Environmental stress upon hepatopancreatic cells of freshwater prawns (Decapoda: Caridea) from the floodplain of Paraná River

In order to evaluate the influence of stressed environments on hepatopancreatic cells of freshwater prawns, Macrobachium borellii Nobili, 1896 and Palaemonetes argentinus Nobili 1901, (Crustacea, Decapoda, Palaemonidae) were collected at three different aquatic environments with different relationship to urban development in Argentina. Furthermore the effects of several cypermethryn concentration on hepatopancreatic cell of M. borellii and P. argentinus were evaluated in a laboratory assays. The "N° 1" lake (Santa Fe Argentina) which is more affected by the anthropogenic pressure and "Don Felipe" lake which is still not strongly by human activities were the studied sites from the floodplain of Paraná river. While Alejandra lake was the intermedia effects sites. Different damaged ultrastructures were found in F- and R-cells of prawns in the stressed lake. The predominant features were: disrupted the microvillous border, swelled mitochondria, reduction of endoplasmic reticulum, dyctiosomes, glycoproteins, desnaturalization of vacuole membrane and premature autolysis. Moreover the F-cell number was higher in the environment near to city than in the others sites. Similar effects were observed in the cypermethryn assays. The observations clearly indicate that the ultrastructure of midgut gland in the both palaemonids varies depending on the site from which animals are collected and the biocid presence. So, in this case it can be stated that the hepatopancreas histology of freshwater prawns is a good tool to monitor the impact of a stressed environment upon freshwater prawns.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; Argentin

Range extension for three species of South American freshwater crabs (Crustacea: Decapoda: Trichodactylidae)

New sampling programs have extended the distribution of three species of freshwater crabs (family Trichodactylidae): Dilocarcinus septemdentatus and Sylviocarcinus pictus from the Amazon basin to southern South America, and S. australis, from the north of Argentina southwards. The three species are now found in the floodplain of the middle Paraná River (31°39´S, 60°45´W). The extension of their distribution is approximately 500 km and 2000 km further south. The number of freshwater crab species in the alluvial valley of the Paraná River has increased by 30% with these new records.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; ArgentinaFil: Giri, Federico. 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; ArgentinaFil: Williner, Verónica. 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; Argentin

Morphological variation of freshwater crabs Zilchiopsis collastinensis and Trichodactylus borellianus (Decapoda, Trichodactylidae) among localities from the middle Paraná River basin during different hydrological periods

Measures of hydrologic connectivity have been used extensively to describe spatial connections in riverine landscapes. Hydrologic fluctuations constitute an important macrofactor that regulates other environmental variables and can explain the distribution and abundance of organisms. We analysed morphological variations among individuals of two freshwater crab species, Zilchiopsis collastinensis and Trichodactylus borellianus, from localities of the middle Paraná River basin during two phases of the local hydrological regime. Specimens were sampled at sites (localities) of Paraná River, Saladillo Stream, Salado River and Coronda River when water levels were falling and rising. The conductivity, pH, temperature and geographical coordinates were recorded at each site. The dorsal cephalothorax of each crab was represented using 16 landmarks for Z. collastinensis and 14 landmarks for T. borellianus. The Canonical Variate Analyses showed differences in shape (for both species) among the crabs collected from the Paraná and Salado Rivers during the two hydrologic phases. We did not find a general distribution pattern for shape among the crab localities. During falling water, the shapes of Z. collastinensis were not related to latitude-longitude gradient (i.e., showing greater overlap in shape), while during rising water the shapes were ordered along a distributional gradient according to geographical location. Contrary, shapes of T. borellianus were related to latitude-longitude during falling water and were not related to distributional gradient during rising water. The cephalothorax shape showed, in general, no statistically significant covariations with environmental variables for either species. These results show that each freshwater crab species, from different localities of the middle Paraná River, remain connected; however, these connections change throughout the hydrologic regime of the floodplain system. This study was useful for delineating how the relation among shapes of crabs of localities varies during two phases of the hydrological regime and for estimating the connections and geographical patterns in the floodplain system.Fil: Torres, María Victoria. 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; ArgentinaFil: Collins, Pablo Agustin. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; 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; ArgentinaFil: Giri, Federico. 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 Humanidades y Ciencias. Departamento de Ciencias Naturales; Argentin

The diel feeding rhythm of the freshwater crab Trichodactylus borellianus (Decapoda: Brachyura) in mesocosm and natural conditions

Biorhythm studies have rarely used feeding rhythms of freshwater crustaceans to assess the internal clock. Even less often, they have compared the diel rhythms of juveniles and adults. In this study, the 24-h cyclic feeding behavior of the freshwater crab Trichodactylus borellianus was investigated in mesocosm and natural field conditions during summer. Sampling occurred throughout the day and included the dawn and dusk periods. The fullness of the stomach was used to characterize the feeding cycle and was analyzed with MESOR and a three-day time series plot. The rhythms of juveniles and adults were analyzed in the field. A bimodal feeding rhythm with midday and midnight peaks was observed in adults in the field, while juveniles had an asynchronous behavior. Mesocosm animals also showed no cyclic behavior. Rhythmic responses to nonphotic cues may result from a trade-off between foraging at an optimum time and shifting the diel rhythm to avoid competition and predation risk. Juvenile feeding asynchrony could be a strategy that allows them to be active in the same habitat as adults.Fil: Azevedo Carvalho, Débora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Santa Fe. Instituto Nacional de Limnologia (i); ArgentinaFil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Santa Fe. Instituto Nacional de Limnologia (i); Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: de Bonis, Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Santa Fe. Instituto Nacional de Limnologia (i); Argentin

Predation ability of freshwater crabs: age and prey-specific differences in Trichodactylus borellianus (Brachyura: Trichodactylidae)

Freshwater crabs are rarely represented in food webs and their role in these ecosystems has been largely ignored. Trichodactylus borellianus is an omnivorous crab species that has a diverse natural trophic spectrum. This paper evaluates, in a laboratory assay, the ability of three ages of this crab to prey on three different organisms. The prey selectivity and relative importance of each prey item was also analyzed. Prey items (cladocerans, oligochaetes, and golden mussels) consisted of organisms of different shapes and mobility, representing the natural diet of this crab. Crabs were sorted according to size (juvenile, sub-adult, and adult) and increasing amounts of one prey was offered to each crab after 24 hrs of starvation. In the selectivity trial, all prey types were offered in a fixed set. Crabs in all three age categories were able to prey on all organisms. Cladocerans and oligochaetes were consumed in greater quantities compared to golden mussels when offered separately. However, only the consumption of oligochaetes exhibited a positive correlation with the crabs? size. When cladocerans and oligochaetes were offered together, more oligochaetes were consumed, both as percentage of volume and occurrence. Age-specific changes in consumption could be related to differences in the stomach capacity of the crab, the digestion time of each prey, and the predator?prey encounter probability. The selection of the most elongated prey with the lowest mobility indicated that the balance of the gain and loss of energy made it an advantageous species to prey on, as it was susceptible to predation. Additionally, the mussel, which is an invasive species, although not positively selected by T. borellianus in the present study, represented a new trophic resource for this crab.Fil: de Azevedo Carvalho, Débora. 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; ArgentinaFil: 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; ArgentinaFil: de Bonis, Cristian. 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; Argentin

Comparing Weak- and Unsupervised Methods for Resonant Anomaly Detection

Anomaly detection techniques are growing in importance at the Large Hadron Collider (LHC), motivated by the increasing need to search for new physics in a model-agnostic way. In this work, we provide a detailed comparative study between a well-studied unsupervised method called the autoencoder (AE) and a weakly-supervised approach based on the Classification Without Labels (CWoLa) technique. We examine the ability of the two methods to identify a new physics signal at different cross sections in a fully hadronic resonance search. By construction, the AE classification performance is independent of the amount of injected signal. In contrast, the CWoLa performance improves with increasing signal abundance. When integrating these approaches with a complete background estimate, we find that the two methods have complementary sensitivity. In particular, CWoLa is effective at finding diverse and moderately rare signals while the AE can provide sensitivity to very rare signals, but only with certain topologies. We therefore demonstrate that both techniques are complementary and can be used together for anomaly detection at the LHC.Comment: 39 pages, 17 figure

Effects of Chlorpyrifos Over Reproductive Traits of Three Sympatric Freshwater Crustaceans

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.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; ArgentinaFil: Estrubia, J. F.. 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; ArgentinaFil: Rivera, F.. 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; ArgentinaFil: 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; Argentin

Spatial and temporal variation in the activity of freshwater prawn Macrobrachium jelskii (Miers, 1877) (Crustacea, Decapoda, Caridea, Palaemonidae)

Los ecosistemas manifiestan diferentes ciclos influenciados por factores endógenos y exógenos. Los organismos que los componen presentan, acordes a esos cambios, periodicidades en sus actividades. El objetivo del estudio fue determinar el ritmo nictemeral del camarón Macrobrachium jelskii en una lagunas del Parque Nacional Río Pilcomayo, Argentina, y su variación en una transecta perpendicular a la costa. Las capturas fueron realizadas con trampas cada cuatro horas durante tres días consecutivos. En la noche se registró mayor actividad en las zonas vegetadas, caracterizadas por la presencia de ejemplares adultos, principalmente machos. La actividad trófica resultó elevada durante el día en áreas vegetadas, pudiendo ser atribuida a la disponibilidad de abundantes recursos alimenticios. En zonas de transición entre aguas abiertas y vegetadas, los valores mínimos se presentaron durante el día. Contrariamente, en aguas libres de vegetación la actividad trófica fue menor durante la noche, respondiendo al ciclo de la oferta trófica y a la actividad desarrollada por algunos predadores potenciales. La actividad diaria en esta población mostró cierta elasticidad o ajuste de acuerdo a las características del medio, observándose variaciones relacionadas con la edad, el sexo y con la presencia o ausencia de vegetación (y con ésta la oferta de recursos tróficos y de refugio contra los predadores potenciales).Exogenous and endogenous factors model different kind of cycles in ecosystems. Organisms reveal the influence of these components upon their activities. The aim of this study was to examine the circadian rhythm of shrimp Macrobrachium jelskii in a pond at Río Pilcomayo National Park and their possible variation along a transect perpendicular to the coast. Samples were taken with traps every four hours during three days. The highest activity was recorded in the macrophyte zone, mainly by adult males. Feeding process was high during the night in the vegetated area, due to resource abundance. The minimum activity level was recorded in the transition between open and vegetated waters during daylight hours. In open water, feeding activity was almost passive during nighttime, as a response to the trophic cycle and to predator activity. The studied population showed some degree of adjustment to environmental conditions, and showed variations related to sex, age, and presence or absence of vegetation (which provides resources and shelter)

Eficiencia de captura del camarón dulceacuícola Palaemonetes argentinus (Nobili 1901) sobre larvas de mosquito Culex pipiens s.l. (Linnaeus 1758).

The predation consists of a chain of events divided in three phases: encounter, capture and ingestion. We filmed the prawn Palaemonetes argentinus depredate on mosquitoes larvae (Culex pipiens s.l.) in aquaria, watching an increment in the swimming activity of prawns then to recognize the movement of the larvae by mechanoreceptors. The encounters of prey demand in the aquaria with small prawns 13.9 ± 9.39 seconds, in the aquarium with big prawns 26.6 ± 23.47 seconds, and in the pools with mixed prawns 17.9 ± 16.32 seconds. The attacks were more efficiently in small prawn (73%) that in big prawn (44%), maybe because the small prawns are better swimmers than big ones. The capture of prey was made with the second pereiopods and rapidly will be carried to its cephalic appendices. These larvae are preferment eaten by the cephalic region (79.33 %) and in this manner the prawns neutralized its possible escapes. The time utilized into manipulation depends of the larvae number depredated. In general, the time to eat the mosquitoes larvae is longer in the small prawns (91.0 ± 90.3 seconds) that the big prawns (25.0 ± 27.9 seconds).La depredación consiste en eventos encadenados divididos en tres etapas: búsqueda, captura e ingestión. Se filmó al camarón Palaemonetes argentinus depredando larvas de mosquito (Culex pipiens s.l.) en acuarios, reconociendo un incremento en la actividad natatoria de los camarones luego de percibir el movimiento de las larvas por mecanorreceptores. La búsqueda de presas insumió en camarones pequeños 13,9 ± 9,39 segundos, en camarones grandes 26,6 ± 23,47 segundos y en los acuarios con ejemplares de ambas tallas (mixtos) 17,9 ± 16,32 segundos. La efectividad de los ataques fue mayor en ejemplares pequeños (73 %) que en grandes (44 %), quizás por una relativa mayor capacidad natatoria. La captura de presas la realizan con los segundos pereiópodos y rápidamente son llevadas hacia los apéndices bucales. Estas larvas son preferentemente comidas por la región cefálica (79,33 %) neutralizando el posible escape. El tiempo empleado en el manipuleo depende del número de larvas depredadas. En general, se puede decir que el tiempo empleado en consumir una larva de mosquito es mayor en los ejemplares pequeños (91,0 ± 90,30 segundos) que en los camarones grandes (25,0 ± 27,9 segundos)