Are there any single-cell organisms that eat multi-cellular organisms?

08 August 2017

Question

Are there any single-cell organisms that eat multi-cellular organisms?

Answer

Chris asks biologist Sarah Harrison...

Sarah - It’s certainly a great question because it makes us think about how we view the food chain, and we tend to think of it as a linear progression where a small animal or organism is eaten by a larger animal, and then a still larger animal eats large animal. But, actually, feeding really when we define it properly is more about one organism drawing resources, probably organic compounds and nutrients, from another. So when you think about it like that unicellular organisms are resources from multicellular organisms all the time, it’s just we don’t call that predation we call it parasitism. This is really common in evolution because if there’s a niche, evolution will evolve some kind of organism to exploit it. So, when you think about it, when you think of an arch predator like a great white shark who think those poor people who die in a plane crash, the only thing above that arch predator in the ecosystem is the parasite which feed off it really. There are examples where perhaps more true to the question a large single cell, or organism can engulf very microscopic multicellular organisms as well.

Chris - I suppose, if you’re thinking about a human being is outnumbered by the bacteria that live on the human being, and some of those bacteria are surviving by damaging our own cells, busting them open, and then they vacuum up the debris and eat it, and assimilate it. That’s sort of what you’re saying? In essence, a single cell thing like a bacteria is eating you therefore deriving a life from us.

Sarah - If it’s pathogenic, yeah. In some cases it’s a bit of back and forth so even though a bacteria’s drawing some resources from its host, it might also be giving something back that's beneficial. So these things can work both ways as well and then it’s less one feeding off the other.

 

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