Stauroteuthis syrtensis
Encyclopedia
Stauroteuthis syrtensis 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
.
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
relationships difficult. Some authorities adopt the traditional view that the genus Stauroteuthis
is part of the family
Stauroteuthidae. The World Register of Marine Species however considers that it should be placed in the family Cirroteuthidae
, basing this decision on ribosomal DNA
and other evidence, and that Stauroteuthidae is a synonym
of this family.
length of Stauroteuthis syrtensis is about 5 centimetre and its width about 4 cm (1½ in). The fins are some 4 to 6 cm (1½ to 2½ in) in width. There are eight arms of unequal length, the longest extending to about 35 cm (13.8 in). 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. There are a total of about 60 adhesive suckers on each arm. Twenty-five of these are larger and extend to the edge of the web. In the male, the first eight suckers are reduced and the rest large and conical but in the female they are of an even size. 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. There are a further 30 to 40 smaller, closely packed suckers on the arm extensions and tips. The general texture is gelatinous and the animal is reddish-brown and translucent, with the internal organs being visible through the skin. There is a vestigial, U-shaped, internal shell which supports the fins, the only other hard parts of the animal being the two beaks.
on the eastern coast of the United States and has also been observed at similar depths off the British Isles.
of octopuses that exhibit bioluminescence
. Stauroteuthis syrtensis emits a blue-green light from about 40 modified suckers known as photophore
s situated in a single row between the pairs of cirri on the underside of each arm. The distance between these decrease 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 cyclic 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
, and also as a lure for the plankton
ic crustacean
s that form its main diet. The light may also be used for sexual signalling
, 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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of small pelagic octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
found at great depths in the north Atlantic Ocean. It is one of a very small number of octopuses to exhibit bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
.
Taxonomy
The cirrateCirrata
Cirrina is a suborder of octopuses. Cirrate octopuses have a small, internal shell and two fins on their head, while their sister suborder Incirrina has neither....
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
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
relationships difficult. Some authorities adopt the traditional view that the genus Stauroteuthis
Stauroteuthis
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....
is part of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Stauroteuthidae. The World Register of Marine Species however considers that it should be placed in the family Cirroteuthidae
Cirroteuthidae
Cirroteuthidae is a family of cirrate octopuses comprising three species in two genera.-Species:*Genus Cirroteuthis**Cirroteuthis muelleri*Genus Cirrothauma**Cirrothauma magna**Cirrothauma murrayi, Blind Cirrate-External links:**...
, basing this decision on ribosomal DNA
Ribosomal DNA
Ribosomal DNA codes for ribosomal RNA. The ribosome is an intracellular macromolecule that produces proteins or polypeptide chains. The ribosome itself consists of a composite of proteins and RNA. As shown in the figure, rDNA consists of a tandem repeat of a unit segment, an operon, composed of...
and other evidence, and that Stauroteuthidae is a synonym
Synonym
Synonyms are different words with almost identical or similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greek syn and onoma . The words car and automobile are synonyms...
of this family.
Description
The mantleMantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
length of Stauroteuthis syrtensis is about 5 centimetre and its width about 4 cm (1½ in). The fins are some 4 to 6 cm (1½ to 2½ in) in width. There are eight arms of unequal length, the longest extending to about 35 cm (13.8 in). 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. There are a total of about 60 adhesive suckers on each arm. Twenty-five of these are larger and extend to the edge of the web. In the male, the first eight suckers are reduced and the rest large and conical but in the female they are of an even size. 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. There are a further 30 to 40 smaller, closely packed suckers on the arm extensions and tips. The general texture is gelatinous and the animal is reddish-brown and translucent, with the internal organs being visible through the skin. There is a vestigial, U-shaped, internal shell which supports the fins, the only other hard parts of the animal being the two beaks.
Distribution
Stauroteuthis syrtensis is found in the North Atlantic at an extreme depth range of 500 to 4000 m (1,640.4 to 13,123.4 ft). It is most frequently found a few hundred metres from the bottom of the ocean at depths between 1500 and 2500 m (4,921.3 and 8,202.1 ft). It seems to be fairly common off the edge of the continental shelfContinental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
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 generaGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of octopuses that exhibit bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
. Stauroteuthis syrtensis emits a blue-green light from about 40 modified suckers known as photophore
Photophore
A photophore is a light-emitting organ which 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 decrease 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 cyclic 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
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, and also as a lure for the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s that form its main diet. The light may also be used for sexual signalling
Signalling theory
Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals. The central question is when organisms with conflicting interests should be expected to communicate "honestly"...
, 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.