If you wanted to know what was happening in the head of the fish of the kind of Maluta Macropinna, then you will not be difficult to do this - because this fish has a completely transparent head!
This species was discovered in 1939, but the first photos of the animal managed to receive only in 2004. Malrota Macropinna lives at a big depth of about 1000 meters in the northern part of the Pacific, so it is extremely difficult to study it. And when lifting on the surface, the fish does not withstand the pressure drop, because of which, for a long time, scientists could not study the structure of her head in detail. It was possible only in 2008.
It turned out that the camera filled with a transparent liquid needs a fish to protect the eyes that are located right in the head. That is, the fish literally sees the word through the head. And those brown dots on the transparent surface, which initially could be taken for sad eyes, are actually olfactory receptors that help the mother of Macropin at the hunt.
The size of the fish is small - about 15 centimeters in length, and it feeds in the main zooplankton, which in large quantities accumulates on the tentacles of the book - multicellular animals such as stripping. Their tentacles contain cutting cells, deadly for marine inhabitants. But the transparent shell, protecting the vital organs in the head of the fish, reliably protects the Macropingen from the attack of the book.