2023-09-22 17:17:15
The Caribbean box jellyfish (Tripedalia cistophora) can learn to associate a particular visual cue with a sensation of hit. – JAN BIELECKI
MADRID, 22 Sep. (EUROPA PRESS) –
Jellyfish can learn from past experiences like humans, mice and flies, even without a central brain, a first published in the journal ‘Current Biology’.
The authors of the research trained box jellyfish – cubic-shaped jellyfish – from the Caribbean (‘Tripedalia cystophora’) to learn to detect and avoid obstacles. The study challenges the idea that advanced learning requires a centralized brain and sheds light on the evolutionary roots of learning and memory.
These seemingly simple jellyfish, the size of a fingernail, have a complex visual system with 24 eyes embedded in its flared body. They live in mangroves and use their vision to navigate through murky waters and avoid tree roots to catch their prey.
The scientists showed that jellies could acquire the ability to avoid obstacles through associative learning, a process by which organisms form mental connections between sensory stimuli and behaviors.
“Learning is the peak performance of nervous systems,” says first author Jan Bielecki of the University of Kiel in Germany. To successfully teach a new trick to jellyfish, he says, “it’s best to take advantage of their natural behaviors, something that makes sense to the animal, so that it reaches its full potential.
The team dressed a round tank in gray and white stripes to simulate the jellyfish’s natural habitat, with the gray stripes mimicking mangrove roots that would appear far away. They watched the jellyfish in the tank for 7.5 minutes.
At first, the jellyfish swam close to these seemingly distant rays and collided with them frequently. But at the end of the experiment, the jellyfish increased its average distance to the wall by about 50%, quadrupled the number of successful turns to avoid the collision, and reduced its contact with the wall by half. The results suggest that jellyfish can learn from experience through visual and mechanical stimuli.
“If you want to understand complex structures, it is always good to start as simple as possible,” says Anders Garm, lead author of the study and professor at the University of Copenhagen (Denmark). “Looking at these relatively simple nervous systems of jellyfish, “We have a much better chance of understanding all the details and how they come together to perform behaviors.”
Next, the researchers tried to identify the process underlying associative learning in jellyfish by isolating the animal’s visual sensory centers, called rhopalia. Each of these structures houses six eyes and generates pacemaker signals that govern the pulsating movement of the jellyfish, whose frequency increases when the animal deviates from obstacles.
The team showed the stationary rhopalium moving gray bars to mimic the animal’s approach to objects. The structure did not respond to the light gray bars, interpreting them as distant. However, after researchers trained the rhopalia with weak electrical stimulation when the bars approached, began generating obstacle avoidance signals in response to the light gray bars.
These electrical stimuli mimicked the mechanical stimuli of a collision. The results further demonstrated that the combination of visual and mechanical stimuli is necessary for associative learning in jellyfish and that the rhopalium serves as a learning center.
The team plans to delve deeper into the cellular interactions of the jellyfish nervous system to unravel memory formation. They also plan to better understand how the bell’s mechanical sensor works to get a complete idea of the animal’s associative learning.
“It’s amazing how quickly these animals learn; at about the same rate as advanced animals,” says Garm. “Even the simplest nervous system appears to be capable of advanced learning, and this could turn out to be a cellular mechanism.” extremely fundamental invented at the dawn of the evolution of the nervous system.”
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