Fig. 7. Ionic dependence of T- and L-potentials. (A) T-potentials during substitution of sodium in ASW by choline and after restitution of ASW. Data below the traces indicate time after exchange of solution. (B) T-potentials during superfusion with `0 Ca²⁺-ASW' (i.e. no Ca²⁺ added) and subsequent exchange with regular ASW. Data below records as in A. (C) L- and superimposed T-potentials during superfusion with ASW containing 1 mmol l^–1 Ca²⁺ and double the Mg²⁺ concentration (96 mmol l^–1 Mg²⁺); highest response amplitude recorded immediately before switching to the test medium; progressively reduced amplitudes recorded at 3, 4 and 5 min of superfusion by the test medium. Records from Dipurena. Lower trace: excursion of the stimulus probe pulling at a stinging thread of a discharged nematocyst. (D) Effect of reduced Mg²⁺ concentration on T-potentials: upper trace before, lower trace 1 min after reduction of [Mg²⁺] to 10% (5 mmol l^–1) in ASW. All records except those in C from Stauridiosarsia.