Range: Tropical and warm temperate oceans worldwide Habitat: Open ocean Size: 0.177 inches (4.5mm) long Diet: Fish eggs, mollusks, and more Threats: Fish, marine birds, anemones, and more Life span: Unknown; Theoretically immortal

Transcript:

Today on Animal Fact Files we’re discussing the immortal jellyfish. Technically immortal jellyfish are not “true” jellyfish as they’re not classified in the class of true jellyfish. Immortal jellyfish, instead, are classified in the Hydrozoa class. Some other members of this group include the blue button and Portuguese man of war who are both often mistaken as jellyfish, as well. Since the common name for the immortal jellyfish is the immortal jellyfish we’ll stick with that name for this video, though we felt it was important to note this classification distinction.

Originally, these hydrozoans were classified as a different species. They have since been separated into their own species as separate from other members of their genus, however, more research needs to be completed before the relationships of this genus are settled, so their classification may change again in the future. This video is focused on the animal most commonly known as the “immortal jellyfish”.

These tiny animals can be found throughout tropical and warm temperate waters. The immortal jellyfish only reaches about 4.5mm wide at full size as an adult. That’s about half the width of the average person’s thumbnail! These animals are planktonic, however, it’s believed that humans may have helped them travel around the world. The immortal jellyfish is able to live inside the ballast tanks of ships and thus gets transported to different areas. They eat other planktonic items like fish eggs and small molluscs which are digested in the immortal jellyfish’s red colored stomachs, however these animals can manage without food if the need arises. This is because this hydrozoan’s common name isn’t entirely misleading! They really are considered immortal!

Immortal jellyfish are kind of like the legendary phoenix that rises from its own ashes. Their ability to do this was found by accident when individuals used for research were forgotten and then rediscovered months later to have survived their prolonged period without care. Like true jellyfish, they start as an egg, hatch as planktonic larvae, and then settle to the sea floor or other surface. From here a polyp colony will form that produces copies of itself through asexual reproduction. These polyps break off and become free swimming adults, called medusa, which reach adult size within about a month. The temperature of the water can impact how quickly they develop.

Most jellyfish, after reaching this stage, live out their lives, typically short in span, and die, however, immortal jellyfish can regress. The medusa will fall to the seafloor and after a few days polyps will once again form from the cells of the medusa’s body. As of right now, it’s believed they can do this indefinitely, effectively making them biologically immortal.

Of course they can still die if they’re eaten, they just can’t die to old age. Immortal jellyfish simply reset the clock so to speak and return to a younger version of themselves. The aging process is known as senescence and while most animals die to this, the immortal jellyfish is immune to this type of death thanks to its phoenix like ability. These aren’t the only known immortal animals, either, we’ve previously discussed hydras which regenerate their cells every month or so and effectively never age.

Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! Thank you to Mugiwara for today’s request! For more facts on the immortal jellyfish, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!