Turritopsis dohrnii, immortal jellyfish
Jellyfish, often admired for their elegance and mystery underwater, undergo a dramatic transformation when removed from their aquatic habitat, appearing as simple blobs due to their composition, which is approximately 95% water. These remarkable creatures lack brains, blood, and even hearts, possessing a basic nervous system that enables them to sense light, smell, and respond to various stimuli.
Body structure
Structurally, they consist of three layers: an outer epidermis, a middle elastic and gel-like mesoglea, and an inner gastrodermis. Their radial symmetry allows them to detect food or danger from any direction, a feature common to all members of the Cnidaria phylum, which includes sea anemones, sea whips, and corals.
Jellyfish are known for their ability to sting through their tentacles, with the severity of stings typically resulting in minor discomfort in humans. The majority of jellyfish species are sized between 2 to 40 cm in diameter, although some can grow much larger, up to 2 meters.
lions mane jellyfish ( the largest species of jellyfish)
They feed primarily on copepods, fish larvae, and other small aquatic organisms that they capture using their stinging cells called nematocysts. Some species, however, engage in suspension feeding, extracting tiny animals and algae (phytoplankton) directly from the water.
"True jellyfish", are members of the class Scyphozoa ,a group of invertebrate animals composed of about 200 decribed species ( as currently known to science). Jelly fish fall under the phylum Cnidaria which includes sea anemones, sea whips and even corals. The term is also frequently applied to certain other cnidarians (such as members of the class Hydrozoa) that have a bell- or saucer-shaped body form, as, for example, the highly venomous Portuguese man-of-war. Unrelated forms such as comb jellies (phylum Ctenophora) and salps (phylum Chordata) are also referred to as jellyfish.
comb jellyfish
Scyphozoan jellyfish can be categorized into two groups: free-swimming medusae and sessile forms, which attach to objects via a stalk. Free-swimming jellyfish inhabit oceans worldwide, including the familiar disk-shaped species often found drifting along shorelines. Most have a relatively short lifespan, typically a few weeks, but some can survive for a year or more. However, there's one extraordinary exception.
stalked jellyfish ( a species of jellyfish that is sessile)
Immortality( kind of...)
The hydrozoan species Turritopsis dohrnii, commonly known as the "immortal jellyfish," possesses a unique ability to reverse its life cycle. When subjected to physical damage or environmental stressors such as starvation, instead of perishing, it reverts to a juvenile state. During this transformation, it reabsorbs its tentacles and loses its ability to swim, settling on the seafloor as a cyst-like structure. Over the next 24-36 hours, this blob-like cyst develops into a new polyp, which represents the jellyfish's previous life stage. Once matured, this polyp generates new medusae through budding. This process, called transdifferentiation, is exceptionally rare in the animal kingdom.
lifecycle of jellyfish
This phenomenon can be likened to that of a butterfly which, instead of dying, would be able to transform back into a caterpillar and then metamorphose into an adult butterfly once again.
Transdifferentiation reprograms specialized cells in the medusa to become specialized polyp cells, enabling the jellyfish to regenerate in an entirely different body plan from the free-swimming medusa it was before. This cycle can be repeated, and under ideal conditions, these jellyfish may never experience natural aging or death.
An accidental discovery
The discovery of the immortal jellyfish was first documented by scientists in 1883, but it wasn't until the 1980s that its unique immortality became widely known. Students Christian Sommer and Giorgio Bavestrello inadvertently stumbled upon this phenomenon when they collected Turritopsis polyps, expecting them to mature before spawning. However, they observed that the stressed medusae would transform into polyps without the typical fertilization or larval stage, defying conventional expectations.
No one can cheat death
Despite their extraordinary regenerative abilities, immortal jellyfish are not invincible. They remain vulnerable to predation by other animals such as fish, turtles, sea slugs, and crustaceans. The delicate balance between their longevity and susceptibility to predators complicates understanding their true lifespan.
Initially originating in the Mediterranean Sea, immortal jellyfish have now spread to oceans worldwide, likely due to human activities. It's believed that ships, through ballast water exchange, unintentionally facilitated their dispersal across the globe. The jellyfish's ability to reverse its life cycle when facing stresses, such as limited food, makes it a resilient traveler. The creature's inconspicuous appearance, which can vary depending on its location, further contributed to its unnoticed spread. Notably, it doesn't exhibit negative impacts typically associated with invasive species.
Can the jellyfish teach us anything?
In the field of medicine, the immortal jellyfish has intrigued researchers due to its remarkable cellular regeneration capabilities. Transdifferentiation, the process responsible for its rejuvenation, is an area of interest for studies on tissue regeneration and stem cell biology. Understanding how these jellyfish achieve such regeneration could hold promise for regenerative medicine.
Furthermore, Turritopsis dohrnii's ability to seemingly bypass senescence has implications for aging and longevity research. Scientists hope to uncover the genetic and biochemical factors underlying its biological immortality, potentially offering insights into extending the human lifespan and improving the quality of life in old age.
While the immortal jellyfish itself has not directly contributed to medical treatments, research inspired by its regenerative abilities could eventually lead to therapies for age-related diseases and tissue damage. It also fuels philosophical and ethical discussions about the potential for human longevity and its broader implications in healthcare and research funding. Additionally, studying these jellyfish can aid in environmental monitoring, helping assess the health of marine ecosystems and understand the impact of climate change on marine life.
The immortal jellyfish, with its unique characteristics and regenerative abilities, has not only captured scientific fascination but also holds the potential for influencing various fields, including regenerative medicine, aging research, and environmental science, with potential medical applications on the horizon.
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