The AP reports
that a hydrozoan jellyfish can revert to a polyp stage through a biological process known as transdifferentiation, meaning that the animal has the capacity to change one form of cell to another. This is the same process that allows starfish to regenerate lost arms and salamanders to re-grow tails. This capacity for an individual to return to its youth means that it is theoretically possible for an individual to live forever.
While hydrozoan may fall prey to predators, if they survive with wounds, face starvation, or other biological crisis, they can transmute their cells to any needed component, including reverting its entire body to an earlier stage of development. They can turn a muscle cell into a nerve cell, or even into an egg. Worldhealth.net reports
that hydrozoan, first discovered in 1883, and the size of a pinkie nail when fully developed, can also reproduce itself by transmuting cells into hundreds of replicas of itself.
As a result of this cellular flexibility, they have extended their domain from the Caribbean to temperate and tropical oceans and seas world-wide. Their spread to other regions is further attributed to their ability to stowaway on commercial and leisure ships as they traverse the globe. However, the ability of a hydrozoan to live forever may depend upon its ability to first reach sexual maturity. While laboratory studies have revealed that hydrozoan exhibit their immortal ability at all stages of life, younger jellyfish are likely to be eaten by predators, or succumb to disease. When hunted successfully by a predator, or killed by disease prior to the completion of their transmutation, the hydrozoan face their own, elusive mortality.