The raptorial siphonal apparatus of the carnivorous septibranch Cardiomya planetica Dall (Mollusca:Bivalvia), with notes on feeding and digestion

Abstract

Cardiomya planetica Dall is a carnivorous septibranch bivalve. The food-capturing organ is the inhalant siphon, which can be rapidly extended by a surge of blood. The increase in blood pressure is brought about by the contraction of the septum. The sensory mechanism is constituted by seven siphonal tentacles with mechanoreceptors at their tips. The mechanoreceptors are composed of clumps of clubbed cilia in apical pits lined with microvilli. The activity of the septum, inhalant siphon, and pallial valve is coordinated with the sensory input through a large siphonal ganglion. Food consists largely of ostracods and digestion appears to be periodic.