Grimpoteuthis

As noted above, many species collected on the Challenger expedition were initially classified in the genera Cirroteuthis and Stauroteuthis.[15][12] Several species formerly classified in this genus were moved to other opisthoteuthid genera. A new family, Grimpoteuthididae, has been proposed to accommodate these species and those of genus Enigmatiteuthis.[4][24] The persistent confusion and disparity about the taxonomy of these species has been attributed to the poor quality and limited number of specimens available for study.[24]

Species of Grimpoteuthis are assumed to have a worldwide distribution, living in the cold, abyssal depths ranging from 1000 to 7,000 metres. Specimens have been found off the coast of Oregon, the Philippines, Martha's Vineyard, the Azores, New Zealand,[25] Australia, California, Gulf of Mexico, Papua, and New Guinea. Dumbo octopuses are among the deepest living octopuses known. In 2020, Grimpoteuthis was spotted ~ 7000m deep down in the Java Trench.[26]

Species of Grimpoteuthis face few direct threats from humans, living at depths of 1,000 meters (3,300 ft) and below. Natural predators include sharks and predatory cephalopods. The Grimpoteuthis does not have an ink sack and therefore, they change colors and size due to their chromatophore cells that helps them protect themselves from predators.[27] Some color changes can be red, white, pink, brown, or they become an invisible color so that they can blend in with the ocean floor.[28] Besides the threats they face Grimpoteuthis feed on worms, crustaceans, shellfish, and copepods.[29]

The genus has a distinct habit of swimming. Whilst it appears that the large fins on the side of the head are propelling the creature, it is actually a siphon, pushing water out the back, creating propulsion. The fins are in fact primarily used for stabilization and steering.[30] Movement of the arms can be used to help the animal move in any direction. The arms permit the animal to crawl along the seafloor, to capture prey, lay eggs, explore, etc. Dumbos hover above the sea floor, searching for polychaete worms, pelagic copepods, isopods, amphipods, and other crustaceans for food.[31] Prey is captured by pouncing on the target, which then is swallowed whole.[32] It is also interesting to know that in contrast to other octopuses, dumbo octopuses do not produce ink. This makes sense considering the fact that their habitat is a deep, dark place in the ocean. Instead of ink sacs, dumbo octopuses take advantage of a strand-like structure on their suckers to help them sense the surrounding environment as well as looking for food. The dumbo octopus has a distinct characteristic, what was once thought to be white spot(s) above their eyes, near the base of the fins is transparent patches. These patches function to detect (unfocused) light.[33]

Females have no distinct period for breeding. Females carry multiple eggs in various stages of maturation, suggesting that they have no optimal breeding period. Male octopuses have a separate protuberance on one of their arms that carries an encapsulated sperm packet to the female. It is hypothesized that the female can then distribute this sperm to the eggs at any given time based on environmental conditions. The females lay the eggs under small rocks or on shells in the deep ocean or can even carry them on her arms, by tucking the eggs behind the wide webbing, until she finds a safe place that would provide them with the best fitness. As with other octopuses, females do not invest any further time in the young after they hatch because once they are born they are able to defend themselves. In 2018, Shea et al. determined that Grimpoteuthis hatchlings emerge as "fully competent" juveniles with all of the sensory and motor features to survive on their own.[34] Females can be distinguished from males by body type. Females have a much more prevalent gelatinous body type with size being more width than length, having 1.5 to 2 time more short arms. Other differences include females having broadly U-shaped shells, larger eyes, and gills with six lamellae.[35]

• Dumbo Octopus video at BBC