Inhalant and exhalant pressures in Mytilus edulis L. and Cerastoderma edule (L.)

Abstract

Pressure in the mantle and suprabranchial cavities has been measured by means of a catheter inserted into either the inhalant or exhalant siphon respectively. In Mytilus mean mantle pressure is 0.54 mm of water below ambient, and mean suprabranchial pressure is 1.23mm of water above ambient. In Cerastoderma held in gravel the ventral mantle margin is open and increases the effective inhalant aperture. In native silt water enters only through the inhalant siphon. In gravel mean mantle pressure is 0.46 mm of water below ambient, in silt it is 0.91 mm of water below ambient. In gravel mean suprabranchial pressure is 2.33 mm of water above ambient, in silt it is 2.07 mm of water above ambient. These values are greater than previously published values. Although not directly comparable with filtration pressure gradients, the magnitude of these pressures suggests that pressure gradients are more than adequate to allow filtration by the latero-frontal cirri of the ctenidial filaments.