Ants engage in a specialized communication that relies on pheromone chemicals produced by more than one gland in their bodies, including Dufour’s gland, venom gland, etc. They release different types of pheromones in varying situations, as their alarm pheromones are different from those released during foraging and breeding season.
On 14 June 2023, a research article was published in the journal Cell about research conducted by Taylor Hart, Daniel Kronauer, and a few other researchers from The Rockefeller University, to explain about specialized communication processing center in ants. They observed that the core glomerulus in clonal raider ants’ brains gets activated in response to danger signals, a type of signal processing not found in other insects.
Their antennae have multiple olfactory receptors to recognize molecules of different natures and signal the brain. Their brain can efficiently process the information and respond accordingly.
Each antennal lobe works like a brain network and contains multiple glomeruli or neuropils that are densely packed. Glomeruli help identify the nature of molecules and pheromone signals.
Study of ants’ neurobiology by introducing engineered protein
The behavior of ants seems to be highly mysterious, particularly when the whole colony disappears after only one trail of worker ants is treated to remove them from home.
Daniel Kronauer, Taylor Hart, and a few other scientists from the Laboratory of Social Evolution and Behavior at The Rockefeller University, USA, conducted research to study ants’ neurobiology.
They introduced an engineered protein (GCaMP) in clonal raider ants (Ooceraea biroi) to study neurobiology and published results on 14 June 2023 in the well-known journal, Cell.
They included female worker clonal raider ants in their research to study the brain activity of ants having a common sex, caste, or gender in the colony.
GCaMP, a genetically encoded calcium indicator, illuminates when the calcium ions bind to it, so it determines the presence of calcium ions that are second messengers in the nervous system.
These researchers introduced an engineered protein and determined the brain activity of transgenic ants expressing GCaMP in the olfactory sensory neurons due to external signals.
They observed brain activity under a high-resolution microscope to detect fluorescence that was produced when the calcium ions were attached to GCaMP after detecting the extracellular signals.
It was found that a specific part of their brain gets activated in response to alarm signals usually produced in danger. Kronauer said their brains have a sensory hub that detects threats.
Activation of a core glomerulus in response to danger signals
The researchers found that only a small section of an ant’s brain gets activated when their olfactory receptors detect a threat or an alarming signal.
This activated part of their brain showed luminescence when observed under a microscope, which helped determine that a distinct part of their brain actively responds to alarm signals.
Through two-photon imaging, it was seen that 4 different alarm pheromones activated 6 glomeruli in one glomerulus in response to signals that led to the initiation of a panic response.
Moreover, they observed that their brain activity was not compromised by activating only a core glomerulus in response to the danger signals.
Generally, it initiates a behavioral response quickly when ants run away from the spot to avoid danger or move to a new location after detecting a disturbance in their nest.
Similarly, it indicates that the dead or threatened ants begin to release danger signals or pheromones captured by the olfactory receptors of other colony members.
A small section of their brain detects these danger signals, allowing them to behave similarly and leave their nests quickly.
So, this mystery was solved after this research work focused on knowing the reasons for the disappearance of the colony after the death of a few members.
After mapping clusters of 3 glomeruli, it was observed that the number of activated glomeruli in ants and drosophila remained the same when the pheromone cues or odor molecules were the same.
However, the activated glomeruli in ants are localized in one glomerulus and remain fixed, but they did not mention the localization of activated glomeruli in the drosophila.
Such specialized communication processing was not found in other social insects because ants produce different types of pheromones in different situations and detect them efficiently.
Impact of colony size on communication processing in ants
The colony size significantly influences the type of pheromones released by the colony members to communicate with their fellows.
In the wild, the clonal raider ants have smaller colonies with only a few dozen or a few hundred members and lack queens. Accordingly, they have a collective panic response to ensure survival.
Smaller colonies have to be more agile and active for survival so that they can respond quickly after detecting an alarm signal produced by their fellows when they are in danger.
Lack of ability to detect alarm cues and respond to the signals quickly leads to short-term survival. So, they remain alert and detect the cues to avoid the loss of life and colony death.
In contrast, larger colonies have different modes of communication and sensitivity to alarm signals, as seen in army ants that have hundreds of thousands or millions of members in the ant colony which is not found in other insects.
They do not bother an individual risk due to the presence of a large number of members in the colony; that’s why they do not produce alarm signals in a way similar to clonal raider ants.