Giant Siphonophore

Quick Take

• The giant siphonophore can outgrow a blue whale in length, but what you'd actually be looking at isn't a single animal at all. Understand the colonial structure →
• Its body would literally fall apart if it ever reached the surface, and the reason why says everything about how it survives in the deep. See how pressure shapes it →
• Although it has no known natural predators, the giant siphonophore is not completely safe from threats. Explore its threats →
• It uses bioluminescence to hunt, but not in the way you'd expect. Its mimicry trick is stranger than any deep-sea lure you've heard of. Discover its mimicry hunting →

The deeper into the ocean you go, the more likely you’re going to run into an animal that looks less like an animal and more like an alien from your favorite sci-fi movie. The siphonophore is one such animal, with a long rope-like body made up of multiple biological pieces, stinging tentacles, and a gassy floating structure. The giant siphonophore gets confused with jellyfish all the time. If you happen to see one, don’t touch it. It packs a painful but rarely fatal sting, to humans that is.

Giant Siphonophore Facts

• Giant siphonophores are bioluminescent. Some use glowing lures to attract prey, though this behavior is considered rare among siphonophores.
• Giant siphonophores are not just one animal, but a group of specialized, individual organisms that work together in a colony. These individual animals wouldn’t be able to survive on their own.
• At up to 130 feet in length, giant siphonophores can grow longer than blue whales and are among the longest animals in the ocean.
• The giant siphonophore’s body is no bigger than a broomstick.

Classification and Scientific Name

The giant siphonophore is classified as Praya dubia. It belongs to the family Prayidae, suborder Calycophorae, and order Siphonophorae. The name siphonophore comes from the Greek words siphon, which translates to “tube” and pherein, which means “to bear.” This refers to the shape and appearance of the siphonophore, which is made up of multiple individuals called zooids. The zooid colony is attached to a hollow stalk, which looks like a very long tube.

Evolution and History

Giant siphonophores belong to the class Hydrozoa, which consists of tiny predatory animals that may exist alone or in colonies and predominantly inhabit saltwater.

The history of the Hydrozoan class may go back over half a billion years, to the late Precambrian period, though the fossil record from that era remains sparse.

Siphonophores also belong to the phylum Cnidaria, which dates back approximately 580 million years.

Siphonophores have no known fossils, although studies show that they have accumulated extensive evolutionary modifications over a long period of existence.

Appearance

The giant siphonophore is not actually a single animal, but rather a group of individual entities called zooids. These zooids are prolifically created through asexual reproduction to form a long chain system called a colony. The colony is attached to a hollow stem, which is usually transparent.

Siphonophores come in three basic morphologies: Cystonecta, Physonecta, and Calycophorae. The giant siphonophore adopts the Calycophorae body morphology. This means that it has a gas-filled float at the front end of the colony’s stem called a pneumatophore, which provides buoyancy. It also possesses a nectosome, a structure that houses the nectophores, the colony’s primary propulsion units. The nectophores help the colony move by streaming back jets of water, which propel the siphonophore forward.

Appearance and Function

Some of the zooids have specialized functions without which the colony would not be able to survive. These zooids are located on the siphosome. Some of these zooid functions include capturing prey, circulation of nutrients, excretory systems, locomotion, and defense. Some zooids have a tentacle that is used to sting their prey.

Giant siphonophores are very venomous animals. They have stinging structures called nematocysts on their tentacle branches known as tentilla. These stingers fire paralyzing toxins at their prey and are capable of inflicting great pain.

The giant siphonophore can grow up to a staggering 130 feet in length, making it one of the longest creatures in the ocean. Its incredible body surpasses even the largest sea mammal, the blue whale, in length.

The color of a giant siphonophore can vary depending on where it resides. For example, the greater the depth at which the animal is found, the redder it is. It can also produce a blue bioluminescent light, mostly used to attract and capture prey.

Giant siphonophores live in great depths of thousands of feet, and they have adapted to living in an environment with an equally extreme level of pressure. Their bodies are held together by the surrounding pressure, meaning they will rupture if brought to the surface.

Behavior

Giant siphonophores are symbiotic animals. They are made up of many individual zooids with specialized functions that work together to live and thrive as a unit. Without this symbiosis, the colony would not be able to survive.

These siphonophores are avid swimmers. They ambush their prey using the “sit and wait” method, holding out their tentacles and waiting for the unsuspecting prey to bump into the stingers accidentally.

Diet

Giant siphonophores are carnivorous predators. They feed on copepods, gelatinous critters, zooplankton, small crustaceans, small fish, and fish larvae. The hunting tactics of these creatures usually vary.

Giant siphonophores that live in areas with low food concentration usually employ an ambush tactic wherein they sit and wait for the prey to swim by before subduing it. These animals have stinging organs called nematocysts on branches of their tentacles, which are known as tentilla. These branches form a web around the unsuspecting prey and shock them into paralysis with toxins.

Some siphonophores catch their prey through mimicry. In this method, they use their bioluminescence to lure, stun, or confuse the prey and mimic its general swimming behavior before stinging it.

Habitat and Population

Giant siphonophores live deep in the sea, which may be reassuring news for avid swimmers. These ocean dwellers can be found anywhere from 2,300 feet to 3,300 feet below sea level.

This jellyfish-like animal has been sighted throughout the waters of the globe, from the South Pacific to the North Atlantic. They live near coasts, and their habitats include the ocean floor as well as the ocean twilight zone.

The giant siphonophore is not currently listed on the IUCN Red List of Endangered Species. It is not considered to be a vulnerable species.

Reproduction and Lifespan

Siphonophores reproduce asexually through a budding method. New colonies form by sexual reproduction.

The reproductive methods of all siphonophore species are still in the exploration phase. However, the consensus is that every zooid in the siphonophore colony came from one externally fertilized egg, so their genetic makeup is identical. A siphonophore comes into existence when one zygote becomes a protozooid. This then begins the budding process, and eventually, it creates a new zooid. This process repeats over time until the colony forms around the central stalk.

Siphonophores create the sexual gametes in their colonies by the use of gonophores. The gonophores can either be male or female. Siphonophores with both male and female gonophores within a single colony are a monoecious species. Those with only one type of gonophore in their colony, with the other sex found in a separate colony, are a dioecious species.

When it comes to asexual reproduction, siphonophores are a collective of multiple zooids, and therefore, only one bud — called the probud — initiates the reproductive process within a colony, and it reproduces by fission.

Because siphonophores reproduce primarily asexually, it is natural that their genetic makeup does not undergo any major changes as generations progress. There is virtually no diversity in the genetics of each new spawn, except that mutations occur. These mutations produce unique zooids that have their own particular functions.

The lifespan of the giant siphonophore is not on record.

Predators and Threats

The giant siphonophore has no known natural predators, though fishermen do catch siphonophores by accident. They appear as white, gelatinous blobs stuck to fishing nets.

Potential threats these deep-sea dwellers could face include habitat disruption due to human activities such as deep-sea mining.