A type of tropical butterfly that has unique brain structures exhibits an intriguing mosaic pattern of neural development associated with cognitive progress.
A type of tropical butterfly that has unique brain structures exhibits an intriguing mosaic pattern of neural development associated with cognitive progress.
The research, published today in Current Biology, explores the neural underpinnings of behavior innovation in Heliconius butterflies, the only group known to consume both nectar and pollen. As part of their feeding habits, these butterflies reveal an extraordinary ability to learn and recall spatial information regarding their food sources—abilities that have been linked to the growth of a brain area called the mushroom bodies, which are crucial for learning and memory.
Dr. Max Farnworth, the lead author from the University of Bristol’s School of Biological Sciences, noted: “There is significant interest in how larger brains may enhance cognitive abilities, improve behavioral accuracy, or increase flexibility. However, it is often challenging to distinguish the impacts of overall brain size from those of internal structural changes during brain expansion.”
To investigate this, the researchers examined the alterations that took place in the neural circuits responsible for learning and memory in Heliconius butterflies. Neural circuits function similarly to electrical circuits, where each cell connects to definitive targets, forming a network through its connections. This network then generates specific functionalities by creating circuitry.
Upon a thorough examination of the butterfly’s brain, the team found that certain clusters of cells, called Kenyon cells, expanded at varying rates. This discrepancy resulted in what is known as mosaic brain evolution, wherein some brain regions grow while others stay the same, much like unevenly shaped mosaic tiles.
Dr. Farnworth explained: “We anticipate that these observable patterns of neural variation will correlate with distinct improvements in behavioral performance—consistent with various learning studies showing that Heliconius excel over their closest relatives in specific areas, such as long-term visual memory and pattern recognition.”
To effectively feed on pollen, Heliconius butterflies require efficient foraging routes since pollen-producing plants are quite scarce.
Project supervisor and co-author Dr. Stephen Montgomery remarked: “Instead of following random paths while foraging, these butterflies seem to select established routes between flowering resources—similar to a bus route. The planning and memory necessary for this behavior are managed by the neuron assemblies within the mushroom bodies, which is why we’re intrigued by the internal circuitry. Our findings suggest that certain components of these circuits have been fine-tuned to enhance the capabilities of Heliconius butterflies.”
This research enhances understanding of how neural circuits evolve to reflect cognitive innovation. Investigating neural circuits in manageable model systems like insects is expected to unveil genetic and cellular processes that are common across all neural circuits, potentially bridging understanding—at least mechanistically—to other organisms, including humans.
In the future, the team intends to study neural circuits beyond the butterfly brain’s learning and memory centers. They also plan to enhance the resolution of their brain mapping to visualize how individual neurons link at a more detailed level.
Dr. Farnworth expressed: “I found it incredibly interesting that we observe such high levels of conservation in brain structure and evolution, alongside significant yet distinct changes.”
“This presents an intriguing and beautiful illustration of a type of biodiversity that isn’t typically visible—the variance in brain and sensory systems, and how animals interact with and process information from their surrounding environment,” concluded Dr. Montgomery.
