Box Jellies: Cubozoa

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SEA WASP (Chironex fleckeri): SPECIES ACCOUNT


Box jellies have a cube-shaped body, or bell, also called an umbrella. The mouth is inside the bell. Tentacles are attached to each of the four lower corners of the bell. Some box jellies have several tentacles attached to each corner, and others have only one tentacle at each corner. A structure near the base of the bell contains one balance organ and six eyes.


Box jellies live in warm coastal waters worldwide.


Box jellies live over sand just above the sea bottom during the day and move toward the surface at night.


Box jellies eat fish and crustaceans (krus-TAY-shuns), which are water-dwelling animals that have jointed legs and a hard shell but no backbone.


Because box jellies can see, they are difficult to study because they react to the presence of their human observers by swimming away. Box jellies are active swimmers capable of moving 10 to 20 feet (3 to 6 meters) per minute. They move toward light and are active during the day and night, although they may feed only during the night or predawn hours.

The life history of box jellies has two stages: bottom-dwelling polyp and freely swimming medusa. A polyp (PAH-luhp) is a body type that consists of a tubular sac with a mouth and tentacles on the top. The medusa (mi-DOO-suh) is the tentacled, jelly-like, umbrella-shaped body form. The eggs and sperm from male and female medusae (mi-DOO-see, the plural of medusa) are released into the water and combine outside the body to form a larva (LAR-vuh), or early stage of the animal that changes form before becoming an adult. The larva settles on the bottom and becomes a polyp. The entire polyp of a box jelly becomes the young medusa.


Box jellies are often known as "killer box jellies," although only one type, the sea wasp, is lethal to humans.


Although it keeps undischarged box jelly stingers from firing, vinegar stimulates stinger firing from other jellyfish.


The sting of a box jelly can kill a person in thirty seconds. The venom from one sea wasp can kill sixty adults.


Box jellies are not threatened or endangered.

SEA WASP (Chironex fleckeri): SPECIES ACCOUNT

Physical characteristics: Sea wasps reach a diameter of about 12 inches (30 centimeters) but because they are transparent, they are difficult to see despite their large size. There are as many as fifteen tentacles in each corner of a sea wasp, and the tentacles can be as long as 98 feet (30 meters).

Geographic range: Sea wasps live in waters on the northern shore of Australia, on the coast of Papua New Guinea, around the Philippines, and on the coast of Vietnam.

Habitat: Sea wasps live in shallow seawater near the coast.

Diet: Sea wasps eat fish and shrimp.

Behavior and reproduction: Sea wasps swim around pier pilings. Polyps have been found in mangrove swamps and river outlets, but scientists do not know how the larvae (LAR-vee, the plural of larva) find their way to these locations. Polyps start to transform into medusae in the spring and continue until the rainy season, when they are flushed out into the ocean.

Sea wasps and people: The venom of sea wasps causes nerve, heart, and skin damage. Death occurs very quickly. Antivenin is available but must be administered rapidly. Vinegar can be used to remove undischarged stingers.

Conservation status: Sea wasps are not threatened or endangered. ∎



Aaseng, Nathan. Invertebrates. New York: Venture, 1993.


Seymour, Jamie. "One Touch of Venom: A Box Jellyfish Is a Killer." Natural History (September 2002): 72–75.

Web sites:

"Sea Wasp." Extreme Science. (accessed on January 28, 2005).