When a jelly dies, its whole body swiftly
decays. The few jelly fossils that exist
are jelly prints, not jelly parts. They are
just impressions left in the sediment
where a dead jelly settled.
Cassiopea xamachana jellies are often
mistaken for sea anemones. Scientists
have used the upside-down jelly to
research the evolution of the Hox gene,
which plays a role in human development
of reproductive function.
(Non-) Jelly fact
Salps are in the phylum chordata, which
includes vertebrates. This makes them
more closely related to humans than to
Polyps and Ephyrae are two life cycle
stages. Polyps are the next stage after the
larva (fertilized egg) attaches to a surface
and grows. Ephyra are after the polyp
splits into many flat segments and then
falls off one at a time
Bittersweet Snack: Sea turtles use their
flippers to brush away the stinging cells of
jellies once they’ve had a bite. But eating
jellies can make their eyes swell from the
Blue Blubber (Catostylus mosaicus):
Often considered a Japanese and
Chinese delicacy, it is described as
crispy yet elastic. The blue color is a
result of symbiotic algae living in the
jelly. With no tentacles, the blue blubber
pulses in a distinct, quick rhythm.
Invasion: By 2000, the total weight of the
Black Sea’s comb jellies was more than
ten times the weight of all fish caught
throughout the world in a year –
Atlantic Sea Nettle (Chrysaora
quinquecirrha): This jelly is native to the
Gulf of Mexico. It feeds on comb jellies,
larval crabs and zooplankton. Oyster
fishermen are in favor of the nettles
because comb jellies feed on oysters.
For your convenience, this information sheet is also available as part of the full Amazing Jellies teachers guide pdf.
Sea jellies have lived on earth for millions of years. They can be found in all of the oceans of the world.
- Jellies are key species in the ocean food web.
- Jellies are indicators of ocean health and are fl ourishing in disturbed systems, while other species are declining.
- Human activity is causing large changes in the ocean, and we can make choices that affect future ocean health.
Jellies have seen the dawn of fishes, the extinction of dinosaurs, the ice ages and the arrival of humans. Jellies have existed for millions of years, lived in all oceans of the world, inhabited some lakes and rivers, and rarely changed. Their lack of body structure has allowed them to live simply. These transparent floaters have long been mysterious and under-studied. However, we now realize that jellies can offer significant insights into the oceans.
The upside-down jelly (Cassiopea xamachana) inhabits tropical lagoons or mangroves and has developed a symbiotic relationship with algae. By living in shallow, sunny areas, the algae converts the sunlight into food for the jelly and the jelly provides the algae with a new home. The lagoon jelly (Mastigias papua)
does this as well, but in a more aggressive manner. By following the sunrise and sunset, it minimizes the time spent in shady areas.
Jellies may be beautiful, but they’ve got bite. In addition to sharing fragile appearances, jellies seem to share huge appetites. Most are hungry predators of other zooplankton, krill, copepods, larval fishes and fish eggs. Jellies, except for ctenophores, move with the currents to sting prey. Their nematocysts (stinging cells) stun and kill prey. They then transfer food to their mouths by oral arms.
Seasonal jellies appear when the water is warm and die when it gets cold. Global warming causes water to warm earlier in the spring and stay warm further into fall. This allows jellies to begin feeding earlier in the season and continue feeding later. Warmer water also speeds up the jelly metabolism, causing them to reproduce faster.
Although jellies are mostly water, they are a main food source for animals such as sea turtles (especially leatherbacks and loggerheads) and fish (salmon and ocean sunfish). In Japan, Korea and China, people dehydrate and eat jellies.
Rising jelly populations have caused problems in many ocean areas. Jellies consume fish eggs and larvae. Booming populations of jellies can affect regional fisheries because they often compete for the same food. A jelly’s own survival is more certain when it has eaten its predator!
Pollution affects the health of the oceans and often causes the numbers of animal populations to decrease. So why are pollution and overfertilization not problems for hardy jellies?
Fertilizer from lawns, farms, etc. runs into lakes, streams and eventually into the ocean, causing the presence of excess nutrients. Phytoplankton thrive on excess nutrients and grow rapidly, giving off oxygen. The phytoplankton eventually die and rot, using up oxygen in the water. This process is called eutrophication. Animals such as large fish, sea turtles and shrimp can escape, but others, such as larval fishes, mollusks and crabs cannot. Jellies live successfully in low-oxygen levels and feed on their stunned, oxygen-deprived prey.
It’s good to be a jelly in the Gulf of Mexico. The populations of native jellies have increased in recent years. In addition, new species such as Australia’s spotted jelly and the Caribbean’s big pink jelly have moved in. These swarms have depleted the larval fish stocks and have made it difficult for fishermen to cast their nets.
The jellies also thrive because they can survive in the Dead Zone, an area encompassing 7,000 square miles of the Gulf of Mexico that becomes oxygen-depleted during the summer. Across the ocean, another area is affected by jellies, specifically comb jellies. Introduced into the Black Sea in the 1980s through ballast water, the comb jellies have survived free of competition. With no natural predators and voracious appetites, these ctenophores have caused the extinction of several commercial fisheries.
In 1997, a jelly that feeds on the comb jellies was introduced through ballast water into the Black Sea. The populations have decreased, but the ecological damage has already been done. The fishing industry has lost $350 million and tourism has fallen.
Fish decline while jellies thrive in unhealthy oceans. Your choices can turn the tide. Whenever you use less electricity or gasoline, you are helping to stop global warming.
- Use public transportation.
- Line dry your laundry when possible.
- Use a fan instead of air-conditioning.
- Learn more about conservation
Overfishing threatens the population of jelly predators and changes the balance of ocean ecosystems.
- Ask your supermarket to label where their fish is caught.
- Diversify. Choose a variety of sustainably harvested fish.
- Learn more about sustainable fisheries and the Aquarium's research and conservation efforts
- Anderson, J. and Bertrand, J.F., “NEAq Moon Jellies update,” July 1994.
- www.aquariumofpacifi c.org/CURRENT_EXHIBIT/Jellies/jellies_species_list.htm, viewed August 2003.
- Bornhofft, L. and Engeldrum, L. “Living Links: An Interpretation Guide,” New England Aquarium Publication, 2003.
- Finnerty, J.R., and Martindale, M.Q., “Ancient origins of axial paltering genes: Hox genes and ParaHox genes in the Cnidaria,” Evolutionary Development, 1999.
- Gowell, E. “Sea Jellies: Rainbows in the Sea,” New England Aquarium Publication, 1993.
- Gowell, E. “Amazing Jellies: Jewels of the Sea,” Bunker Hill Publishing, Boston, 2004.
- www.mbayaq.org, viewed July 2003.
- www.oceanexplorer.noaa.gov/explorations/02arctic/logs/aug31/media/Chrysaora.html, viewed August 2003.
- Pearlman, M., content development for Amazing Jellies, 2004.
- www.tnaqua.org/special/ecnettle.html, viewed August 2003.
- Whiteman, J., “The Blobs of Summer,” Onearth, Vol.24, No.2, Pgs. 15-19, Summer 2002.
- www.marinestingers.com.au/marinestingers/pdfs/Catostylus.pdf, viewed July 2003.