The cannonball jellyfish (''Stomolophus meleagris''), also known as the cabbagehead jellyfish, is a species of

jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...

in the family

Stomolophidae ''Stomolophus'' is a genus of true jellyfish from the West Atlantic and Pacific. It is the only genus in the monotypic family Stomolophidae. Formerly, Nomura's jellyfish (''Nemopilema nomurai'') was also included in this genus, but has now been r ...

. Its common name derives from its similarity to a

cannonball A round shot (also called solid shot or simply ball) is a solid spherical projectile without explosive charge, launched from a gun. Its diameter is slightly less than the bore of the barrel from which it is shot. A round shot fired from a lar ...

in shape and size. Its dome-shaped bell can reach in diameter. The rim is often colored with brown pigment. There are several known undescribed ''Stomolophus'' species found in the Pacific and South Atlantic that exhibit pale to blue pigment. They are genetically different from the individuals found in the North Atlantic - but are commonly misidentified as such. 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. Cannonballs are prominent from North America's eastern seaboard to the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

Habitat

They are common on the southeastern coast of the United States, including the

Gulf Coast The Gulf Coast of the United States, also known as the Gulf South or the South Coast, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Tex ...

. 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.

Diet

Cannonballs eat mainly

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

such as

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxono ...

s, and also all forms of

red drum The red drum (''Sciaenops ocellatus''), also known as redfish, channel bass, puppy drum, spottail bass, or simply red, is a game fish found in the Atlantic Ocean from Massachusetts to Florida and in the Gulf of Mexico from Florida to northern Mexi ...

larvae. They have a

symbiotic relationship Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

with the

portly spider crab ''Libinia emarginata'', the portly spider crab, common spider crab or nine-spined spider crab, is a species of stenohaline crab that lives on the Atlantic coast of North America. Distribution ''Libinia emarginata'' occurs from Nova Scotia to th ...

, which also eats the small zooplankton. The crab feeds on the prey captured by the cannonball and also on the

medusa In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...

e of the jellyfish.

Reproduction

As in most

cnidarians Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

sexual

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...

is not an imperative way for cannonballs to reproduce. They can reproduce both sexually and asexually. 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.

Toxin

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. Although cannonballs do not commonly sting humans, they do have toxins which can, but not usually, cause cardiac problems in animals and humans. The toxin can cause irregular heart rhythms and problems in the

myocardial Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of ...

conduction pathways. Such complications are associated also with toxins of other

cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

. 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. As such they are among the most common causes of minor stings to humans in US and

Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...

waters.

Predators

One of the main predators of cannonball jellyfish is the endangered species leatherback sea turtle. Cannonball jellyfish are also commercially harvested as food for humans.

Commercial fishing

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. In Georgia, fishermen target jellyfish with modified trawl nets, and studies have shown low quantities of bycatch are typically seen in the fishery. 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.

References

''This article incorporates public domain text from the Voice of America'', at https://www.voanews.com/a/us-jellyfish-land-on-asian-dinner-tables-143681576/179134.html {{Taxonbar, from=Q311541 Stomolophus Cnidarians of the Atlantic Ocean Cnidarians of the Pacific Ocean Animals described in 1860 Taxa named by Louis Agassiz