Press Release: Scientists Peer into Bug Brains

Bug brains are helping Johns Hopkins University scientists understand the connections between neurology and behavior, and a new study published in PLOS One affirms the promise of a novel technique that refines their view at a molecular level.

While an insect’s brain is far less complex than a human’s, this research can help unlock foundational knowledge about behavior and the molecular processes behind it. Previous studies hint that humans largely owe our neurological complexities to the number of our neurons.

“Even though these brains are simple [in contrast to mammalian brains], they can do a lot of processing, even more than a supercomputer,” said co-author Christopher Potter. “They enable the insects to navigate, find food and perform other complicated tasks at the same time, and our study offers one answer to the question of how many brain cells come together to conduct these behaviors.” 

Applying isotope fractionation (IF) to identify and separate the cells within tiny insect brains, the researchers were able to achieve single-cell suspensions, revealing greater detail of cell types and quantities than routine, stereological methods. They applied IF to brains of the Drosophilia melanogaster fruit fly, as well as three species of mosquito (Ae. aegypti, An. coluzzii, and C. quinquefasciatus), isolating neurons to determine a more precise estimate of their quantities. The data revealed that the mosquitos had around 220,000 neurons, while fruit flies have closer to 180,000.

This insight is an early step to unlocking neurological processes and their role in behavior across  time—and species. As mosquitos and fruit flies shared a common ancestor 260 million years ago, neuron variations in modern bugs may reveal the cellular processes behind behaviors that evolved differently as evolutionary branches diverged.

“It would be interesting to apply this approach to social insects like bees, and see if there are differences between queens and drones,” Potter said.

Beyond bugs, these data contribute to our understanding of the foundational role neurons play in human brains too. Knowledge about neurons can help scientists understand how they influence and inform our behavior.

This research was conducted at The Center for Sensory Biology of the Solomon H. Snyder Department of Neuroscience at Johns Hopkins University School of Medicine. It is supported by grants from the United States Department of Defense, the National Institute of Allergy and Infectious Diseases, and a Johns Hopkins Malaria Research Institute Postdoctoral Fellowship

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Study citation & link: Raji JI, Potter CJ (2021) The number of neurons in Drosophila and mosquito brains. PLoS ONE 16(5): e0250381. https://doi.org/10.1371/ journal.pone.0250381