Complex sentence: Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, although, in nature, most "Turritopsis" are likely to succumb to predation or disease in the medusa stage, without reverting to the polyp form.
Split into simpler sentences: Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, However, it doesn't mean that they won't die. In nature, most "Turritopsis" are likely to succumb to predation or disease in the medusa stage, without reverting to the polyp form.