Jellyfish are not actually fish. They are actually creatures belonging to the Cnidarians' family. There are a variety of sub species like the Hydrozoa, which have more than two thousand varieties of Jellyfish included. More than two hundred species are included in the Scyphozoa, and almost fifty types in the Staurozoa.
Some but not all of these Jellyfishes have a certain protein in the body fluid. This protein is called as Aequorin and was derived from the species Aequoria Victoria. These proteins are luminescent or they glow in the dark. These properties of fluorescence are derived from two proteins in the body fluid, called as GFP (green fluorescent protein) and the Aequorin.
These proteins were discovered by Osamu Shimomura in the year 1961. Later on after about thirty years later in the twentieth century, Douglas Prasher also did extensive research on these proteins and successfully cloned and sequenced the clone for the green fluorescent protein (GFP)
He was followed later on by Martin Chalfie. Chalfie researched on this protein and tried to find out a useful application of these proteins in humans. He was the first person to discover the practical use of GFP as a tissue marker when introduced in to body of animals or humans.
He was followed by Roger Tsien who found out yet another innovation of obtaining colors from these GFP proteins and was further used as colored markers.
All the three scientists were duly rewarded for their discovery and useful and practically applicable research. They received the Nobel Prize for chemistry in 2008.
There are various other uses of these luminescent proteins. Like in art and painting or even in sculptures. Artists have extensively used the colorful pigments in this luminescent and fluorescent protein to create beautiful sculptures and paintings which glow in the dark.