Cirrate shell

Last updated
Dorsal (left) and ventral aspects of a mature female Grimpoteuthis innominata (73 mm ML). Grimpoteuthis innominata 73 mm ML.jpg
Dorsal (left) and ventral aspects of a mature female Grimpoteuthis innominata (73 mm ML).

Cirrate octopuses possess a well-developed internal shell that supports their muscular swimming fins. This is in contrast to the more familiar, finless, incirrate octopuses, in which the shell remnant is either present as a pair of stylets or absent altogether. [1]

The cirrate shell is quite unlike that of any other living cephalopod group and has its own dedicated set of descriptive terms. [2] [3] It is usually roughly arch- or saddle-shaped and is rather soft, being similar in consistency to cartilage. [4] Each of the eight extant cirrate genera is characterised by a distinct shell morphology: [5]

The comparatively simple shells of Opisthoteuthidae and Stauroteuthidae are thought to approximate the ancestral shape, with those of Cirroteuthidae being more derived. [8] The shell of Cirroctopus appears transitional in form between those of incirrate octopuses and other cirrates, and resembles the reduced shell of the Late Cretaceous Palaeoctopus newboldi . [8] The paired, rod-shaped stylets of incirrates are evolutionarily derived from the lateral wings and horns of the cirrate shell. [8]

Related Research Articles

<i>Grimpoteuthis</i> Genus of cephalopods known as the dumbo octopuses

Grimpoteuthis is a genus of pelagic cirrate (finned) octopods known as the dumbo octopuses. The name "dumbo" originates from their resemblance to the title character of Disney's 1941 film Dumbo, having a prominent ear-like fin which extends from the mantle above each eye. There are 17 species recognized in the genus. Prey include crustaceans, bivalves, worms and copepods. The average life span of various Grimpoteuthis species is 3 to 5 years.

<span class="mw-page-title-main">Umbrella octopus</span> Family of molluscs

Umbrella octopuses are a group of pelagic octopuses. Umbrella octopuses are characterized by a web of skin between the arms, causing them to somewhat resemble an opened umbrella when the arms are spread.

<span class="mw-page-title-main">Cirrina</span> Suborder of octopuses

Cirrina or Cirrata is a suborder and one of the two main divisions of octopuses. Cirrate octopuses have a small, internal shell and two fins on their head, while their sister suborder Incirrina has neither. The fins of cirrate octopods are associated with a unique cartilage-like shell in a shell sac. In cross-section, the fins have distinct proximal and distal regions, both of which are covered by a thin surface sheath of muscle.

<span class="mw-page-title-main">Octopodiformes</span> Superorder of molluscs

Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid. All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid or modifying the tentacles into thin filaments. Octopodiformes is often considered the crown group of octopuses and vampire squids, including all descendants of their common ancestor. Some authors use the term Vampyropoda for the same general category, though others use "Vampyropoda" to refer to the total group. Another term is Octobranchia, referring to cephalopods without prominent tentacles.

<i>Stauroteuthis syrtensis</i> Species of octopus

Stauroteuthis syrtensis, also known as the glowing sucker octopus or bioluminescent octopus, is a species of small pelagic octopus found at great depths in the north Atlantic Ocean. It is one of a very small number of octopuses to exhibit bioluminescence.

<span class="mw-page-title-main">Cephalopod fin</span>

Cephalopod fins, sometimes known as wings, are paired flap-like locomotory appendages. They are found in ten-limbed cephalopods as well as in the eight-limbed cirrate octopuses and vampire squid. Many extinct cephalopod groups also possessed fins. Nautiluses and the more familiar incirrate octopuses lack swimming fins. An extreme development of the cephalopod fin is seen in the bigfin squid of the family Magnapinnidae.

<i>Cirroctopus</i> Genus of octopuses

Cirroctopus is a genus of four species of octopuses within the monotypic family Cirroctopodidae. Members of this genus have larger fins than other cirrate octopuses, and tend to be more muscular. They are found in the southern hemisphere, where they live at depths of over 300m.

<i>Opisthoteuthis</i> Genus of octopuses

Opisthoteuthis is a genus of cirrate octopuses, sometimes known as flapjack octopuses, which are found in all the world's oceans.

<i>Opisthoteuthis chathamensis</i> Species of octopus

Opisthoteuthis chathamensis is a species of cirrate octopus restricted to demersal habitats surrounding the Chatham Rise in New Zealand. It is commonly known as the roughy umbrella octopus.

Opisthoteuthis calypso or calypso flapjack octopus is a species of genus Opisthoteuthis, which are known as the cirrate octopuses. Octopuses in this genus are known as the flapjack octopuses and can be found in a variety of oceans across the world.

<i>Opisthoteuthis agassizii</i> Species of octopus

Opisthoteuthis agassizii, known as the Agassiz's flapjack octopus, is a lesser-known, deep-sea octopus first described in 1883 by Addison E. Verrill.

Opisthoteuthis borealis is a lesser-known species of octopus found near Greenland and Iceland, especially in the Davis Strait. The species was described from 9 specimens, and is one of the most recent Opisthoteuthis species described. Not much is known about it besides its anatomy and habitat.

Opisthoteuthis bruuni is a species of finned cirrate octopus found along the western coast of South America. Their tissue is almost jelly-like, and they have short, round bodies.

<i>Opisthoteuthis extensa</i> Species of octopus

Opisthoteuthis extensa is a species of octopus found off the west coast of Sumatra, an Indonesian island. It lives at a recorded depth of 768 m (2,520 ft). O. extensa lives in a benthic habitat, like many other cirrate octopuses. It occupies a deep part of the ocean where little sunlight penetrates.

<i>Opisthoteuthis grimaldii</i> Species of octopus

Opisthoteuthis grimaldii is an octopus found near the Azores.

Opisthoteuths hardyi is a lesser-known octopus species. It was described in 2002 from a male caught off the Shag Rocks, which are far south in the Atlantic Ocean near the Falkland Islands.

Opisthoteuths massyae is an octopus living in the eastern Atlantic Ocean.

<i>Opisthoteuthis medusoides</i> Species of mollusc

Opisthoteuthis medusoides is a cirrate octopus living off the coast of Tanzania near Dar es Salaam. However, its actual range may be more extensive.

Opisthoteuthis philipii is an octopus of the Indian Ocean. It lives off the coast of Kerala, India. Known specimens were found between 275–365 m (902–1,198 ft) deep in the Arabian Sea near Alappuzha.

Opisthoteuthis pluto is a deep-sea cirrate octopus found in the Great Australian Bight south of Australia. They live 270–810 m (890–2,660 ft) below the surface in the bathyal zone. Although their habitat is threatened, it is unclear how the species is affected, if at all. O. pluto is named for the Greek and Roman god of the Underworld.

References

  1. Fuchs, D., C. Ifrim & W. Stinnesbeck (2008). A new Palaeoctopus (Cephalopoda: Coleoidea) from the Late Cretaceous of Vallecillo, north-eastern Mexico, and implications for the evolution of Octopoda. Palaeontology51(5): 1129–1139. doi : 10.1111/j.1475-4983.2008.00797.x
  2. Young, R.E., M. Vecchione & K.M. Mangold (1999). Cephalopoda Glossary. Tree of Life Web Project.
  3. Young, R.E., M. Vecchione & K.M. Mangold (2002). Cirrate Shell Terminology. Tree of Life Web Project.
  4. Vecchione, M., K.M. Mangold & R.E. Young (2010). Cirrata Grimpe, 1916. Tree of Life Web Project.
  5. Collins, M.A. & R. Villanueva (2006). Taxonomy, ecology and behaviour of the cirrate octopods. In: Gibson, R.N., R.J.A. Atkinson & J.D.M. Gordon (eds.) Oceanography and Marine Biology: An Annual Review. Aberdeen University Press, Aberdeen. pp. 277–322.
  6. Collins, M., R. Villanueva & R.E. Young (2008). Cryptoteuthis Collins, 2004. Tree of Life Web Project.
  7. Villanueva, R., R.E. Young & M. Vecchione (2008). Opisthoteuthis Verrill 1883. Tree of Life Web Project.
  8. 1 2 3 Bizikov, V.A. (2004). Evolution of shell in Octopodiformes (Cephalopoda) Archived 2013-10-21 at the Wayback Machine . In: Abstracts of the conference Mollusks of the Northeastern Asia and Northern Pacific: Biodiversity, Ecology, Biogeography and Faunal History. October 4–6, 2004, Vladivostok, Russia. pp. 21–23.

Further reading