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Daphnia magna is a cladoceran used as a model organism in aquatic ecology and ecotoxicology studies. Because growth is a critical parameter to study the effect of environmental conditions on the development of zooplankters, the somatic growth of D. magna was measured here and described by the von Bertalanffy growth equation (VBGE), a mathematical model widely used in fisheries management. For this purpose, the effect of two temperatures (20 and 25°C) and two photoperiod conditions (12:12 and 16:8, light:dark) was assayed. Experiments began with neonate females and were finished when parthenogenetic females reached the age of 41 days; they were fed the microalga Ankistrodesmus falcatus (400,000 cell ml -1, 12 mg l -1, dry weight). According to the VBGE, maximal length (L max) was inversely correlated with the growth rate (K). The highest L max (6.45 mm) was for the females grown at 20°C with the 12:12 photoperiod, whereas the maximum growth rate (K = 0.182 ± 0.010) was for individuals grown at 25°C with the 12:12 photoperiod. The number of clutches during the studied period was significantly higher for females grown at 25°C, 12:12. Temperature affected the growth rate and the maximum size in D. magna; interaction of temperature with photoperiod was also noteworthy. The VBGE was a nifty way to assess the effects of the tested environmental factors. © 2011 The Japanese Society of Limnology. Source

Olvera-Ramirez R.,Laboratorio Of Fisiologia Vegetal | Centeno-Ramos C.,Laboratorio Of Fisiologia Vegetal | Martinez-Jeronimo F.,Laboratorio Of Hidrobiologia Experimental
Hidrobiologica | Year: 2010

Some cyanobacteria can produce toxins that affect the aquatic biota and represent a human health risk. The cyanobacterium Pseudanabaena tenuis was isolated from the Valle de Bravo dam, and cultured in the laboratory under controlled conditions. We determined the acute toxic effects and performed a chronic (consumption) test in the cladocerans Daphnia magna (a reference test organism) and Ceriodaphnia dubia (a cosmopolitan species). To determine acute toxicity, three exposure ways were assayed: a) cell-free culture medium, b) crude cell extracts of the cyanobacterium after lysing, and c) aqueous extracts of P. tenuis phycobiliproteins. On the other hand, both cladocerans were fed P. tenuis, assessing the effects on survival and reproduction. For comparison, a control culture of both cladocerans was fed the green microalga Pseudokirchneriella subcapitata. Exposure to the cell-free culture medium did not produce any mortality in either cladoceran, but the aqueous and crude extracts generated acute toxicity. D. magna and C. dubia were negatively affected when fed P. tenuis, since their survival, total progeny, average number of neonates per clutch, and the number of clutches decreased. C. dubia was more sensitive than D. magna, both in the acute toxicity tests and to the effects of P. tenuis consumption. Although most of the blooms around the world are dominated by cyanobacteria of the genus Microcystis, attention should be given to other species, such as P. tenuis, because, frequently, it is not recognized that smaller cyanobacteria could exceed the larger species in terms of biomass, and produce noxious biological effects. Source

Garcia-Garcia P.L.,Institute Ecologia | Martinez-Jeronimo F.,Laboratorio Of Hidrobiologia Experimental | Vazquez G.,Institute Ecologia | Favila M.E.,Institute Ecologia | Novelo-Gutierrez R.,Institute Ecologia
Hidrobiologica | Year: 2012

This study evaluated the effect of water quality of streams from micro-watersheds with different land use (cloud forest, coffee plantation, pasture and under urban influence) during the dry and rainy seasons, lying within the upper watershed of the La Antigua river in Veracruz, Mexico. Water characteristics were measured and laboratory subchronic toxicity tests were performed to evaluate average accumulated progeny, broods per female, and non-reproductive females of Ceriodaphnia dubia. The cloud forest contained chemically undisturbed streams, while the lowest levels of chemical alteration were detected in pasture streams: low fecundity of C. dubia was observed in both types of streams. The most disturbed streams were those associated with coffee plantations and under urban influence, which resulted in enhanced C. dubia fecundity; however, the highest chemical disturbance, found in a stream with urban influence, led to reproduction suppression in the dry season. The most favorable conditions for reproduction were provided by nutrient and probably organic enrichment in streams associated with urban environments and coffee plantations, while in cloud forest and pasture streams, the natural, and close to natural water chemistry caused a reduction in fecundity. Female fecundity was higher during the rainy season. Source

Figueroa-Lucero G.,Metropolitan Autonomous University | Hernandez-Rubio M.C.,Laboratorio Of Hidrobiologia Experimental | Gutierrez-Ladron de Guevara M.J.,Laboratorio Of Hidrobiologia Experimental
Revista Internacional de Contaminacion Ambiental | Year: 2012

The prawn shrimp Macrobrachium tenellum is a potential species for culture in México. The effect of ammonia on larvae was evaluated to provide basic information on safe levels for larviculture. A 72 h static assay was performed on 5 days old M. tenellum larvae. The nominal concentrations tested ranged from 2.89 to 185.48 mg NH4-N/L which represent 0.103 to 6.585 mg NH3-N/L at 20 g/L salinity, 28 oC and pH 7.79. LC50 for 12, 24, 48 and 72 h were 2.939 ± 0.505, 0.749 ± 0.301, 0.477 ± 0.163 and 0.409 ± 0.068 mg NH3-N/L, respectively. These results suggest that M. tenellum exhibits a slightly higher tolerance to ammonia in the zoea stage when compared to most of the prawn and shrimp species. Source

Alberto A.-C.M.,Laboratorio Of Hidrobiologia Experimental | Rocio O.-B.,Laboratorio Of Fisiologia Humana | Fernando M.-J.,Laboratorio Of Hidrobiologia Experimental
Journal of Environmental Biology | Year: 2011

It has been accepted that for most species newborns and senescent organisms are more sensitive than other ages to environmental stressors. Nevertheless, it must be considered that there are several biochemical and physiological compensatory processes which are not expressed with the same magnitude during the whole life cycle. With this aim, Daphnia magna individuals of different age were exposed to hexavalent chromium, Cr (VI), at two different sublethal concentrations (0.032 and 0.0064 mg l-1), and the activity of some antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) were evaluated during most of the life cycle of this cladoceran. The antioxidant enzymatic activity showed an inverse relationship with respect to age. The activity of CAT, GR and GPx were increased in the two treated groups, at all life stages tested. On the other hand, the activity of SOD decreased in the same groups. Both, increase and decrease in the antioxidant enzymatic activities, showed significant differences with respect to the control group, being higher for the 0.032 mg l-1 group. The Cr (VI) LC50 was also estimated for these age groups, finding statistical differences among them. Even though adults exhibited higher responses, these enzymatic activity changes should not be interpreted as higher sensitivity, since the daphnids acute chromium toxicity followed a different pattern, with increasing LC50 values according to age. © 2011 Triveni Enterprises Vikas Nagar, Lucknow, INDIA. Source

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