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Ant Brain Complexity Revealed at the Cellular Level for the First Time Using Single Cell Technology

Overview: Using single-cell technology, researchers discover how the social division of labor in an ant colony is reflected in the functional specialization of the ant’s brain at the cellular level.

Source: BGI Group

International researchers led by China’s BGI-Research used single-cell technology to study the brains of ants and explained for the first time how the social division of labor within ant colonies is reflected in the functional specialization of their brains at the cellular level.

In a study, “A single-cell transcriptomic atlas tracking the neural base of division of work in an ant superorganism,” published in Nature Ecology and Evolution, scientists from BGI-Research of the BGI Group, Kunming Institute of Zoology, Chinese Academy of Sciences, University of Copenhagen and others applied BGI’s DNBeLab single-cell library platform to obtain more than 200,000 single-nucleus transcriptomes from pharaoh ant brains and constructed a single-cell transcriptome map encompassing all adult phenotypes of this ant species: workers, males, gynes (virgin queens) , and queens.

Ants are one of the most successful organisms on Earth and have been around for over 140 million years. The biomass (determined by multiplying an estimated population by the average weight of the members) of ants is estimated to be comparable to the biomass of humans. The success of ants is generally attributed to their remarkable social behavior with a clear division of reproductive tasks.

Ant colonies have been considered super-organisms for more than a century. Taking advantage of single-cell technology, scientists have been able to systematically determine the cellular complexity in an ant’s brain and assess the difference in brain cell composition between individuals within the same colony.

“Our discoveries suggest that functional specialization of their brains appears to be a mechanism underlying the social division of labor among individual ants,” said Dr. Qiye Li, lead author of the article and researcher at BGI-Research. “We humans learn and train ourselves to perform different tasks, while ants are born with a specific role in their colony.”

The research team found that the brains of worker ants and male ants are highly specialized and highly complementary. The neurons responsible for learning and memory and processing olfactory information are particularly abundant in workers, while the abundance of optic lobe cells responsible for processing visual information is very low. This trend is reversed in male ant brains where there is an abundance of optic lobe cells but fewer neurons for olfactory processing, learning and memory.

“These findings support our observations in the lab that the pharaoh ant workers are responsible for all colony maintenance tasks requiring multifunctional brains, while males do not participate in colony maintenance tasks as their sole function is to find and inseminate a virgin. queen,” said Dr. Weiwei Liu, a researcher at the Kunming Institute of Zoology, Chinese Academy of Sciences, and co-corresponding author of the paper.

The analysis also identified significant changes in the brains of gynes when they turned into queens after mating. For example, the abundance of optic lobe cells decreased as the queens adapted to the darkness of the nest, while dopaminergic neurons and enveloping glia increased, which may explain the queens’ fertility and longevity.

“This is the first single-cell atlas to cover all social roles in an ant colony. Its performance benefits from the development of massively parallel single-cell profiling technology with high sensitivity and accuracy at low cost.” said Dr. Chuanyu Liu, co-corresponding author and researcher at BGI-Research.

By comparing the brain cells of pharaoh ant with Drosophila fruit fly, the researchers also found many conserved cell types in insect brains. For example, a population of optic lobe cells in Drosophila responsible for perceiving object movements during courtship also exists in ants and is especially common in males.

This shows an ant on a leaf
Ants are one of the most successful organisms on Earth and have been around for over 140 million years. Image is in the public domain

The molecular signature and spatial location of these cells are very similar in the two distantly related insects, suggesting that these cells likely play a conserved role in regulating male mating behavior in insects, regardless of sociality.

“This study helps us understand the complexity of ant brains and how the complementary brain specialization enables ants in a colony to function as a superorganism,” said Prof. Guojie Zhang, co-corresponding author of Evolutionary & Organismal Biology Research Center, School of Medicine, University of Zhejiang.

“The brains of different castes and sexes are specialized in different directions and complementary to each other, allowing the entire ant colony to perform the full range of functions, including reproduction, breeding, foraging and defense.

“This strategy for the life of superorganisms has allowed ants to compete for more than 140 million years and eventually become a very dominant animal group on Earth.”

Ethical approval has been obtained for this study.

About this neuroscience research news

Author: Richard Lic
Source: BGI Group
Contact: Richard Li – BGI Group
Image: The image is in the public domain

Original research: Open access.
A single-cell transcriptomic atlas tracing the neural basis of task division in an ant superorganism” by Qiye Li et al. Natural Ecology and Evolution

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Abstract

A single-cell transcriptomic atlas tracing the neural basis of task division in an ant superorganism

Ant colonies with permanent caste division of labor and widely different roles of the sexes have been conceptualized as superorganisms, but the cellular and molecular mechanisms mediating caste/sex-specific behavioral specialization have remained unclear.

Here we characterized the brain cell repertoire of queens, gynes (virgin queens), workers and males of Monomorium pharaonic by obtaining 206,367 single-nucleus transcriptomes.

In contrast to Drosophilathe mushroom body Kenyon cells are abundant in ants and show great diversity, with most subtypes enriched in worker brain, the evolutionarily derived caste.

Male brains are as specialized as worker brains, but with opposite trends in cell composition with higher abundances of all optic lobe neuronal subtypes, while gynecological and queen brain composition remained generalized, reminiscent of solitary ancestors.

Role differentiation from virgin gynes to inseminated queens induces abundance changes in approximately 35% of cell types, indicating active neurogenesis and/or programmed cell death during this transition.

We also identified insemination-induced cell changes likely related to the longevity and fertility of the reproductive caste, including increase in envelope glia and a population of dopamine-regulated Qh31-expressing neurons.

We conclude that permanent caste differentiation and extreme sex differentiation caused major changes in the neural circuitry of ants.

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