Turritopsis dohrnii- Immortal jellyfish

Illustration by Nibras Abdalla

Classification:

Description:

Turritopsis dohrnii, is a genus of minor, biologically immortal jellyfish discovered in the Mediterranean Sea and in the waters of Japan (Piraino, 1996). It is the only known case of animal accomplished of relapsing entirely to a sexually immature, colonial stage after having gone sexual maturity as introverted individual. Turritopsis dohrnii is thought to have originated in the pacific but has spread all over the world through trans-Arctic migrations. Since Turritopsis is immortal, its population is unaccounted and the number of individuals could be rising fast than estimated. (Mintowt, 2009) believe the jellyfish is dispersal across the world is becoming excessive as ships are discharging ballast water in ports.

Like most hydrozoa, Turritopsis dohrnii has two morphological states medusa and polyp. The medusa is bell-shaped and it can grow up to 4.5 millimeters. The jellyfish walls of the bell are homogeneously thin except for generally thickening at the apex. The stomachs of this specie tend to be comparatively large, bright red and have a cruciform structure in cross section. The medusa stage is free-living, young medusa would be about 1mm in diameter and contain eight tentacles uniformly spread out along the edge, on the other hand adult medusa could have about eighty to ninety tentacles (C. Mclean, 1937). When a medusa is sexually mature they have been known to prey on other jellyfish species at rapid speed. The polyp live at the ocean floor, or hydroid, which is made up of stolons that track beside the substrate, and standing branches with nourishing polyps that can manufacture medusa buds. All the polyps and jellyfish arising from a single planula are genetically identical clones.

Life Cycle:

The eggs mature in gonads of female medusa, which are found in the walls of the manubrium and in the screen formed by the cave in the jellyfish planula. (Piraino, 1996) Mature eggs are deposited and fertilized in the sea by sperm produced and released by male medusa, as is the case for most hydromedusae, Fertilized eggs develop into planula larvae, which settle onto the sea-floor or even the rich marine communities that live on floating docks, and develop into polyp colonies. The hydroids bud new jellyfishes, which are released at about one millimeter in size, elongate and bud off many young jellyfish that will grow and feed in the plankton, becoming sexually mature after a few weeks. The exact duration depends on the ocean temperature; at 20 °C (68 °F) it is 25 to 30 days and at 22 °C (72 °F) it is 18 to 22 days (Qossay Takroori, 2009).

Immortality:

The typical life cycle of hydrozoa involves the asexual budding of medusa from colonial polyps, most with a life span, which varies fron hours to many months. If starved or injured medusa of most hydrozoan species would normally die. However, medusa of Turritopsis, when starved or damaged, are able to revert their life cycle, going back to the polyp stage through a process called trans differentiation (Nathaniel Rich, 2012). The medusa of Turritopsis dohrnii is the only identified specie to have developed the capability to return to a polyp state, by a specific transformation process that requires the presence of certain cell types, tissue from both the jellyfish bell surface and the circulatory canal system (C. E. Mills, 1983). Laboratory experiments have publicized that all stages of the medusa, from newly released to fully mature individuals, can transform back into polyps (Anderi Mihai, 2008). The converting medusa is characterized first by weakening of the bell and tentacles, with following growth of a periarc sheet and stolons, and finally feeding polyps (Stefano Piraino, 1996). Polyps promote increase by growing additional stolons, branches and then polyps, to form colonial hydroids (Sterfano Piraino, 1996). In this transdifferentiation procedure, the medusa is transformed into the stolons and polyps of a hydroid colony. First, the umbrella change and the tentacles and mesoglea are resorbed. The everted medusa attaches to the substrate by the end that had been at the opposite end of the umbrella, and depositing occurs shortly. The cnidarian then secretes a perisarc and stolons. Two days after the stolons are first seen, polyps differentiate. These polyps feed on zooplankton and soon they are able to bud off new medusa (Sterfano Piraino, 1996).

Secret of Immortality

The ability to reverse the biotic cycle and allow the jellyfish to bypass death is unique in the animal kingdom, making Turritopsis dohrnii possibly biologically immortal. Studies in the laboratory presented that 100% of specimens could return to the polyp stage, but so far the process has not been observed in their natural habitat, in part because the process is fairly rapid and field observations at the right moment are unlikely (Stefano Piraino, 1996). Turritopsis dohrnii's cell development technique of transdifferentiation has motivated researchers to find a way to construct stem cells using this process for renewing damaged or dead tissue in human.

Researchers have tried studying turritopsis but it turns out, is extraordinarily difficult to culture in a laboratory. It necessitates close attention and a massive amount of monotonous, dull labor and it leaves under certain conditions to be able to produce offspring, which are still unknown to biologists (Nathaniel Rich, 2012). Shin Kubota the only scientist that has successfully cultured Turritopsis consistently said, “The mystery of life is not concealed in the higher animals, it is concealed in the root. And at the root of the Tree of Life is the jellyfish.” Kubota works alone, without major financing and for the time being that’s our best chance of understanding the biological immortality of turritopsis. Marine biologists are reluctant to make such grand claims about Turritopsis’ promise for human medicine and they would prefer scientist to focus on a slightly more rational form of science (Nathaniel Rich, 2012).

“Immortality might be much more common than we think, There are sponges out there that we know have been there for decades. Sea-urchin larvae are able to regenerate and continuously give rise to new adults. This might be a general feature of these animals. They never really die." Peterson said (Nathaniel Rich, 2012) Emphasizing that human have similar genetic information as hydra and it is important to keep in mind that we are not dealing with something that's completely different from us (Nathaniel Rich, 2012).

Reference:

Bavestrello, Giorgio; Christian Sommer; Michele Sarà (1992). "Bi-directional conversion in Turritopsis nutricula (Hydrozoa)". Scientia Marina 56 (2–3): 137–140.

Piraino, Stefano; F. Boero; B. Aeschbach; V. Schmid (1996). "Reversing the life cycle: medusae transforming into polyps and cell transdifferentiation in Turritopsis nutricula (Cnidaria, Hydrozoa)". Biological Bulletin (Biological Bulletin, vol. 190, no. 3) 190 (3): 302–312.

Kramp, P. L. (1961). "Synopsis of the medusae of the world". Journal of the Marine Biological Association of the United Kingdom 40: 1–469.

Mintowt-Czyz, Lech (26 January 2009). “Turritopsis nutricula: the world’s only ‘immortal’ creature”. Times Online. Retrieved 2009-03-22.

Fraser, C. McLean (1937). Hydroids of the Pacific Coast of Canada and the United States. University of Toronto Press. pp. 201 plus 44 plates.

Qossay Takroori. Meet The Only Immortal Species on Planet Earth. http;//palscience.com/2009/01/28the-onlyimmortal-species-on-planet-earth/#. 2009.

Nathaniel Rich (November 28, 2012). “Can a jellyfish unlock the secret of immortality?”. The New York Times Magazine.

Mills, C. E. (1983). "Vertical migration and diel activity patterns of hydromedusae: studies in a large tank". Journal of Plankton Research 5 (5): 619–635.

Mihai, Andrei (December 5, 2008).. ZME Science. Retrieved January 10, 2015.