We evaluated the effectiveness of different types of spawning substrates in retaining the eggs of rosy red fathead minnow Pimephales promelas, the potential substrate preference of the fish, and the effectiveness of different concentrations of sodium sulfite for detaching eggs from substrates without affecting egg survival. Egg adherence was determined by placing replicate sections of four types of conveyor belt material of varying roughness into a pool stocked with fathead minnow. A screened tray was suspended below each substrate to catch the eggs that did not adhere. Substrate preference was evaluated by following a similar protocol, but only three males were stocked (equal to the number of replicates of each substrate). To test the efficacy of sodium sulfite in removing eggs, substrates with eggs were placed in 0.0, 1.5, and 3.0% solutions and uniformly agitated. The effect of exposure time and egg age was tested by exposing eggs to a 1.5% solution of sodium sulfite for 0 (control), 5, 10, 15, 20, 25, and 30 min. The two rougher substrates retained a significantly greater percentage of eggs than the two smoother ones (72–77% versus 34–39%). Nest locations near the water inlet and air stones were preferred regardless of substrate type. The 1.5% sodium sulfite solution was as effective as the 3.0% solution in removing eggs from substrates. There were no significant differences in hatching rate or percentage of atypical fry resulting from exposure of eggs to 1.5% sodium sulfite for up to 30 min. An egg harvesting system consisting of placing a rough or textured substrate in well‐aerated locations and subsequent egg removal with sodium sulfite appears to be feasible, although economic questions remain.
Water movement modeling in plain areas requires digital elevation models (DEMs) adequately representing the morphological and geomorphological land patterns including the presence of civil structures that could affect water flow patterns. This has a direct effect on water accumulation and water flow direction. The objectives of this work were to analyze, compare and improve DEMs so surface water movement in plain areas could be predicted. In order to do that, we evaluated the accuracy of a digital elevation data set consisting in 4064 points measured with a differential global positioning system (GPS) in a plain Several topographic attributes (i.e., height, surface area, land slope, delimitation of geomorphological units, civil structures, basin boundaries and streams network) and different interpolation methods were analyzed. The results showed that both the SRTM and the ALOS PALSAR DEMs had a ± 4.4 m root mean square error (RMSE) in contrast to the ASTER DEM which had a ± 9 m RMSE. Our analysis proved that the best DEM representing the study area is the SRTM. The most suitable interpolation methods applied to the SRTM were the inverse distance weighting and the ANUDEM, whereas the spline method displayed the lowest vertical accuracy. With the proposed method we obtained a DEM for the study area with a ± 3.2 m RMSE, a 33% error reduction compared to the raw DEM.
The dinoflagellate Amyloodinium ocellatum, a major pathogen in warm water mariculture, has a trophont, a tomont and a dinospore life history stage. This paper presents a population model for A. ocellatum infecting spotted seatrout Cynoscion nebulosus and red snapper Lutjanus campechanus and evaluates the relative effect of each vital rate on the A. ocellatum population growth rate. The vital rates were estimated by incubating trophonts in vitro and tracking their development through the successive life history stages at 25°C and 33 ppt. The A. ocellatum population growth rate was 1.90 d-1 for spotted seatrout and 1.92 d-1 for red snapper. Highest elasticity values (0.24 and 0.23 in spotted seatrout and red snapper, respectively) corresponded to transitions from the dinospore to the trophont stage, the trophont stage to the tomont stage and the tomont stage back to the dinospore stage in both host species (self-loops not included). A 50% change in vital rates showed that the mean number of dinospores produced by a tomont had the largest effect on the A. ocellatum population growth rate (15%), followed by the dinospore infection rate (14%), the tomont sporulation rate (12%) and the dinospore mortality rate (10%) in both host species. A comparison of modeled and experimental vital rate threshold values revealed a 2.5- (spotted seatrout) or a 2.6-fold (red snapper) difference in the values for dinospore mortality, which is the smallest difference among all the modeled and experimental vital rates. Therefore, measures that increase dinospore mortality have a greater likelihood of influencing the outcome of an epidemic.
ABSTRACT. The response of the midgut gland of Artemesia longinaris to salinity changes was evaluated by analyzing its histological changes. Animals were exposed gradually and abruptly to 33, 29, 25 and 16 psu for different time intervals and readapted to 33 psu for 30 days. Individuals maintained 10 days at 16 psu showed the lowest survival and presented histopathologies which were not present in those readapted to 33 psu. Shrimps abruptly transferred from 33 to 16 psu died in 3-5 h but did not show midgut gland alterations likely due to the brief exposure. Only shrimps abruptly transferred from 33 to 25 psu presented histopathologies after 96 h. When readapted to 33 psu for 30 days, the midgut gland recovered an unaltered structure. Except E-cells, which did not vary in height among treatments, F, R and B-cells were taller in animals gradually adapted to 29 than to 16 psu. Abrupt salinity changes had a significant effect on the mean height of F, R and B-cells of those animals transferred from 33 to 25 psu (from 24 to 96 h after transfer F and R-cells heights decreased, and from 96 to 144 h after transfer B-cells height increased). Our study shows the effect of osmotic stress at the tissue level on the midgut gland and, at least partially, explains the reason for the mortalities at low salinities. Keywords: midgut gland, hepatopancreas, osmotic stress, histopathology, salinity, A. longinaris, Argentina. Efecto de los cambios de salinidad sobre el hepatopáncreas deArtemesia longinaris (Decapoda, Penaeidae) RESUMEN. Se evaluó la respuesta del hepatopáncreas de Artemesia longinaris a los cambios de salinidad. Los animales fueron expuestos gradual y abruptamente a 33, 29, 25 y 16 psu durante distintos intervalos y readaptados a 33 psu por 30 días. Los individuos gradualmente adaptados a 16 psu tuvieron baja supervivencia y presentaron alteraciones histológicas ausentes en los readaptados a 33 psu. Aquellos transferidos repentinamente de 33 a 16 psu murieron en 3-5 h pero no mostraron alteraciones, posiblemente debido a la breve exposición. Sólo los transferidos repentinamente de 33 a 25 psu por más de 96 h presentaron daño tisular. Cuando se readaptaron a 33 psu durante 30 días, el hepatopáncreas mostró una estructura normal. Exceptuando las células E que no variaron en altura entre tratamientos, las F, R y B fueron más altas en los animales gradualmente adaptados de 33 a 29 psu. Los cambios súbitos de salinidad tuvieron un efecto significativo en la altura media de las células F, R y B solamente en animales transferidos de 33 a 25 psu (24 a 96 h después de la transferencia disminuyó la altura de las células F y R, y 96 a 144 h después hubo un aumento en la altura de las células B). El presente estudio muestra el efecto de los cambios de salinidad sobre el hepatopáncreas y explica, al menos parcialmente, la razón de la mortalidad a bajas salinidades.
Using the USEPA methodology we estimated the probabilistic chronic risks for calves and adult cows due to pesticide exposure through oral intake of contaminated surface and ground waters in Tres Arroyos County (Argentina). Because published data on pesticide toxicity endpoints for cows are scarce, we used threshold levels based on interspecies extrapolation methods. The studied waters showed acceptable quality for cattle production since none of the pesticides were present at high-enough concentrations to potentially affect cow health. Moreover, ground waters had better quality than surface waters, with dieldrin and deltamethrin being the pesticides associated with the highest risk values in the former and the latter water compartments, respectively. Our study presents a novel use of the USEPA risk methodology proving it is useful for water quality evaluation in terms of pesticide toxicity for cattle production. This approach represents an alternative tool for water quality management in the absence of specific cattle pesticide regulatory limits.
Amyloodinium ocellatum is a parasitic dinoflagellate that infects warm-water marine and estuarine fishes and causes mortalities in aquaculture. Its life cycle consists of 3 stages: a feeding trophont that parasitizes the gills and skin where it interferes with gas exchange, osmoregulation, and tissue integrity; a detached reproductive tomont; and a free-swimming infective dinospore. We compared the susceptibility and tolerance of juvenile spotted seatrout, Cynoscion nebulosus, and red snapper, Lutjanus campechanus, to this parasite by individually exposing fish in 3-L aquaria (at 25 C and 33 practical salinity units) to several dinospore doses over different time periods and quantified the size and number of resulting trophonts. We estimated the trophont detachment rate and trophont size at detachment, the 24-hr dinospore infection rate, the dinospore 48-hr median lethal dose (LD(50)), and the trophont lethal load at the 48-hr LD(50). There were no significant differences in dinospore infection rates or dinospore lethal doses between spotted seatrout and red snapper; however, trophonts remained attached longer and attained a larger size in red snapper than in spotted seatrout. The trophont lethal load was significantly higher in spotted seatrout than in red snapper. A proposed model simulating the trophont dynamics reflected our experimental findings and showed that A. ocellatum reproductive success is linked both to the number of dinospores and the size of the trophont, factors that, in turn, are linked to the time the trophont spends on the host and the number of trophonts the host can tolerate.
: Due to the socioeconomical impact of water extremes in plain areas, there is a considerable demand for suitable strategies aiding in the management of water resources and rainfed crops. Numerical models allow for the modelling of water extremes and their consequences in order to decide on management strategies. Moreover, the integration of hydrologic models with hydraulic models under continuous or event-based approaches would synergistically contribute to better forecasting of water extreme consequences under different scenarios. This study conducted at the Santa Catalina stream basin (Buenos Aires province, Argentina) focuses on the integration of numerical models to analyze the hydrological response of plain areas to water extremes under different scenarios involving the implementation of an eco-efficient infrastructure (i.e., the integration of a green infrastructure and hydraulic structures). The two models used for the integration were: the Soil and Water Assessment Tool (SWAT) and the CELDAS8 (CTSS8) hydrologic-hydraulic model. The former accounts for the processes related to the water balance (e.g., evapotranspiration, soil moisture, percolation, groundwater discharge and surface runoff), allowing for the analysis of water extremes for either dry or wet conditions. Complementarily, CTSS8 models the response of a basin to a rainfall event (e.g., runoff volume, peak flow and time to peak flow, flooded surface area). A 10-year data record (2003–2012) was analyzed to test different green infrastructure scenarios. SWAT was able to reproduce the waterflow in the basin with Nash Sutcliffe (NS) efficiency coefficients of 0.66 and 0.74 for the calibration and validation periods, respectively. The application of CTSS8 for a flood event with a return period of 10 years showed that the combination of a green infrastructure and hydraulic structures decreased the surface runoff by 28%, increased the soil moisture by 10% on an average daily scale, and reduced the impact of floods by 21% during rainfall events. The integration of continuous and event-based models for studying the impact of water extremes under different hypothetical scenarios represents a novel approach for evaluating potential basin management strategies aimed at improving the agricultural production in plain areas.
Low-gradient, prairie streams from the Pampa Plain, Argentina, constitute the southernmost geographic occurrence for many Neotropical fish species. Fish assemblages in Neotropical streams have shown drastic responses to the modification of habitat and water quality. Under this scenario it could be hypothesized that the water quality will be influenced by the anthropic activities and the natural conditions and that the ichthyofauna will be responsive. Therefore, understanding the functioning of these ecosystems is crucial for their conservation in a world with ever-growing anthropic pressures. In order to explore patterns in fish assemblage and water quality under urbanization pressure, the Del Azul stream (Buenos Aires, Argentina) was sampled. The objectives of the study were: (1) to explore trends in water quality and fish assemblage structure along the stream, (2) to study the relationship between fish assemblage structure and water quality, and (3) to pinpoint individual species with potential for biomonitoring. Seven sites were selected along the stream, and they were sampled twice during each of five consecutive summer periods. Through the use of multivariate analysis, we revealed trends in water quality and fish assemblage structure where water quality characteristics were more distinctive of a basin sector than the fish species abundances. Irrespective of that, the Indicator Species Analysis evidenced some key species indicative of given groups of sites sharing similar water quality characteristics. Namely, Cnesterodon decemmaculatus was associated to polluted reaches downstream from the point-source urban effluent, and Cheirodon interruptus, Pimelodella laticeps and Oligosarcus jenynsii to lower salinities and less polluted reaches upstream from the point-source urban effluent. All these species could be useful for biomonitoring temperate Neotropical streams.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.