The European Eel goes through several coloring variations as it transitions from egg to grown eel. One of those phases is completely transparent and is known as the “glass eel” stage.
Native to the Western coasts of Europe, the European Eel spends most of its life in coastal freshwaters. However, when they return to the ocean to spawn and to die.
What makes them truly unique is the fact that when they are young their bodies have no color and they contain no red blood cells, making them completely transparent. During this stage, they are called “glass eels”.