No Heart, No Brain.
Thought to have been around for over 650 million years, these primitive evolutionary survivors can range from the size of a pin head, to over 8ft in diameter with tentacles stretching out for up to 50 meters. Comprised of 95% water, Jellys have no need for respiratory or circulatory systems. They have no blood, no hearts, no bones, no eyes or brains, and do not posses a central nervous system like that of more complex lifeforms.
These ancient asexual marine creatures can be found drifting the ocean currents or using their bell shaped medusa heads to move through the worlds seas. Jellys manage to kill more people per year than Sharks, and one particular species of Jelly is said to be immortal, possessing the ability to revert back to its infant state after mating and reaching sexual maturity.
Jellyfish also provide us with somewhat of an evolutionary enigma. Given the complexity of the jellyfish’s anatomy and hunting techniques, it’s hard to imagine how “developmental” species could have survived while a non-jellyfish was evolving into a “modern” jellyfish.
Each of the jellyfish’s special features, from the sacs that keep it swimming upright to the sensory organs that alert it to passing prey and the nematocysts, critical for stunning or killing that prey – is vital for its survival. So, logically, any phase that did not have these features fully developed would have led to extinction fairly quickly. The only alternative, then, is that jellyfish must have always been jellyfish.
Either way these are truly fascinating creatures and give us a beautifully surreal glimpse back in time on life’s evolutionary journey.