''Stauroteuthis gilchristi'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of small

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

octopus An octopus (: octopuses or octopodes) 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, cuttlefish, and nautiloids. Like oth ...

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 emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorgani ...

, 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 ...

'' Stauroteuthis syrtensis''.

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 (; : radulae or radulas) is an anatomical structure used by mollusks 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 enters ...

. It can be distinguished from the otherwise similar '' Stauroteuthis syrtensis'' 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 sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

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

was taken from near

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

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

South Georgia South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

. There is a certain difference between these and the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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, and off

Macquarie Island Macquarie Island is a subantarctic island in the south-western Pacific Ocean, about halfway between New Zealand and Antarctica. It has been governed as a part of Tasmania, Australia, since 1880. It became a Protected areas of Tasmania, Tasmania ...

(south of Australia), and it may therefore have a circum-polar distribution throughout the Southern Ocean.

Ecology

In a study, the stomach contents of a top

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

sub-antarctic The sub-Antarctic zone is a physiographic 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 inc ...

waters, the

Patagonian toothfish The Patagonian toothfish (''Dissostichus eleginoides''), also known as Chilean sea bass, mero, and icefish, is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern ...

''(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 pecking, grasping, and holding (in probing for food, eating, manipulating and ca ...

. In waters around the

Crozet Islands The Crozet Islands (; 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 Antarctic Lands. History ...

, 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 Cephalopods described in 1924 Bioluminescent molluscs