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First published online October 10, 2003

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Energy metabolism and valve closure behaviour in the Asian clam Corbicula fluminea

Christian Ortmann^* and Manfred K. Grieshaber

Institute of Zoophysiology, Heinrich-Heine-University, Düsseldorf 40225, Germany

View larger version (26K): [in a new window]   Fig. 1. Measuring principle of the bivalve monitors. (A) The Dreissena-Monitor® (Borcherding, 1992) contained 34 and (B) the Mosselmonitor® 8 measuring units at the same time (Hoffmann et al., 1994). Both figs slightly modified and reproduced with permission.

View larger version (19K): [in a new window]   Fig. 2 Flowthrough-system. AFW, artificial freshwater (5 l-reservoir); TF, twin-flow-respirometer with two oxygen sensors and a 500 ml reservoir inside a waterbath (WB; 15°C); A/D, analogue-digital converter inside TF-monitor; P, peristaltic pump; TAM, calorimeter with reaction and reference chamber; W, waste.

View larger version (40K): [in a new window]   Fig. 3. Valve movements of the eight specimens (M1-M8) in Koblenz during 11-17 June 1998, recorded by the Mosselmonitor®. Water temperature varied between 19.1°C and 22.4°C. (A) Continuous recordings of individual magnitudes of shell gape, in arbitrary units. For each trace, closed is the baseline level. Dotted lines mark the change of date (0:00 h). Periods of monitor maintenance are indicated. (B) Individual means of the magnitude of shell gape at hourly intervals throughout the day, calculated from the maximum of arbitrary units (in A) set as 100%, minimum as 0%. White diamonds are mean values ± S.D. of the eight clams at each hour. *Minimum values, from 2:00 h to 3:00 h (22%), and maximum, from 18:00 h to 19:00 h (87%), differ significantly.

View larger version (21K): [in a new window]   Fig. 4. Valve movements of the eight specimens (M1-M8) in Koblenz during 11-17 February 1999, recorded by the Mosselmonitor®. Water temperature varied between 3.1°C and 4.3°C. Continuous recordings of individual magnitudes of shell gape, in arbitrary units. For each trace, closed is the baseline level. Dotted lines mark the change of date (0:00 h).

View larger version (27K): [in a new window]   Fig. 5. Metabolic rates of C. fluminea (J h-1 g-1 dry mass) over a time period of nearly 2 weeks, measured as heat dissipation (red) and rate of oxygen consumption O2 (transformed via the oxycaloric equivalent: 450 kJ mol-1 O2; black), recorded in artificial freshwater at 15°C. During the eighth day the water was bubbled with nitrogen.

View larger version (32K): [in a new window]   Fig. 6. Comparison of metabolic rates [J h-1 g-1 dry mass] of C. fluminea measured by direct (heat dissipation) and indirect (rate of oxygen consumption) calorimetry. Integration of periods with open (A) and closed (B) valves in artificial freshwater at 15°C. Heat dissipation (; dark grey bars), oxygen consumption (O2; light grey bars). Each pair of bars (means ± S.D.) represents one of the 18 specimens used for calorespirometry, with open (A) and closed (B) valves. The oxycalorific equivalent = 450 kJ mol-1 O2.

View larger version (28K): [in a new window]   Fig. 7. Concentrations of (A) propionate and (B) succinate in foot, adductor muscles and gills (µmol g-1 fresh mass) and in the mantle cavity fluid (µmol ml-1) of C. fluminea in controls and after N2 incubation. Values are means ± S.D.; numbers above the bars indicate the number of animals analysed. *Significant difference (P<0.05) compared to the controls; significant difference (P<0.05) of a whole group of tissues from the controls.

View larger version (22K): [in a new window]   Fig. 8. Concentrations of succinate in foot, adductor muscles and gills (µmol g-1 fresh mass) and in the mantle cavity fluid (µmol ml-1) of C. fluminea in controls and after different times within `voluntarily' closed valves. Clams were taken out of the Mosselmonitor® (MM), where they experienced a permanent flow of well-aerated artificial freshwater at 15°C without light. Values are means ± S.D.; numbers above the bars indicate the number of animals analysed. *Significant difference (P<0.05) compared to the controls; significant difference (P<0.05) of a whole group of tissues from the controls.

View larger version (32K): [in a new window]   Fig. 9. O2 content (O2-data from North Rhine-Westphalia State Environment Agency) and valve closure behaviour of C. fluminea (27 specimens in parallel) inside the Rhine at Bad Honnef during July 23-31 1998, recorded by the Dreissena-Monitor®. Illustrated are the proportions of opened clams inside the two parallel flumes of the monitor. Dotted lines indicate the change of date, 0:00 h, water temperature varied between 22°C and 24°C.

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