The cannonballjellyfish, 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 in diameter and, in the Atlantic and Gulf of Mexico, the rim is sometimes colored with brown pigment. In the Pacific, this jellyfish can also have a blue 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. Cannonballs are prominent from North America's eastern seaboard all the way to Brazil, but are also found in parts of the Pacific.
Habitat
They have been found in Pacific Ocean and the mid-west Atlantic Ocean. 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.
Diet
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.
Reproduction
As in most cnidarianssexual reproduction 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 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. 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.
Predators
One of the main predators of cannonball jellyfish is the endangered speciesleatherback 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 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 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.
