The ciliary-cone sensory cell of anemones and cerianthids.

An ultrastructural study of the tentacles of Stomphia and of Ceriantheopsis has revealed that the so-called 'ciliary-cone sensory cell' consists of a cluster of five to seven apparent receptors rather than just one cell as reported previously. At the center of a cluster is a single cell, whose dendrite bears one cilium surrounded by about ten large stereocilia. Surrounding this cell are a number of peripheral cells whose dendrites bear large numbers of small stereocilia and, in Ceriantheopsis, one cilium. The sensory apparatuses of all cells in a cluster unite to form a single unit projecting above the tissue surface: the ciliary cone. Their possible physiological role is discussed in relation to new behavioural observations.