Effect of mono- and divalent cations on polyp morphogenesis in isolated tentacles of Aurelia aurita(Scyphozoa)

Tentacles excised from syphistoma polyps of Aurelia aurita undergo rapid regeneration to form whole polyps following exposure to an excess or absence of specific ions. It has been shown that a 12-18 h exposure of isolated tentacles to 58 mM excess of Cs⁺ results in a rapid firing of nematocysts, followed by an accelerated, synchronous polyp morphogenesis. Absence of Mgt²⁺ from the culture solution for 4-24 h also led to an accelerated, synchronous polyp regeneration. In either experimental set-up, incubation in 5-10 mM hydroxyurea effectively halted regeneration. Exposure to an excess of Li⁺ (50-200 mm) or K⁺ (10-50 mM) caused no firing of nematocysts and a percentage of polyp regeneration only slightly higher than control tentacles. Use of the K⁺ channel blocker tetraethylammonium (TEA; 100-300 mM) lead to similar levels of regeneration. A Ca²⁺ or K⁺-reduced artificial culture solution did not enhance regeneration. Ouabain (1 mM) dampened the Cs⁺ induced acceleration of polyp morphogenesis, and when given without Cs⁺, elicited a control level response.