Changing Planet

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.

Follow Stefan Sirucek on Twitter.       

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.
  • Mark Yarbrough

    Is there room for one more car on this train?

  • Stefan Siebert

    Siphonophores are considered an example for a particular type of colonial organization, which differs from colonial systems like the mentioned honeybee hive. They are made of multiple bodies but they do not arise by aggregation and cooperation of multiple solitary organisms. Siphonophore development starts with a single fertilized egg. A small larva will form, which will develop into a founding body. In the following the formation of additional specialized bodies sets in, which stay integrated. New bodies are continuously added in dedicated growth zones and the system grows into what can be observed in the footage. A simple scheme of such a life cycle can be found here:

    All animals are multicellular (and so are the siphonophores). They may be considered a colony of single cells. In an animal all cells are specialized for a particular function and a single cell cannot survive when separated from the organism. In case of multicellular colonial forms like the siphonophores a second unit is at play – single bodies modified for particular tasks, which cannot survive on their own. Therefore multicellularity can serve as an analogy. There are some siphonophore relatives in which new individuals form by asexual reproduction without subsequent physical separation (coral forms, hydroid colonies). In some cases one can still remove a single body and this body can survive and form a new colony. This body still has all what it takes to live on its own. We think that siphonophores evolved from such an ancestor and acquired a pelagic life style (i.e. they live in the water column in contrast to their relatives, which are attached to hard substrate like rocks). However in case of siphonophores the bodies are highly specialized and fulfill only a subset of the tasks a single solitary individual would have to take care of. In siphonophores single bodies cannot be removed from the system any more. Whereas some bodies still resemble bodies present in living relatives others do not due to their highly derived nature.

    In the front part of the animal (to the left) one can see bodies whose sole function is to move the whole system. In this species all bodies are arranged along and connected to a hollow stem. The locomotory bodies receive their fuel/nutrients from feeding zooids located in the hind part of the animal. The type of coloniality observed in siphonophores is one way modular organization can arise, which makes them a very interesting subject from an evolutionary point of view.

    We do not know anything about the life span of these large deep-sea forms but expect it to span multiple years. Smaller shallow water species might live for a season.

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