Jellyfish are a gelatinous zooplankton from the Cnidaria strain. From an anatomical point of view, they are a little more than a cam in a bag. Their body composition is 95% water. They have no brain, not even a central nervous system. They lack anything that remotely resembles a skeletal system. Most jellyfish don’t even have eyes. In addition to eating, their only interaction with the immediate environment is the ability to distinguish between up and down, light from darkness, or physical contact. Nevertheless, their light sensory abilities allow them to perceive foreign objects and maneuver around them.
Jellyfish are one of the oldest extinct forms of life. This should come as a small surprise given that they are only one step higher on the evolutionary ladder of single-celled organisms. Jellyfish fossils were discovered as early as the Cambrian period about 600 million years ago. The Cambrian period preceded not only the extinction of the dinosaurs, but also their very existence. These mysterious creatures are likely to swim in the Earth’s oceans long after humanity is gone.
The largest known species of jellyfish is the main jellyfish of the Arctic lion, followed closely by the Nomura jellyfish off the coasts of China and Japan. The largest left lion ever officially documented was washed by the Massachusetts Bay in 1870. Its bell measured 7.5 feet (2.28 meters) in diameter and its grippers stretched to 120 feet (36.5 meters). Since then, allegations of the discovery of larger jellyfish have emerged, but none have been officially documented.
Is it possible to keep jellyfish in the aquarium?
Most people don’t realize this, but until a few short decades ago, scientists did not have the technological know-how to keep jellyfish alive in captivity. Jellyfish make up 95% of the water. If they were sucked into a conventional water filtration system, they would liquefy immediately. Jellyfish cannot be placed in a typical square aquarium. They get stuck in the corners and lack a higher brain function to get out. If there is no turbulence in the water, they are reduced to the equivalent of a jelly bowl. Keeping a jellyfish in a home aquarium was unthinkable. Nowhere in the world was there a single jellyfish exhibit in the public aquarium.
Jellyfish were first exhibited in a public aquarium more than twenty years ago in Monterey, California. This performance was made possible by the pioneering work of the German oceanographer Dr. Wolf Greve.
Dr. Greve invented a circular aquarium that circulated water in a horizontal circular pattern. He called his invention the tank Kreisel (German carousel). This revolutionary aquarium was originally designed to study Arctic plankton. The circular design of the tank and the flow of water gently pushed the plankton from the outer perimeter of the aquarium towards the center of the tank. This technological breakthrough was necessary to keep the jellyfish alive in a man-made environment.