Stauroteuthis gilchristi
Encyclopedia
Stauroteuthis gilchristi is a species
of small pelagic octopus
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
, like its sister taxon
Stauroteuthis syrtensis
.
by the larger suckers. Only a few specimens have been examined, and from these it seems that there is no sexual dimorphism
. However, this may not be the case, as most specimens so far collected have been either males or immature females.
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.
in sub-antarctic waters, the Patagonian toothfish
(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. In waters around the Crozet Islands
, 53 beaks of Stauroteuthis 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.
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 south Atlantic Ocean. It is believed to be 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...
, like its sister taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
Stauroteuthis syrtensis
Stauroteuthis syrtensis
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.-Taxonomy:...
.
Description
Stauroteuthis gilchristi has a secondary web, a small mantle aperture and a vestigial, U-shaped, fragment of shell supporting the fins. The arms are fringed with long cirri but these do not extend as far as the tip. There is no radula. It can be distinguished from the otherwise similar Stauroteuthis syrtensisStauroteuthis syrtensis
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.-Taxonomy:...
by the larger suckers. Only a few specimens have been examined, and from these it seems that there is no sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. However, this may not be the case, as most specimens so far collected have been either males or immature females.
Distribution
Stauroteuthis gilchristi is found in deep waters in the southern Atlantic Ocean. The type specimen was taken from near South Africa and is the only specimen recovered from that locality. A small number of individuals have since been recovered from near South Georgia. There is a certain difference between these and the holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
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 predatorPredation
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...
in sub-antarctic waters, the Patagonian toothfish
Patagonian toothfish
The Patagonian toothfish, Dissostichus eleginoides , is a fish found in the cold, temperate waters of the southern Atlantic, southern Pacific, Indian, and Southern Oceans on seamounts and continental shelves around most sub-Antarctic islands.A close relative, the Antarctic toothfish , is found...
(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. In waters around the Crozet Islands
Crozet Islands
The Crozet Islands 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.-Geography:...
, 53 beaks of Stauroteuthis 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.