''Stauroteuthis syrtensis'', also known as the glowing sucker octopus or bioluminescent octopus, 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 north Atlantic Ocean. It is 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 ...

Taxonomy

The cirrate octopuses are deep sea species that have been relatively little studied. Some have been described on the basis of a single, poorly preserved specimen, and this makes deducing their

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

relationships difficult. Some authorities adopt the traditional view that the genus '' Stauroteuthis'' is part of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Stauroteuthidae ''Stauroteuthis'' is a genus of deepwater octopus, a cephalopod mollusk. This is the only genus in the family Stauroteuthidae, and only two species have been described in this genus. The organisms live below water depth; although sometimes foun ...

that is characterized by the presence of a secondary web. The

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialist ...

, however, considers that it should be placed in the family Cirroteuthidae, basing this decision on

ribosomal DNA Ribosomal DNA (rDNA) is a DNA sequence that codes for ribosomal RNA. These sequences regulate transcription initiation and amplification, and contain both transcribed and non-transcribed spacer segments. In the human genome there are 5 chromos ...

and other evidence, and that Stauroteuthidae is a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

of this family.

Description

The mantle length of ''Stauroteuthis syrtensis'' is about and its width about . The

fins A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

are some in width. The eight arms are of unequal length, the longest extending to about . These are joined for two-thirds of their length by two webs, a dorsal complete membrane and a ventral partial one, giving the animal an umbrella-like shape. The number of adhesive suckers ranges from 55 to 65. These suckers vary in size and distance among males and females. However, suckers generally decrease in diameter and distance as they extend down the arm. Female suckers reach a maximum diameter of 6.5 mm at suckers 1 to 3 while male suckers, on the other hand, are relatively larger. Between suckers 8 to 25 there are conspicuous cirri. These are elongate, fleshy tendrils borne on the sides of the oral surface of the arms, the longest being at sucker 20 which can be up to 50 mm in length.''Stauroteuthis syrtensis'' - Verrill 1879
The Tree of Life Web Project. Retrieved 2011-10-04. The oral cavity and mouth area are pink or purple in color that extends towards the arms and lightens as it reaches the tips. The general texture is gelatinous and the animal is reddish-brown and translucent, with the internal organs being visible through the skin. A vestigial, U-shaped, internal shell supports the fins, the only other hard part of the animal being the two-part beak.''Stauroteuthis''
Encyclopedia of Life. Retrieved 2011-10-04.

Distribution

''Stauroteuthis syrtensis'' is found in the North Atlantic at an extreme depth range of . It is most frequently found a few hundred metres from the bottom of the ocean at depths between . It seems to be fairly common off the edge of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

on the eastern coast of the United States, and has also been observed at similar depths off the British Isles.

Bioluminescence

''Stauroteuthis'' is one of only two

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

of octopuses to exhibit

. ''S. syrtensis'' emits a blue-green light from about 40 modified suckers known as

photophore A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, ...

s situated in a single row between the pairs of cirri on the underside of each arm. The distance between these decreases towards the ends of the arms with the light becoming fainter. The animal does not emit light continuously, but can do so for a period of five minutes after suitable stimulation. Some of the photophores emit a continuous stream of faint light, while others are much brighter and switch on and off in a cyclical pattern, producing a twinkling effect. The function of the bioluminescence is believed to be for defence, being used by the animal to scare off

predators 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 ...

, and also as a lure for the

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s that form its main diet. The light may also be used for

sexual signaling Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (i ...

, but this is considered to be an unlikely function, as the light is deployed by both sexes and by immature, as well as mature, individuals.

References

{{Taxonbar, from=Q1964816 Octopuses Molluscs described in 1879 Molluscs of the Atlantic Ocean Bioluminescent molluscs Taxa named by Addison Emery Verrill