Blanket octopus

Blanket octopi
Adult female Tremoctopus
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Superfamily: Argonautoida
Family: Tremoctopodidae
Tryon, 1879
Genus: Tremoctopus
Chiaje, 1830
Species

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.[2] 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.

Tremoctopus violaceus exhibits the most extreme degree of sexual size-dimorphism known in any non-microscopic animal.[3][4] Females may reach 2 m (6.6 ft) in length, whereas the males are 2.4 cm. The weight ratio is at least 10,000:1, and can probably reach as much as 40,000:1. The males have a large arm in a spherical pouch modified for mating, known as a hectocotylus. During mating, this arm is detached, and kept by the female in her mantle cavity until used for fertilisation. The male almost certainly dies shortly after mating.[5] The females carry more than 100,000 eggs attached to a sausage-shaped calcareous secretion held at the base of the dorsal arms and carried by the female until hatching.[6]

Blanket octopuses are immune to the venomous Portuguese man o' war, whose tentacles the male and immature females rip off and use for offensive and defensive purposes.[7] Like many other octopuses, the blanket octopus uses ink to intimidate potential predators.[8] Also, when threatened, the female unfurls her large net-like membranes that spread out and billow in the water, greatly increasing her apparent size.

Species

Lower (left) and upper beaks of female Tremoctopus gracilis (54 mm ML) in lateral view
3D red cyan glasses are recommended to view this image correctly.

References

  1. ↑ Allcock, L. (2016). "Tremoctopus violaceus". IUCN Red List of Threatened Species. Version 2015.4. International Union for Conservation of Nature. Retrieved 2 October 2016.
  2. ↑ Tree of Life web project: Tremoctopus
  3. ↑ 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 Archived January 19, 2005, at the Wayback Machine.. New Zealand Journal of Marine and Freshwater Research 36: 733–736.
  4. ↑ Pickrell, John (Aug. 12, 2003). "Walnut-Size" Male Octopus Seen Alive for First Time. National Geographic News.
  5. ↑ M. D. Norman; D. Paul; J. Finn & T. Tregenza (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 Volume 36, Issue 4. 36: 733–736. doi:10.1080/00288330.2002.9517126. Retrieved 5 February 2016.
  6. ↑ Tree of Life web project: Tremoctopus Eggs, Embryos and Hatchlings
  7. ↑ Jones, E. C. (1963). "Tremoctopus violaceus uses Physalia tentacles as weapons". Science. 139: 764–766. doi:10.1126/science.139.3556.764.
  8. ↑ 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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