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Last updated: July 24, 2014

Northwest District Envirofact Northwest District - Envirofact/Jellyfish and Sea Nettles


Sea Nettles-Photograph by Cheryl Bunch

Sea Nettles (Chtysaora quinquecirrha)

Known for its tentacles which contain toxins used to paralyze and capture prey, these jellyfish also cause painful and annoying stings to swimmers who happen to cross their path. The sea nettle is known for its tolerance to a wide range of salinities and can reportedly live in habitats varying from 10-35 PPT. At lower salinities, they are white in color and where salinities are higher, they often have reddish marking along the central tentacles and swimming bell.



Dead Cannonball Jellyfish at Santa Rosa Sound  Pensacola Beach, Florida-photographer Cheryl Bunch


Cannonball Jellyfish (Stomolophus meleagris)

Commonly known to inhabit the Southeastern Coast and the Gulf of Mexico and its dome shaped bell can reach up to 10 inches in diameter with eight arms that extend from the mouth which aid in movement and capturing prey. This jellyfish is eatable and known for is nutritional value as well as being low in fat and cholesterol but caution must be emphasized as they should only be eaten when caught and prepared properly. They eat mainly zooplankton and red drum larvae and are themselves an important food source for the leatherback turtle whose survival depends on them. They expel a neurotoxin that harm fish and drive off predators. They can sting humans and although normally mild reactions occur, exposure to the eyes can be severe as well as possible heart problems have been reported. It is recommended to avoid contact with this local jellyfish.


Portuguese Man O' War


Portuguese Man o' War (Physalia physalia)

Although commonly thought of as a jellyfish because of its sever stinging ability, the Portuguese Man o' War is a species called a siphonophore, which is made up of multiple organisms or a colony of organisms that function together in a symbiotic relationship allowing it to thrive in a marine environment. This invertebrate is comprised of four polyps (or zooids). The uppermost polyp, a pneumatophore, is a gas filled purple-blue bladder which transports the colony using currents and winds. Commonly referred to as "bluebottles" because of this bladder, the man o' war is thought to resemble an old English warship at full sail.
Other zooids in the colony control digestive and reproductive functions.

The colony organism of concern to the relational swimmer is the long tentacles, averaging 30 feet in length, which are covered by venom-filled nemocysts used to paralyze the prey of this carnivorous animal. Although rarely deadly, its venomous sting can be very painful and accompanied by such serious effects that medical attention is advised. Even dead the man o' war is dangerous and contact with the tentacles should be avoided.



Moon Jellyfish

Moon Jellyfish (Aurelia aurita)

Present in Florida panhandle waters. Contact does not normally produce stings in humans.


Reference Source:

Moon Jellyfish Woods Hole Oceanographic Institute
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