Scientists discover a way to read the thoughts of jellyfish

Although jellyfish do not have brains, scientists have come up with a way to read a jellyfish's thoughts, so to speak. And with some clever genetic tweaks, we can now watch how neurons in a small transparent jellyfish work together to make complex intelligent, independent movements, such as grabbing and eating prey.

When researchers genetically modified jellyfish so that their neurons glow when activated, they found an "unexpected degree of neural regulation". The study was published in the journal Cell on November 24.

Perfect model for studying

As a report by Science Alert points out , Clytia hemisphaerica is a jellyfish-like organism, which is the ideal model for studying this type of behavior. Because this type of jellyfish is so small (only about a centimeter in diameter), its entire nervous system can be easily placed under a microscope.

This small animal has emerged as a promising model organism for life cycle study, and its genes are relatively easy to manipulate and study closely in a laboratory setting. and healing of wounds.

Like most cnidarians, "Clicia hemispherica" ​​has a relatively simple morphology, and its entire genome was sequenced in March of 2019, and its genome turned out to be very simple, as its transparent body contains only about 10,000 neurons, making it easy to track all messages. nervousness;

living fossils

Some researchers believe that the nervous system of this type of jellyfish evolved more than 500 million years ago and has not changed much since then. Compared to animal brains today, the neurons in these "living fossils" are arranged in a much simpler way. However, there is no central system that coordinates all of a creature's movements, so how does it accomplish anything?

The new research suggests that the neurons of one hemisphere are enclosed in a canopy-like network, which closely mirrors its body. These neurons further divide into slices, almost similar to a pie or pizza.

Each tentacle on the edge of a jellyfish bell is attached to one of these slices; So when the arms of a jellyfish detect and capture prey, such as shrimp, neurons in that single slice are activated in a specific chain.

First, the neurons at the edge of the 'pie' send messages to the neurons in the middle, where the jellyfish's mouth is. This moves the edge of the pie slice inward toward the mouth, and brings the tentacles with it. Meanwhile, the mouth, in turn, signals the incoming food.

Within a minute of being introduced to the shrimp, the authors found that 96 percent of the jellyfish attempted to "move food" and 88 percent succeeded. Ultimately, all types of marine shrimp were eaten using this feeding behavior.

Domino effect

To find out exactly which neurons cause this domino effect, the researchers deleted a type of neuron called RFA neurons at the edge of the pie slice. When they did, the asymmetric inner folding of the jellyfish did not, and the The transmission of shrimp occurs from the tentacles to the mouth.

In their study, the authors write that '+RFA' neurons are required for both food-induced and chemically induced marginal folding. In contrast, there was no other neuronal dysregulation, with respect to swimming and wrinkling, suggesting that other neuronal types control in these behaviours.

To find out how the neurons that control the mouth communicate with the neurons that control the jellyfish's bell and vice versa, the researchers began surgically removing specific parts of the jellyfish's body. When the jellyfish's mouths were removed, the creatures continued to try to pass food from their tentacles into their nonexistent mouths, even when the jellyfish's tentacles were removed, chemical extracts from the shrimp could induce the mouth to turn toward the food source.

Nervous feedback

The results suggest that some jellyfish behaviors are coordinated by different groups of functionally organized neurons, which are located around the perimeter of the canopy. The neural network that connects a jellyfish bell to its mouth, for example, can be connected to the digestive system.

When the jellyfish was deprived of food, the authors found that it captured prey faster than when it was not hungry. This suggests a kind of neurological feedback, letting the jellyfish "know" it needs to fill its digestive system, and putting other specific "feeding" networks on high alert.

The authors suggest that "if this hierarchical view is correct, coordinated behaviors in organisms lacking a central brain might have emerged via duplication and modification in smaller independent units, to form functionally interacting supermodules." But how are these interactions achieved? It hasn't been decided yet!