“You can hold them under water as long as you please – they do not mind it – they are only proud of it," American author Mark Twain wrote as he described the alkali flies in his 1872 book Roughing It.
It has long been known that these strange alkali flies (Ephydra hians) can “scuba dive” under the super salty and alkaline Mono Lake in California. They have these perfectly-formed air bubble that fits the skin on its body perfectly. That means, they're eyes are covered as they pop below and enabling them to see their underwater algae targets.
How they become seemingly waterproof, though, isn't yet established. So, Michael Dickinson and Floris van Breugel at the California Institute of Technology tested alkali flies and six other fly species. They plunged each into water that contains different salt concentrations.
And when placed into high levels of sodium carbonate salts (similar when in Mono Lake), the alkali flies indeed stayed drier and escaped the water better than other species. “That’s when we discovered there was something very weird about the lake – it’s very ‘wet’,” says Dickinson.
Insects' secret to keeping themselves dry are their tiny hairs and wax. However, these don't seem to be adequate enough in keeping Mono Lake water off their skin. So, Dickinson and van Breugel utilized an electron microscope to see what alkali flies have.
With that, they found that these peculiar flies are actually extra hairy. Add that up with their hydrocarbon-based wax, and you're good to go underneath! This wax barricades electricity, insulating their positively-charged skin from the Mono Lake water which is abundant of negatively-charged particles.
Moreover, when plunged in water with higher levels of sodium carbonate, these flies actually got wet, points out Zoe Simmons at the Oxford University Museum of Natural History. This means the pollution can be a threat to them as lots of salts are added to Mono Lake for just a short period of time.
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