Hexactinellid tissue is unusual among animals. Instead of discrete cells separated by membranes, large regions form a syncytium, a continuous mass of cytoplasm with many nuclei, connected through cytoplasmic bridges. This continuity provides a pathway for propagated electrical activity of the kind normally associated with nerve or muscle tissue.
Laboratory work on deep-water species recorded a body-wide arrest of the flagellated pumping cells within seconds of mechanical or sediment stimulation, and the arrest spread at a measurable conduction velocity. Stopping the pump protects the delicate filter chambers from being clogged by a sediment plume.
The finding is sometimes reported as sponges having nerves after all. They do not: there are no neurons, no synapses and no action potentials in the vertebrate sense being claimed. What the work shows is an independent route to fast coordination. How the syncytium is formed and maintained, and how widely this conduction occurs across the class, remain open.