Dumbo Octopus

November 20, 2008

Science loves order, breaking down the world into categories, subcategories, levels and classifications. Every element on earth is neatly placed in numerical order from 1 to 113 on the periodic table based on the number of protons in the nucleus of each one’s atoms. Geologists label layers of earth’s crust based on the time period it was laid down in. Every living thing on earth is assigned a unique taxonomic sequence of names, from kingdom down to species, based on its evolutionary relationship to other organisms.

The ocean is no exception, and can be categorized in many ways. For example, the open ocean is known as the pelagic zone and the ocean floor, whether it is found two inches below the surface or two miles, is the benthic zone. We can also break the ocean environment down based on sunlight penetration. The photic zone is the area of daylight, but go deep enough, say 3000 feet or so, and all sunlight is filtered out and we enter the aphotic zone.

The actual definition of the aphotic zone is the area below which all but 1% of sunlight is blocked out. There are probably more animals left undiscovered here than any other habitat on earth, but as the ocean depths are explored using more and more sophisticated equipment, many of these strange creatures are coming to light. In the past the animals pulled up to the surface had to be studied in their dead and deformed states, as the tissue and organ damage done by the tremendous pressure differences made getting a live specimen impossible.

Today’s technology enables us to study strange beasts like the dumbo octopus, and even post their movements and habits on YouTube for anyone to see. 

The term "dumbo" is a fairly recent way of referring to octopods that belong to the genus Grimpoteuthis, as their popularity increased with the internet exposure they’ve received. There are about fifteen species in this genus, and were formerly called "jelly heads" by researchers before the "dumbo" meme took over. An equally silly, as well as apt, name.

While most octopuses are bottom-dwelling, it is believed that Grimpoteuthis are mainly pelagic since most specimens have been caught or filmed swimming in open water, although in the video above we can see they are also fairly comfortable crawling along the sand as well. The big ears that give this animal its common name are actually fins. By using these fins, as well as jet propulsion supplied by the animal’s siphon (which is the "nose-like" protrusion in the very top image), it can swim suspended a few inches off the bottom as it searches for crabs and shrimp to eat. While some resources call this cephalopod "benthic" and other sites say it is "pelagic", I think a more appropriate term, given the behavior described above, is "benthopelagic".

Not a lot is known about the reproduction habits of these deep-sea octopods, but much can be inferred. For example, dissected females were found to have multiple eggs inside their body, but these eggs were all at various stages of development, meaning they probably lay eggs all year long rather than having a specific breeding season. We also know that males have an enlarged segment of one their arms. This arm, like in other species of octopuses, is used to transfer the spermatophore, with is an enclosed packet full of gametes, into the mantle cavity of the female. Once the spermatophore is in place it ruptures, fertilizing the eggs internally. The female then lays the eggs on the underside of rocks and shells and leaves the young to fend for themselves.

While thinking about how I was going to structure this essay, my son was making Ramen noodles. I thought the packet of spices he tore open and poured into the pot was a perfect analogy for the spermatophore. Here is a drawing of this structure. The part labeled "cap" is where the packet is torn open once inside the female’s body.

Dumbos have been found all over the world, but always at depths measured in the thousands of feet. One pulled up from 7000 feet currently holds the record for deepest dwelling octopus of any kind. Given how little we know about animals of the aphotic zone, this record will probably be broken by an as yet undiscovered species

Other essays in this series can be found here.

Update: Here's another video.

back to Mark’s EssaysMarks_Essays.html