Voltage-dependent calcium currents in vertebrate (Scyliorhinus canicula), protochordate (Branchiostoma lanceolatum), and invertebrate (Alloteuthis subulata) skeletal and striated muscle were examined under whole-cell voltage clamp. Nifedipine (10 µM) suppressed and cobalt (5 mM) blocked striated/skeletal muscle calcium currents in all of the animals examined, confirming that they are of the L-type class. Calciseptine, a specific blocker of vertebrate cardiac muscle and neuronal L-type calcium currents, was applied (0.2 µM) under whole-cell voltage clamp. Protochordate and invertebrate striated muscle L-type calcium currents were suppressed while up to 4 µM calciseptine had no effect on dogfish skeletal muscle L-type calcium currents. Our results demonstrate the presence of at least two sub-types of L-type calcium current in these different animals, which may be distinguished by their calciseptine sensitivity. We conclude that the invertebrate and protochordate L-type current sub-type that we have examined has properties in common with vertebrate 'cardiac' and 'neuronal' current sub-types, but not the skeletal muscle sub-type of the L-type channel. Experimental Physiology (2001) 86.6, 689-694.