Optimising the application of 5-methoxy-2-methyl-indole to induce strobilation in moon jellyfish polyps

Abstract

Indoles, including 5-methoxy-2-methyl-indole (5MeO2MeIn), are a potent trigger of strobilation in jellyfish polyps. Indoles may be an alternative method to cooling to induce strobilation, but the ephyrae produced should have similar or better rates of survival, deformities, growth, and behaviour to those produced by cooling, and polyps should remain viable after strobilating. We used two experiments to optimise the use of 5MeO2MeIn to induce strobilation in Aurelia coerulea (Scyphozoa). First, we compared rates of strobilation, survival, and deformities of ephyrae and budding of polyps exposed to 1.25, 2.5, and 5.0 µM 5MeO2MeIn for 3 days to cooling at 14 °C. Polyps in the indole and cooled treatments strobilated after 10 days and produced similar numbers of ephyrae, but more ephyrae were deformed in the 5.0 µM treatment and survival of ephyrae was lower in the 2.5 and 5.0 µM treatments than the cooled treatment. Polyps exposed to all three concentrations of indoles failed to bud or died after strobilation. Next, we exposed polyps to 0.7, 1.25, and 2.5 µM 5MeO2MeIn for four hours. Polyps exposed to all indole concentrations strobilated and produced similar numbers of ephyrae, but more ephyrae were deformed in the 2.5 µM treatment. Survival, behaviour, and sizes of ephyrae were similar 7 and 14 days after strobilation (although ephyrae pulsed faster in the 1.25 µM treatment at 14 days) and budding rates were similar in the indole and cooled treatments. Thus, exposing polyps to 0.7–1.25 µM 5MeO2MeIn for 4 h is a viable and efficient alternative to cooling to induce strobilation in polyps.