Near the rhopalia are statoliths which detect gravitational pull and help the animal to orient itself. Box jellyfish also have twenty ocelli (simple eyes) that do not form images, but detect light and dark they therefore have a total of twenty-four eyes. This enables the animal to see specific points of light, as opposed to simply distinguishing between light and dark. Each contains two rhopalial ocelli with lenses, one directed upwards and the other downwards and inwards towards the manubrium. Their eyes are set in clusters called rhopalia, located in pockets halfway up the outer, flat surfaces of the bell. Whereas some other jellyfish have simple pigment-cup ocelli, box jellyfish are unique in the possession of true eyes, complete with retinas, corneas and lenses. They possess a nerve ring around the base of the bell that coordinates their pulsing movements, a feature found elsewhere only in the crown jellyfish. The box jellyfish's nervous system is more developed than that of many other jellyfish. The complex rhopalial ocelli of Tripedalia cystophora Each septum is extended into a septal funnel that opens onto the oral surface and facilitates the flow of fluid into and out of the animal. The margins of the septa bear bundles of small gastric filaments which house nematocysts and digestive glands and help to subdue prey. The eight gonads are located in pairs on either side of the four septa. It is divided by four equidistant septa into a central stomach and four gastric pockets. The interior of the bell is known as the gastrovascular cavity.
In the center of the underside of the bell is a mobile appendage called the manubrium which somewhat resembles an elephant's trunk. As a result, box jellyfish can move more rapidly than other jellyfish speeds of up to 6 metres (20 ft) per minute have been recorded. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates. From each of the four lower corners of this hangs a short pedalium or stalk which bears one or more long, slender, hollow tentacles. The medusa form of a box jellyfish has a squarish, box-like bell, from which its name is derived. "Cubomedusae", from Ernst Haeckel's Kunstformen der Natur, 1904 Ĭubozoa represents the smallest cnidarian class with approximately 50 species. A few new species have since been described, and it is likely that additional undescribed species remain. These are grouped into two orders and eight families. 5.3 Malaysia, Philippines, Japan, Thailand, and TexasĪt least 51 species of box jellyfish were known as of 2018.
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