Some bugs have greater than 200,000 mind cells •


Scientists at Johns Hopkins Medicine describe why insects are way smarter than expected. After carefully counting the neurons in fruit flies and three types of mosquitoes, the experts found that their brains contained an average of 200,000 cells.

A human brain contains 86 billion neurons, while a rodent brain contains about 12 billion. According to the researchers, the average number of brain cells found in the insects likely provides a “floor” for the number needed to perform complex tasks.

“Although these brains are simple (as opposed to mammalian brains) they can process a lot, even more than a supercomputer,” said Dr. Christopher Potter.

“They allow the insects to navigate, find food, and perform other complicated tasks at the same time. Our study provides an answer to the question of how many brain cells come together to perform these behaviors.”

According to Dr. Potter, those studying the behavior and brain function of insects have long suspected that these insects must have hundreds of thousands of brain cells. In collaboration with Dr. Joshua Raji searched for evidence to support this theory, but came up with no evidence.

The experts set out to find their own evidence using a relatively simple counting method called an isotropic fractionator. This method is used to determine the cellular composition of nerve tissue.

First of all, Dr. Raji degraded the entire brain tissue of individual insects. He then used a pipette to break the tissue apart and evenly distribute the cells through a buffered solution.

Dr. Potter said the hardest part of the technique was microdissecting a brain that was smaller than the tip of a pencil. “It takes a very steady hand and a lot of practice.”

The solution containing the brain cells was spread on a slide and placed on a small grid. Dr. Raji carefully counted the cells on each slide.

The experiment found that the fruit fly Drosophila melanogaster had 199,380 brain cells plus or minus 3,400.

For three mosquito species, the researchers found 217,910 plus or minus 6,180 in Aedes aegypti; 223,020 plus or minus 4,650 in Anopheles coluzzii; and 225,911 plus or minus 7,220 in Culex quinquefasciatus.

About 90 percent of the brain cells of each species were made up of neurons, while the rest are most likely support cells called glia, the experts said.

Dr. Potter said researchers have determined the number of brain cells in just a few species of insect, including wasps and ants. “It would be interesting to apply this approach to social insects like bees and see if there are any differences between queens and drones.”

The counting technique used for this study is a simple one that most researchers could do, said Dr. Potter, and it is an opportunity for every researcher to contribute the censuses to the scientific literature.

The study is published in the journal PLUS ONE.

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By Chrissy Sexton, Employed author

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