Jellyfish Few marine creatures are as their radial symmetry (body parts salinities. Most live in shallow mysterious and intimidating radiating from a central axis). This coastal waters, but a few inhabit as jellyfish. Though easily symmetry allows jellyfish to detect depths of 12,000 feet! recognized, these animals are and respond to food or danger often misunderstood. Some from any direction. Life Cycles bathers and beachcombers react Instead of a brain, jellyfish The life cycle of a typical with fear upon encountering possess an elementary nervous jellyfish is complex and involves these invertebrates but, in fact, system, or nerve net, which an alteration of generations in most jellyfish in South Carolina consists of receptors capable which the animal passes through waters are harmless. This article of detecting light, odor and two different body forms. The was prepared to help coastal other stimuli and coordinating dominant and conspicuous residents and vacationers learn the appropriate responses. difference between the jelly fish to Jellyfish are composed of avoid and the ones you can safely an outer layer (epidermis), JELLYFISH LIFE CYCLE ignore. which covers the external body Jellyfish are members of the surface, and an inner layer medusa phylum Cnidaria, a structurally (gastrodermis), which lines the simple marine group of both gut. Between the epidermis and fixed and mobile animals: sea gastrodermis is a layer of thick anemones, sea whips, corals and elastic jellylike substance called planula hydroids are polyps that grow mesoglea (“middle jelly”). Jellyfish larva attached to rocks or other hard have a simple digestive cavity, ephyra surfaces; jellyfish and colonial (coelenteron), which acts as a siphonophores like the Portuguese gullet, stomach and intestine, with budding man-of-war are mobile (either one opening for both the mouth polyp polyp actively swimming or subject to and anus. Four to eight oral arms winds and currents). Inherent are located near the mouth and to both types of life histories is are used to transport food that has been captured by the tentacles to the mouth. GENERAL MEDUSA BODY PLAN medusa is the familiar form, Jellyfish come in a wide variety while the smaller polyp form tentacles of sizes, shapes and colors. Most mouth is restricted to the larval stage. are semi-transparent or glassy and Jellyfish reproduce sexually, and bell-shaped, measuring less than individuals are either male or an inch to over a foot across the female. The reproductive organs bell, although some may reach 7 (gonads) develop in the lining of feet in diameter. The tentacles of the gut. During reproduction, the some jellyfish can reach lengths male releases sperm through its greater than 100 feet. Regardless mouth into the water column. of their size or shape, most jellyfish Some of the swimming sperm are very fragile, often containing are swept into the mouth of the less than 5% solid organic matter. female, where fertilization occurs. Jellyfish inhabit every major oral arm Early embryonic development gonad oceanic area of the world and begins either inside the female are capable of withstanding a bell stomach or in brood pouches along the wide range of temperatures and oral arms. Small swimming larvae (planulae) leave the mouth or NEMATOCYST BEFORE DISCHARGE can have hundreds or thousands brood pouches and enter the cnidoblast of nematocysts embedded in water column. After several days hollow the epidermis. Nematocysts are the larvae attach themselves to thread activated when tentacles make something firm on the sea floor nematocyst contact with an object. Pressure (rocks, shells, etc.) and gradually within the nematocyst forces the transform into flower-like polyps stinging thread to rapidly uncoil. (scyphistoma). These polyps use The thousands of nematocysts act tentacles to feed on microscopic as small harpoons, firing into prey, organisms in the water column. major barb injecting paralyzing toxins. Polyps can multiply by producing trigger Stings usually paralyze or kill buds or cysts that separate from only small creatures (fish, small the first polyp and develop into crustaceans), but some jellyfish new polyps. When conditions NEMATOCYST AFTER DISCHARGE are harmful to humans. Although are right, fully developed polyps jellyfish do not “attack” humans, develop constrictions in their cnidoblast swimmers and beachcombers bodies that eventually produce can be stung when they come a larval stage (the strobila) that nematocyst into contact with the jellyfish resembles a stack of saucers. Each tentacles with functional individual saucer develops into a nematocysts. The severity of the tiny jellyfish (ephyra stage), which sting depends on the species of separates itself from the stack and jellyfish, the penetrating power becomes free swimming. In a few of the nematocyst, the thickness weeks, the ephyra will grow into of exposed skin of the victim and an adult jellyfish (medusa), thus trigger the sensitivity of the victim to the completing the complex life cycle. venom. The majority of stings from Jellyfish normally live for a few major barb jellyfish occur in tropical and warm months, however the polyp stage temperate waters. Most species off may be perennial. the southeastern coast are capable of inflicting only mild stings that Locomotion jellies and occasionally other result in minor discomfort. The adult jellyfish drifts in the jellyfish. Larger species, however, water with limited control over are capable of capturing and Local Jellyfish its horizontal movement. It is, devouring large crustaceans and Although most jellyfish that however, endowed with muscles other marine organisms. Jellyfish inhabit South Carolina waters are that allow it to contract its bell, are themselves preyed upon by harmless to humans, there are a reducing the space under it and spadefish, sunfish, sea turtles and few that require caution. Learning forcing water out through the other marine organisms. Some how to identify the different opening. This pulsating rhythm species including the mushroom species can help you decide which allows for regulation of vertical and cannonball jellyfish, are even ones can be safely ignored. movement. Because jellyfish are considered a delicacy by humans. sensitive to light, this vertical Pickled or semi-dried mushroom movement can be important. jellyfish are consumed in large Some jellyfish, like the sea wasp, quantities in Asia, where they descend to deeper waters during constitute a multi-million dollar the bright sun of the midday and part of the seafood business. surface during early morning, late afternoon and evenings. Despite Venom Apparatus this ability to move vertically, Jellyfish are equipped with a jellyfish largely depend upon specialized venom apparatus ocean currents, tides and wind for (cnidoblast) for defense and horizontal movement. feeding. A capsule (nematocyst) inside the cnidoblast contains a CANNONBALL JELLY Food trigger and a stinging structure. The To some, jellyfish may appear to stinging structure varies according Cannonball Jelly have no apparent value, but they to species, but generally consists (Stomolophus meleagris) are, in fact, a very important part of a hollow coiled thread with (Also known as the jellyball, and of the marine food web. Jellyfish barbs lining its length. Nematocysts the cabbage head jelly) are carnivorous, feeding mostly on are concentrated on the tentacles Cannonball jellyfish are the most a variety of zooplankton, comb or oral arms. A single tentacle common in our area. During the summer and fall, large numbers of South Carolina waters. It has a jellyfish is saucershaped with this species appear near the coast transparent, saucer-shaped bell brown or red pigments, usually and in the mouths of estuaries. and is easily identified by the four 6-8 inches in diameter. Four oral Cannonball jellies can be easily pink horseshoe-shaped gonads arms and long marginal tentacles identified by their round white visible through the bell. It typically hang from the bell and can extend bells that are bordered below by a reaches 6-8 inches in diameter, brown or purple band of pigment. but some are known to exceed 20 They have no tentacles, but they inches. Recent evidence suggests do have a firm, chunky feeding that there are several similar- apparatus formed by the joining of looking species of moon jellies the oral arms. Cannonballs rarely within a group of species that were grow larger than 8-10 inches in once called the moon jelly Aurelia diameter. They are considered aurita. The southern populations, to be pests by commercial trawl including those in South Carolina, fishermen because they clog and are now considered to be a damage nets and slow down distinct species (A. marginalis). sorting and trawl times, although The moon jelly is only slightly turtle excluder devices in trawl nets venomous. Contact can produce alleviate that problem, somewhat. symptoms from immediate prickly Fortunately, this species is one of sensations to mild burning. Pain the least venomous of our jellyfish. is usually restricted to immediate area of contact. Mushroom Jelly (Rhopilema verrilli) SEA NETTLE The mushroom jelly is often mistaken for the cannonball jelly, but it differs in many ways. The larger mushroom jelly, growing several feet. Considered moderate 10-20 inches in diameter, lacks to severe, symptoms from sea the brown band associated with nettle stings are similar to those of the cannonball and is much flatter the lion’s mane. Given that they and softer. Like the cannonball, the are most abundant in the summer, mushroom jelly has no tentacles when the greatest number of and chunky feeding apparatus, people are likely to be swimming however, it possesses long finger- in the ocean, this species is like appendages hanging from the thought to be responsible for most feeding apparatus. This species of the jellyfish stings that occur in is also considered a pest by Lion’s MANE South Carolina. Exercise caution commercial fishermen, but they if sea nettles are observed in the are much less of a problem than Lion’s Mane water, and do not swim if large cannonball jellies.