''Vulcanoctopus hydrothermalis'', also known as the vent octopus, is a small

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

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 ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...

s. It is the only known species of the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Vulcanoctopus''. This vent octopus is endemic to the hydrothermal vent habitat that is located in the East Pacific Rise. ''V. hydrothermalis'' has evolved unique adaptations to accommodate for the distinct circumstances of this very dynamic habitat. In particular, they are characterized as having double rows of suckers on each arm. ''V. hydrothermalis'' has been shown to exhibit feeding that relies on the coordination of their arms to entrap their prey. In terms of external appearance, both the female and male vent octopuses exhibit similar physical traits. Internally, the anatomy of the reproductive and digestive tract is different between female and male vent octopuses.

Habitat

''Vulcanoctopus hydrothermalis'' lives along the

East Pacific Rise The East Pacific Rise (EPR) is a mid-ocean rise (usually termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), at a divergent tectonic plate bound ...

which borders the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

, Cocos, and

Nazca Plate The Nazca plate or Nasca plate, named after the Nazca region of southern Peru, is an oceanic list of tectonic plates, tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru– ...

s. The vent octopus is found near colonies of

giant tube worm ''Riftia pachyptila'', commonly known as the giant tube worm and less commonly known as the giant beardworm, is a marine invertebrate in the phylum Annelida (formerly grouped in phylum Pogonophora and Vestimentifera) related to tube worms ...

s,González, A. F., A. Guerra, S. Pascual and P. Briand. (1998). ''Vulcanoctopus hydrothermalis'' gen. Et sp. nov. (Mollusca, Cephalopoda): an octopod from a deep-sea hydrothermal vent site. Cah. Biol. Mar. 39: 169–184. which are located at hydrothermal vents. These environments are made very hostile as hot water rises through vents, releasing a black 'cloud,' or plume, of metal sulfides and other toxic chemicals that result in acidic conditions. The temperature of the hydrothermal vent in the East Pacific Rise varies from 1-10 degrees celsius depending on its surroundings of seawater or plumes and is around 2640 m deep. ''V. hydrothermalis'' are regarded as the only

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

endemic to this environment. The vent octopus has been observed to congregate around vents, but isolated elsewhere. It is because of this close proximity that ''V. hydrothermalis'' are thought to be more prone to infections by the parasite ''Genesis vulcanoctopusi'', which is described further in Host-Parasite Relationships.

Description

The morphology of ''Vulcanoctopus hydrothermalis'' is characterized by some unusual traits. Due to the selection pressures of the deep sea, ''V. hydrothermalis'' has adapted traits in response to these unique conditions. One such adaptation is that they do not have an

ink sac An ink sac is an anatomical feature that is found in many cephalopod mollusks used to produce the defensive cephalopod ink. With the exception of nocturnal and very deep water cephalopods, all Coleoidea (squid, octopus and cuttlefish) which dwell ...

. Additionally, its

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

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 longer than the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

arms and feature biserial suckers. Overall, ''V. hydrothermalis'' has a mean total length of . The first female ''V. hydrothermalis'' was discovered at the Gromit hydrothermal vent site in 2004 and captured for comparison against the male species. The ratio of recovered individuals is skewed towards males, indicating fewer females or spatial segregation by sex. The female was found to have similar external characteristics to males, but differed in its reproductive and digestive systems. Unlike the digestive systems of this male vent octopus, the females lacked the appearance of dark swelling. Females also lack spermathecae, which internally holds

spermatophores A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially ...

Behavior

''Vulcanoctopus hydrothermalis primary defense mechanism against a predator is to freeze in place. The secondary defense involves pushing away from the bottom of the seafloor and then drifting back down once the threat has dissipated. ''V. hydrothermalis'' uses its front arms (I dorsal and II dorsolateral) to detect and catch prey. The back arms (III ventrolateral and IV ventral) function to support the weight of the vent octopus and move it forward. This species has not been observed to use jet propulsion. One specimen exhibited “tactile feeding,” using its dorsal arms to sense prey while crawling on the

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. It attempted to seize a crab with arms I and II, but aborted the capture upon realizing the crab’s large size, subsequently altering its course. As for reproductive behavior, five mature specimens were observed displaying a reproductive patterns described as "mounting" or "mating at a distance." Three specimens were observed mounting a fourth while a fifth mated from a distance using its

hectocotylus A hectocotylus (: hectocotyli) is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. Depending on the species, the male may use it merel ...

. The transparency of their skin allowed the observers to note their sexual maturity without specimens being gathered.

Predator-prey relationships

Its confirmed prey consist of the

amphipod Amphipoda () is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphipod species cur ...

and

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

, which are thought to be their primary food sources. Analyzing the materials within the digestive tracts of ''Vulcanoctopus hydrothermalis'', researchers believe that these vent octopuses engage in a foraging behavior and feed on large aggregates of amphipods. At 2,620 meters depth, the HOV Alvin has captured video evidence of ''V. hydrothermalis'' wrapping their arms around these

bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypela ...

amphipods. Specifically, they coordinate their arms in a starburst pattern to form a water-filled web and engulf their prey. Considering the fact that this predator-prey relationship has been predominantly observed around the hydrothermal vent site in the East Pacific Rise, researchers propose that

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

spires located along the hydrothermal vent may serve to benefit ''V. hydrothermalis predatory behavior. The current hypothesis is that the spires enable the octopuses to effectively grip onto this section of the vent and gain access to the dense aggregations of their prey.

Host-parasite relationships

''Genesis vulcanoctopusi'', a

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

parasite, is described from ''Vulcanoctopus hydrothermalis.'' An endoparasitic relationship is characterized by the presence of all copepodid stages, found within the connective tissue beneath the epithelium of ''V. hydrothermalis'' ' head and mantle. The parasitism leads to structural integrity loss in the ''V. hydrothermalis''' tissue, with signs of compression, deformation, and mechanical disruption due to the copepods' presence, which causes significant cell-mediated immune response by cephalopod

amoebocytes An amebocyte or amoebocyte () is a motile cell (moving like an amoeba) in the bodies of invertebrates including cnidaria, echinoderms, molluscs, tunicates, sponges, and some chelicerates. Moving by pseudopodia, amebocytes can manifest as blood ce ...

References

External links

''Vulcanoctopus hydrothermalis''
at

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(pictures) {{Taxonbar, from2=Q1948648, from1=Q21229929 Enteroctopodidae Taxa described in 1998 Monotypic cephalopod genera