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Praya dubia

life science Maturity 5-7 Next article →

*Praya dubia* is a giant siphonophore that lives in the deep ocean. It inhabits the mesopelagic and bathypelagic zones. These are the dark layers far below the sea surface. This creature is truly massive in length. It is the second-longest sea organism on Earth. Only the bootlace worm is longer than this animal. Its length can rival that of a blue whale. However, it is very thin, much like a broomstick.

Unlike many animals, *Praya dubia* is not a single multi-cellular organism. Instead, it is a compound animal. It is a colony of tiny biological components called zooids. Each zooid has evolved to perform a specific function. These zooids cannot survive on their own. They rely on symbiosis, which is a close living relationship, to survive. Together, they form a complete specimen. They arrange themselves into a long, often transparent stalk called a physonect colony.

The body of the colony is divided into specialized sections. The first part is the nectosome. This section contains nectophores, which are powerful medusae. These parts pulsate in rhythmic coordination to propel the colony through the water. Below the nectosome is the siphosome. This section extends to the far end of the animal. It contains many different types of specialized zooids in repeating patterns.

Many different zooids work together to keep the colony alive. Pneumatophores contain gas to provide flotability, helping the animal stay at the right depth. Gastrozooids act as the mouth and stomach for the entire colony. Dactylozooids are tentacles equipped with stinging cells for defense and hunting. These stinging cells are called nematocysts. Some zooids are also used to catch food and distribute nutrients. Other parts, called palpons, may assist with excretion or defense. Transparent bracts, or hydrophyllia, are leaf-shaped organs. These may force other zooids to contract during times of danger.

For a long time, humans did not realize this was a unique creature. When fishing nets dredged them up, the remains looked like blobs of gelatin. This made identification very difficult. Scientists did not identify them as a unique species until the 19th century. In 1987, the Monterey Bay Aquarium Research Institute made a major discovery. They observed living *Praya dubia* during a study of the water column. This allowed researchers to see the animal in its natural habitat.

*Praya dubia* is an active swimmer that uses light to hunt. It uses bioluminescence, which is the production of light by a living thing. It produces a bright blue light to attract prey in the dark. Once it finds food, it deploys a curtain of tentacles. These tentacles use their toxic sting to paralyze or kill prey. Their diet includes small crustaceans and gelatinous sea life. They may also eat small fish and fish larvae. Interestingly, this animal has no known predators.

This animal is found in many parts of the world's oceans. It lives from Iceland in the North Atlantic to Chile in the South Pacific. It can also be found in the Gulf of Mexico. One important thing to note is how the animal's body is built. It has a hydrostatic skeleton, which is held together by water pressure. Because of this, the animal will burst if it is brought to the surface. This makes studying them in the deep ocean very important.

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