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BOX JELLYFISH INFORMATION
 

Please Note: This safety information is provided strictly as a courtesy in an effort to educate beachgoers and ocean enthusiasts on beach safety and not intended as medical advise. 808jellyfish is not a medical site. If a severe reaction occurs as the result of a box jellyfish sting immediately see a lifeguard for assistance, seek treatment at the nearest medical facility, or contact a physician.
   
Jellyfish are any planktonic marine member of a group of invertebrate animals composed of about 200 described species of the class Scyphozoa (phylum Cnidaria) or of the class Cubozoa, which was formerly considered an order of Scyphozoa. The term, jellyfish, is also often used in referring to certain other cnidarians that have a medusoid (saucer- or bell-shaped) body form, such as hydromedusae, the siphonophores (including even the Portuguese man-of-war which technically is not a jellyfish but a pelagic colonial hydroid or hydrozoan), as well as unrelated forms such as salps and comb jellies.

Seventy of the 200 species of jellyfish are known to sting - causing a range of reactions in humans: from mild skin irritation to death. The sting of the sea wasp, Chironex fleckeri, is so toxic that it can cause death. Some even call this creature the "deadliest animal on earth." Chironex fleckeri is not found in Hawai`i.

The sting of box jellyfish found in Hawai`i, Carybdea alata and Carybdea rastonii, is very painful and can even cause anaphylactic shock in some individuals. Carybdea alata and Carybdea rastonii, regularly "swarm" to Hawaii's Leeward shores 9 to 10 days after the full moon. Carybdea alata cause the most "trouble" for humans here.
[Tamanaha RH and Izumi AK. Persistent cutaneous hypersensitivity reaction after a Hawaiian box jellyfish sting (Carybdea alata). J Amer Acad Dermatol. 1996 Dec;35(6):991-3.]

There are basically two types of Scyphozoan jellyfish. Those that are free-swimming medusae and those that are sessile (stem animals that attach to seaweed and other objects by a stalk). The order Stauromedusae constitute the sessile polyplike forms. The free-swimming medusoid types, especially the Portuguese man-of-war, are the common, dangerous ones in Hawaiian waters.

Differences Between the Man-of-war and the Box Jellyfish

Free-swimming Scyphozoan medusae jellyfish occur in all oceans and include the commonly familiar disk shaped animals that are often found floating along the shoreline. The bodies of most range in diameter from about 1 to 16 inches (2 to 40 centimeters); however, some species are considerably larger with diameters of up to 6 1/2 feet (2 meters). The bulk of the Scyphozoan medusae jellyfish consists of almost ninety-nine percent water as a result of the composition of the jelly that forms the bulk in nearly all species.

Like their close relatives, sea anemones and corals, jellyfish have no head, no heart and no skeleton. Jellyfish don't have brains - because their bodies are organized differently from ours. Most animals we encounter have what's called bilateral - or two-sided - symmetry. They have a head end and a tail end. In the head end, they have a concentration of nerve cells -- where these cells are complex, we call it a brain.

The box jellyfish, Tripedalia cystophora, a cubozoan, is a bizarre, highly poisonous predator . "These are fantastic creatures with 24 eyes, four parallel brains and 60 arseholes," says Dan Nilsson, a vision expert from the University of Lund in Sweden. (Source: New Scientist, 8 November 2003, p. 34)

The eyes occur in clusters on the four sides of the cube-like body. Sixteen are simply pits of light-sensitive pigment, but one pair in each cluster is surprisingly complex, with a sophisticated lens, retina, iris and cornea, all in an eye only 0.1 millimetres across.

The lens structure is unusual because the refractive index - the extent to which it bends light - is graded from one side to the other. Because the image is focused way behind the retina, it appears blurry. So cubozoan eyes are good for spotting large, stationary objects, while filtering out unnecessary detail such as plankton drifting with the current. (Source: New Scientist magazine, 14 May 2005, p. 18)

Most jellyfish feed on small animals that they catch in their tentacles' stinging cells (nematocysts). Others simply filter feed, extracting minute animals and plants (i. e., plankton and nekton, loosened benthos) from the ocean water as they drift. Like all cnidarians, their bodies are made up of two cellular layers, the ectoderm and the endoderm. Between these dermal layers lies the mesoglea, a layer of connective tissue composed of a gelatinous substance, the jelly. In jellyfish the mesoglea is much enlarged to form the buoyant, transparent jelly. Most live for only a few weeks, although some are known to survive a year or longer.

 


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