Coordination of Compound Ascidians by Epithelial Conduction in the Colonial Blood Vessels

Bursts of electrical potentials propagate at ca. 2.0 cm s-1 within the colonial vascular system of Botryllus, Botrylloides, and Metandrocarpa, serving to coordinate contractions of the vascular ampullae and mediating protective closure and ciliary arrest in zooids. Nerves are absent from the vessels and ampullae. Impulses are presumed to propagate from cell to cell in the vascular epithelium via gap junctions, shown to be present by electron microscopy.