Study Explains Why Ghost Catfish Might Have A Rainbow Shimmer

Many people opt for colorful fish to put into their aquariums.

We have the neon tetras that have blue bodies and bright red stripes, a wide variety of guppies that come in different colors, or the goldfish that, contrary to their name, don’t always just have gold scales.

PHOTO: Unsplash/Vikram Mudaliar

One particularly eye-catching yet also somehow imperceivable freshwater fish is popular with hobbyists and in the aquarium trade in general.

Ghost catfish or glass catfish are scaleless, and they’re typically described as having no pigment and being transparent. Their scientific name is kryptopterus vitreolus; “kryptos” and “pteron” are Greek for “hidden” and “wing” respectively, while “vitreolus” comes from the Latin word “vitreus” which means “glass.”

And this is what they look like:

Pretty amazing, right? But their eerie look is not all they have to offer, because when light hits their body just right, their body turns iridescent.

a few of my glass/ghost cats refracting light!
byu/psyclone__ inAquariums

The ghost catfish can turn your aquarium from having a macabre vibe to being a delight in a matter of seconds. Also, ghost catfish are known for their schooling nature, so just imagine having several of these fish display their colorful shimmer in an aquarium at the same time.

But what exactly causes the rainbow-like iridescence in ghost catfishes?

Iridescence in fish is typically caused by light bouncing off the textures on the surfaces of their scale. But as I’ve mentioned before, the ghost catfish are scaleless. In addition to being scaleless, ghost catfish are transparent, so light can still pass through their body. Where exactly can light be reflected in their tiny bodies?

Researchers went to work and looked for the answer as to how the ghost catfish creates its iridescent glow.

Simply put, a study found out that the ghost catfish gets its iridescent shine from its internal organs, not its nonexistent scales. The muscles of these tiny fish cause light waves to bend, which causes diffraction, which then creates that striking rainbow effect.

“The iridescence originates from the collective diffraction of light after passing through the periodic band structures of the sarcomeres, and the muscle fibers thus work as transmission gratings,” the study said.

With how the ghost catfish skin is able to allow more than 90% of light to pass directly through the muscles, this allows the diffracted light to exit the body.

What makes the ghost catfish unique is its transparent skin. Other species also possess the same type of muscle, but we aren’t able to see any iridescence because they aren’t transparent.

Although it’s still not clear why the ghost catfish have this ability, the researchers speculate that it may be a form of camouflage to avoid predators, or they may be used as a signal for communication in these types of schooling fishes.

Read here for more rainbow-colored creatures, or watch the video below to see how the ghost fish display their iridescence.

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