Turritopsis dohrnii is known as the immortal jellyfish. This small, transparent creature begins life as a larva called a planula that settles on the sea floor and grows into a cylindrical colony of polyps. These spawn free-swimming, genetically identical medusae – jellyfish which grow to adulthood in weeks. In response to physical damage or starvation, they revert to an earlier stage of their life cycle, transforming back into a polyp. The born-again polyp colony eventually buds and releases medusae that are genetically identical to the injured adult.
The species T. dohrnii was first described by scientists in 1883. It was 100 years later, in the 1980s, that their immortality was accidentally discovered.
Students Christian Sommer and Giorgio Bavestrello collected Turritopsis polyps, which they kept and monitored until medusae were released. It was thought that these jellyfish would have to mature before spawning and producing larvae, but when the jar was next checked, they were surprised to find many newly settled polyps.
They continued to observe the jellyfish and found that, when stressed, the medusae would fall to the bottom of the jar and transform into polyps without fertilisation or the typical larval stage occurring.
Credit : National History Museum
Picture Credit : Google
