Observations On the Rate of Water Pumping of the Freshwater Mussel Anodonta Cygnea Zellensis (Gmelin)

The pumping rate of Anodonta cygnea zellensis (Gmelin) has been determined using the apparatus developed by DRINNAN, that operates via the direct method. 2. The average pumping rate of Anodonta with a shell-length of 8-10 cm is at a temperature of 18-20° C is 250-300 ml per hr. The variations, however, are great: between 100 and 1000 ml per hr. These fluctuations in the pumping rate are independent of environmental conditions. 3. The exhalent current of Anodonta is not continuous; interruptions of the water current occur at regular intervals, their frequency being 6-40 per hr, and their duration from less than 15 secs to 2-3 min. These interruptions are caused by the closing of the exhalent siphon; their occurrance is independant of environmental conditions.