Is angler fish a natural source of light?

No, the anglerfish is not a natural source of light. The light-emitting organ on the anglerfish's head, called the esca, is actually a modified dorsal fin ray that has been adapted to produce light through a process called bioluminescence. Bioluminescence is the production and emission of light by a living organism, and it occurs when a chemical reaction in the body produces light energy. The anglerfish uses its esca to attract prey, such as small fish and crustaceans, which are drawn to the light and become easy targets for the anglerfish to catch.