JELLYFISH AS PREY
Jellyfish are preyed on by sea anemones, some birds and some sea turtles. Fish generally don't mess with them because of their toxic and watery tissue.
Since jellyfish are mostly water a predators has to consume a lot of them to get enough nourishment to make it worthwhile. Moreover, they need to get rid of a lot of water. Sunfish, leatherback turtles and some other fish species have pharyngeal "teeth" at the back their throats. After swallowing a jellyfish they regurgitate it against these teeth, which strains out the water and leaves behind the edible material which is swallowed and digested.
To protect themselves from predators some jellyfish shed their tentacles as a diversion. Some even light up their attackers with bioluminescence so predators that feed on the attackers will feed on them before they get to the jellyfish. Their best protection is that they are nearly transparent sea water predators can’t pick them out.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Jellyfish, Turtles and Salmon
Sea turtles are among the few creatures that feed on jellyfish. Leatherback turtles feed almost exclusively on jellyfish. They play an important ecological role by eating jellyfish that feed on the fry of tuna and swordfish and other fish. They usually feed at the surface but are capable of making deep dives.
Autopsies of dead leatherbacks have revealed they have huge stomachs, often filled with masses of relatively low-calorie and mostly-water jellyfish, stingers and all. Massive salt glands collect excess salt from the jellyfish and excrete it as viscous tears. A favored prey is the lion’s mane. Among the largest jellyfish, it can weigh more than five kilograms. Leatherback turtles, sunfish and some other species have backward-pointing pharyngeal "teeth" at the back their throats that prevent slippery prey from sliding back out their mouths. After swallowing a jellyfish they regurgitate it against these teeth, which strains out the water and leaves behind the edible material which is swallowed and digested.
Jellyfish offer little nutrition and sustenance. Like pandas eating bamboo, leatherbacks have to eat a lot of jellyfish and spend a lot of time eating it to get enough calories to power their large bodies. By some estimates leatherbacks need to eat their weight in jellyfish every day to get the nutrition they need. One turtle video taped devoured 60 lion’s mane jellyfish in three hours.
In August, 2002, dense shoals of tiny jellyfish killed almost one million salmon at fish farms in the Western Isles in Scotland. It is thought that the jellyfish — known as Solmaris — may have found their way to Scottish waters from the Pacific Ocean. They killed the salmon by stinging them and clogging up their gills. Fish with an estimated value of more than $ 3 million were destroyed at two farms off the Isle of Lewis. Vast blankets of jellyfish moved up the sea lochs where the salmon cages are moored. [Source: BBC]
The larger fish were suffocated while smaller ones were stung to death. Western Isles Sea Foods said almost all the fish at the two farms had been destroyed. Managing director Alan Anderson said 750,000 fish were lost at one site and 150,000 at the other. The dead fish are being taken away by boat to a fish meal factory in Shetland. It is thought the jellyfish made their way into the Atlantic from the Pacific by attaching themselves to vessels passing through the Panama Canal in Central America.
Jellyfish and Humans
Korean jellyfish dish Jellyfish are the scourge of many swimmers, who find large numbers of floating in the water at some beaches, and fishermen, who find them fowling their nets. Jellyfish have done well in places that have been overfished. With fish they competed with for food gone and turtles that fed on them also gone they consume plankton and their population explodes.
Spicy jellyfish salad and soup are popular in China, South Korea and Japan. Of the 200 or so species of jellyfish, only about 10 are commercially harvested, The largest fisheries are off China and other Asian nations, new ones are being developed in Australia, the United States, Britain, Namibia, Turkey and Canada. Some fishermen have given up fishing and chosen to devote their energy to catching jellyfish for Asian seafood market.
Jellyfish are being studied for various medical applications. A rhesus monkey has been genetically engineered to have jellyfish DNA in every one of its cells. The manipulation was done as step towards genetically manipulating human cells to fight disease. Powerful toxins from the irukandji jellyfish are being studied as a possible cure for impotence
At Okayama University in Japan a team of researchers led by Prof. Toshiyoshi Fujiwara is using genes from fluorescent jellyfish to make cancer cells glow green to understand where the cells will spread and to what extent thereby reducing the amount of tissue needed to be removed in surgery.
Bioluminescent Jellyfish and the Nobel Prize
Florescent protein extracted from a North Pacific jellyfish have been used to make the human brain glow so its cells can be studied by scientists. The same protein has been used to make green-glowing engineered mice and provide color for the film version of the Hulk.
In 2008, Japanese biologist Osamu Shimonmura won the Noble Prize in Chemistry for discovering and developing a glowing jellyfish protein that has helped shed light on such key processes as the spread of cancer, the development of brain cells, the growth of bacteria, damage to cells by Alzheimer’s disease, and the development of insulin-producing cells in the pancreas.
Osamu Shimomura works at the Marine Biological Laboratory in Wood Hole, Massachusetts and the Boston University Medical School. He discovered the jellyfish protein, green fluorescent protein, or GFP, after extracting it from 100,000 jellyfish caught off the coast of Washington state, and figured out how to isolate it. American Martin Chalfie and Roger Tsien explored how it worked and applied it to medicine and other fields.
Shimomura needed a large number of jellyfish to extract and refine GFP. He collected them with the help of students, assistant researchers and his wife and kids. At certain times of the years the jellyfish that bore GFP — “Aequora victoreai” “were so thick local people said you could walk on water. For his research Shimomura needed about 3,000 jellyfish a day which were collected from a pier with long-handled nets and buckets. Many locals thought he intended to eat the jellyfish as sashimi. Over the past decade the number of jellyfish off the Washington coast have declined drastically and it is no longer easy to collect huge masses of them.
Cutting up the jellyfish was another problem. At first Simomura used scissors but later refashioned a meat slicer that he bought at a hardware store. He then dedicated himself to extracting and purifying GFP. In 1979 Shimomura unraveled the structure of GFP and discovered how it became luminous. At this juncture in his career he showed one scientist a fluid solution of GFP, saying “This has been purified from 100,000 jellyfish.”
GFP turns green when exposed to ultraviolet light and easily attaches to other protein whose movements can be tracked. . The Swedish Academy compared the discovery GFP to the development of the microscope and said the protein has been “a guiding star for biochemist, biologist, medical scientists and other researchers.” Shimomura told the Daily Yomiuri, “I was able to extract aequorin because I thought other researchers ideas were wrong...I became successful because I tried to extract only the illuminating substance.”
Relieving Jellyfish Stings
If you get stung by a jellyfish some people recommend applying meat tenderizer, vinegar or even urine to relieve the sting.
According to the University of Hawaii: Cnidarian venom is a protein. The best way to treat a sting is to break down the protein chemically with a “sting kill” medication or meat tenderizer. Because heat also helps to break down proteins, hot water can be used on a sting. Some people develop an allergic reaction to the venom after repeated stings. It is important to seek medical help for a sting victim who faints or shows signs of unusual swelling or breathing distress. [Source: University of Hawaii]
According to the Medicine Man on HealthExpertAdivce.com, “The theory of urinating on a sting is that the urine contains some ammonia which helps with the stinging. Ideally vinegar is what you'd want to use, though unseasoned meat tenderizer, baking soda, or one-quarter-strength household ammonia can be used. Never wash the sting with fresh water. Use salt water if nothing else as fresh water may release more venom. Taking Benadryl, along with using an ice pack and treating the sting with bacitracin afterwards for about 3 days is what you'd ultimately want to wind up doing.”
According to stupidquestion.net: “Susan Scott, “Oceanwatch” columnist for the Honolulu Star-Bulletin, has investigated jellyfish stings in the field (as well as in the lab) probably as much as anyone, having spent years visiting injured tourists and the like on Hawaii’s beaches. A registered nurse, she and husband Dr. Craig Thomas authored “All Stings Considered: First Aid and Medical Treatment of Hawaii’s Marine Injuries.” In her column in 2001, Scott summed up years of study on a variety of sting “cures”: “Nothing worked.” In an e-mail to me, she summed it up another way: “Anything works.” This paradox goes to the heart of the urine myth. “Nothing worked” means that none of the main folk remedies — including urine, meat tenderizer and commercial sprays — did anything to stop the pain of a sting. On the other hand, “Anything works,” because the vast majority of jellyfish stings are not severe and their effects disappear within a few hours at most, no matter whether you urinate on yourself or simply do nothing.
Giant Jellyfish Invade Japan
Echizen jellyfish — nasty creatures that can weigh up to 200 kilograms and reach a size of two meters in diameter — have caused havok in the Japanese fishing industry, particularly in the Sea of Japan off of Fukui, Shimane and Ishikawa Prefecture in western Honshu. The jellyfish have brown poisonous tentacles that kill fish and cause them to lose their color. Their huge numbers spoils fish catch and fouls fishing nets with a nasty smell. Their massive weight tears the nets when they are pulled out of the water.
The damage to the fishing industry has been in the tens of billions of yen. On fisherman told the Yomiuri Shimbun, “The nets were fouled by hundreds of jellyfish as soon as they were put out. There was little room for other fish, The fish that touched the tentacles of the jellyfish turned white, and the retail value of the fish is reduced to zero.”
The jellyfish population explosions have been blamed on global warming, increased nutrients in the water, and overfishing of jellyfish competitors. In the old days Echizen jellyfish disappeared by the time the autumn fishing season peaked. But warmer waters, perhaps caused by global warming, have caused the jellyfish to stick around longer than in the past. Some blame China for the problem, saying the jellyfish originate in waters off the coast China and their growth has been triggered by pollutants dumped in the sea.
giant jellyfish off Japan Large masses of jellyfish are called blooms, swarms or smacks. Jellyfish blooms make waters off of popular beaches unswimmable, clog seawater intake valves for nuclear power plants, foul fishing nets and catches. Jellyfish blooms sometimes wipe out all the larvae during mass spawns. They can all eat up large amount anchovies and similar fish and can deprive larger fish of food.
No one knows what causes jellyfish blooms. Pollution and fertilizer run-off may be causes. They create increase of plankton which suck oxygen from the water, creating an environment in which jellyfish thrive. Global warming may play a role by heating up the water to above-normal temperatures, creating conditions in which jellyfish are more likely to bloom. Jellyfish do well in conditions created by global warming. Nearly all jellyfish breed better and faster in warmer waters Dr. Jennifer Purcell, a jellyfish expert at Shannon Point Marine Center of Western Washington University told the New York Times.
Jellyfish blooms may also be partly the result of overfishing of species like sharks, swordfish, tuna, oysters and cod that eat the same sea creatures that jellyfish feed on. Overfishing also seems to have benefitted jellyfish by removing fish as competitors for plankton, their food, and allowing them to bloom out of control.
Jellyfish do well in oxygen-poor “dead zones” because their bodies are 95 percent water and hold enough oxygen to support them when they drift into oxygen-poor waters. They thrive in such zones because they also often have plentiful in food and low in fish competitors in part
In recent years huge swarms of jellyfish with numbers unseen before have been showing in places around the globe — from Spain to New York to Hawaii to Australia to Japan — where they hadn’t been seen before with a frequency and timing that are so alarming that some scientists suggest they may be a sign that the oceans are in decline. [Source: New York Times]
Huge swarms in Spain made headlines. "Spectacular growth has been found in jellyfish populations in Japan, Namibia, Alaska, Venezuela, Peru, Australia ... this is an international ecological problem," Josep-María Gili, at the Barcelona-based Institute of Marine Sciences (ICM),i said. In December 2007 hundreds of swimmers were stung off south-eastern Brazil.
Fishermen are also feeling the strain. Many of them complain when they pull up their nets they are often filled more with jellyfish than with fish.
Causes of Jellyfish Swarms
Jellyfish swarm often appear in seas that have been overfished. They can make matters worse by feeding on larvae and eggs and competing for food such as zooplankton. According to a report by the National Science Foundation: “Human-caused stresses including global warming and overfishing, are encouraging jellyfish surpluses in many tourist destinations and productive fisheries.”
The Guardian reported: Global warming has also brought about the ideal conditions for jellyfish to breed: mild temperatures, little rain and a lack of the usual winter rainstorms. Plagues of jellyfish are nothing new — they often recur in cycles of up to 10 years, but recently, these cycles have become ever shorter, and the blooms more widespread and populous. According to Josep-María Gili, at the Barcelona-based Institute of Marine Sciences (ICM), the recent growth in jellyfish numbers "is a message from the sea that something is wrong. People need to realise that fish, especially adult fish, play an important role in the sea — they are the principal carnivores. We must change the laws about overfishing and the type of fishing." [Source: Paul Hamilos in Madrid, The Guardian, February 29, 2008]
Dr Reyes Tirado, at the Greenpeace research laboratories in Exeter, said the plagues were not just caused by overfishing: "Our activities on land also play a big part ... overloading of coastal waters with nutrients both from sewage and from agricultural fertiliser runoff are also important," she said. "Excess nutrients can have disastrous effects on estuaries and coasts, causing blooms of harmful algae and helping jellyfish populations to increase. "Add to these factors the warmer waters and changing marine currents caused by climate change and the problem of jellyfish invasions seems set to get much worse in the future."
Decreases in leatherback turtles have also been blamed. A principal jellyfish predator, they have been driven to the point of extinction because the beaches where they lay eggs have been used for tourism. In 2016 Israeli researchers found that 94 percent of jellyfish swarms that occur in Israel arrived after the middle of the year when the seas are warmer and during the second and third weeks of the lunar month. [Source: AFP, August 25, 2016
Jellyfish Swarms in Spain
In 2012, swarms of mauve jellyfish invaded Spain's Costa del Sol beaches and a large number of tourists were stung. The BBC reported: “Holidaymakers on Spain's Costa del Sol have been warned of large numbers of stinging jellyfish in seas around the Malaga coastline. Spain's tourism ministry said overfishing, winds and ocean currents had caused blooms of jellyfish to gather around coves and beaches. Red flags are being raised when a bloom is seen close to popular areas. Other reports have said about 1,000 people in Malaga been treated for jellyfish stings. "The 'blooms' of jellyfish rarely last more than 48 hours and in the vast majority of cases jellyfish stings are harmless," Spain's Tourist Office said in a statement, without giving details of the breed of jellyfish involved. [Source: BBC, July 12, 2012]
Invasions of mauve stinger jellyfish on Spain's coastal waters are not unusual and have been reported in the past. In August 2010 beaches in Alicante and around San Sebastian in the north were hit by swarms of the scyphozoa, including more venomous jellyfish such as the Portuguese man o'war.
In 2006, the Red Cross treated 21,000 people who had been stung on the beaches of Catalonia, while on a single day in August, 400 bathers were treated at a beach in Málaga. ne swarm that hit beaches in Barcelona left 300 people needing treatment for stings and sent 11 to the hospital. Dr. Joseph-Maria Gili, a leading Spanish jellyfish expert, told the New York Times, “These jellyfish near the shore are a message the sea is sending is, saying, “Look how badly you are treating me.” An offshore swarm of “Pelagia noctiluca” “an iridescent purplish jellyfish that issues a nasty sting — more than 1.6 kilometers long was spotted off Murcia, Spain.
In November 2007, scientists at the Barcelona-based Institute of Marine Sciences (ICM) began studying the life cycles of jellyfish off the Costa Brava, and were alarmed to detect large numbers of the Pelagia noctiluca, commonly known as the "mauve stinger", growing in the winter, ready for an assault on Spain's beaches. The study revealed that jellyfish proliferate throughout the year, not just in the summer. Between November and January, scientists discovered 30 colonies, or blooms, ranging in size from four to 10 jellyfish per cubic meter of water, all along the Catalan coast. [Source: Paul Hamilos in Madrid, The Guardian, February 29, 2008]
According to Josep-María Gili, research professor at the ICM these groups were born last autumn, and the summer tides will carry them inland from deeper waters, causing the plagues that have seen millions of jellyfish wash up on Spain's beaches in recent years. "The problem seen on the beaches is not the main concern for scientists," said Professor Gili, "For us the major worry is the global disequilibrium in the sea caused by overfishing."As a result of overfishing, the jellyfish do not have to face their usual predators and competitors, which usually regulate population growth. Numbers of large fish such as swordfish and red tuna, which eat jellyfish, have been drastically reduced by bad fishing practices, as have the smaller fish, such as sardines and whitebait, which compete for food with the stingers.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023