This is the story of an absolute rule breaker in the history of animal evolution, where a billion year old pact has been broken by a little tiny worm.
Hydroides elegans lives in a hard calcified tube and attaches itself to ships and all kind of submerged man-made structures in ports. It can grow in massive numbers (millions of individuals packed together), hitchhiking by ships and causing serious costs for marine industries.
This worm shares a key trait with humans: remarkable adaptability! It can survive in many different environments, except for the very cold polar waters. This is the key to it’s success, turning to one of the most known invasive species and conquering the globe. I study its genes to understand more about this worm. This guy is so cool and special at genetic level. Maybe one of the coolest worms ever!
Every animal has two sets of gene pools; one in the heart of our cells (the nucleus) and one in the backyard (cytoplasm). The incredible diversity of life on Earth has been built through the constant reshuffling of nuclear genes: mixing genetic ingredients from both parents to create new combinations generation after generation. But the second genetic system follows a completely different rule.
Inside every single cell, there is a survivor of an ancient invasion, the one in the backyard; a bacterium that was captured as a food but never digested. The cell and the bacterium formed a partnership.
You give me energy, I give you a home.
That captured bacterium became what we now call the mitochondrion. This partnership has lasted for over a billion of years, but it follows one strict rule: mitochondrial DNA must only be inherited only from the mother. This helps keep the system stable and avoids conflicts between the two genome sets.
Hydroides elegans appears to challenge this rule. In this species, mitochondrial DNA can come from both parents. Some individuals carry two very different, and diverged DNA types. This is surprising and odd! Cause in all animals, even small changes in mt DNA can lead to serious health problems. Our cells are built to function with only one mitochondrial DNA type. And yet, this worm has managed to be supper successful worldwide.
Despite a “rule-breaking” system expected to fail, this worm thrives worldwide; turning a typical disadvantage into an advantage. My job is to understand whether this “unexpected system” is real, how it works, and whether it is actually stable.
This worm shows that evolution is dynamic: Even the most stable systems can be challenged, and what has been a disadvantage can become a key to success. But what I’d like to ask you is to rethink about the evolution. Think about what made us what we are today (rules) and what happens if we always follow the traditions.
Evolution is not about the best system, but the most fit. And when conditions change, that fit can change too.
What works today may fail tomorrow.
But remember; Only when there is enough diversity can new “winners” emerge.
- Illustrated worm characters by Hooman Ahmadi ↩︎
