#siluridae

Sure! There are three species of glass catfish that are somewhat transparent (and more outside that), so I'll do the species most common in the aquarium trade.

A see-through fish? Now that's just supernatural! That's why this species is commonly referred to as the ghost catfish; these fish lack body pigment of any kind in their skin or muscles. However, that doesn't mean they are without color! In fact, scientists recently discovered that special structures within the ghost catfish's muscles can refract light as it passes through their bodies, causing them to light up in a brilliant rainbow.

(Image: A ghost catfish (Kryptopterus vitreolus) showing its colors by Qibin Zhao)

Ghost Catfish (Kryptopterus vitreolus)

Family: Siluridae (Typical Catfish Family)

IUCN Conservation Status: Least Concern

Also known as the glass catfish (although this name may be applied to several other species, some of which are not closely related to this species), this small and very unusual catfish is found only in the rivers and streams of southern and south-eastern Thailand. The scaleless skin, fins, and muscles below the Ghost Catfish’s head are completely devoid of pigment and are thus transparent, with its heart, reproductive system, digestive tract and other internal organs being housed just behind the skull and only the vertebrae being visible. This odd adaptation helps to make the fish highly inconspicuous and difficult to spot (particularly when swimming in murky water) and also prevents it from casting a notable shadow, making it incredibly difficult for predators to spot. Typically seen  in small schools, Ghost Catfish use their long and highly sensitive barbels (the thin, whisker-like organs that extend from the sides of their mouth through which they are able to taste chemicals in the water around them) to locate small invertebrate prey, and are also capable of filter-feeding by using specialised comb-like structures known as gill rakers to filter zooplankton (microscopic animals suspended in the water) out of water as it passes through their gills. They spawn between October and December when seasonal rainfall and water levels are at their highest, with females laying clusters of small, white eggs on the underside of leaves and males fertilising them externally.