resumo
Bivalves are commonly used in biomonitoring programs to track pollutants. Several features, including its filter feeding abilities, cumulatively argue in favour of the use of the Asian clam (Corbicula fluminea) as a biosentinel and an ecotoxicological model. Filtration in bivalves is very sensitive to external stimuli and its control is dictated by regulation of the opening/closure of the valves, which may be used as an avoidance defence against contaminants. Here, we investigate the filter-feeding behaviour of the Asian clam as an endpoint for assessing exposure to pollutants, driven by two complementary goals: (i) to generate relevant and sensitive toxicological information based on the ability of C. fluminea to clear an algal suspension, using the invasive species as a surrogate for native bivalves; (ii) to gain insight on the potential of exploring this integrative response in the refinement of chemical control methods for this pest. Clearance rates and proportion of algae removed were measured using a simple and reproducible protocol. Despite some variation across individuals and size classes, 50-90% of food particles were generally removed within 60-120 min by clams larger than 20 mm. Removal of algae was sensitive to an array of model contaminants with biocide potential, including fertilizers, pesticides, metals and salts: eight out of nine tested substances were detected at the mu g l(-1) or mg l(-1) range and triggered valve closure, decreasing filter-feeding in a concentration-dependent manner. For most toxicants, a good agreement between mortality (96 h - LC50 within the range 0.4-5500 mg l(-1)) and feeding (2 h - 1050 within the range 0.005-2317 mg l(-1)) was observed, demonstrating that a 120-min assay can be used as a protective surrogate of acute toxicity. However, copper sulphate was very strongly avoided by the clams (IC50 = 5.3 mu g l(-1)); on the contrary, dichlorvos (an organophosphate insecticide) did not cause feeding depression, either by being undetected by the clams' chemosensors and/or by interfering with the valve closure mechanism. Such an assay has a large potential as a simple screening tool for industry, environmental agencies and managers. The ability of dichlorvos to bypass the Asian clam's avoidance strategy puts it in the spotlight as a potential agent to be used alone or combined with others in eradication programs of this biofouler in closed or semi-closed industrial settings.
palavras-chave
INVASIVE ASIAN CLAM; VALVE CLOSURE BEHAVIOR; DAPHNIA-MAGNA; FILTRATION-RATES; DREISSENA-POLYMORPHA; ZEBRA MUSSEL; WATER; COPPER; RESPONSES; BIVALVES
categoria
Marine & Freshwater Biology; Toxicology
autores
Castro, BB; Silva, C; Macario, IPE; Oliveira, B; Goncalves, F; Pereira, JL
nossos autores
Inês Adriana Patrunilho Efe Macário
Estudante de doutoramentoagradecimentos
This work was supported by the strategic programs UID/AMB/50017/2013 (POCI-01-0145-FEDER-007638) and UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569), funded by the European Regional Development Fund through COMPETE2020 and PT2020, and by National Funds through the Portuguese Science Foundation (FCT). Funding entities had no role in the study design, in the collection, analysis and interpretation of data, in the writing of the paper, or in the decision to submit the article for publication. JL Pereira is a recipient of an individual research grant by FCT (SFRH/BPD/101971/2014).