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.

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