101 — Crimson (immortal) jelly, Turritopsis rubra

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Turritopsis rubra, south Piha, 26/04/17.

Turritopsis is a genus of small hydrozoan jellies (<10mm). There are a few species and there appears to be some debate regarding the number. They have a complex lifecycle, which starts off when eggs are released by the medusa (jelly) phase into the plankton. Assuming they survive, they then hatch and settle as a cyst-like blob and form polyps. The polyps then grow and bud off small medusa, which then swim off and grow, produce eggs, and then die. The end.

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Turritopsis rubra, mussel farm,
Waiheke Island, Auckland, 27/02/14.

Except in Turritopsis dornii it's not necessarily the end. This species can reverse this process, so when times get tough they can revert back into a polyp and wait for conditions to improve. This lifecycle reversal is called transdifferentiation and essentially cheats death, making the jelly biologically immortal.

This transdifferentiation ability enables the jelly to survive long ocean voyages in the ballast tanks of ships and so there is a perception that these little jellies are silently taking over the world's oceans.

As a consequence of their biological immortality, there has been interest regarding the implementation of transdifferentiation in regenerative medicine. However, so far, it appears that the jellies are really hard to keep alive in aquaria making them difficult to study (which seems ironic).

The species pictured here is T. rubra (Farquhar, 1895), which has a south Pacific distribution. It is currently unknown whether this species can transdifferentiate its cells like its close relatives.

These little jellies have quite a painful sting, especially if their tentacles get trapped between a swimmer's (or surfer's) clothing and their skin. The tentacles are long and very fragile, so can break off easily. There was quite a bloom of these little jellies during the summer of 2016–17 on the North Island west coast. Many people thought they were being bitten by sea lice, when in fact they were probably being stung by these jellies. I think "being bitten by sea lice" is a myth.


More info:

Regenerative medicine: http://singularityhub.com/2011/04/25/immortal-jellyfish-provides-clues-for-regenerative-medicine/