Hydrozoans and death

Hydrozoans are a smaller class in the Cnidarian order (In taxonomical chart). They look like and are close relatives of jellyfish. Even though they are not "True" jellyfish their common name is still jellyfish. Their life cycle consists of multiple stages and also metamorphism like the caterpillar's. 

These Hydrozoans can reproduce sexually and asexually. They first release sperm and egg cells, which fertilize (External fertilization ; In some species eggs are retained and fertilized internally, in which case embryos may be releases as larvae or retained until even more developed.) and forms a "Planula" and then sticks to a surface like the sea bed or a rock, develops into a polyp. (you most probably couldn't differentiate them in this stage from hydra, corals and sponges etc. ). 

A Typical Polyp

From a polyp it's fragments morph and form a jellyfish or a more technical term "Medusa" form.

Your body replaces dead cells with newly formed/reproduced cells, Whenever you get wounded your body automatically heals it up and fills the area with new fresh and healthy cells. Then ever wondered why we grow weaker and weaker as grow older and die at some point due to age, If the body really does replace all the injuries, wounds then why do we die?

Every time Your cells duplicate/reproduce they make about 120,000 mistakes which leads to tumors and cancer and apart from the fading of telomere in our DNA. (More details) 

Telomere is a gene (at the end of the DNA strand) solely to protect other genes from getting shortened (copied wrong). At each cell division, the telomeres shorten because of the incomplete replication of the linear DNA molecules by the conventional DNA polymerases. In simple words cells are not exact copiers and make mistakes and most likely at the end of the strands , so to protect genes and DNA to shorten out inwards from the ends telomere protects them, otherwise they don't have any considerable function and their absence wouldn't make a difference. Thus fading of these telomeres and then after your actual genes causes the cell to dysfunction, die and eventually resulting in the death of the whole organism. 

Turritopsis dohrnii is a species of the hydrozoa nicknamed "Immortal Jellyfish" has escaped this problem with the help of a special protein called "TELOMERASE" which replicates and lengthens telomere genes from time to time to prevent the complete loss of it, thus no damage is done to the other main chromosal genes, meaning that it has no death with respect to time or age (thus nicknamed so). Then if it really can live forever , the ocean and even the whole world must be populated by them but it is not so because of the innumerous and various predators of the marine world. This gives us a rough estimate that even if a species has an ability to not die of age and is still not thriving in numbers this indicates the other undiscovered marine species and the marine biodiversity.

These jellyfish also have an ability to go back in it's life cycle like growing into polyp again from the medusa stage/phase and then split/morph into 10-15 more jellyfishes, this is like cloning but not done by humans; natural. There so many other bizarre traits of this species like Cellular Trans-differentiation seen nowhere else in the animal  and plant kingdom.

Cellular Trans-differentiation is nothing but .................................

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J. Maanavendra roy,
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