November 7, 2024

Sofia McGrath

11th Grade

The Young Women's Leadership School of Queens

Jellyfish are often thought of as very simple creatures, as they are ninety-five percent water and lack a brain, blood, bones, and even a heart. Even so, this elastic jelly-like marine animal is more complex than it is perceived. In fact, a certain species of jellyfish can reverse its aging through transdifferentiation in specific environmental stress, making it “immortal.” Medical professionals have gained invaluable insight through jellyfish reverse aging that can help revolutionize medicine in the future, or at least pave the way forward.

The lifecycle of a jellyfish commences during the late summer when the medusa (adult jellyfish) releases eggs and sperm. The size of the medusa affects this stage in the process by determining the quantity of offspring produced. Additionally, there are also environmental factors such as light availability, food availability, and proximity to other medusae, which influence the spawning events in a medusa's life. Next, the fertilized eggs grow into spores that weakly swim and flow called “planula.” When they grow to a sufficient size, they attach themselves to a hard surface such as a rock or oyster shell. This occurrence marks the beginning of the polyp stage of a jellyfish’s life, which may persist for years. Interestingly, under insufficient environmental conditions, the polyp will wait to mature. As the polyp develops, it begins to reproduce asexually. This process is indicated when the polyp begins to elongate, segment, and clone itself, known as the “scyphistoma stage.” Strobilation takes place when these segments begin to separate and their first tentacles (feeling tentacles) are absorbed. The budded segment of the polyp becomes an ephyra, which eventually grows by feeding on zooplankton to become a medusa, commonly known as “jellyfish.”

The Turritopsis dohrnii jellyfish life cycle differs in a unique way from typical jellyfish. Despite being a mere 4.5 mm in size, these minuscule, transparent jellyfish have the ability to reverse their lifecycle. When subjected to significant amounts of stress, such as starvation or harm, the Turritopsis medusa reverts to a polyp after shrinking itself and settling into a cyst-like blob on the seafloor. These polyps will develop and break away from the jellyfish. Transdifferentiation drives this survival instinct by allowing adult specialized medusae cells to become specialized polyp cells. Therefore, this process permits the reversion of their life cycle and regrowth back into medusae. Though remarkable, their reverse aging doesn’t prevent the “immortal jellyfish” from succumbing to its predators when eaten. 

A better understanding of the cellular and genetic mechanisms behind jellyfish aging can help medical professionals find solutions to age-related diseases. For example, in comparison to the mortal Turritopsis rubra, the “immortal” Turritopsis dohrnii has double copies of genes that can protect and repair DNA, as well as mutations that inhibit cell division and prevent telomeres—chromosomes’ protective caps—from deteriorating (Dinh, 2022). These features delay cell death because, as the cell divides, it becomes shorter until eventual death. Furthermore, a better understanding of transdifferentiation (where one cell type converts to another) can help influence the evolution of regenerative medicines and/or treatments. In fact, according to an article by Peniel M. Dimberu, there was a breakthrough in using transdifferentiation for therapeutic purposes.