Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Development and Significance of Cysteamine and Propionitrile Models of Duodenal Ulcer

Cysteamine is widely used in rodents to induce duodenal ulcer. Herein, the pathogenesis of duodenal ulceration in its earliest stages was reviewed using findings from cysteamine-and propionitrile-induced duodenal ulcer in rodent models, especially taking into account changes in the secretion of gastric acid, duodenal and pancreatic bicarbonate as well asgastroduodenal motility. The effect of cysteamine-HCl in inducing ulcers in rats is circadian rhythm-dependent. The effect is greatest from just before the end of diurnal rest to just after the start of nocturnal activity. The chronobiologic effect may be in part due to the circadian rhythm-dependent increased gastric acid production from cysteamine. Titratable acidity was found to be twice as great in the gastric juice of rodents when cysteamine was given by injection at 2000 (just after the start of nocturnal activity) in comparison to when given at 0800 or 1200 (at the beginning or middle span of daily rest). Further studies have shown that adrenalectomy of rats 7 days before cysteamine administration obliterated the observed circadian susceptibility to ulcer formation. Duodenal ulceration, at least in the cysteamine model, appears to be under chronobiologic neuroendocrine control or influence, seemingly mediated by the adrenal glands.     

Fatty acid composition of the amphipod Dikerogammarus villosus: feeding strategies and trophic links

Fatty acid (FA) compositions were determined for the invader amphipod Dikerogammarus villosus collected from July to September 2002, in an overheated, high-conductivity dammed reservoir in north-eastern France. Predominant fatty acids were the polyunsaturated fatty acids (PUFA): eicosapentaenoic acid (EPA), linoleic acid (LA), arachidonic acid (ARA), linolenic acid (LNA) together with the monounsaturated fatty acid 18:1omega9 and the saturated fatty acid 16:0. FA markers indicated that available food was constituted of incompletely degraded phytodetritus and terrestrial inputs, as well as animal remains. PUFA contents depended on the diet and the capacity of animals to desaturate and elongate LNA and LA in long chain PUFA as EPA and ARA respectively. Based on their FA compositions, we showed that gammarids represent naturally-occurring freshwater sources of essential PUFA, and could play a fundamental role in pelagic-benthic coupling and energy recycling in the ecosystem. The complexity of the feeding strategies of D. villosus--detritivorous, omnivorous, carnivorous--makes this species efficient at exploiting different components of the available food and may be a key factor in its high invasive success.     

The pericardial glands of the zebra mussel: Ultrastructure and implication in lead detoxication process

Summary— Ultrastructural and microanalytical investigations of the pericardial gland of the freshwater mussel, Dreissena polymorpha have been performed to investigate the possible functional role of this organ in the detoxication process of lead. The cell-type of this organ exhibits the feature characteristics of podocytes, ie the typical pedicel-basal lamina complex and the well developed lysosomalvacuolar system. X-ray microanalysis demonstrated that large electron-dense granules referred to as lysosomes are the main target organelles in these cells to accumulate and sequestrate lead where the metal was associated with phosphorus and sulphur. Consequently, the pericardial gland plays an important role in the detoxication process and allows the organism to tolerate high lead concentration without suffering severe cell injury.     

Habitat Use by YOY in the Littoral Zone of an Artificially Heated Reservoir

Both temporal and spatial distributions of a young of the year (YOY) fish community were studied in the littoral zone of a French reservoir. The time survey indicated that littoral occupation highly depends on YOY time of appearance. During late spring and summer, the smallest white bream YOY (L_T < 20 mm) were restricted to complex habitats whereas those of pumpkinseed occupied all available habitats. Growing white bream progressively migrated to open water areas. At that time, pumpkinseed was the only species sampled in abundance in the littoral zone and was still collected in all habitats. The success of the introduction of pumpkinseed might be explained by both its late hatching and its opportunistic strategy in habitat selection enabling it to exploit physical spaces left vacant. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pumping behaviour and filtration rate of the freshwater mussel Potomida littoralis as a tool for rapid detection of water contamination

In order to evaluate the ability of the freshwater bivalve Potomida littoralis for use as a biodetector of aquatic pollution, the short-term effects of some pollutants (metals, antifouling product and effluents) on pumping activity of this mussel were studied qualitatively (pumping behaviour) and quantitatively (filtration rate). The method of the flow sensing at the exhalent siphon showed that the normal activity of P. littoralis was characterized by a continuous pattern of pumping with occasional and brief interruptions. When exposed to toxic stress, the exhalent flow immediately shifted to an intermittent pattern with periods of pumping alternating with periods of pause that could last several minutes. The threshold concentrations of heavy metals/antifouling agent inducing this type of activity within 2 h were: 25 g l^–1 for copper, 90 g l^–1 for cadmium, 5 g l^–1 for mercury, 3000 g l^–1 for zinc and 700 g l^–1 for the antifouling agent Mexel. Both the effluent samples of the urban wastewater of Marrakech city tested were found to be toxic.The filtration rate of control animals ranged from 0.91 to 1.72 l h^–1 g^–1 animal, while after 3 h exposure to Cu, Cd, Hg and the effluent E1 and E2, filtration rates were decreased by concentrations above the threshold levels set as toxic for the pumping activity.The sensitivity of P. littoralis to pollution and its usefulness as biodetector for rapid toxicity screening is discussed and a procedure for the detection of pollution in Moroccan freshwater is proposed.     

Discharge of sediments, nitrogen (N) and phosphorus (P) during the emptying of extensive fishponds: effect of rain-fall and management practices

In 1997 and 1998 we assessed the input and output of suspended matter, nitrogen and phosphorus during the exploitation period of a fishpond in the Domaîne Départemental de Lindre (Moselle, north-eastern France). Special attention was given to the emptying period which was studied under different meteorological conditions (rainy and dry periods). The pond has a surface area of 2 ha, a volume of 16000 m³ and is used for the production of various Cyprinidae (roach, bream, chub, pike, perch, carp). During the emptying operation, 630 and 2830 kg ha^–1 of suspended matter, 10.8 and 36.5 kg ha^–1 of Total-nitrogen and 1.2 and 5.1 kg ha^–1 of Total-phosphorus were discharged from the pond during drought and heavy rainfall (50.5 mm in 166 h), respectively. Except for the emptying period, the pond retained 6850, 117 and 6.6 kg ha^–1 of suspended matter, nitrogen and phosphorus, respectively. In the course of the emptying period, more than 32% of the suspended matter was discharged as was 8.5% of the nitrogen and 25% of the phosphate. For the whole exploitation period 4020 – 6220 kg ha^–1 of suspended matter, 80–106 kg ha^–1 of nitrogen and 1.6–5.5 kg ha^–1 of phosphorus accumulated in the pond.     

One-step, non-denaturing purification method of carp (Cyprinus carpio) vitellogenin

A new single-step purification procedure was developed to purify carp (Cyprinus carpio) vitellogenin (VTG), from estradiol-treated carp plasma. This method was performed by high performance liquid weak anion-exchange chromatography, using a discontinuous elution gradient of NaCl (0-0.5 M, steps of 12.5 mM/4 min). SDS and native-PAGE analysis, of treated-fish plasma and purified solution, showed the appearance of a 370 kDa phospholipoprotein, composed of two 130 kDa monomers, with all VTG characteristics. The sequencing of a 130 kDa monomer confirmed that it was carp VTG. Consequently, this procedure is a rapid method, permitting high quantities of non-denatured carp VTG to be obtained.