Blanket octopus

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Blanket octopuses
Pelagic octopus Tremoctopus.jpg
Adult female Tremoctopus
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Superfamily: Argonautoida
Family: Tremoctopodidae
Tryon, 1879
Genus: Tremoctopus
Chiaje, 1830

Tremoctopus gelatus
Tremoctopus robsoni
Tremoctopus gracilis
Tremoctopus violaceus

Tremoctopus is a genus of pelagic cephalopods, containing four species that occupy surface to mid-waters in subtropical and tropical oceans.[1] They are commonly known as blanket octopuses, in reference to the long transparent webs that connect the dorsal and dorsolateral arms of the adult females. The other arms are much shorter and lack webbing.

These species exhibit an extreme degree of sexual dimorphism.[2][3] Females may reach 2 metres (6.6 ft) in length, whereas the tiny males are at most a few centimeters long. The males have a specially modified third right arm which stores sperm, known as a hectocotylus. During mating, this arm detaches itself and crawls into the mantle of the female to fertilize her eggs. The male dies shortly after mating. The females carry more than 100,000 tiny eggs attached to a sausage-shaped calcareous secretion held at the base of the dorsal arms and carried by the female until hatching.[4]

Blanket octopuses are immune to the venomous Portuguese man o' war, whose tentacles the male and immature females rip off and use for defensive purposes.[5] Like many other octopuses, the blanket octopus uses ink to intimidate potential predators.[6] Also, when threatened, the female unfurls her large net-like membranes that spread out and billow in the water, greatly increasing her apparent size.


Lower (left) and upper beaks of female Tremoctopus gracilis (54 mm ML) in lateral view
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  1. ^ Tree of Life web project: Tremoctopus
  2. ^ Norman, M.D.; Paul, D.; Finn, J.; and Tregenza, T. (2002). First encounter with a live male blanket octopus: the world's most sexually size-dimorphic large animal. New Zealand Journal of Marine and Freshwater Research 36: 733–736.
  3. ^ Pickrell, John (Aug. 12, 2003). "Walnut-Size" Male Octopus Seen Alive for First Time. National Geographic News.
  4. ^ Tree of Life web project: Tremoctopus Eggs, Embryos and Hatchlings
  5. ^ Jones, E. C. 1963. Tremoctopus violaceus uses Physalia tentacles as weapons. Science 139: 764–766.
  6. ^ Thomas, R.F. 1977. Systematics, distribution, and biology of cephalopods of the genus Tremoctopus (Octopoda: Tremoctopodidae). Bulletin of Marine Science 27(3): 353-392.

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