A lateral line analogue in cephalopods: water waves generate microphonic potentials in the epidermal head lines ofSepia andLolliguncula

Summary Many cephalopods have lines of ciliated cells on their head and arms. In the cuttlefishSepia and the squidLolliguncula, electrophysiological recordings clearly identify these epidermal lines as an invertebrate analogue to the mechanoreceptive lateral lines of fish and aquatic amphibians and thus as another example of convergent evolution between a sophisticated cephalopod and vertebrate sensory system. Stimulation of the epidermal lines with local water displacements, generated by a vibrating sphere, causes receptor potentials that have many features known from lateral line microphonic potentials. The minimal threshold of the head lines is 0.2 m peak-to-peak water displacement (calculated at the skin surface) at 75–100 Hz.