The causes of marine life's luminescence

Marine life refers to all kinds of life in the ocean, including marine animals, marine plants, microorganisms, viruses and so on. Among them, marine animals include invertebrates and vertebrates. Invertebrates include various snails and shells. Vertebrates include various fishes and large marine animals, such as red starfish, whales and sharks. The reason why marine life glows is that terrestrial life rarely glows, only a few species such as fireflies, and almost all marine life, from bacteria to fish, has luminous species. So, why do marine life shine? Let's start with unicellular algae. In Puerto Rico, Latin America, there is a famous scenic spot, Fluorescent Bay. Take a boat through the mangrove forest and enter the sea at night. As long as it is stirred by hand, the water surface will glow with dim fluorescence. The faster you stir, the more fluorescence you get. When we set sail, we left a trail of light, which is the light from the unicellular plant dinoflagellate. Why does dinoflagellate glow? Scientists speculate that its natural enemies are arthropods or water winds, which are usually called fish worms or water winds. Sudden light can scare them away, or use light to attract more power and eat small plankton first. This method of sending optical drives to enemies is a common trick of marine life, and it is not the patent of dinoflagellate. The same is true of echinoderms: when you touch it, its wrist will glow to scare off the enemy. For example, the belly glow of some squid is a kind of camouflage, which aims to be similar to the light of the surrounding seawater and avoid being discovered by the enemy; Some squid have glowing feet. Of course, marine bioluminescence is not only for protection, but also as bait to attract prey, which is a common technology used by many carnivorous fish. In addition, in the dark deep sea, luminescence is an important tool for intraspecific communication. Some fish, octopus and ostracods have this function, and they determine the date by emitting light during mating season. In fact, we don't know the truth about the luminescence of marine life. For example, both kinds of unicellular plankton have opal bones, in which radioactive insects can emit light, while diatoms can't. In addition, the use of cold light is also controversial. Some people say that some marine life glows not because it is useful, but as a residual habit of early evolution. For example, dinoflagellate evolved very early, when the earth was still in a reducing environment, free oxygen was harmful, and luminescence was an oxidation, so it was a way to consume oxygen and avoid harm. Now the earth's atmosphere has been oxidized, but the ancient power has been preserved. On the contrary, the evolution of diatom appeared many times later, and the atmosphere was oxidized when it appeared, so it was unnecessary to appear. So diatoms don't glow. Of course, this is just a guess, which needs to be verified in the future.