The life cycle of jellyfish can seem almost alien. Some species are closer to true immortality than anything we see in the animal kingdom!
These gelatinous marine animals, known for their stinging cells and umbrella-shaped bubbles, live in oceans around the world, but how long do jellyfish live?
The typical life cycle of jellyfish
Understanding the lifespan of jellyfish is crucial for the management and conservation of marine ecosystems, as jellyfish play an important role in food webs and nutrient cycling in the ocean.
Polyp stage: the early life of a jellyfish
The life cycle of a jellyfish is a story of transformation. Jellyfish begin their lives in the polyp stage, as larvae that attach to a solid surface on the ocean floor.
In this stage polyps are small, cylindrical structures that can reproduce asexually. They are small factories that either more polyps or move on to the next stage of life on their own.
This stage is crucial because it forms the basis for the jellyfish’s life. Polyps can remain in this stage for years, waiting for the right environmental conditions to develop further.
For example, in the Mediterranean Sea, where a few species of jellyfish thrive, polyps can form dense colonies on submerged rocks and other surfaces. These tiny jellyfish polyps are resilient and can withstand all sorts of environmental stresses (think changes in temperature and salinity).
Polyps also play an important role in the reproductive process, as they produce medusae through a process called budding.
Medusa stage: the adult life of a jellyfish
Jellyfish begin to Look like jellyfish after transitioning to the adult medusa stage. This is when they become the free-floating creatures we know, complete with an umbrella-shaped bell “head” and tentacles.
This is also the period when jellyfish transition from asexual to sexual reproduction, releasing eggs and sperm into the water, creating polyps that form the next generation.
Adult jellyfish—from the cannonball to the box jellyfish and beyond—are known for their ability to swim and capture prey, including small fish and crustaceans. The stings from jellyfish’s tentacles immobilize their prey, allowing them to eat efficiently.
The medusa stage varies in length between species. For example, the moon jellyfish has a relatively short lifespan, about a year. Other species, such as the lion’s mane jellyfish, one of the largest on Earth, can live for several years.
Jellyfish species and their lifespan
The lifespan of jellyfish varies greatly by species: from a few months to (theoretically) 66 million years.
Environmental factors, including water temperature, food availability, and pollution levels, have a significant impact on jellyfish lifespan. Predation by sea turtles and other marine animals also plays a critical role in determining how long jellyfish live.
3 Major Factors Causing Jellyfish Mortality
The mortality rates and lifespans of jellyfish vary greatly. Some species live only a few hours, others a few months or a few years — and then there’s the immortal jellyfish, but we’ll get to that later. The answer essentially depends on which type of jellyfish you mean.
1. Predation
Predation is a major factor in jellyfish mortality. Sea turtles, for example, are known predators of jellyfish. Other natural predators include fish, birds, and even other jellyfish species. For example, comb jellies, which are closely related to jellyfish, are known to feed on smaller jellyfish and their larvae.
Polyps are also vulnerable to predation by animals such as sea snails and crustaceans. These predators can significantly reduce the number of polyps that survive to transition to the medusa stage, which has consequences for the overall jellyfish population.
2. Environmental factors
Environmental factors such as temperature changes and pollution also affect the lifespan of jellyfish. Temperature changes can even have a major impact on jellyfish populations. For example, in tropical areas, jellyfish grow and reproduce faster because of the warmer water.
However, sudden changes in temperature or prolonged exposure to pollutants can lead to higher mortality in jellyfish populations.
Pollution, particularly plastic waste and chemical contaminants, pose a major threat to jellyfish, affecting their health and reproductive capacity.
3. Disease and other health related problems
Jellyfish are susceptible to disease and other health problems that can affect their lifespan. Bacterial and fungal infections can weaken jellyfish and make them more vulnerable to predation and environmental stressors.
Relationship with coral and sea anemones
Jellyfish belong to the same phylum as rough corals and serpentine sea anemones: cnidarians. They are like distant cousins in the ocean world.
While jellyfish are the free-floating members of this family, coral stays put, forming huge underwater structures called reefs that provide homes for many marine creatures. Then there are sea anemones, which look like strange underwater flowers but are actually predatory animals that attach themselves to rocks or coral and use their tentacles to catch food.
Despite their differences, the three cnidarians have one thing in common: they possess stinging cells that allow them to capture prey and defend themselves.
Understanding the Death of Jellyfish
Jellyfish can die from a variety of factors, including injury, disease, and natural aging (also called old age).
Injuries from predators or environmental hazards can also lead to jellyfish deaths. Diseases and other health problems can have a significant impact on jellyfish populations, especially in polluted or stressed environments.
In addition, jellyfish stings can sometimes cause injuries to the jellyfish themselves or to other jellyfish, which can lead to an early death.
The role of aging in jellyfish mortality
Aging can affect the lifespan of jellyfish, with some species experiencing a decline in health and function as they age. For most jellyfish, aging eventually leads to death as their biological functions decline.
However, the immortal jellyfish species can revert to an earlier life stage, allowing it to bypass the usual aging process. This provides valuable insights into cellular mechanisms that could influence human health and aging.
Do immortal jellyfish live forever?
While the immortal jellyfish (Turritopsis dohrnii) can theoretically live forever, it is not immune to predation, disease, or other environmental factors that could ultimately lead to death.
But under the right conditions, the creature can continually rejuvenate itself. When faced with environmental stress, physical damage, or simply aging, this jellyfish can revert to the polyp stage and essentially start its life cycle over again.
Implications beyond jellyfish life stages
The astonishing ability of the immortal jellyfish has important implications for scientific research, particularly in the fields of aging and regenerative medicine. By studying how these jellyfish seemingly circumvent death, researchers hope to unlock secrets that could lead to breakthroughs in understanding human aging and developing treatments for age-related diseases.
We created this article using AI technology and then fact-checked and edited it by an editor from HowStuffWorks.
Original Article: How Long Do Jellyfish Live? Are They All Immortal?
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