2023-09-24 01:44:34
Tripedalia cystophora, also called Caribbean jellyfish or box jellyfish, has a remarkable ability to navigate murky water and a labyrinth of submerged mangrove roots, reveals a study by Jan Bielecki of the University of Kiel and Anders Garm, from that of Copenhagen.
She does very well thanks to a device common to specimens of her species: four sensory structures, arranged like so many cardinal points around her body. Each structure, called a rhopalie, includes two lens-shaped eyes and an image-processing center, all with just a thousand neurons for each rhopalie. For comparison, the tiny Drosophila fly has 200,000 neurons in its small brain.
Learn to predict a problem
Unlike almost all species in the animal kingdom, the cnidarians, the lineage to which the jellyfish belongs, do not have a brain per se, but rather have a dispersed nervous system. The study establishes that despite this, the animal responds to “operant conditioning”, that is to say training allowing it to anticipate a possible consequence, in this case bumping into a root.
This ability, remarks Anders Garm, is “a step above classical conditioning”, like that of Pavlov’s dog, where the animal cannot help but salivate when seeing its bowl.
With its training, the jellyfish “learns to foresee a future problem and try to avoid it.” This ability has never before been demonstrated for an animal with such a primitive-looking nervous system, notes the study published in Current Biology on Friday.
The presence of such a capacity in such a simple organism “indicates that it might be a fundamental property of nervous systems”, according to Anders Garm. Indeed, the cnidarians, a group in the animal kingdom to which the box jellyfish belong, considered a “sister group to that of all other animals”, continues the biologist.
He hypothesizes that the common ancestor of these two groups, more than 500 million years ago, developed a nervous system already possessing such a capacity for learning by association.
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