''Stauroteuthis gilchristi'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of small

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...

found at great depths in the south Atlantic Ocean. It is believed to be one of a very small number of octopuses to exhibit

bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

, like its

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

Stauroteuthis syrtensis ''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 bi ...

''.

Description

''Stauroteuthis gilchristi'' has a secondary web, a small mantle aperture and a vestigial, U-shaped shell supporting the fins. The

arms Arms or ARMS may refer to: *Arm or arms, the upper limbs of the body Arm, Arms, or ARMS may also refer to: People * Ida A. T. Arms (1856–1931), American missionary-educator, temperance leader Coat of arms or weapons *Armaments or weapons **Fi ...

are fringed with long cirri but these do not extend as far as the tip. There is no

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

. It can be distinguished from the otherwise similar ''

'' by the larger suckers. Only a few specimens have been examined, and from these it seems that there is no

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. However, this may not be the case, as most specimens so far collected have been either males or immature females.''Stauroteuthis gilchristi'' (Robson 1924)
The Tree of Life Web Project. Retrieved 2011-10-06.

Distribution

''Stauroteuthis gilchristi'' is found in deep waters in the southern Atlantic Ocean. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was taken from near

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

and is the only specimen recovered from that locality. A small number of individuals have since been recovered from near

South Georgia South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east� ...

. There is a certain difference between these and the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

in that the cirri start further up the arm in the South Georgia specimens, and it is possible that there are in fact two different species, one on each side of the Atlantic. More recently, evidence has been found of the presence of this species in the southern Indian Ocean.

Ecology

In a study, the stomach contents of a top

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

sub-antarctic The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...

waters, the

Patagonian toothfish The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most ...

''(Dissostichus eleginoides)'', were examined in order to see what octopuses and squid formed part of the diet. These could be identified by the undigested remains of their

beaks The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for food, ...

. In waters around the

Crozet Islands The Crozet Islands (french: Îles Crozet; or, officially, ''Archipel Crozet'') are a sub-Antarctic archipelago of small islands in the southern Indian Ocean. They form one of the five administrative districts of the French Southern and Antarcti ...

, 53 beaks of ''S. gilchristi'' were found among a total of 1725 cephalopod beaks, and this cirrate octopus formed 3% of the diet of the toothfish. This study extended the range of ''S. gilchristi'' into the southern Indian Ocean.

References

{{Taxonbar, from=Q2500665 Octopuses Molluscs described in 1924 Bioluminescent molluscs