In the deep, deep ocean lives a group of rare and mysterious octopuses named after one of Disney’s most iconic characters.
The group, commonly known as Dumbo octopuses, are found around the world in deep ocean habitats, thousands of feet below the surface, where they are rarely seen by humans.
Michael Vecchione, a cephalopod specialist with the NOAA National Systematics Laboratory at the Smithsonian Museum of Natural History in Washington, said Newsweek Here are different interpretations of what constitutes a dumbo octopus. Understanding what exactly it is is difficult.
Some researchers use this term only to refer to the genus (group of species) Grimpoteuthiswhile Vecchione and other experts call the broader group of so-called “cirrate” octopuses—which consists of about 45 recognized species in total—Dumbo octopuses.
The main characteristic that characterizes cirrates is that, unlike most octopuses, they have fins. These body parts, located on their heads, resemble the ears of Dumbo – the cartoon elephant – hence the name.
The other distinguishing feature of Dumbo octopuses, according to Vecchione, are the finger-like muscular protrusions called “cirri” found between each of the gills on their arms. This is where the name “cirrate” comes from.
“We don’t really know what [the cirri] are used, but we assume it has to do with the handling of the prey they feed on,” Vecchione said.
Cirrate octopuses also have webbed arms, and often, this webbing is quite extensive, reaching the tips of the arms.
These creatures are mostly found in the deep sea, although it is not uncommon to find some in relatively shallow water in the polar regions. Dumbo octopuses are the deepest living cephalopods known – the group of molluscs that includes squid, octopuses and cuttlefish.
“[They] they live all the way down in the upper parts of the trenches, which are the deepest parts of the ocean,” Vecchione said. “They probably reach about 7,000 meters deep [around 23,000 feet]. And the shallowest ones are near the edge of the continental shelf, so about 200 meters [256 feet]. So the range of the group in general is really big.”
Currently, it appears that a large percentage of Dumbo Octopus species are very widespread. However, sightings of these cephalopods are rare.
“There is a species down in Antarctica which in some places we have found quite abundant. But in general, Dumbos are rare and people get excited every time they see them underwater. So I’d say they’re rare, except in a few limited areas,” said Vecchione, whose research focuses on deep-sea and polar cephalopods.
One of the most unusual aspects of these octopuses is the curious ear-like fins they use to propel themselves through the water, steering with the help of their hands.
“Their swimming behavior is unusual. Most cephalopods swim by jet propulsion – they suck water into their bodies and then eject it through a little funnel. We don’t think that the walking octopuses do that at all anymore. What they do is they swim either by flapping their fins or by using their arms and webs to swim like a jellyfish swims,” Vecchione said.
How these octopuses catch prey — usually invertebrates swimming above the sea floor — is somewhat of a mystery, according to Vecchione.
“They have a web between the arms, so the arms are all connected together. And we think they catch their prey by putting the animal in that web, trapping it with the arms, and then doing something with the circuitry to bring the prey into the mouth,” he said. “It might involve secreting mucus, for example, and then using the circuit to move the animal into the mouth. But that’s just speculation right now.”
Another unusual aspect of their behavior is the way they lay their hard eggs, which in some cases can be up to about an inch long.
“As far as we know, they attach their eggs to things like deep-sea coral. We know that’s true for a few species because we found the eggs and they probably all have similar behavior,” Vecchione said.
“So unlike shallow-water octopuses, where the female lays a whole bunch of eggs, and then sits there and tends them, these seem to lay their eggs one at a time, attaching them to deep-sea corals and maybe sponges . Then, after laying that one egg, they swim away. Again unlike shallow water octopuses, which spawn a whole bunch at once, these seem to keep spawning over and over again, over an extended period of time. “
Dumbo octopuses are highly specialized for life in deep water, where temperatures can be extremely cold and sunlight is often very limited or absent, depending on the depth. For example, in order to increase their chances of finding a mate and successfully reproducing in the vast darkness of the deep, females seem to always carry eggs at different stages of development and can store sperm for a long time after mating.
As a result, the female can transfer the sperm to the more developed eggs whenever the environmental conditions are suitable.
Because they rarely encounter predators in the deep sea, these octopuses generally do not have ink sacs. Many cephalopods are capable of jetting ink as a defense mechanism to escape predators.
Given the types of environments they tend to inhabit, circulating octopuses are not greatly threatened by human activities such as fishing to the extent that other marine life is. But they could face threats from global climate change, according to Vecchione.
“The deep sea is warming, and in some areas there is less and less oxygen in the water. So the areas of low oxygen are expanding. Both of these can be threats to these mobile octopuses. The third aspect of climate change is acidification. And the deep ocean suffers from that too. But I think it’s less of a threat to them than to other deep-sea animals.”