What’s That Weird Purple Sea Creature? Explaining Viral Video

It may look like a billowing piece of garbage, but this odd-looking purple creature is actually a rare discovery that has scientists giddy with excitement.

Scientists aboard the E/V Nautilus research vessel, led by Titanic discoverer and National Geographic Explorer-in-Residence Robert Ballard, recently recorded this siphonophore swimming at the bottom of the Gulf of Mexico (map).

Siphonophores, a member of the phylum Cnidaria, are among the group of organisms that includes the famous—and famously painful when it stings—Portuguese man-of-war.

Siphonophores are not actually jellyfish; they’re “colonial animals” comprised of small, interdependent life-forms called zooids. They’re also tough to see.

“I’m not sure exactly what the population of siphonophores is globally (I wouldn’t be surprised if no one really knew)—but I do know that I’ve watched a LOT of underwater exploration and have seen a few siphonophores over the years, but [none] like that!” Katy Croff Bell, chief scientist of the Nautilus Exploration Program and a National Geographic Emerging Explorer, said by email from the ship.

The species in the video is most likely Erenna richardi, Stefan Siebert of the Dunn Lab at Brown University, which specializes in Cnidaria, said by email. There are about 180 species of known siphonophores and five to six species in the genus Erenna, half which are currently undescribed, said Siebert, who was not involved in the Nautilus research.

Though they’re not jellyfish, these siphonophores do sting: “The waving structures observed at the back end are contracted tentacles equipped with stinger capsules. When undisturbed, they are lowered and form a curtain used to fish for prey,” he said.

More Than the Sum of Its Parts

Made up of a diverse group of living things (zooids) that form the whole, a siphonophore can reach lengths of up to 130 to 160 feet (40 to 50 meters), making them among the longest creatures in the world.

“Each zooid is an individual animal, but they all have adapted to fill specialized roles,” said Croff Bell. “For example, some are for protection, some are for eating, some are for reproduction, and some even ‘bioluminesce,’ or light up to attract food.” (See “Deadly Beauty: A Portrait of the Portuguese Man-of-War.”)

But here’s where the language gets tricky. Because the zooids cannot reproduce or survive independently, they can’t be considered true organisms, said Brown University’s Siebert, who calls the zooids that make up a siphonophore “bodies.”

To understand how an organism could be made up of many smaller bodies, Siebert noted it’s important to understand asexual reproduction.

“Many life-forms can reproduce asexually, i.e., they can make identical copies of themselves. In [the] case of colonial systems like corals or siphonophores, those newly formed bodies do not become physically separated but instead remain attached and integrated,” said Siebert.

Evolutionary History

They weren’t always like this, though. The zooids, or bodies, that make up a siphonophore were once independent organisms that at some point in evolution joined forces into one.

Siebert said that now the zooids essentially act as organs for the siphonophore. (See more jellyfish pictures.)

“Interestingly, both humans and siphonophores are complex systems with organs dedicated to a particular function. They, however, achieved it in very different way,” he said.

“In the case of humans, one body got compartmentalized and organ systems evolved within this body. The siphonophores basically modified bodies to fulfill organ function in the colony.”

Which, in truth, sounds like a level of cooperation humans can only aspire to.

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Changing Planet

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Stefan Sirucek is a writer and journalist who reports from both sides of the Atlantic. He's written for the Huffington Post and Wall Street Journal. Follow him on Twitter at @sirstefan.