Mosquito brain, is that really an insult?

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A mosquito’s brain is almost like yours and mine. And not only because it is made up mainly of neurons, but also because mosquitoes are capable of performing superior functions and advanced behaviors that allow them to survive and reproduce in their environment.

After all, the complexity of an organism’s nervous system is not entirely related to the species’ position on the phylogenetic scale. That is, with the place they occupy in the representation of evolutionary relationships between different organisms or species. This scale or phylogenetic tree is based on the idea that all living things have evolved from a common ancestor to give rise to all forms of life. Thus, the different groups of species have adapted to the pressure of the environment by having, among other evolutionary advantages, a more or less complex nervous system.

Mosquito brain, is that really an insult?

In general, we can say that there is a certain tendency for more evolved organisms to have more complex nervous systems than organisms located further back on the phylogenetic scale. For example, a fish, which is a vertebrate that occupies a more evolved position on the phylogenetic scale, has a more complex nervous system than an invertebrate like a jellyfish. And within vertebrates, mammals have even more complex nervous systems than fish.

However, there are exceptions to this trend in evolutionary position. There are invertebrates, like octopuses, that show more advanced behaviors than other invertebrates; for example, problem solving and their ability to learn.

Another unique case is that of crows, vertebrates that have a less developed nervous system than that of mammals but are also known for their ability to solve problems and use tools, as well as for their extraordinary memory.

And what about bees, invertebrates that, with a nervous system much less complex than that of vertebrates, communicate using the language of dance and show spatial memory: they can learn and remember the location of flowers, and perform simple calculations on their search for nectar.

A bee colony in a hive in the backyard of Nathalie Steinhauer, a bee researcher at the University of Maryland, on Wednesday, June 21, 2023, in College Park, Maryland. (AP Photo/Julio Cortez)

Flies and mosquitoes to study behavior

There are species of insects, such as flies and mosquitoes, that make excellent animal models for investigating the cellular and molecular mechanisms that produce certain types of behavior.

Among these species, the fruit fly (Drosophila melanogaster) stands out, which can learn and remember information, associating smells and flavors with positive or negative events. In addition, he is able to navigate and orient himself in his environment using visual cues and other sensory cues.

The fruit fly also exhibits social behaviors: aggregation and communication between individuals, complex courtship and mating, and bolting if threatened. And the pairs of flies even get to synchronize their behavior.

The importance of knowing the map of a brain

To establish the relationship between the structure of the brain and higher cognitive functions (behavior), the ideal is to know in advance how many neurons there are in the brain, how they are distributed by areas and how they are connected.

And this is not easy. It is estimated (and only estimated) that in the human brain there are about 86 billion neurons and hundreds of trillions of connections between them. Imagine how difficult it is to get to know exactly where each one is, and how and with which other neurons it connects.

Although there are much fewer neurons in the brain of a mosquito (around one hundred thousand) or in that of the fruit fly (around two hundred thousand), neither their exact number nor the connections they establish are known, which are surely millions. .

Well, the first map of the brain of a fly larva has just been published, research that has taken 12 years to detect and characterize its 3,016 neurons and the 548,000 connections (synapses) between them. And yes, they have studied one by one all these neurons and their thousands of synapses.

The larva of the fly, even with fewer neurons and connections than when they are adults, also shows complex behavior and the structure of its brain is like that of its elders.

From a functional point of view, the authors have found that the most active brain circuits in the larva are those involved in learning. And that his analysis techniques, both experimental and computational, can be the basis for obtaining the map of other species.

And they even propose that the type of learning networks detected can serve as inspiration for the development of new artificial intelligence algorithms.

We will see (interesting colloquial expression) how far knowing the map of the brain of a fly larva can take us. Nothing insignificant is, then, that our brain works at least like that of a mosquito.

* Professor of Cellular Biology, University of Jaén. The Conversation.