This is Scientific Americans 60 Second Science. I'm Jason Goldman. Got a minute?

Hundreds of millions of years ago, a humble fish swam in the lakes and rivers of the supercontinent Gondwana.

Eventually, Gondwana broke apart becoming the continents we know today, and the descendants of that fish, now

called cyclids, continue to swim the fresh waters of both Africa and South America.

Sicklids have some of the most incredible visual systems known.

Humans have genes that code for three different types of visual pigments called

opson's. Sicklids have seven.

But what is interesting within sicklets, which is this group of very diverse fishes, is that they can express different sets of these seven genes.

So they only express three typically, but different species express different groups of these

seven genes.

Biologist Daniel Escobar Camacho from the University of Maryland in College Park.

So for example, we have an obstinine gene that goes for the blue, green, and red obscene and red option whereas thicklids have genes that are sensitive

to UV to violet to blue to blue-green to green let's say light green and red.

But selection pressure has kept only some of those genes intact.

African cyclids, whose visual systems are well studied, evolved in fairly clear, calm blue lakes with plenty of sunlight.

And it was known that they've maintained the genes for seeing short wavelength light at the

blue end of the spectrum.

But their South American counterparts live in the murky waters of the Amazon River basin, bathed mostly in reds and oranges.

Escobar Camacho analyzed DNA from three different Amazonian cyclids, the freshwater angelfish, the discus, and the

Oscar, all of which are also popular in home aquariums. He discovered that each species has

completely lost at least one of the seven ops in genes, and some have even lost two.

But they've each lost different genes.

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