1. Description

2. Behavior

3. References

4. External links

• Diphyes dubia Quoy & Gaimard, 1833
• Nectocarmen antonioi Alvariño, 1983
• Praia dubia Blainville, 1830
• Prayoides intermedia Leloup, 1934

Praya dubia or giant siphonophore is an invertebrate, a siphonophore that lives in the deep sea at {{convert|700|m||abbr=on}} to {{convert|1000|m||abbr=on}} below sea level. It has been found off the coasts of a rapidly-growing list of nations around the world — 19 countries so far, from Iceland in the North Atlantic to Chile in the South Pacific^[1] — thanks to advancements in deep-sea submersible technology.

The giant siphonophore is not a single, multi-cellular organism, but a huge colony of tiny biological components called zooids, each having evolved with a specific function. These zooids cannot survive on their own,^[4] relying on symbiosis in order for a complete Praya dubia specimen to survive.

Description

Praya dubia zooids arrange themselves in a long stalk that is whitish and transparent, known as a physonect colony.^[5] The larger end features a transparent, dome-like float known as a pneumatophore,^[6] filled with gas that provides buoyancy, allowing the organism to remain at its preferred ocean depth. Next to it are the nectophore,^[7] powerful medusae which pulsate in rhythmic coordination to propel Praya dubia through ocean waters in any direction.^[8] Together, the array is known as the nectosome.

Beneath the nectosome is the siphosome which extends to the far end of Praya dubia, containing several types of specialized zooids in repeating patterns.^[5] Some have a long tentacle used for catching and immobilizing food and distributing their digested nutrients to the rest of the colony. Other zooids known as palpons or dactylozooids appear to contain an excretory system that may also assist in defense, though little is known about their precise function in Praya dubia.^[9] Transparent bracts (also called hydrophyllia), are leaf-shaped organs generally thought to be another type of zooid which covers and forces other zooids to contract in times of danger.

These animals burst,^[10] when raised to the surface because their hydrostatic skeleton is held together by water pressure above {{convert|460|bar|MPa|order=flip|abbr=on}}. Because of this, Praya dubia remains dredged up in fishing nets resemble a blob of gelatin, preventing their identification as a unique creature until the 19th century. In 1987, Monterey Bay Aquarium Research Institute observed living Praya dubia during a systematic study of a water column, the animal’s natural habitat, in Monterey Bay.^[11][12][13]

Behavior

Praya dubia is an active swimmer that attracts its prey with bright blue bioluminescent light.^[14] When it finds itself in a region abundant with food, it holds its position and deploys a curtain of tentacles covered with nematocysts which produce a powerful, toxic sting that can paralyze or kill prey that happen to bump into it.^[15] Praya dubia’s diet includes gelatinous sea life, small crustaceans, and possibly small fish and fish larvae.^[16] It has no known predators.

A Praya dubia specimen, filmed in its native habitat, was featured in Episode 2 of the David Attenborough television series Blue Planet II, produced for the BBC.^[17]

References

External links

• [https://www.youtube.com/watch?v=_EWYfedtLrc Giant Siphonophore Sighting].YouTube, 22 May 2015, by E/V Nautilus during the 2015 ECOGIG dives in the Gulf of Mexico, Accessed 28, January 2018..
• [https://www.youtube.com/watch?v=8Vkn94C_iGk Deep sea siphonophore off Roatán Honduras - 2300 feet], YouTube, 10 June 2013, Roatán Institute of Deepsea Exploration, Accessed 28, January 2018.
• Praya dubia Distribution Map at Ocean Biogeographic Information System
• Praya dubia Habitat at Encyclopedia of Life

• William Edward Bosomworth
• William Edward Burghart Dubois
• William edward campbell
• William Edward Childs
• William Edward Cleary
• William Edward Colby
• William Edward Collinson
• William Edward Cousins
• William Edward Crump
• William Edward Cule
• William Edward Dargie
• William Edward David Allen
• William Edward de Winton
• William Edward Dodd
• William Edwardes, 1st Baron Kensington
• William Edwardes, 2nd Baron Kensington
• William Edwardes, 3rd Baron Kensington
• William Edwardes, 4th Baron Kensington
• William Edward Felix Hodgman
• William Edward Goschen
• William Edward Hanley Stanner
• William Edward Harney
• William Edward Hearn
• William Edward Hickman
• William Edward Hickson