A Tiny, See-Through Fish Was Recently Discovered in the Amazon, Is Totally Radical

A joint Brazilian-British team just found a new species of fish, which also is the sole member of a new genus, in the Rio Negro in the Amazon. The Rio Negro is the Amazon River's largest tributary, and the fish in question was found in a region that's pretty well explored. So how could an entire new genus of fish be found? Well, because the fish in question happens to be less than two centimeters long and is almost completely clear. How's that for an incredible find?

Mattox et al. published their discovered of what's been dubbed Cyanogaster noctivaga in Ichthyological Explorations of Freshwaters, and it's quite the unique specimen. As you can see in the image above, it's totally clear from its belly back, while its belly and head are a riot of neon blue and orange.

That striking coloration is what made the team first notice the tiny fish (Paedocypris progenetica, the world's smallest fish, is about seven millimeters shorter) in their nets. But that color fades away to a milky white soon after the fish die, which means the team had to quickly transfer the tiny things into a photo tank they'd set up. That was a tougher task than expected, as the fish were only found at night.

"I set up a photo tank right at the shoreline with the camera and flashes ready to shoot," co-author Ralf Britz of the Natural History Museum in London said in a release. "Then my colleague George [Mattox] and I went into the water and pulled the net towards the shoreline. I then used a large spoon to scoop them out of the net and transfer them into the photo tank without lifting them out of the water."

The team argues C. noctivaga deserves its own genus because of the fish's dentition. Despite being so small, it actually has two different rows of teeth on its upper jaw. The outside consists of a single, conical tooth (highlighted by the dotted line in the inset image) and four larger teeth in the inner row.

"All other members of the subfamily Stevardiinae and actually most members of the family Characidae have a different number and arrangement of teeth," Britz said. "So this helps to demonstrate that our little 'bluebelly' is something quite different, a new genus."

Zoology aside, the fish is just fascinating as all heck. That such a tiny creature could be found on a river in the middle of the night is cool enough on its own. But how trippy is that clear body?

There's something awe-inspiring about being able to see a living creature's vertebrae (which houses its all-important spinal cord) that simultaneously makes you think of your own mortality and all that. I mean, if our skin was clear, we too would just be a pile of bones, organs, and goo, but for some reason our inability to see that in daily life makes us think we're somehow more than that.

@derektmead