Browsing by Author "Coelho, M. R."
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- Biomarkers in Ruditapes decussatus: a potential bioindicator speciesPublication . Bebianno, Maria João; Géret, F.; Hoarau, P.; Serafim, Angela; Coelho, M. R.; Gnassia-barelli, M.; Roméo, M.The clam Ruditapes decussatus is distributed worldwide and due to its ecological and economical interest has been proposed as a bioindicator in areas where mussels are not available. The accumulation of several anthropogenic compounds in their tissues suggests that they possess mechanisms that allow them to cope with the toxic effects of these contaminants. Besides pollutant uptake, the use of biomarkers is pointed out in this paper since it is a promising approach to monitor the effect of these contaminants in the marine environment. Biomarkers complement the information of the direct chemical characterization of different types of contaminants. Therefore, the aim of this paper is to review the role of several biomarkers: (metallothioneins (MT), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and selenium-dependent), lipid peroxidation (measured as MDA, one of the final products of lipid peroxidation), glutathione S-transferase (GST) and acetylcholinesterase (AChE), measured in different tissues of the clam R. decussatus, in laboratory conditions and under various environmental stresses, in two ecosystems (Ria Formosa lagoon- Portugal) and Bizerta lagoon (Tunisia) in a perspective of a multibiomarker approach to assess environmental changes. Experiment and field studies are in good agreement since MT levels, especially in the gills, the first target tissue of these contaminants, can be used as biomarker of exposure to Cd. GPx and MDA may also be determined in this respect. AChE activity is inhibited by pesticide and, to a less extent, by metal exposure in the gills and whole soft body of clams. However, the induction of GST isoforms experimentally demonstrated is not observed in the field because only global GST activity was determined. The whole set of results opens new research perspectives for the use of this species to assess the effect of mixtures of pollutants in the aquatic environment.
- Effect of TBT on Ruditapes decussatus juvenilesPublication . Coelho, M. R.; Langston, W. J.; Bebianno, Maria JoãoThe effects of sublethal concentrations of tributyltin (TBT) on growth of juvenile clams Ruditapes decussatus were determined during exposure to TBT concentrations of 50, 100 and 250 ng l(-1) (as Sn) for a period up to two years. Length and weight of clams increased continuously in all treatments throughout the experimental period, and, overall, rates were not significantly influenced by TBT exposure, although final length and weight were inversely related to increasing TBT concentration. Juvenile R. decussatus therefore appear to be less sensitive to TBT than larval stages. Some juveniles exposed to TBT developed abnormal shell growth, laterally, changing the typical flattened shape of clams into a more "rounded" form. This characteristic was more visible in the anterior margins of valves than posteriorly, and mainly observed in clams exposed to TBT at 50 ng l(-1) (as Sn).
- Evidence of the differential sensitivity of neogastropods to tributyltin (TBT) pollution, with notes on a species (Columbella rustica) lacking the imposex responsePublication . Gibbs, P. E.; Bebianno, Maria João; Coelho, M. R.Five neogastropod species collected from a tributyltin (TBT)-polluted site near the port of Fare within the Ria Formosa on the Algarve coast of Portugal were examined in April 1996 for 'imposex'. All females of four of these species - Hexaplex trunculus, Ocenebra erinacea, Ocinebrina aciculata (all Muricidae) and Nassarius reticulatus (Nassariidae) - exhibited the characteristic development of male sex organs (penis plus vas deferens) but no female of the fifth Columbella rustica (Columbellidae) - showed any sign of being similarly masculinised. Only two neogastropods have been previously described as lacking the imposer response to TBT exposure. These two species, along with C. rustica, can be considered as 'zero-response' forms. Other species can be grouped according to the maximum level of masculinisation they exhibit: level I species develop just a penis and vas deferens; in level II forms oviduct structure and function are disrupted, and in level III species ovary transformation to testis is observed. Such a comparative scheme of ordering can be used as a guide to the differential sensitivity of species to TBT pollution.