PARENT SESSION
MP2 Chemical, biological and combined methods for the detection of pollutants
3:00 PM to 6:30 PM, Monday, 07 May 2001
Session Chair: D. Santiago Laguna
Room 2

(082) Simultaneous monitoring of valve movements and pumping activity of Mytilus galloprovincialis and their response to contaminants.

Mouabad, Abdelfattah¹, Ait Fdil, Mohamed¹, Outzourhit, Abdelkader², Maarouf, Abdelmalek¹, ^{1 2}

ABSTRACT- Under the assumption that a reduction in the shell gape of mussels is necessarily concomitant with decrease in the filtering activity, the valve movement response to pollutants was used as biodetector for water contamination (Sluyts et al., Env. Tox. Chem.,15 (8),1317, 1996). However, this assumption has never been assessed by a direct method to screen the relationship between the two activities. For this purpose, a simultaneous study of the valve movements using an inductive monitor and the pumping activity using a flow sensor was carried out on the mussel Mytilus galloprovincialisunder normal and stress conditions. The normal behaviour was characterised by a wide opening of the valves with very scarce and little movements whereas the pumping flow was continuous except some short and occasional interruptions due to brief closures of the exhalent aperture. These closures occurred without any change in the valve activity. The appearance of an intermittent exhalent flow or its stoppage were set as detection criteria for the pumping activity whereas a reduction by at least 50 % of the valve full opening was the criterion for the valve activity. In a 2 h exposure to copper (20, 30, 60 and 100 g/l) changes in both activities were recorded for all treatments but differed in their pattern depending on concentrations. At 20 g/l Cu, the pumping activity response was faster than the valve response. The other concentrations induced a simultaneous detection by both activities, however, in the course of time, the two responses did not always coincide in their length except at 100 g/l. As a general obsevation, a delay was frequently noted betwen the impairment of the pumping activity and the valve response, especially in the beginning of the exposure. In some sequences, the pumping activity was intermttent without any valve response being recorded. The tested concentrations induced reductions of, respectively, 46.8 %, 58.2 %, 81.8 % and 83.6 % of the pumping time and 34.8 %, 63.2 %, 86.0 % and 77.9 % of the valve opening. These results show that at threshold concentrations the toxicity may be underestimated when assessed by the valve response and the liability of detectors based on this criterion would be weak.

Key words: bivalves, behaviour, biodetection, pollution