Jellyfish are fascinating aquatic organisms, seemingly endowed with immortality. Constructed mostly of water, without brains or bloodstream, and equipped with multiple tentacles that sting for protection, jellyfish seem to possess all the elements required for success and may even help people live forever.
Turritopsis dohrnii jellyfish have recently come to our attention due to a remarkable discovery: their ability to avoid death by switching back into polyp state. This unusual behaviour has ignited further research on how animals may go backwards in their life cycle.
The body of a jellyfish
Jellyfish have long been an abundant and fascinating feature of ocean currents, spanning both warm and cold waters. Characterized by tentacles that trail behind them and can sting prey, jellyfish have bell-shaped bodies with an opening called their mouth that serves both for feeding and waste removal. Jellyfish have existed on our planet for millions of years – they make up one of the most populous subclasses within Cnidaria (phylum Cnidaria). Although lacking brains or respiratory systems they still possess complex bodies filled with nerve receptors – this makes them very captivating to scientists who study them closely.
Scientists have recently discovered that certain jellyfish species can defy the laws of aging by turning back its biological clock – known as transdifferentiation. Similar to what happens when caterpillars transition into butterflies instead of dying off and becoming dust, researchers observed Turritopsis dohrnii could transform back into its polyp stage, or youth form when threatened by stress or injury.
Defiance of cellular aging is an amazing feat that could enable blobs to avoid their normal career path that eventually ends with death and continue on indefinitely, possibly becoming immortal in the process.
Marine biologist Joan Soto-Angel was taken aback when she saw an adult comb jellyfish with its gelatinous lobes twisted into the shape of larva. This was the first time anyone in science had witnessed such an event in real time.
Soto-Angel and her colleagues Michael Sars and Pawel Burkhardt kept 65 comb jellyfish in tanks to study how they responded to various challenges, such as starvation. When a jellyfish reverted back to its juvenile form after experiencing starvation, all tentacles that identified it as an adult medusa vanished completely – suggesting that its lobes may serve as physical indicators of maturity. Of all 75 jellyfish included in their study only seven experienced any change, but six did so after having undergone this procedure lobectomy procedure revert back.
The team conducted extensive analysis on reverted jellies, discovering that certain cells switched functions; this likely allows comb jellyfish to avoid aging through changing cell functions; further investigation will focus on whether other cnidarians possess this capability and the genetic mechanisms regulating this.
The mouth
When we observe a jellyfish, our initial thoughts tend to focus on its tentacles. But its seemingly drape-like lips – known scientifically as oral arms – may actually be its lips and one of only two entryways into its body, so whatever enters must also leave again through its mouth. Jellyfish feed by sucking up water from the sea through their oral arms before exhaling out through their mouth once food has been digested and inhaled through them into its digestive tract and out through its mouth again when exhaled again by sucking up water from seafloor currents while exhaling food through these arms before exhaling through mouth which then returns directly through its mouth after digestion has taken place and out again through its mouth again before emerging through oral arms into its digestive systems before returning through oral arms before coming out through its mouth again as food is processed through oral arms before entering its system before exiting back out through its mouth once digested again out via its digestive tracks before returning through which food enters their bodies through oral arms before leaving again through it’s mouth to leave their bodies through two ways in and out again through mouth once swallowed through swallowed water which food brought into their bodies through orificatory pores into it’s back out again through another port in turn through mouth as soon as digested through this way before leaving their bodies again through it again through another exit port on its exit port before exit port again through to be released through their mouth again through another hole on exiting through oral arms into another entry and exiting out through its exit port by sucking and out via mouth again via mouth again exit again through its exit ports then out again after exit port then exits out again as soon as it again from ocean until then mouth via its final destination ports before exit back out through either its mouth another exit port of exit back out again using sucking up again then out through another passageway then back out port out then exit after consumption then out again as their final destination from either end then exit port once it again through mouth back on it out through another opening which after again when back again to be then.
The jellyfish’s body consists of an intricate system of digestive canals which deliver nourishment to its cells. When swallowing food, it passes through these two-way canals before reaching its stomach for digestion of proteins and carbohydrates. Furthermore, this creature contains organs to maintain its shape and orient itself appropriately, such as its bell that contains cells called rhopalia which detect changes in light conditions to give the creature a sense of its surroundings.
Many species of jellyfish live for only months at most; however, some can survive for years in polyp form as pre-adults. Polyps are similar to coral in that they grow in size over time but lack the energy and stinging power associated with medusae jellyfish.
Scientists are keen to study these pre-adult polyps, in hopes they might contain clues as to the longevity secrets of medusae. First however, they need to gain an understanding of why these medusae can survive so long.
Researchers were amazed to discover that one species of jellyfish can reverse its life cycle in an astonishing similarity to how humans can return to being children. While not the first time an animal has defied biological laws, this one stands alone as defying them without external stressors or drugs being needed.
Researchers from Norway’s Universities of Oslo and Bergen recently conducted an experiment in which they witnessed Turritopsis dohrnii jellyfish breaking its own lifecycle through transdifferentiation. They observed them shrinking in size, changing body structure, and eating differently during an experiment involving starving them of food.
The tentacles
Jellyfish belong to the cnidarian family, which also includes sea anemones and coral. Jellyfish use their tentacles to capture food and reproduce, with stinging arms used against predators as protection and to float. Their skin colors may change to blend in more easily with their surroundings or hide from predators.
Scientists have recently discovered that certain jellyfish can reverse their aging process through something known as “reversal of life cycle”. This reversal is accomplished via transcriptional activation – which involves turning on genes which would normally programme cells to die and transforms them into other types. Similar processes take place with stem cells which transform into tissues or organs capable of performing specific functions.
Reversal of aging is an impressive feat among animals, which explains why scientists are so fascinated with jellyfish. By understanding how this process works and applying this knowledge to humans, scientists hope it can lead to the creation of regenerative medicine therapies.
Scientists reported in PNAS that Turritopsis dohrnii, an immortal jellyfish species, can reprogram its DNA to switch back into an earlier stage in its lifecycle when stressed or encountering danger – this process allows it to bypass death and avoid becoming permanently older. Scientists made this discovery by comparing its genetic sequence with that of Turritopsis rubra; T. dohrnii contains double copies of genes for protecting and repairing DNA as well as mutations which prevent its telomeres from shortening over time.
T. dohrnii was the first cnidarian shown to have the ability to reverse its own aging process, and scientists are currently exploring another species – Mnemiopsis leidyi – which has several unusual biological traits, including de-aging physically into its larval state and regeneration of body parts.
The oral arms
Tentacles and oral arms of jellyfish play an integral role in their predatory nature. Tentacles possess stinging cells called nematocysts which stun prey before eating can take place. A jellyfish’s mouth consists of a semi-moon-shaped opening lined with muscles which tighten and relax to help move it around, and its body has one opening through which food enters, waste exits, water circulates freely inside it, as well as any chemicals present within it.
Oral arms are frilly extensions of tentacles. Oral arms are one of the distinguishing characteristics of “true” sea jellies belonging to Scyphozoa class; in addition to being capable of stinging, these structures also pulsate and expel jet streams of water from them.
Studies have revealed that jellyfish locomotion depends on both the number and length of oral arms, with Pacific sea nettle Chrysaora fuscescens displaying four long frilly oral arms which protrude from its bell and can be seen from below. Length is important as it determines how quickly jellyfish swim across water bodies.
K. Katija conducted a study showing that Australian Spotted Jellyfish (Phyllorhiza punctata) with and without oral arms swam at different speeds, the ones with them moving 360% slower. Researchers speculate that this may be caused by their inhibiting forward swimming speed.
As tentacle length increases, their work- and power-based velocity decreases due to taking up more room in the bell, thus inhibiting vortex formation and diminishing its downstream wake. As its contraction cycles speed up, so too does its work-based velocity decrease, yet its Strouhal number remains roughly constant; fluid mixing seems to provide compensation. Lower forward swimming speed may also be due to reduced size of vertical vortex wake. Furthermore, longer oral arms could be less effective at propelling jellyfish downward due to having greater surface area that requires additional energy input from energy resources.
