The siphons of Scrobicularia plana (Bivalvia: Tellinacea). Observations on movement and extension

Simultaneous recordings of mantle cavity pressure and valve movements, together with observations of the siphons of Scrobicularia show that extension is achieved both by the intrinsic musculature of the siphon wall and by low pressure (0.3‐0.4 kPa) generated in the mantle cavity water by valve adductions. Such low pressures are produced by valve movements of less than 0.5 mm at their ventral margins. Experiments on isolated siphons, relaxed by narcotization, confirm that pressures of 0.4 kPa are sufficient to elongate them.