Comparative population biology of fish digenes : The case of 3 Helicometra (Trematoda, Opecoelidae) mesoparasites of marine teleosts in a mediterranean lagoon

International audienceIn the Etang de Thau (Herault, France), three species of Helicometra parasitize in their adult stage the digestive tract of the black goby Gobius niger, the grass goby Zosterisessor ophiocephalus, the grey wrasse Symphodus cinereus, and the common eel Anguilla anguilla (Teleostei). These fish act as definitive hosts in the biological cycle of these platyhelminths. Also H. gobii exists in G. niger, Z. ophiocephalus, S. cinereus and A. anguilla ; H. fasciata is found in G. niger ; and H. pulchella is only found in S. cinereus. In the case of the two gobies and the eel, these three congeneric digenes sometimes coexist in the same infracommunity. Spatio-temporal analysis of these different populations has enabled : 1) detection of seasonal variations in their structure, 2) identification of the relationships between the nature of their specificity and demographic strategy, and 3) the global absence of statistical dependence between the intensities of different species in the same infracommunity to be show. Implications arising from previous research concerning the demographic behaviour of these trematodes in their first intermediate host (mollusc compartment), were taken into account when interpreting structures observed in the definitive hosts. The problems of coexistence between these species, which are taxonomically very close in the same parasite community, and the under-lying speciation mechanisms are discussed in the light of population structuration

Comparative population biology of digenes and their 1st intermediate host mollusc : the case of three Helicometra (Trematoda, Opecoelidae) endoparasites of marine prosobranchs (Gastropoda)

International audienceIn the Etang de Thau (Herault - France), Helicometra gobii, H. fasciata and H. pulchella parasitize the Calliostoma striatum, Gibbula adansoni and Tricolia tenuis gastropods respectively. A comparative analysis of these host populations and their trematodes reveals a relation between the spatial and temporal structures of these populations, the parasite specificity and the specific richness of parasite settlements of these molluscs. Thus, although it has by far the rarest gastropod and has the strictest specificity relative to the definitive host fish, H. pulchella nevertheless has a capacity for colonizing its first intermediate host comparable to it congeners. This is also the only species with no known potential competitor (digene) in its mollusc. The evolutionary implications of the demographic strategies of the three phylogenetically closely related trematodes are finally discussed

Structure of monogenean populations, ectoparasites of the gilthead sea bream Sparus aurata

International audienceIn the Western Mediterranean, the gilthead sea bream Sparus aurata Linnaeus, 1758 is parasitized by two gill monogeneans, Furnestinia echeneis (Wagener, 1857) Euzet and Audouin, 1959 (Monopisthocotylea : Diplectanidae), and Sparicotyle chrysophrii (van Beneden and Hesse, 1863) Mamaev, 1984 (Polyopisthocotylea : Microcotylidae). The spatial structure of these parasitic populations were studied on the French coast in the Gulf of Lions in 1984 and 1985. The relations between the two species forming this guild have been demographically analyses. Their distribution profiles are very similar and display some stability with time, although some increasing trends are perceptible in the spring. These two monogeneans are globally frequent, but always present in only moderate intensities in infrapopulations. Recruitment of F. echeneis is independent of that of S. chrysophrii. This mode of contamination limits massive and simultaneous infestations of a single host, and interspecific competition risks are consequently considerably reduced. Our results suggest these parasites can affect the size of a natural gilthead population to only a limited degree

Polymorphismes phénotypique et enzymatique : intérêt et limites dans la description d'espèces d'Helicometra (Trematoda, Opecoelidae), mésoparasites de téléostéens marins.

International audienceThree trematodes belonging to the genus Helicometra from the "Golfe du Lion" (Etang de Thau, France) are identified and renamed on the basis of isoenzyme electrophoresis (Reversat et al., 1989). After the bibliographical review of the genus Helicometra in the Mediterranean basin, the following results are proposed: (1) the specimens which possess the allele MDH-1a are only found in Symphodus cinereus (Labridae) : this taxon is considered to belong to Helicometra pulchella (Rudolphi, 1819) Odhner, 1902 ; (2) the trematodes bearing the allele MDH-1b parasitise S. cinereus, Gobius niger (Gobiidae), Zosterisessor ophiocephalus (Gobiidae) and Anguilla anguilla (Anguillidae) : these helminths are defined as Helicometra gobii (Stossich, 1883) Stossich, 1904 ; (3) and the digeneans defined genetically by the alleles MDH-1c and MDH-1d are found in A. anguilla, G. niger and Z. ophiocephalus, and are named Helicometra fasciata (Rudolphi, 1819) Odhner, 1902. The importance of the biochemical genetics for the study of taxonomy of trematodes is shown, but the problems these techniques raise are also discussed. The case of Helicometra gobii is typical : it exhibits a strong phenotypical polymorphism for an enzymatic type (MDH-1b). The problem of diagnostic characters for species definitions is therefore introduced

Changes in eucalypt litter quality during the first three months of field decomposition in a Congolese plantation

In fast-growing tree plantations, decomposition of leaf litter is considered as a key process of soil fertility. A three-month field experiment, spanning both rainy and dry seasons, was conducted to determine how changes in litter decomposition affect the main parameters of litter quality-namely, the concentrations of phenolic and non-phenolic carbon (C) compounds, nitrogen (N), and fibres, and the litter C mineralization rate. This Study was conducted to test (1) if these changes vary according to the Compound and to the season, and if they are greater for soluble compounds, and (2) if after a three-month period of field decomposition, the chemical composition of the remaining litter drives C mineralization, as measured in laboratory conditions, through a greater influence on the concentration of N and lignin. We found that the concentrations of water- and methanol-soluble phenolic compounds and the concentrations of non-phenolic compounds decreased during decomposition in all plots and in each season, while the fibre and N concentrations increased. The relationships among litter decomposition, C mineralization, and litter quality depended on the season, which strongly suggests that different processes are involved in dry and rainy seasons. The C mineralization rates were driven by soluble organic Compounds in the initial litter and by soluble phenolic compounds in the decomposed litter

Assessment of Isoprostanes in Human Plasma: Technical Considerations and the Use of Mass Spectrometry

International audienceOxygenated lipid mediators released from non-enzymatic peroxidation of polyunsaturated fatty acids (PUFA) are known to have functional roles in humans. Notably, among these lipid mediators, isoprostanes molecules are robust biomarkers of oxidative stress but those from n-3 PUFA are also bioactive molecules. In order to identify and assess the isoprostanes, the use of mass spectrometry (MS) for analysis is preferable and has been used for over two decades. Gas chromatography (GC) is commonly coupled to the MS to separate the derivatized isoprostanes of interest in biological samples. In order to increase the accuracy of the analytical performance, GC-MS/MS was also applied. Lately, MS or MS/MS has been coupled with high-performance liquid chromatography to assess multiple isoprostane molecules in a single biological sample without derivatization process. However, there are limitations for the use of LC-MS/MS in the measurement of plasma isoprostanes, which will be discussed in this review

Characterization and modulation of brain lipids content of rainbow trout fed with 100% plant based diet rich in omega-3 long chain polyunsaturated fatty acids DHA and EPA

International audienceBrain functions are known to be mainly modulated by adequate dietary intake. Inadequate intake as can be an excess or significant deficiency affect cognitive processes, behavior, neuroendocrine functions and synaptic plasticity with protective or harmful effects on neuronal physiology. Lipids, in particular, u-6 and u-3 long chain polyunsaturated fatty acids (LC-PUFAs) play structural roles and govern the different functions of the brain. Hence, the goal of this study was to characterize the whole brain fatty acid composition (precursors, enzymatic and non-enzymatic oxidation metabolites) of fish model of rainbow trout fed with three experimental plant-based diet containing distinct levels of eicosapentaenoic acid (EPA, 20:5 u-3) and docosahexaenoic acid (DHA, 22:6 u-3) (0% for low, 15.7% for medium and 33.4% for high, total fatty acid content) during nine weeks. Trout fed with the diet devoid of DHA and EPA showedreduced brain content of total u-3 LC-PUFAs, with diminution of EPA and DHA. Selected enzymatic (cyclooxygenases and lipoxygenases) oxidation metabolites of arachidonic acid (AA, 20:4 u-6) decrease in medium and high u-3 LC-PUFAs diets. On the contrary, total selected enzymatic oxidation metabolites of DHA and EPA increased in high u-3 LC-PUFAs diet. Total selected non-enzymatic oxidation metabolites of DHA (not detected for EPA) increased in medium and high u-3 LC-PUFAs diets. In conclusion, this work revealed for the first time in fish model the presence of some selected enzymatic and non-enzymatic oxidation metabolites in brain and the modulation of brain lipid content by dietary DHA and EPA level