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The cannonball jellyfish (Stomolophus meleagris), also known as the cabbagehead jellyfish, is a species of jellyfish in the family Stomolophidae. Its common name derives from its similarity to a cannonball in shape and size. Its dome-shaped bell can reach 25 cm (10 in) in diameter and the rim is sometimes colored with brown pigment. Underneath the body is a cluster of oral arms that extend out around the mouth. These arms function in propulsion and as an aid in catching prey.[2] Cannonballs are prominent from North America's eastern seaboard all the way to Brazil, but are also found in parts of the Pacific.

Cannonball jellyfish
Stomolophus meleagris.jpg
Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Scyphozoa
Order: Rhizostomae
Family: Stomolophidae
Genus: Stomolophus
Species: S. meleagris
Binomial name
Stomolophus meleagris
(Agassiz, 1860[1])

Contents

HabitatEdit

 
A cannonball jellyfish in the water near Dog Island, Florida, in the United States

Cannonballs live in warm, estuarian waters, with an average temperature of 23.1 °C (73.6 °F) and average salinities of 33.8 ppt (parts per thousand).[3]

They have been found in the northwest and east-central Pacific Ocean (South China Sea to Sea of Japan, and California to Ecuador) and the mid-west Atlantic Ocean (New England to Brazil).[4] They are common on the southeastern coast of the United States, including the Gulf Coast. On the southeast coast they are extremely abundant in the fall and summer months. During these months, cannonballs make up over 16% of the biomass in the shallow inshore areas.[5]

DietEdit

Cannonballs eat mainly zooplankton such as veligers, and also all forms of red drum larvae. They have a symbiotic relationship with the portly spider crab, which also eats the small zooplankton. The crab feeds on the prey captured by the cannonball and also on the medusae of the jellyfish.[4]

ReproductionEdit

As in most cnidarians sexual reproduction is not an imperative way for cannonballs to reproduce. They can reproduce both sexually and asexually.[6]

During sexual reproduction, cannonballs shoot sperm out of their mouth. The sperm are then caught by another cannonball through the mouth and fertilization happens. The embryo begins to develop in specialized pouches found on the arms around the mouth. After about 3–5 hours the larvae fall to the bottom and attach themselves to a hard structure. There they develop into polyps and catch small prey that swims by. After several days the polyp will detach and become a swimming ephyra, and will eventually turn into an adult jellyfish.[7]

ToxinEdit

When disrupted the cannonball secretes a mucus out of its nematocyst that contains a toxin. The toxin harms small fish in the immediate area, and drives away most predators, except for certain types of crabs.[8] Although cannonballs do not commonly sting humans, they do have toxins which can cause cardiac problems in animals and humans. The toxin causes irregular heart rhythms and problems in the myocardial conduction pathways. Such complications are associated also with toxins of other cnidaria.[9] The toxin is also harmful to the eyes; contact with a nematocyst can be very painful, followed by redness and swelling. However, cannonball jellyfish are mostly harmless to humans. Contact with them may cause the skin to itch slightly, or minor eye irritation.

PredatorsEdit

One of the main predators of cannonball jellyfish is the endangered species leatherback sea turtle. When leatherbacks migrate north from the Caribbean from April to early summer they feed on the cannonballs. Cannonballs are a main source of food for the leatherbacks, so conservation of cannonball jellyfish is important to the survival of the leatherbacks.[10]

Cannonball jellyfish are commercially harvested as food for humans.[11][12]

Commercial fishingEdit

 
Georgia jellyfish are dried, preserved and packaged before being sold to a seafood distributor that ships them to Japan, China and Thailand.

Along the coast of the southern U.S. state of Georgia, jellyfish are a valuable export, which end up on dining tables across Asia. The jellyfish are dried, preserved and packaged before being sold to a seafood distributor that ships them to Japan, China, and Thailand.

Jellyball (as they are known locally) fishing is Georgia’s third largest commercial fishery — after shrimp and crabs — but only five boats are permitted to catch them.[13] In Georgia, fishermen target jellyfish with modified trawl nets, and studies have shown low quantities of bycatch are typically seen in the fishery. [14]

Recently, Mexican coasts have experienced an increase in the abundance and frequency in blooms of this jellyfish. In 2012 El Golfo de Santa Clara harvested 20,000 tons (~$3.5 million USD) from late April to early July, which elevated the importance of this resource in the region. However, further studies need to be done in order to increase the predictability and improve the management strategies.[15]

See alsoEdit

ReferencesEdit

  1. ^ Agassiz, Louis (1860). Contributions to the natural history of the United States of America. Vol. 3. Boston: Little Brown and Co. p. 301. 
  2. ^ "Cannonball Jellyfish". Georgia Department of Natural Resources. Retrieved 2009-02-10. 
  3. ^ Griffin, Dubose B.; Murphy, Thomas M. "Cannonball Jellyfish" (PDF). Retrieved 2008-11-17. 
  4. ^ a b DuBose B. Griffin. "Cannonball Jellyfish" (PDF). South Carolina Department of Natural Resources. Retrieved 2007-11-10. 
  5. ^ SHALLOW WATER TRAWL SURVEY, SEMAP-SA. "Results of the Trawling Efforts in the Coastal Habitat of the South Atlantic Bight" (PDF). SEAMAP-SA: 72. Retrieved 2008-11-03. 
  6. ^ Daphne Gail Fautin (2002). "Reproduction of Cnidaria". Canadian Journal of Zoology. 80 (10): 1735–1754. doi:10.1139/z02-133. 
  7. ^ Whitaker, J. David; King, Dr. Rachael; Knott, David. "Jellyfish". Marine Resources Division. Retrieved 2008-11-17. 
  8. ^ Shanks, AL; Graham, WM (1988). "Chemical defense in a scyphomedusa.". Pro Quest. Retrieved 2009-01-27. 
  9. ^ Toom, PM; Larsen, JB; Chan, DS; Pepper, DA; Price, W. "Cardiac effects of Stomolophus meleagris (cabbage head jellyfish) toxin.". Retrieved 2008-11-12. 
  10. ^ Murphy, Sally; Murphy, Tom. "Leatherback Turtles" (PDF). Retrieved 2009-01-30. 
  11. ^ Jellyfish#Culinary uses
  12. ^ Hsieh, Y-H. Peggy; Leong, Fui-Ming; Rudloe, Jack. "Jellyfish as food". Hydrobiologia. 451: 11–17. doi:10.1023/A:1011875720415. Retrieved 2009-10-08. 
  13. ^ "US Jellyfish Land on Asian Dinner Tables". Retrieved 2012-03-28. 
  14. ^ Page, J.W. (2015). "Characterization of bycatch in the cannonball jellyfish fishery in the coastal waters off Georgia". Marine and Coastal Fisheries 0: 1–10. 
  15. ^ Girón-Nava, A.; López-Sagástegui, C.; Aburto-Oropeza, O. (March 2015). "On the conditions of the 2012 cannonball jellyfish ( ) bloom in Golfo de Santa Clara: a fishery opportunity?". Fisheries Management and Ecology. 22: 261–264. doi:10.1111/fme.12115. 

This article incorporates public domain text from the Voice of America, at http://www.voanews.com/english/news/usa/US-Jellyfish-Land-on-Asian-Dinner-Tables-143681576.html

Further readingEdit