Abstract
The mechanism for preventing the loss of blood in Scrobicularia plana (Da Costa) after siphonal wounding has been examined by histological techniques. Loss of blood appears to be prevented by local contraction of the radial muscles in the siphon wall at the tip only, so forming an immediate mechanical seal. Experiments in which (14C) inulin was injected into the circulatory system indicated that very little or no blood is lost at wounding and that the seal continues to function efficiently afterwards. The blood volume of Scrobicularia was estimated by measuring the dilution of a known quantity of (14C) inulin injected into the blood system via the pedal sinus. To assess the accuracy of this method the blood volume of a second bivalve, Anodonta cygnea (L) was estimated by both pedal and ventricular injections. The blood volumes of Scrobicularia and Anodonta, when expressed as a percentage of the wet weight, are 52 and 55 % respectively, values which agree with those of previous workers for other bivalves.
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