Little worms that make complex decisions

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Little worms who make complex decisions

A C. elegans worm (right) escapes from the predatory worm P. pacificus (left).

Worms with no more than 302 neurons can analyze several factors and choose between two different actions, shows a study by American scientists.< /p>

Professor Sreekanth Chalasani and his colleagues at the Salk Institute in California were surprised to discover flexible decision-making abilities in a worm with so few neurons.

Even Simple organisms like worms can choose between two strategies, deciding which suits them best in a given situation, says Professor Chalasani in a press release published by the Institute.

Scientists have been trying for decades to understand the decision-making process in animals by studying their brains and the connections between different types of cells, including neurons.

In their work published in the journal Current Biology (in English) and devoted to the worm Pristionchus pacificus ( P. pacificus), the scientists of the Californian institute approached the question differently by analyzing instead the behavior of an animal, a predatory worm.

  • Neurons are the specialized nerve cells that carry bioelectrical signals called nerve impulses.
  • The mammalian brain contains between 100 million and 100 billion neurons, depending on the species.
  • A human has about 86 billion of them.

The main tool of attack or defense of the predatory worm P. pacificus is its bite. It is used to hunt prey or protect its food sources.

If P. pacificus prefers to eat bacteria, it also sometimes uses its teeth to attack and eat another prey, the wormCaenorhabditis elegans (C. elegans).

In their experiment, the Salk Institute team wanted to determine the intention of the worm when biting. She therefore created an environment in the laboratory bringing together the two species of worms, P. pacificus and C. elegans, and a bacterial food source.

The team discovered that P. pacificus always chooses between two strategies to biting C. elegans:

  • the predatory strategy, in which the goal of the bite is to kill in order to eat.
  • the territorial strategy, in which the purpose of the bite is to keep it away from a food source.

Experiment has also established that P. pacificus usually chooses the predatory strategy against C. elegans larvae, which are easy to kill, and the territorial strategy against C. /em> elegans adults, which are difficult to kill, but still compete for food.

Researchers believe that P.< /em> pacificusis thus able to weigh the costs and benefits of an action. This type of behavior is considered usual in vertebrates, but unexpected in a worm.

Scientists have always thought that worms are simple. When P. pacificus bites, we thought it was always for predation, says Kathleen Quach, first author of the work.

“In reality, P. pacificus is versatile. It can bite C. elegansto achieve various long-term goals. I was surprised to find that P. pacificus could turn what seemed like a predation failure into a successful, goal-oriented territoriality.

— Kathleen Quach

The California team would now like to consider whether the cost/benefit calculation of P. pacificus is wired or flexible. She hopes that further research of this type will lead to a better understanding of the molecular basis of decision-making.

“Our study shows that the #x27;one can use a simple organism like the worm to study something complex, like goal-directed decision-making. ”

— Sreekanth Chalasani, professor at the Salk Institute

This will allow us to understand how these decisions are made in more complex systems, such as humans, concludes Prof. Chalasani.

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