Structure and function of an entoproct tentacle with a discussion of ciliary feeding types

Abstract

Electron microscopical studies of Loxosomella elegans have demonstrated that a cross section of a tentacle typically shows the following cells: one large frontal cell with short cilia and in some cases small mucus vesicles; a pair of narrow laterofrontal cells with short cilia and bundles oflongitudinal myofilaments; a pair of large lateral cells with long cilia in groups of 6- 10;a number of abfrontal cells with branched microvilli with swollen caps; and a number of small mesodermal elements, among which nerves in contact with the lateral cells have been identified. The lateral and laterofrontal cilia beat in a plane perpendicular to the length axis of the tentacle with the effective stroke towards its frontal midline; the frontal cilia beat parallel with the length axis of the tentacle with the effective stroke towards its base. The feeding mechanism is discussed.