The South Carolina Department of Natural Resources published a series of educational webpages and brochures on marine science. This issue focuses on jellyfish

King, Rachel

Knott, David

Whitaker, J. David

South Carolina State Documents Depository

Few marine creatures are as 
mysterious and intimidating 
as jellyfish. Though easily 
recognized, these animals are 
often misunderstood. Some 
bathers and beachcombers react 
with fear upon encountering 
these invertebrates, but, in fact, 
most jellyfish in South Carolina 
waters are harmless. This article 
was prepared to help coastal 
residents and vacationers learn the 
difference between the jellyfish to 
avoid and the ones you can safely 
ignore. 
Jellyfish are members of the 
phylum Cnidaria, a structurally 
simple marine group of both 
fixed and mobile animals: sea 
anemones, sea whips, corals and 
hydroids are polyps that grow 
attached to rocks or other hard 
surfaces; jellyfish and colonial 
siphonophores like the Portuguese 
man-of-war are mobile (either 
actively swimming or subject to 
winds and currents). Inherent 
to both types of life history is 
their radial symmetry (body parts 
radiating from a central axis). This 
symmetry allows jellyfish to detect 
and respond to food or danger 
from any direction. 
Instead of a brain, jellyfish 
possess an elementary nervous 
system, or nerve net, which 
consists of receptors capable 
of detecting light, odor and 
other stimuli and coordi na ting 
appropriate responses. 
Jellyfish are composed of 
an outer layer (epidermis), 
which covers the external body 
surface, and an inner layer 
(gastrodermis), which lines the 
gut. Between the epidermis and 
gastrodermis is a layer of thick 
elastic jellylike substance called 
mesoglea (“middle jelly”). Jellyfish 
have a simple digestive cavity, 
(coelenteron), which acts as a 
gullet, stomach and intestine, with 
one opening for both the mouth 
and anus. Four to eight oral arms 
are located near the mouth and 
are used to transport food that has 
been captured by the tentacles to 
the mouth.
Jellyfish come in a wide variety 
of sizes, shapes and colors. Most 
are semi-transparent or glassy and 
bell-shaped, measuring less than 
an inch to more than a foot across 
the bell, although some may reach 
7 feet in diameter. The tentacles 
of some jellyfish can reach lengths 
General medusa body plan
Jellyfish
tentacles
gonad
oral arm
bell
stomach
mouth
water column. After several days 
the larvae attach themselves to 
something firm on the sea floor 
(rocks, shells, etc.) and gradually 
transform into flower-like polyps 
(scyphistoma). These polyps use 
tentacles to feed on microscopic 
organisms in the water column. 
Polyps can multiply by producing 
buds or cysts that separate from 
the first polyp and develop into 
new polyps. When conditions 
are right, fully developed polyps 
develop constrictions in their 
bodies that eventually produce a 
larval stage (the strobila), which 
resembles a stack of saucers. Each 
individual saucer develops into a 
tiny jellyfish (ephyra stage), which 
separates itself from the stack and 
becomes free swimming. In a few 
weeks, the ephyra will grow into 
an adult jellyfish (medusa), thus 
completing the complex life cycle. 
Jellyfish normally live for a few 
months; however, the polyp stage 
may be perennial. 
Locomotion
The adult jellyfish drifts in the 
water with limited control over 
its horizontal movement. It is, 
however, endowed with muscles 
that allow it to contract its bell, 
reducing the space under it and 
forcing water out through the 
opening. This pulsating rhythm 
allows for regulation of vertical 
movement. Because jellyfish are 
sensitive to light, this vertical 
movement can be important. 
Some jellyfish, like the sea wasp, 
descend to deeper waters during 
the bright sun of the midday and 
surface during early morning, late 
afternoon and evening. Despite 
this ability to move vertically, 
jellyfish largely depend upon 
ocean currents, tides and wind for 
horizontal movement.
Food
To some, jellyfish may appear to 
have no apparent value, but they 
are, in fact, a very important part 
of the marine food web. Jellyfish 
are carnivorous, feeding mostly on 
a variety of zooplankton, comb 
jellies and occasionally other 
jellyfish. Larger species, however, 
are capable of capturing and 
devouring large crustaceans and 
other marine organisms. Jellyfish 
are themselves preyed upon by 
spadefish, sunfish, sea turtles and 
other marine organisms. Some 
species, including the mushroom 
and cannonball jellyfish, are even 
considered a delicacy by humans.
Pickled or semi-dried mushroom 
jellyfish are consumed in large 
quantities in Asia, where they 
constitute a multimillion-dollar part 
of the seafood business.
greater than 100 feet. Regardless 
of their size or shape, most jellyfish 
are very fragile, often containing 
less than 5% solid organic matter. 
Jellyfish inhabit every major 
oceanic area of the world and 
are capable of withstanding a 
wide range of temperatures and 
salinities. Most live in shallow 
coastal waters, but a few inhabit 
depths of 12,000 feet! 
Life Cycles
The life cycle of a typical 
jellyfish is complex and involves 
an alteration of generations in 
which the animal passes through 
two different body forms. The 
dominant and conspicuous 
medusa is the familiar form, 
while the smaller polyp form 
is restricted to the larval stage. 
Jellyfish reproduce sexually, and 
individuals are either male or 
female. The reproductive organs 
(gonads) develop in the lining of 
the gut. During reproduction, the 
male releases sperm through its 
mouth into the water column. 
Some of the swimming sperm 
are swept into the mouth of the 
female, where fertilization occurs. 
Early em bryo nic development 
begins either inside the female 
or in brood pouches along the 
oral arms. Small swimming larvae 
(planulae) leave the mouth or 
brood pouches and enter the 
medusa
polyp
ephyra
budding
polyp
planula
larva
Jellyfish life cycle
are harmful to humans. Although 
jellyfish do not “attack” humans, 
swimmers and beachcombers 
can be stung when they come 
into contact with the jellyfish 
tentacles with functional 
nematocysts. The severity of the 
sting depends on the species of 
jellyfish, the penetrating power 
of the nematocyst, the thickness 
of exposed skin of the victim and 
the sensitivity of the victim to the 
venom. The majority of stings from 
jellyfish occur in tropical and warm 
temperate waters. Most species off 
the southeastern coast are capable 
of inflicting only mild stings that 
result in minor discomfort. 
Local Jellyfish
Although most jellyfish that 
inhabit South Carolina waters are 
harmless to humans, a few require 
caution. Learning how to identify 
the different species can help you 
decide which ones can be safely 
ignored.
cannonball Jelly  
(Stomolophus meleagris) 
(Also known as the jellyball, and 
the cabbage head jelly)
Cannonball jelly fish are the most 
common in our area. During the 
summer and fall, large numbers of 
this species appear near the coast 
and in the mouths of estuaries. 
Cannonball jellies can be easily 
identified by their round white 
bells that are bordered below by a 
brown or purple band of pigment. 
They have no tentacles, but they 
do have a firm, chunky feeding 
apparatus formed by the joining of 
the oral arms. Cannonballs rarely 
grow larger than 8-10 inches in 
diameter. They are considered 
to be pests by commercial trawl 
fishermen because they clog and 
damage nets and slow down 
sorting and trawl times, although 
turtle excluder devices in trawl nets 
somewhat alleviate that problem. 
Fortunately, this species is one of 
the least venomous of our jellyfish.
lion’s mane 
(Cyanea capillata)
Also know as the winter jelly, the 
lion’s mane typically appears during 
colder months of the year. The bell, 
measuring 6-8 inches, is saucer-
shaped with reddish-brown oral 
arms and eight clusters of tentacles 
hanging underneath. Cyanea are 
generally considered moderate 
stingers. Symptoms are similar to 
those of the moon jelly but, usually 
more intense. Pain is relatively mild 
and often described as burning 
rather than stinging.
mushroom Jelly  
(Rhopilema verrilli)
The mushroom jelly is often 
mistaken for the cannonball jelly, 
but it differs in many ways. The 
larger mushroom jelly, growing 
10-20 inches in diameter, lacks 
the brown band associated with 
the cannonball and is much flatter 
and softer. Like the cannonball, the 
mushroom jelly has no tentacles 
Venom Apparatus
Jellyfish are equipped with a 
special ized venom apparatus 
(cnidoblast) for defense and 
feeding. A capsule (nematocyst) 
inside the cnidoblast contains a 
trigger and a stinging structure. The 
stinging structure varies according 
to species but generally consists of 
a hollow coiled thread with barbs 
lining its length. Nematocysts are 
concentrated on the tentacles 
or oral arms. A single tentacle 
can have hundreds or thousands 
of nematocysts embedded in 
the epidermis. Nematocysts are 
activated when tentacles make 
contact with an object. Pressure 
within the nematocyst forces the 
stinging thread to rapidly uncoil. 
The thousands of nematocysts act 
as small harpoons, firing into prey, 
injecting paralyzing toxins. 
Stings usually paralyze or kill 
only small creatures (fish, small 
crustaceans), but some jellyfish 
cannonball Jelly
lion’s mane
nematocyst after discharGe
nematocyst before discharGe
trigger
hollow
thread
major barb
cnidoblast
nematocyst
major barb
cnidoblast
nematocyst
trigger
and chunky feeding apparatus; 
however, it possesses long finger-
like appendages hanging from the 
feeding apparatus. This species 
is also considered a pest by 
commercial fishermen, but they 
are much less of a problem than 
cannonball jellies. The mushroom 
jelly does not represent a hazard 
to humans.
southern moon Jelly  
(Aurelia marginalis) 
Probably the most widely 
recognized jellyfish, the moon 
jelly is relatively infrequent in 
South Carolina waters. It has a 
transparent, saucer-shaped bell 
and is easily identified by the four 
pink horseshoe-shaped gonads 
visible through the bell. It typically 
reaches 6-8 inches in diameter, 
but some are known to exceed 20 
inches. Recent evidence suggests 
that there are several similar-
looking species of moon jellies 
within a group of species that were 
once called the moon jelly, Aurelia 
aurita. The southern populations, 
including those in South Carolina, 
are now considered to be a 
distinct species (A. marginalis).
The moon jelly is only slightly 
venomous. Contact can produce 
symptoms from immediate prickly 
sensations to mild burning. Pain 
is usually restricted to immediate 
area of contact. 
sea nettle 
(Chrysaora quinquecirrha) 
The sea nettle is frequently 
observed in South Carolina waters 
during summer months. This 
jellyfish is saucer-shaped with 
brown or red pigments, usually 
6-8 inches in diameter. Four oral 
arms and long marginal tentacles 
hang from the bell and can extend 
several feet. Considered moderate 
to severe, symptoms from sea 
nettle stings are similar to those of 
the lion’s mane. Given that they 
are most abundant in the summer, 
when the greatest number of 
people are likely to be swimming 
in the ocean, this species is 
thought to be responsible for most 
of the jellyfish stings that occur in 
South Carolina. Exercise caution 
if sea nettles are observed in the 
water, and do not swim if large 
numbers are present. 
sea Wasp 
(Chiropsalmus quadrumanus)
Known as the box jelly because 
of its cube-shaped bell, the sea 
wasp is the most venomous 
jellyfish inhabiting our waters. 
Their potent sting can cause 
severe dermatitis and may even 
require hospitalization. Sea wasps 
are strong, graceful swimmers 
reaching 5-6 inches in diameter 
and 4-6 inches in height. Several 
long tentacles hang from the four 
corners of the cube.
A similar species, the four-
tentacled Tamoya haplonema, also 
occurs in our waters. 
portuGuese man-of-War
portuguese man-of-War
(Physalia physalis)
Although a member of the 
phylum Cnidaria, the Portuguese 
man-of-war  is not a “true” 
jellyfish. These animals consist of 
a complex colony of individual 
members, including a float, 
modified feeding polyps and 
reproductive medusae.
Physalia typically inhabit the 
warm waters of the tropics, sub-
tropics and Gulf Stream. Propelled 
by wind and ocean currents, they 
sometimes drift into nearshore 
waters of South Caro lina. Though 
they infrequently visit our coast, 
swimmers should learn to iden tify 
these highly venomous creatures. 
The gas-filled float of the man-
of-war is purple-blue and can 
reach lengths of 10 inches. Under 
the float, tentacles equipped with 
thousands of nemato cysts hang 
from the feeding polyps extending 
as  much as 30 to 60 feet. 
The man-of-war can inflict 
extremely painful stings. Symptoms 
include severe shooting pain 
described as a shock-like sensation, 
and intense joint and muscle 
pain. Pain may be accompanied 
by headaches, shock, collapse, 
sea nettle
moon Jelly
faintness, hysteria, chills, fever, 
nausea and vomiting. 
 Initial contact with Physalia 
may result in only a small number 
of stings. However, efforts to 
escape from the tentacles may 
further discharge nematocysts 
and intensify stings. Care should 
be taken when removing the 
adhering tentacles. Severe stings 
can occur even when the animal 
is beached or dead. Another 
jellyfish that could potentially be 
confused with the man-o-war is 
the Vellela vellela, which has the 
common name of “by-the-wind-
sailor.” This relatively small (4 
inches) colonial hydrozoan has a 
bright blue bladder. It is typically 
oceanic but may be blown into 
coastal waters. This species is of 
little threat to humans, causing 
perhaps a mild tingling. Given the 
significant danger of Physalia, all 
jellyfish having a blue float should 
be considered dangerous unless 
specified by an expert. 
Treatment of Sting
Primary first aid for any jellyfish 
sting should be to minimize the 
number of nematocysts discharging 
into the skin and to reduce the 
harmful effects of the venom. 
 If stung by a jellyfish, the 
victim should carefully remove 
the tentacles that adhere to the 
skin by using sand, clothing, 
towels, seaweed or other available 
materials. As long as tentacles 
remain on the skin, they will 
continue to discharge venom. 
A variety of substances have 
been used to reduce the effects 
of jellyfish stings. Meat tenderizer, 
sugar, vinegar, plant juices and 
sodium bicarbonate have all 
been used with varying degrees 
of success. Methylated spirits and 
other forms of alcohol formerly 
recommended for inhibiting 
stinging cells actually stimulate 
them and may increase pain and 
cause severe skin reactions. Picric 
acid and human urine also cause 
a discharge of nematocysts and 
should not be used.
Victims of serious stings should 
make every effort to get out of the 
water as soon as possible to avoid 
drowning. If swelling and pain 
from more serious stings persist, 
prompt medical attention should 
be sought. Recovery periods 
can vary from several minutes to 
several weeks. 
The following information should 
not be regarded as informed 
medical advice. Courses of 
treatment for jellyfish stings vary 
among medical practitioners, and 
recommended treatment changes 
over time. Primary care should 
be followed by qualified medical 
examination in all but mild cases. 
 
Prevention
Care should be taken when 
swim ming in areas where 
dangerous jellies are known to 
exist or when an abundance of 
jellies of any type is present. Keep 
in mind that tentacles of some 
species may trail a great distance 
from the body of the organism 
and should be given lots of room. 
Stings, resulting from remnants of 
damaged tentacles, can occur in 
waters after heavy storms. Rubber 
skin-diving suits offer protection 
against most contact. 
 Be careful when investigating 
jellyfish that have washed ashore. 
Although they may be dead, 
they may still be capable of 
inflicting stings. Remember to 
take precautions when removing 
tentacles after contact or additional 
stings may result. 
Saltwater Fishing Conservation 
& Ethics
Although most people once 
considered ocean resources to be 
unlimited, recent rapid declines 
in the populations of many 
commercial and recreational 
species have demonstrated the 
opposite.
Numerous types of saltwater 
game fish now are being over-
harvested, and other species 
will face a similar fate unless all 
anglers practice wise conservation 
and adopt an ethical approach to 
fishing.
Size and catch limits, seasons 
and gear restrictions should 
be adhered to strictly. These 
regulations change from time 
to time as managers learn more 
about fish life histories and how 
to provide angling opportunities 
without depleting stocks.
The challenge of catching, 
not killing, fish provides anglers 
with the excitement and the 
reward of fishing. Undersized 
fish or fish over the limit should 
be released to ensure the future 
of fish populations. The number 
of saltwater finfish tagged and 
released annually in South 
Carolina has increased significantly 
in recent years as more and more 
fishermen take up this practice, 
providing information on growth 
and movement of fish as well as 
conserving resources.
Saltwater fishermen can further 
contribute to conservation 
by purchasing a Saltwater 
Recreational Fishing License, 
which is required to fish from a 
private boat or gather shellfish in 
South Carolina’s salt waters. Funds 
generated by the sale of licenses 
must be spent on programs that 
directly benefit saltwater fish, 
shellfish and fishermen. Help 
ensure the outdoor enjoyment 
of future generations by strictly 
adhering to all rules, regulations, 
seasons, catch limits and size 
limits, and through the catch and 
release of saltwater game fish.  
06MR5467
Our mission is to serve as the principal advocate for and steward of South Carolina’s natural 
resources. 
Our vision for South Carolina is an enhanced quality of life for present and future generations 
through improved understanding, wise use, and safe enjoyment of healthy, diverse, sustainable and 
accessible natural resources.
Our vision for the DNR is to be a trusted and respected leader in natural resources protection and 
management, by consistently making wise and balanced decisions for the benefit of the state’s natural 
resources and its people.
The South Carolina Department of Natural Resources prohibits discrimination on the basis of race, color, 
gender, national origin, disability, religion, or age.  Direct all inquiries to the Office of Human Resources, 
P.O. Box 167, Columbia, South Carolina 29202.
printed on recycled paper
This publication was made possible in part with funds from the sale of the South Carolina Saltwater 
Recreational Fishing License and the U.S. Fish and Wildlife Service Sportfish Restoration Fund. The South 
Carolina Department of Natural Resources publishes an annual Rules and Regulations booklet that lists all 
saltwater fishing regulations. Have an enjoyable fishing trip by reading these requirements before you fish. 
author credentials: J. David Whitaker, Dr. Rachael King and David Knott, Marine Resources Division
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Jellyfish

https://dc.statelibrary.sc.gov/bitstream/10827/10607/1/DNR_Sea_Science_Jellyfish_2006.pdf

Jellyfish

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