Bioaccumulation d'aluminium chez la truite Salmo truffa fario soumise au retombées des pluies acides : étude structurale, ultrastructurale et microanalytique

Des études microanalytiques ont été menées sur des truites Salmo trutta fario, âgées de deux ans, récoltées dans une rivière des Vosges soumise aux retombées des pluies acides et sur des truites témoins récoltées dans une rivière d'Auvergne, non soumise aux pluies acides. La rivière des Vosges est caractérisée par un pH de 5,42 et par une concentration en aluminium de 200 µg/L-1. Notre but étant de déterminer les tissus, cellules et organites cibles de bioaccumulation éventuelle de l'aluminium, nous avons analysé rein, foie, branchie et tractus digestif. Deux méthodes microanalytiques ont été utilisées pour localiser l'aluminium à l'échelle cellulaire et subcellulaire et connaître les éléments avec lesquels il peut être associé; ce sont la spectrométrie de masse par émission ionique secondaire (microscope ionique associé à un système informatisé de traitement d'images) et la spectrométrie des rayons X (microsonde électronique de Castaing associée à un microscope électronique à transmission).La microanalyse des rein, foie, branchie et tractus digestif montre l'existence de deux processus conduisant à la bioaccumulation de l'aluminium. Le premier, classiquement connu pour d'autres métaux, met en évidence une insolubilisation de l'aluminium sous forme de phosphate, dans des organites limités par une membrane : les lysosomes et les granules pigmentaires des mélanocytes. Le second, démontre la formation de volumineux dépots extra-cellulaires, atteignant 100 µm de long et entraînant la destruction du tissu. Aucune bioaccumulation significative d'aluminium n'a été observée chez des truites témoins, récoltées dans le centre de la France, où l'eau à pH 7.9 est dépourvue d'aluminium.The major harm caused by acidic precipitation is shown by a disappearance of fish. Other factors besides acidity such as aluminium levels are significantly harmful and many studies have shown that aluminium ions are toxic to fish. The only sensible course of action is to investigate the basic mechanisms by which each of the metal pollutants enters and attacks living systems. For this, one needs to be a combination of physicist, chemist, biochemist, physiologist and toxicologist. Investigations on metal bioaccumulation require very sensitive analytical instrumentation. Total analytical methods commonly used are inadequate : absorbed and adsorbed elements cannot be distinguished.Therefore, interesting information can be obtained by using physical methods of chemical microanalysis : two available microanalytical techniques are particularly suitable, X-ray spectrometry and secondary ion mass spectrometry.X-ray spectrometry, also called Electron Probe X-ray Microanalysis or Electron Microprobe (EMP) provides a means for studying the local chemical composition and structure of biological specimens. EMP can be used in association with a photon microscope or with a transmission electron microscope allowing the detection of elements at subcellular level.The Secondary Ion Mass Spectrometry (SIMS), also called Ion Microscopy, allows to visualize, analyse and photograph the microscopical distribution of the stable or radioactive isotopes of the elements present in a histological section. The sensitivity of the method is very high, ranging from 0.1 to 1 ppm. In association with SIMS, a processing of secondary ion images is used.Two years-old samples of Salmo trutta fario, from wild populations living in acidified waters of Eastern France (near Cornimont in the Vosges moutains) were studied for aluminium detection at cellular and subcellular levels. The acidified waters were characterized by a low pH (5,42) and high aluminium level reaching 200 µg/L-1. Control trouts living in non acidified waters (pH : 7.9 and aluminium free) of central France (near Clermont-Ferrand) were used for comparison. In order top determine the tissues, cells and organelles of a possible aluminium concentration, the following organs were investigated : kidney, liver, gill and digestive tractus, using both microanalytical techniques described above.In the kidney ion images showed aluminium emission from tubule lysosomes with a ring-shaped localization along the apical border of the epithetial cells; aluminium emissions from the tubule lumen and from the pigment granules of the melanocytes were also observed. Using the electron microprobe, X-ray emission spectra of aluminium associated with phosphorus were obtained from lysosomes and pigment granules. In the liver and in the gills, ion images showed a high aluminium emission from the same organelles and X-ray spectra of aluminium and phosphorus were also obtained. Moreover, in the pyloric caeca, large extracellular deposits of aluminium were detected : they measured about 100 µm in length and were located in places where tissues had been destroyed.The same structural, ultrastructural and microanalytical investigations were performed on the control trouts from which non aluminium detection was obtained.In conclusion, two processes appear to be involved in the aluminium accumulation in the brown trout. The first one corresponds to a well known insolubilisation of aluminium phosphate inside the lysosomes, due to an acidic phosphatase enzymatic activity; aluminium is also trapped inside pigment granules. Both of these mechanisms of storage inside membrane-limited organelles, prevent cells from any interior damage. The second one corresponds to the formation of large extracellular deposits which are likely to provoke injuries leading to the tissue destruction. Such data demonstrating basic mechanisms of aluminium accumulation in a fish, could not have been obtained using total analytical methods

Background matching in the brown shrimp Crangon crangon : adaptive camouflage and behavioural-plasticity

A combination of burrowing behaviour and very efficient background matching makes the brown shrimp Crangon crangon almost invisible to potential predators and preys. This raises questions on how shrimp succeed in concealing themselves in the heterogeneous and dynamic estuarine habitats they inhabit and what type of environmental variables and behavioural factors affect their colour change abilities. Using a series of behavioural experiments, we show that the brown shrimp is capable of repeated fast colour adaptations (20% change in dark pigment cover within one hour) and that its background matching ability is mainly influenced by illumination and sediment colour. Novel insights are provided on the occurrence of non-adaptive (possibly stress) responses to background changes after long-time exposure to a constant background colour or during unfavourable conditions for burying. Shrimp showed high levels of intra- and inter-individual variation, demonstrating a complex balance between behavioural-plasticity and environmental adaptation. As such, the study of crustacean colour changes represents a valuable opportunity to investigate colour adaptations in dynamic habitats and can help us to identify the mayor environmental and behavioural factors influencing the evolution of animal background matching

Application of electron probe X-ray microanalysis to the detection of metalpollutant in freshwater zooplankton

International audienc

UPTAKE, STORAGE AND EXCRETION OF URANIUM BY MYTILUS EDULIS, A STRUCTURAL, ULTRASTRUCTURAL AND MICROANALYTICAL STUDY BY SECONDARY ION EMISSION AND X RAY SPECTROMETRY

1-Deux méthodes de microanalyse ont été utilisées : la spectrographie des rayons X à l'échelon des microscopes optique et électronique et l'émission ionique secondaire à l'échelon de la microscopie optique ; elles ont permis de montrer que, des M. edulis récoltées sur les côtes de la Manche, ainsi que des échantillons contaminés expérimentalement, accumulent 238U. 2-Les plus fortes concentrations d'uranium sont détectées dans les animaux prélevés au niveau des zones de rejet des phosphogypses et des résidus de fabrication de TiO2 qui contiennent de l'uranium. 3-L'uranium est absorbé par les voies branchiale et digestive. Le stockage est réalisé dans le manteau, la glande digestive, l'épithélium intestinal et la gonade où les teneurs les plus élevées sont souvent constatées. L'excrétion se fait par le rein. 4-Les organites cibles sont les lysosomes de la glande digestive et les sphérocristaux du rein ; dans ces deux sites électifs d'accumulation, l'uranium est toujours associé à du phosphore. Ainsi, l'uranium absorbé sous forme soluble, est ensuite concentré sous forme de phosphate insoluble dans les organites de stockage. 5-Les hémocytes macrophages jouent un rôle important dans la capture, le transport, le stockage et l'excretion du radionucleide. 6-La Moule commune apparait comme un système biologique capable d'accumuler et de concentrer, sous forme insoluble, l'uranium présent dans le milieu marin à l'état de traces. M. edulis est proposé comme organisme indicateur de pollution par l'uranium.1-Two microanalytical methods have been used : X ray emission at the light and electron microscope levels and secondary ion emission ut the light microscope level. They allowed to show that M. edulis collected on the Channel coasts or experimentally contaminated samples, bioaccumulate 238U. 2-The highest U levels were detected in the samples collected in the areas where phosphogypsum and TiO2 industrial wastes,U containing, are released. 3-Uranium uptake happened via gill and digestive tractus. Storage organs were mantle, digestive gland, intestine epithelium and gonad where the highest values often occured. Excretion happened via kidney. 4-The target organelles were digestive gland lysosomes and kidney sphe rocrystals : within both of these accumulation sites, uranium was always associated with phosphorus. Thus, soluble uranium which was absorbed, was then concentrated in the form of an unsoluble phosphate in the storage organelles. 5-Macrophage haemocytes plaid an important part in ingestion, transport, storage and excretion of the radionuclide. 6-The common marine Musse, appears as a biological system accumulating uranium which, present in the marine environment at trace level, is stored and concentrated under an unsoluble form by the Mussel. M. edulis is proposed as an uranium pollution indicator organism

THULIUM BIOACCUMULATION BY THE SHORE CRAB CARCINUS MAENAS COLLECTED FROM THE FRENCH COASTS OF THE CHANNEL : A STRUCTURAL, ULTRASTRUCTURAL AND MICROANALYTICAL STUDY BY SECONDARY ION MASS AND X RAY SPECTROMETRY

Deux méthodes de microanalyse ont été utilisées : la spectrographie des rayons X à l'échelon des microscopes optique et électronique et l'émission ionique secondaire à l'échelon du microscope optique, pour montrer que des Carcinus maenas récoltés de Novembre 1982 à Janvier 1983, dans 8 stations des côtes de la Manche (de Boulogne à Roscoff), ainsi que des animaux contaminés expérimentalement, accumulent 169 Tm. Le site principal de retention est l'exosquelette et les organites cibles sont les lysosomes qui contiennent des microgranules à haute teneur en Tm associé à P. Les hémocytes macrophages jouent un rôle important dans la capture, le transport, le stockage et l'excrétion de cette terre rare. C. maenas apparait comme un système biologique accumulant Tm qui, présent dans l'environnement marin à l'état de traces, est stocké et concentré sous forme insoluble par le crabe.Two microanalytical methods have been used : X ray emission at the light and electron microscopes levels and secondary ion emission at the light microscope level to show that Carcinus maenas collected from November 1982 to January 1983, in 8 stations of the channel coasts (from Boulogne to Roscoff) and experimentally contaminated samples, bioaccumulate 169 Tm. The major retention site is the exoskeleton and the target organelles are the lysosomes which contain microprecipitates with high level of Tm associated with P. Macrophage haemocytes play an important part in ingestion, transport, storage and excretion of the rare earth. C. maenas appears as a biological systern accumulating Tm which, present in the marine environment at trace level, is stored and concentrated under an unsoluble form by the crab

Pollution du lac Leman. Mise en evidence d'une accumulation d'etain par les crustaces planctoniques : premieres donnees obtenues par spectrographie des rayons X.

National audienc

Microanalyse et hydrothermalisme oceanique. Premiers resultats et perspectives dans le domaine de la biologie

Specimens of hydrothermal vent organisms, Alvinella caudata and Bathymodiolus thermophilus were collected in 1982 from 13 degree N and 103 degree W, on the East Pacific Rise at a depth of 2600 m. The elemental composition was determined for some of their soft tissues at the structural and ultrastructural levels. Two microanalytical methods were used: secondary ion mass spectrometry and X-ray spectrometry. As examples, external and digestive epithelium and lumen of the digestive tract of Alvinella caudata and the gill and digestive gland of Bathymodiolus thermophilus were investigated. Intracellular localization of the elements, performed by electron microscopy, showed that spherocrystals and lysosomes were the target organelles of metal concentration. Moreover, bacteria were shown to be capable of elemental concentration. The correlations between the metal concentrations within the vent organisms and the metal concentrations characteristic of the vent environment are examined