Despite lacking a brain, jellyfish are very intelligent and flexible. They have been bobbing in practically all of the world’s oceans for more than 500 million years, both at the water’s surface and at depths of up to 700 meters. The oldest animal in the world is the jellyfish. Even the dinosaur emerged roughly 250 million years after the first animals in terms of evolution.
More intelligent than believed
Jellyfish are far more evolved than previously assumed. A recent study from the University of Copenhagen has shown that Caribbean box jellyfish can learn at a much higher level than previously thought possible despite having only a thousand nerve cells and no centralized brain. The discovery alters our fundamental view of the brain and may shed light on our own fascinating brains.
According to popular belief, more complex neural systems in animals correspond to more advanced learning potential. Jellyfish and their relatives, known as cnidarians, are thought to be the first living organisms to acquire neural systems, with relatively primitive nerve systems and no centralized brain.
Scientists divide learning into two categories. Habituation is an example of nonassociative learning: if you gently poke an animal multiple times, it will ultimately quit recoiling or shying away. Associative learning is more difficult since it requires an animal to correlate cues in its surroundings.
According to Jan Bielecki, a neurobiologist at Kiel University in Germany, this is due in part to scientists bringing human preconceptions and goals to the research they conduct. That, he considers to be a mistake. The criteria you use must be understandable to the animal.
According to Bielecki, he and his colleagues looked for associative learning in microscopic jellyfish that have four eye structures called rhopalia, each with six eyes and roughly 1,000 neurons. The scientists then devised an experiment that exploited the animal’s urge to defend its bell, the major structure from which its tentacles originate. These jellyfish must use their vision to navigate around tree roots in their native, sometimes hazy, seas.
So scientists placed the jellyfish in tanks painted with three different levels of contrast: high-contrast black-and-white vertical stripes representing nearby tree roots, medium-contrast gray-and-white vertical stripes creating an optical illusion of tree roots far beyond the tank’s walls, or solid gray with no contrast. The jellyfish easily negotiated the black and white stripes. They didn’t learn to avoid the tank because they hadn’t struck it before. The jellyfish in the simple gray aquariums didn’t learn either; they bumped with the walls during their stay.
Better for marine life than previously considered
Scientists at Queen’s University in Belfast revealed that jellyfish provide habitat and room for developing larvae and juvenile fish.
The fish exploit their jellyfish hosts for predator protection and feeding possibilities, which helps to reduce fish mortality and promote recruitment. This allows fish, such as whiting in the North Sea and other commercially significant species, to increase their population and recover from depleted stock levels, thereby preserving a more diverse range of species in our waters.
Jellyfish can provide feeding opportunities for young fish, who can eat microscopic organisms found on the jellyfish or any prey that the jellyfish zaps while traveling. This allows fish, such as whiting in the North Sea and other commercially significant species, to increase their population and recover from depleted stock levels, thereby preserving a more diverse range of species in our waters.
Jellyfish are an important component of many food systems. Jellyfish help to manage species populations and maintain the balance of the ocean’s ecology. In addition to feeding other species, jellyfish are frequently prey, even for other jellyfish.
