'Dumbo octopus' is the common name for octopuses of the suborder Cirrina, especially umbrella octopuses of genus Grimpoteuthis, consisting of at least 15 species; as many species are only known from one or two specimens, it is quite likely that there are more that we have not yet encountered. They are named after Disney's Dumbo, as they have two "ears" on either side of their round body, which they flap to swim.
Dumbos live in oceans around the world, and are the deepest-living of all known octopuses, usually sticking to depths of at least 1,000m, and having been found at depths of up to 7,000m. Grimpoteuthis is primarily benthic, but will use ear-like fins to slowly swim, or drift with the current. They do not have ink sacs, and have more limited chromatophores than many octopuses, as there is little light this far down. There are also comparatively few predators, although deep-diving tunas, sharks, and dolphins may hunt them. They, in turn, hunt pelagic invertebrates including crustaceans, bivalves, worms, and copepods.
Much is made of the dumbo's ability to store sperm; as members of a species are wide-spread and travel mostly with the current, the females maintain eggs in different stages of development, and can store the male's sperm for long periods, allowing her to control when she lays eggs. It should be noted that this is not unusual, as various mammals, birds, reptiles, fish, insects, and etc. also store sperm.
While most dumbos are small, about 20-30 centimetres in total, members of Cirrothauma can reach up to nearly two meters in length. There is some disagreement whether these should be included under the umbrella term of dumbo octopus, but as it is an informal term it is probably best to go by common usage, and Cirrothauma do look Dumbo-like.
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