In the wild mountain ranges of Morocco and northeast Algeria, there’s a small, shimmering butterfly that most people have never heard of. It flutters through cedar forests and scrubby hillsides, unnoticed by nearly everyone. But deep inside its cells, this insect is doing something no other animal has ever been seen to do.

This butterfly, called the Atlas blue, just set a world record. And scientists are paying attention – not just because it’s rare, but because its strange biology could help us understand one of the most complex problems in science: how species evolve, and even how cancer works.

Butterfly with chopped up chromosomes

Inside every living thing, from a mushroom to a whale, there’s DNA – the instruction manual of life. That DNA is packaged into structures called chromosomes. Humans have 23 pairs, and most butterflies have 23 or 24 pairs.

The Atlas blue butterfly carries 229 pairs of chromosomes – more than any other multicellular animal. Scientists had long suspected it held the record, and new genome sequencing has now confirmed it.

And here’s what’s even more surprising: the butterfly’s DNA hasn’t been duplicated. Instead, the chromosomes have been chopped up into smaller pieces – like taking 24 books and ripping them into 229 booklets.

A peek into evolution’s toolbox

The researchers behind the new study came from the Wellcome Sanger Institute in the UK and the Institute of Evolutionary Biology in Barcelona. They produced the first-ever high-quality genome for the Atlas blue and discovered that its extra chromosomes were not caused by copying, but by splitting.

This process happened fast in evolutionary terms. In about three million years, the butterfly went from 24 to 229 chromosomes. That’s like a blink of an eye for species development.

The cuts happened in parts of the DNA that were loosely packed. That means the total genetic information didn’t really change, it was just reorganized. All of the chromosomes, except for sex chromosomes, were broken up.

A rapidly evolving butterfly

Changes in chromosome number are one way that species evolve. They can affect how genes are turned on or off, how traits are passed down, and how well an animal adapts to its environment. The Atlas blue butterfly belongs to a group that evolved rapidly, creating lots of closely related species.

This new research helps explain how that might have happened. The split chromosomes may have allowed more mixing and matching of DNA, possibly helping the species survive in tough environments.

But that same complexity could also come with risks. Too many chromosomes might make a species more vulnerable over time. And unfortunately, the Atlas blue is already in trouble. Climate change, overgrazing, and destruction of cedar forests are putting pressure on its populations.

Butterfly chromosomes and cancer

The implications go far beyond butterflies. Professor Mark Blaxter noted that genomes hold the key to how a creature came to be, but also, where it might go in the future.

“To be able to tell the story of our planet, we must have the story of each species and see where they overlap and interact with each other. It also allows us to apply learnings from one genome to another.”

“For example, rearranging chromosomes is also seen in human cancer cells, and understanding this process in the Atlas blue butterfly could help find ways to limit or stop this in cancer cells in the future.”

That might seem like a stretch – a tiny insect helping us battle a major disease – but it’s happened before. From bacteria to mice and worms, scientists have used all kinds of living things to understand human health.

The extreme Atlas blue butterfly

There are still big questions to answer. What benefits, if any, come from having so many chromosomes? Are there specific genes that make this butterfly more adaptable? Could this give clues about how life responds to a changing planet?

“When we set out to start to understand evolution in butterflies, we knew we had to sequence the most extreme, and somewhat mysterious, Atlas blue butterfly,” said Dr. Charlotte Wright, first author of the study.

She noted that it was thanks to Dr. Roger Vila, who had previously worked with his colleague to find and identify this elusive butterfly, that the team was able to sequence this species.

“Being able to see, in detail, how the Atlas blue butterfly chromosomes have been split over time in specific places, we can start to investigate what benefits this might have, how it impacts their ability to adapt to their environment, and whether there are any lessons we can learn from their DNA that might aid conservation in the future.”

Understanding species evolution

This kind of research is just the beginning. The team now has a “gold-standard” genome to compare with other butterflies and moths, opening the door to understanding more about how species split, adapt, or vanish.

“Breaking down chromosomes has been seen in other species of butterflies, but not on this level, suggesting that there are important reasons for this process which we can now start to explore,” said Dr. Vila, senior author of the study.

“Additionally, as chromosomes hold all the secrets of a species, investigating whether these changes impact a butterfly’s behavior could help form a full picture of how and why new species occur.”

The full study was published in the journal Current Biology.

Image Credit: Roger Vila

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