The spectacle of thousands of jellyfish at Hobart's waterfront dock may be breathtaking, but a leading scientist has warned their presence indicates something in the environment is out of balance.

Medusa Stage: The Adult Life of a Jellyfish Jellyfish start ... The medusa stage varies in duration among species. For example, the moon jellyfish has a relatively short lifespan, living for ...

Over the next 24-36 hours, this blob develops into a new polyp - the jellyfish's previous life stage - and after maturing, medusae bud off. This phenomenon has been likened to that of a butterfly ...