The response of the ampullae of Lorenzini of elasmobranchs to electrical stimulation.

The biological function of the ampullae of Lorenzini of elasmobranch fish remains uncertain, although by now there is considerable evidence concerning the different types of stimuli capable of eliciting responses in the sensory nerves. The ampullae are sensitive to changes of temperature of less than o-i° C. (Sand, 1938), a sensitivity that would normally justify their description as thermoreceptors were it not for the anatomical specialization of the accessory structures of the sense organ, which cannot be accounted for in this way. Mechanical sensitivity has also been described (Murray, i960), again adequate as a basis for sensory function, but the exact manner in which this sensitivity would be employed is unknown. Isolated preparations are sensitive to CO2 (Hensel, 1957) but this is unlikely to be of importance to the fish, for the concentrations concerned are high (2-10 % in the air surrounding the preparation). In this paper a further type of sensitivity is described, namely, to electrical stimuli (and also, as a result, to salinity changes), and in particular to changes in the voltage gradient in the surrounding water. Behavioural responses of other fish to such electrical stimuli are known (e.g. Lissmann & Machin, 1958), but the sensory side of such responses has only been worked out in a few cases (Hagiwara, Kusano & Negishi, 1962).