Of evolution and amber, mosquitoes and things
A mosquito embedded in amber yields clues about the remarkable resilience of malaria
The sweats, the vomiting, the chills. Survivors of malaria are like a club of war veterans who still shudder at the awfulness of it all. It’s what I remember about Tanzania, in East Africa, where I contracted malaria and spun out in a haze of whitish delirium, on a distant beach called Kipepeo. Because of this, I now take a disconcerting interest in all things malarial.
Hence, when my eye fell upon a particularly malarial news alert recently, I was compelled to put finger to keyboard.
Scientists at Oregon State University have found an ancient mosquito, trapped in amber, which reveals some dark history about the zingy little insect. “Wait a minute,” a classmate said when I told her about it. “Does this mean, like, Jurassic Park?” (Don’t tell me you can’t hum that haunting theme tune in your sleep…) Well, not quite. But it’s almost as epic, in evolutionary terms at least.
Amber is a gold mine for evolutionary biologists because it basically freezes time. In this case, a culicine mosquito trapped in amber held ancient traces of the pathogens that cause malaria, from the last meal of blood it sucked from an infected host. Why do we care? Because this shows us that malaria – previously thought to exist largely in the tropics – is also native to North America. More interestingly, it shows that malaria pre-dates humans, having emerged some 100 million years ago – much longer ago than previously conceived.
Malaria’s age is fascinating because it gives powerful clues about parasitic evolution. Considering its survival over time, the malaria parasite has clearly found some remarkable ways to adapt. The amber records show that the parasite has evolved to weaken the immune reactions of its hosts by switching the protective protein coat that surrounds it – a covering that usually alerts the host’s immune system of a threat. But the ability to shift coats makes the parasite unrecognizable, like a criminal in disguise.
Scientists say this explains why it’s so difficult to vaccinate against malaria: for 100 million years the parasite has been in perpetual masquerade. But thinking positively, the research gives us a better idea of how to approach a highly adaptive disease that kills almost one million people a year. By understanding that it survived for millions of years by adapting its protein coat, researchers have a clearer appreciation of the scope of the problem today, and the importance of addressing this prominent adaptive mechanism.
Being a bug sympathizer, my first response to this article was concern: shouldn’t we be careful about galvanizing demonic bug sprayers into action against an insect that is part of several ecosystems? Not so, say some researchers, who tell us that if we blasted every mosquito to the moon tomorrow, we wouldn’t see any negative ecosystem impacts.
Either way, mosquitoes – whether the key to a Jurassic past or the evolution of a destructive disease – continue to infest scientific imagination.