Luminescence

_{-- L u m i n e s c e n c e --} _{click on the question number for the answer}
Q 1.
	What shark glows in the dark?
Q 2.
	What causes the sea to glow at night?
Q 3.
	What makes dead fish shrimp, etc., sometimes glow in the dark? Does moonlight have anything to do with this?
Q 4.
	Do "phosphorescent" sea creatures glow by means of phosphorus in their bodies?
Q 5.
	What causes lobster meat to glow in the dark?
Q 6.
	Are all luminous fishes found in the deep sea?
Q 7.
	What causes the water to be "phosphorescent" at night?
Q 8.
	What causes the phosphorus in the water at night? Does this happen anywhere else?
Q 9.
	When an animal gives off a bright light does that in any way signify the approach of death of the animal?
Q 10.
	While fishing off the Florida Keys at night in a boat, I often have seen pale flashes of light apparently going on and off in one place on the bottom. What causes them?
Q 11.
	What gives the Indian River the phosphorescence at night when either white caps are on the water, a stick is drawn through the water, or an outboard motorboat speeds by? It is both interesting and beautiful.
Q 12.
	During a trip to Puerto Rico I saw what is called phosphorescence, at La Parguera. What causes this phenomenon?
Q 13.
	In the September issue of a sporting magazine, last year, there was an item about a ship which traveled from Tahiti to New Zealand, and en route sighted large groups of brightly luminescent organisms, 7 to 11 inches long and 1 inch in diameter, weird creatures which emitted a constant blue- white light, visible to 100 yards. What were these eerie, blue-white luminescent creatures?
Q 14.
	I am very interested in the phosphorescent protozoans and bacteria of the sea. Could you give me any information on these, or direct me to a source of other information?
Q 15.
	During a recent visit to Puerto Rico, I observed a very dramatic demonstration of bioluminescence. On the southwest coast is a small bay called Phosphorescent Bay. Launches leaving La Parguera take tourists out to observe the fiery displays in the water. What causes this phenomenon?
Q 16.
	During a recent visit to Puerto Rico, I had the opportunity to observe a very dramatic demonstration of bioluminescence. On the southwest shore of the island there is a small bay called "Phosphorescent Bay". I have observed bioluminescence before, but never in such abundance as occurs in this area. Can you tell me what the special environmental conditions are that produce bioluminescent organisms in such extraordinary numbers in this locale?
Q 17.
	I have seen discarded lobster shells glowing like a bed of live coals. It was a greenish-white glow, quite like that of a glowworm. Only the inside of the shells glowed, the outside was completely dull. Can you explain this light?
Q 18.
	In Tampa Bay there are often blooms of a comb jelly, genus Mnemiopsis, that has the ability to emit luminescence from beneath the comb plates. Of what advantage to the animal is this ability? It does not seem to be linked to their feeding habits. I have been told that they glow when there is an abundance of dissolved phosphorus in the water. I have doubted this explanation, but I haven't got any other.
Q 19.
	While cruising in the Bahamas, I put six pieces of boiled spiny-lobster tail meat in an opaque container for possible use as bait. That evening, I was surprised by a greenish glow emanating from the meat. When taken into the dark cabin, it produced enough light to outline features to a distance of about 7 feet. What caused this effect?
Q 20.
	In July 1989, in the dark on Sandbridge Beach, Virginia, I noticed some glowing objects just above the tide line. On closer examination, the objects proved to be mole crabs (Emerita talpoida) giving off a greenish-blue light. Only dead mole crabs glowed; live ones that we dug out of the sand did not. I put some of the dead mole crabs in a seawater-filled container and, by the next day, they had lost their luminescence. I was surprised because I thought the crabs were colonized by luminescent bacteria and that the bacterial activity would increase since a food source (the dead crabs) was available. Were the crabs actually colonized by luminescent bacteria?
Q 21.
	We were told that great numbers of small, swirling, luminescent animals recently appeared at night on the surface of Manatee Bay, Florida. Apparently, these animals also released clouds of a glowing substance in the water. Could you tell us what was taking place?
Q 22.
	One evening, we anchored our boat in the Ronda Keys and watched thousands of two-inch "squiggles" glowing in the water around us. They were constantly moving, deliberately heading toward each other. When they collided, they shot out clouds of what must have been spawn. This event lasted for only about one-half hour. What was going on?


_{-- a n s w e r s a b o u t L u m i n e s c e n c e --}
	Q&A 1.	What shark glows in the dark?
	The little-known deep-sea sharks of the coast of Cuba, Japan, and other areas (Genus Etmopterus) are known from their very small size (slightly over a foot in the adult) and by the fact that the Japanese species, E. pusillus and E. frontimaculatus have rows of luminous spots on the body and tail. Presumably the Cuban species, E. hillianus, is luminous as well, but this is not known for certain. In color these sharks are chocolate brown or blackish, with a few paler markings.
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	Q&A 2.	What causes the sea to glow at night?
	Often the sea will glow brightly at night as the water is disturbed in the wake of a ship or as fish swim through it. This phenomenon is commonly known as "phosphorescence", although it is not actually caused by the presence of phosphorous, as is sometimes believed. The glowing is caused by a microcopic, single-celled protozoan animal known as Noctiluca. As in many other higher sea creatures, Noctiluca produces this “cold light,” in a manner that is not fully understood by scientists, but involves two chemical substances, luciferin and luciferase, which react together in the presence of oxygen and moisture.
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	Q&A 3.	What makes dead fish shrimp, etc., sometimes glow in the dark? Does moonlight have anything to do with this? Crestview, Florida
	The luminosity often observed coming from dead fish, shrimps, and crabs at nigh~ due-to the presence of colonies of luminous bacteria, and not to the organism itself. The light emitted by such decomposing sea creatures is greenish white in color and is believed to be caused by a chemical process within the bodies of the microscopic bacteria. This process involves the oxidation of a substance, luciferin in the presence of a stimulating agent, luciferase. Water and oxygen are required for this production of light which is not accompanied by any measurable heat. "Cold light" produced in this manner is of the same nature as that produced by fireflies, arid has nothing to do with the supposed “absorption” of either sunlight or moonlight.
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	Q&A 4.	Do "phosphorescent" sea creatures glow by means of phosphorus in their bodies?
	No. This idea is erroneous though it is of long standing. All luminous animals and plants, so far as is known, produce their light in the following way: The enzyme luciferin is produced by the organism and suddenly oxydized in the presence of moisture by the combination of another substance, luciferase. Apparently in many, if not all, cases the luciferin can be again reduced to its former state and used again. No heat is produced by this method of light production, and light produced in this way is 95% efficient as compared to 5% efficiency for an electric bulb, where most of the energy supplied by the electricity is lost in the form of heat.
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	Q&A 5.	What causes lobster meat to glow in the dark? Fort Lauderdale, Florida
	Crabs, lobsters, shrimp, and fish flesh may often be seen to glow brilliantly in the dark. This rather common phenomenon is caused, not by any natural phosphorescence in the flesh itself, but by colonies of luminous bacteria growing upon it. The light given off by these bacteria is of a greenish-white appearance. The presence of the bacteria does not necessarily indicate that the meat is spoiled, although it is seldom seen on perfectly fresh lobster or fish flesh.
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	Q&A 6.	Are all luminous fishes found in the deep sea?
	Although the greater majority of luminous fishes typically occur in the great depths of the sea, a few of the light-giving forms normally are found in shallower depths. Perhaps the best-known of these is the midshipman, Porichthys. This fish reaches a length of about a foot and has numerous rows of photophores (light organs) running along its sides and tail. Because of the humming or chimelike grunting sounds by the midshipman and its relative the toadfish, these fishes are sometimes called "singingfish".
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	Q&A 7.	What causes the water to be "phosphorescent" at night? St. Petersburg, Florida
	The term "phosphorescence" is incorrect since it indicates the presence of metallic phosphorous. The proper term for this light display is luminescence. This luminescence is caused by the presence in seawater of microscopic organisms which glow when disturbed, as by a passing boat or a net in the water. One of the commonest of these organisms is called Noctiluca, meaning "night light". The mechanism by which the light is produced is a complicated one. It involves an enzymic chemical reaction of a substance called luciferin to form oxyluciferin. This is a highly efficient reaction, producing light with little or no heat. An understanding of this phenomenon could lead to increased efficiency in commercial light production.
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	Q&A 8.	What causes the phosphorus in the water at night? Does this happen anywhere else? St. Petersburg, Florida
	The "phosphorus" is actually called “phosphorescence” or “bioluminescence” and has nothing to do with phosphorus but is due to the manufacture of light by animals and microscopic organisms. For a long time the problem of bioluminescence remained unso1ved, and was merely a matter of speculation. Recently it was shown that a complicated chemical reaction is involved. Light is, apparently, produced a s a result of the slow burning of a substance called luciferin present in the minute marine animals. When this compound combines with oxygen, light is produced. The reaction can be compared to the burning of a candle, but the energy produced takes the form of light only! This type of light is extremely unusual, since it is a cold light with no heat at all. The phosphorescence in the water which you see is probably due to bacteria and single celled microscopic organisms. However, the production of "cold" light in some form is not restricted to these forms. It is also known in sponges, jellyfish, corals, marine worms, clams, snails, squids, insects, starfishes, sea squirts and fishes.
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	Q&A 9.	When an animal gives off a bright light does that in any way signify the approach of death of the animal? Jacksonville, Florida
	Not generally, although there may be tragedy involved. One of the amphipod beach hoppers, Talitrus, appears to be subject to infection by luminous bacteria. The bacteria flourish within the alimentary tract of the amphipod and by their luminous powers eventually create an internal blaze of light. Such infection is inevitably fatal.
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	Q&A 10.	While fishing off the Florida Keys at night in a boat, I often have seen pale flashes of light apparently going on and off in one place on the bottom. What causes them? Fort Wayne, Indiana
	The pale flashes which are seen on dark nights in the West Indies and in comparatively shallow Florida waters are made by a marine worm, Chaetopteris variopedatus. This worm lives on the bottom, in a parchment-like tube. The flashes which are seen are beams of light coming out of the end of the tube. The animal is also capable of emitting brilliant luminescent displays. Some biologists think that the light is flashed on so that predators can kill any small animal trying to get into the tube to capture the worm. Others think that this is a means of attracting plankton to the entrance of the tube to be eaten.
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	Q&A 11.	What gives the Indian River the phosphorescence at night when either white caps are on the water, a stick is drawn through the water, or an outboard motorboat speeds by? It is both interesting and beautiful. Rockledge, Florida
	There are a number of phosphorescent micro-organisms in the sea including bacteria and certain dinoflagellates. When these are present in any quantity they give a luminescent appearance to the water. When the water is agitated, as in the wake of a motorboat, the light production, which is known as bio-luminescence, is often greatly increased.
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	Q&A 12.	During a trip to Puerto Rico I saw what is called phosphorescence, at La Parguera. What causes this phenomenon? Miami, Florida
	The phenomenon of "phosphorescence," or bio-luminescence, is the emission of light by certain marine organisms. There are several animal species and bacteria which emit light. Some are microscopic in size. Others are larger, such as crustaceans of certain kinds, jelly fishes and true fishes. Some of these generate the light in highly specialized organs while others secrete some sort of luminous slime.
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	Q&A 13.	In the September issue of a sporting magazine, last year, there was an item about a ship which traveled from Tahiti to New Zealand, and en route sighted large groups of brightly luminescent organisms, 7 to 11 inches long and 1 inch in diameter, weird creatures which emitted a constant blue- white light, visible to 100 yards. What were these eerie, blue-white luminescent creatures? Great Neck, New York
	We have not read the article to which you refer, but the description of the luminescent objects almost certainly refers to an organism known as Pyrosoma. This is a colony consisting of a large number of individuals formed by budding, which remains attached to each other in the form of a tubular structure, of the size and appearance you have described. These creatures belong to the pelagic tunicates, a group of primitive chordates. They are highly luminescent and can be seen at quite a distance.
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	Q&A 14.	I am very interested in the phosphorescent protozoans and bacteria of the sea. Could you give me any information on these, or direct me to a source of other information? Savannah, Georgia
	You have made a very common mistake in calling the light produced by living organisms phosphorescence, as does Webster's Dictionary. In the strict sense phosphorescence is derived from the word phosphor, meaning "afterglow." As this implies, it is a term used to describe a material which continues to produce light after the activating mechanism has ceased to function. During the time of activation, the light produced is called luminescence. It is in this last category that biological light is placed and is called bioluminescence. The light is produced by an enzyme, luciferase, acting on a sugar called luciferin in the presence of oxygen. Only a few types of organisms have this enzyme substrate complex, and can thus produce biological light. The classical work on this subject is Bioluminescence by E. N. Harvey, published by Academic Press of New York.
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	Q&A 15.	During a recent visit to Puerto Rico, I observed a very dramatic demonstration of bioluminescence. On the southwest coast is a small bay called Phosphorescent Bay. Launches leaving La Parguera take tourists out to observe the fiery displays in the water. What causes this phenomenon? Hoboken, New Jersey
	The bioluminescence of Phosphorescent Bay is one of the most dramatic manifestations of "living lights" in the sea. The light is caused by myriad tiny organisms called dinoflagellates that produce light under certain conditions, especially when disturbed. For an article on this phenomenon see "Living Lights and Clocks" in the January-February, 1966, Sea Frontiers (Volume 12, Number 1.)
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	Q&A 16.	During a recent visit to Puerto Rico, I had the opportunity to observe a very dramatic demonstration of bioluminescence. On the southwest shore of the island there is a small bay called "Phosphorescent Bay". I have observed bioluminescence before, but never in such abundance as occurs in this area. Can you tell me what the special environmental conditions are that produce bioluminescent organisms in such extraordinary numbers in this locale? Hoboken, New Jersey
	"Phosphorescent Bay" has been famous for many years. Its luminescence is due to the activity of small plant-like organisms called dinoflagellates, which emit light under certain conditions, particularly when they are disturbed. It has been suggested that the very rich growth of dinoflagellates in this bay results from the drainage of nutrients from the surrounding mangrove forests. In addition, the bay is relatively isolated from the sea, which enables nutrient levels to stay rather high and allows continued "blooming" growth of the luminescent organisms.
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	Q&A 17.	I have seen discarded lobster shells glowing like a bed of live coals. It was a greenish-white glow, quite like that of a glowworm. Only the inside of the shells glowed, the outside was completely dull. Can you explain this light? Miami, Florida
	The glow was bioluminescence from luminous bacteria, which can; cause decaying fishes and invertebrates to glow in the dark. Bioluminescence is light produced by living organisms, both animals and plants. Thousands of species of marine animals produce bioluminescence. Most of tl1em are animals of the lower orders. Luminescence is common among salt-water creatures, but very rare in fresh-water animals (see "Luminous Creatures of the Sea," Sea Frontiers, Vol. 10, No.3, July, 1964).
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	Q&A 18.	In Tampa Bay there are often blooms of a comb jelly, genus Mnemiopsis, that has the ability to emit luminescence from beneath the comb plates. Of what advantage to the animal is this ability? It does not seem to be linked to their feeding habits. I have been told that they glow when there is an abundance of dissolved phosphorus in the water. I have doubted this explanation, but I haven't got any other. Lutz, Florida
	Bioluminescence in midwater animals such as fishes is a valuable characteristic, aiding as it does the sex and species recognition, schooling behavior, and other vital activities of those animals. The same property in animals which live close to the surface, such as the comb jelly, is more difficult to explain. In these cases bioluminescence may depend primarily on the inges- tion of bioluminescent microorganisms. The capacity to emit light would therefore be a byproduct of normal feeding behavior and probably has no special value to the organism. If this is valid, it helps explain the increased brilliance of the comb jelly in waters particularly rich in phosphorous which accelerates the growth of planktonic food organisms.
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	Q&A 19.	While cruising in the Bahamas, I put six pieces of boiled spiny-lobster tail meat in an opaque container for possible use as bait. That evening, I was surprised by a greenish glow emanating from the meat. When taken into the dark cabin, it produced enough light to outline features to a distance of about 7 feet. What caused this effect? Arnold, Maryland
	The rather startling greenish glow that you observed was caused by luminescent bacteria that were growing and feeding on the lobster meat. These bacteria are commonly encountered on decomposing fish and invertebrate tissues in tropical regions. Like most bacteria, these luminescent marine forms reproduce rapidly, spreading over the spoiled meat in a very short time. When their population reaches a large enough density, the combined bioluminescence of all the bacteria becomes bright enough to see. Not all luminescent marine bacteria are free-living like the ones you observed. Many kinds live in close association with higher marine organisms such as deep- water cephalopod mollusks, prawns, and fishes. Usually, the bacteria are housed in special light organs and are utilized by the host for intraspecies communication or as prey lures. The long lines of bacteria-filled light organs on the sides of myctophid lanternfishes are probably used for species recognition and schooling in the pitch-black waters of the deep sea. Some fishes, like the deep-sea anglerfish, attract smaller organisms into swallowing range by brandishing a brightly luminous, bacteria-filled lure. When disturbed, several types of deepwater prawns will discharge a large brightly glowing cloud of bacteria-filled mucus-an act that probably startles and confuses potential predators. Both free-living and symbiotic bioluminescent bacteria give off "cold" light generated by a biochemical reaction. For total light production, this luciferin-luciferase cold reaction is 95-percent efficient as opposed to the 5-percent efficiency of a heat-producing light bulb.
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	Q&A 20.	In July 1989, in the dark on Sandbridge Beach, Virginia, I noticed some glowing objects just above the tide line. On closer examination, the objects proved to be mole crabs (Emerita talpoida) giving off a greenish-blue light. Only dead mole crabs glowed; live ones that we dug out of the sand did not. I put some of the dead mole crabs in a seawater-filled container and, by the next day, they had lost their luminescence. I was surprised because I thought the crabs were colonized by luminescent bacteria and that the bacterial activity would increase since a food source (the dead crabs) was available. Were the crabs actually colonized by luminescent bacteria? Winchester, Virginia
	Yes. The mole crabs on the beach were bioluminescing as a result of bacterial action. The reason they ceased to luminesce after a day in your container was probably due to the conditions in it. Bioluminescent reactions require oxygen. As the mole, crabs rotted, bacteria (both bioluminescent and nonluminescent) used up all of the oxygen in the container. As oxygen levels declined, aerobic bacteria, including bioluminescent ones, died and were displaced by nonluminescent anaerobic bacteria capable of utilizing the rotting flesh without oxygen. A constant glow is almost always indicative of bacterial or fungal luminescence. Higher plants and animals tend to produce luminescence only when they are disturbed or are in some other way activated.
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	Q&A 21.	We were told that great numbers of small, swirling, luminescent animals recently appeared at night on the surface of Manatee Bay, Florida. Apparently, these animals also released clouds of a glowing substance in the water. Could you tell us what was taking place? Miami, Florida
	In all probability, it was a swarming of the epitokes (modified, swimming, reproductive individuals) of the luminescent polychaete worm Odontosyllis enopla. Such swarmings are solely for the purpose of reproduction, and the glowing clouds were actually bioluminescent substances released along with the sperm and eggs into the water where fertilization takes place. Such swarmings are related to lunar periodicity, and the swarming time of the tropical Pacific palolo worm can be predicted with considerable accuracy by the people who net them for food. Both the Pacific palolo, Eunice viridis and the Atlantic palolo, E. schemacephala, cast off only their egg or sperm-filled hind portions, which writhe tail-first to the surface. The palolo worms, however, do not exhibit bioluminescence. Further information on the swarming of O. enopla is given in "Odontosyllis at Bermuda and Lunar Periodicity" by A. G. Huntsman (Journal of Fisheries Research Board of Canada, 7(6); 1948).
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	Q&A 22.	One evening, we anchored our boat in the Ronda Keys and watched thousands of two-inch "squiggles" glowing in the water around us. They were constantly moving, deliberately heading toward each other. When they collided, they shot out clouds of what must have been spawn. This event lasted for only about one-half hour. What was going on? Stuart, Florida
	In all probability, you observed a swarming of epitokes of the polychaete worm Odontosyllis enopla. The epitokes, which are modified swimming individuals, swarm solely for the purpose of reproduction. The glow results from bioluminescent substances released along with the sperm and eggs into the water where fertilization takes place. Such swarmings relate to lunar periods. For example, people who net the tropical Pacific palolo worm for food predict swarmings with considerable accuracy. Both the Pacific and Atlantic palolo species cast off only their egg or sperm-filled hind portions, which writhe tail-first to the water surface. The palolo worms don't exhibit bioluminescence.
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