Display Settings:   Send to:  Choose Destination J Exp Biol.
1999 May;202 (Pt 9):1139-50.  Impulse conduction in a sponge.
Biology Department, University of Victoria, British Columbia,
Canada.   All-or-none propagated electrical impulses were
recorded from the hexactinellid sponge Rhabdocalyptus dawsoni
using suction electrodes attached to lumps of aggregated sponge
tissue grafted onto the surface of pieces of the same sponge.
Impulses were normally evoked by means of externally applied
electrical shocks. Recorded externally using an a.c.-coupled
amplifier, the electrical event was triphasic and lasted
approximately 30 s; integration gave a diphasic waveform. A
further integration to give the form of the membrane action
potential produced a monophasic signal. Impulses propagated at
0.27+/-0.1 cm s-1 with an absolute refractory period of 29 s and
a relative refractory period of approximately 150 s. Concurrent
thermistor flow meter recordings confirmed that water flow
through the sponge was arrested following