were observed on day 8 and remained until day 22. In hepatopancreas there was an increase in the number of F and B -cells and affected tubules, especially after 22 days of exposure (p

The lethality (LC50) of endosulfan and chlorpyrifos is higher in adults (1990 and 156.78 lg/L respectively) than in embryos (95380 and 1242.54 lg/L respectively) of the crab Zilchiopsis collastinensis. The thickened embryonic coat of the freshwater species might isolate the embryo inside the egg, reducing the toxicity. Sublethal concentrations of chlorpyrifos and endosulfan caused an increase in hatching time and a decrease in effective hatching (p

Biocides are periodically applied in agricultural activities, reaching aquatic systems and acting upon the biota. Amphipods are widely used in toxicity tests because of their sensitivity to a wide range of pollutants. In this work, we report the differential lethality of a widely used pesticide, endosulfan, on the amphipod Hyalella curvispina at two life stages and in three different adult groups, males and females separated by sex and both sexes grouped together. In addition, oxygen consumption of adult groups was determined as a way to estimate the role of behavioral activities and exposure to toxic agents in metabolism shift. Juveniles were as resistant as adults separated by sex. When grouped without sexual differentiation, adults were more sensitive to toxic agents. The oxygen consumption rate was higher when adults were grouped without sexual differentiation in the control group. The exposure to low concentrations causes an increase in oxygen consumption in all the treatments. Sexual behavior could have increased metabolism and sensitivity to endosulfan. Using only juveniles or adults separated by sex in toxicity tests may inaccurately estimate the lethality of biocides, especially in species with constant reproductive activities. Fil: Negro, Carlos Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Castiglioni, M.. Universidad Nacional del Litoral. Facultad de Bioquimica y Ciencias Biologicas. Escuela Superior de Sanidad; Argentina Fil: Senkman, Lidia Eloisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Autónoma de Entre Ríos; Argentina Fil: Loteste, Alicia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Autónoma de Entre Ríos; Argentina. Universidad Nacional del Litoral. Facultad de Bioquimica y Ciencias Biologicas. Escuela Superior de Sanidad; Argentina

In this work, the effects of a pulse exposure of endosulfan on hepatopancreas, gills and ovary of the burrowing crab Zilchiopsis collastinensis were evaluated. The crabs were exposed to three sublethal concentrations in a pulse system with controlled dilutions. Water samples for pesticide concentrations measurements and crab tissue samples were taken when applications were made and 2, 8, 15 and 22 days after administering the pesticide. The exposure to endosulfan caused an increase in B cell number and a decrease in F and R cell number (p

This report includes a detailed description of the reproductive behaviour of the freshwater crab Zilchiopsis collastinensis in the family Trichodactylidae and some observations on two other genera. It presents observations on the courtship, copulation, spawning, incubation and maternal care in Z. collastin- 15 ensis. No discernible courtship behaviour occurred. We found instead that forced copulation is practised by males. Z. collastinensis copulations were observed in between April and October, for Dilocarcinus pagei between January and August, and throughout the year for Trichodactylus borellianus. The spawning behaviour of all of the species observed took place out of the water. 20 Incubation lasted between 46 and 62 days in D. pagei, 37 and 41 days in Z. collastinensis and 8 and 12 days in T. borellianus. The number of juveniles carried by each ovigerous female ranged from 651 ± 172 in Z. collastinensis, through 582 ± 8 in D. pagei to 63 ± 33 in T. borellianus. The results support the proposition that members of the family Trichodactylidae, comprising 25 exclusively endemic freshwater crabs, have evolved unusual adaptive reproductive behaviours to optimize their reproductive fitness in unstable environments. Fil: Senkman, Lidia Eloisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Facultad de Ciencia y Tecnología; Argentina Fil: Negro, Carlos Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina Fil: Lopretto, Estela Celia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina Fil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina

The use of pesticides in modern agricultural methods may result in the pollution of aquatic ecosystems. Different chlorpyrifos (O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate)) and endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) concentrations, two heavily used insecticides, are generally found in river and lakes. The objectives of this work were to evaluate the effects of environmentally relevant pesticide concentrations in the incubation period, effective hatching and survival of embryos and neonates of the freshwater burrowing crab, Zilchiopsis collastinensis (Decapoda, Trichodactylidae). Both pesticides were prepared from commercial and technical grade products. The exposure to about 100, 200 and 400 ng endosulfan/L; and 48, 240 and 1200 ng chlorpyrifos/L did not cause differences in the incubation period or in effective hatching, but decreased survival of neonates, especially in the concentrations prepared from the technical grade product. Even if these concentrations are below the median lethal concentration (LC50) values for embryos, they caused a significant decrease in the survival of the neonates, i. e., when crabs are outside the egg and not protected by the chorion. The decrease in the neonate population caused by these concentrations, which could be found in the environment, might impact aquatic communities. Fil: Negro, Carlos Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto Nacional de Limnologia (i); Argentina. Universidad Nacional del Litoral; Argentina Fil: Senkman, Lidia Eloisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto Nacional de Limnologia (i); Argentina. Universidad Autónoma de Entre Ríos; Argentina Fil: Marino, Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina Fil: Lorenzatti, Eduardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico Para la Industria Química (i); Argentina. Universidad Nacional del Litoral; Argentina Fil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto Nacional de Limnologia (i); Argentina. Universidad Nacional del Litoral; Argentina

El trabajo se refiere al estudio de casos reales como elemento dinámico en el aprendizaje en el nivel universitario de grado. La estrategia didáctica se fortalece mediante la complementación de la teoría, prácticos de laboratorio y la resolución de una situación de contaminación ambientan en un caso real. El alumno debe resolver los aspectos técnicos básicos tales como conseguir información, evaluar el lugar, tomar muestras, analizarlas, tomar decisiones, encuadrar el caso en el marco legal, afrontar y resolver situaciones adversas tales como impedimentos por parte de entidades rectoras en la materia ambiental, falta de antecedentes o dificultad en el acceso al sitio, entre otros. Los alumnos encuentran en este trabajo un mundo que comienza como desconocido, difícil e incierto y que con el trascurso del tiempo y la resolución de los sucesivos pasos, reconocen en ellos mismos la capacidad de encontrar el camino para la solución. Los docentes deben guiar, cuestionar, advertir y en todo momento acompañar a los alumnos en el desarrollo de un trabajo, que se parece en gran medida, al ejercicio de la profesión en la resolución de casos reales. La aplicación de la teoría en un caso concreto exige la comprensión de aquella, y la elección de por ejemplo los distintos métodos o procedimientos teóricamente disponibles, requiriendo de la racionalización para la justificación de cada alternativa seleccionada. The work refers to the study of actual cases as a dynamic element in learning. The didactic strategy is strengthened by the complementation of the theory, practical laboratory and the resolution of a situation of pollution set in a real case. Student must resolve basic technical aspects such getting information, assess the place, take samples, analyze them, make deci-sions, framing the case in the legal framework, face and resolve adverse situations such as impediments by guiding the environmental entities. Students in this work are a world that begins as unknown and uncertain, and that with the course of time and the resolution of the successive steps, recognize in themselves the ability to find the solution. Teachers must guide, question, warn and constantly accompany students in the development of a work, which largely resembles the exercise of the profession in the resolution of actual cases. The application of theory in a particular case requires an understanding and choosing such different theoretical methods or procedures available, requiring rationalization to justify each selected alternative. Fil: Lorenzatti, Eduardo Antonio. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Escuela Superior de Sanidad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Negro, Carlos Leandro. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Escuela Superior de Sanidad; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina

We examined the bioaccumulation of α- and β-endosulfan and endosulfan sulfate in tissues from the crab Zilchiopsis collastinensis. There was more endosulfan accumulated in the hepatopancreas (from 0.05). The hepatopancreas is a dynamic organ that is able to depurate itself, whereas the gonads act as a sink for pesticides. Fil: Negro, Carlos Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Senkman, Lidia Eloisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina Fil: Vierling, Jaquelina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos; Argentina Fil: Repetti, María Rosa. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos; Argentina Fil: García, Silvia Rosa. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Investigación y Análisis de Residuos y Contaminantes Químicos; Argentina Fil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina