The electrophysiology of the organ-pipe coral, Tubipora musica.

1. Through-conducted electrical activity can be recorded from colonies of Tubipora musica after mechanical and electrical stimulation.2. The recorded potentials, conducted with a maximum velocity of 18 cm/sec, show distinct facilitation of a component interpreted as a muscle action potential. The colonially conducted potentials responsible for muscle activation in the polyps appear on the records as small (5 µV) potentials that precede the muscle action potentials.3. The propagation and form of all recorded electrical activity is unaltered after 55 minutes submersion of Tubipora in a solution containing high magnesium.4. Commonly, potentials similar to those associated with colonial activity can be recorded from only one polyp. These are interpreted as being the result of some form of polarization between the conduction system in the polyp and that in the colony which allows individual polyps to function independently of the remainder in the colony.