Research progress in scyphozoan polyp strobilation-induced factors and regulation mechanism

Strobilation is a key stage for polyp-to-jellyfish transition. Knowledge about the strobilation-induced factors and the underlying molecular regulation mechanism could help control jellyfish bloom in nature, improve jellyfish artificial breeding, as well as get insight about the ancestral molecular origin of metamorphosis of amphibians, insect and cnidarians. Natural factors, including temperature, illumination, salinity, and symbiotic zooxanthellae, could induce strobilation. The mode of strobilation and how these natural factors irritate strobilation are distinct in different jellyfish species. Chemicals including indole derivates, 9-cis retinoic acid, elemental iodine, hydrogen peroxide, could also induce strobilation in laboratory. Indole derivates are effective inducers to most scyphozoan species. The molecular mechanism of strobilation is unclear. Results from moon jelly reveal that RxR signaling pathway plays an important role during strobilation. A secreted moon jelly-special protein named CL390 may serve as a strobilation-induced hormone precursor. These results imply that morphological differences in medusa production may mask similarities at the cellular level in different jellyfish species. The molecular mechanism of metamorphosis in jellyfish may share some consistency with amphibians and insects.