| Vulcanoctopus | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | Octopoda |
| Family: | Enteroctopodidae |
| Genus: | Vulcanoctopus González & Guerra, 1998 |
| Species: | V. hydrothermalis |
| Binomial name | |
| Vulcanoctopus hydrothermalis González & Guerra, 1998 | |
Vulcanoctopus hydrothermalis, also known as thevent octopus, is a smallbenthicoctopusendemic tohydrothermal vents.[1] It is theonly known species of thegenusVulcanoctopus. This vent octopus is endemic to the hydrothermal vent habitat that is located in the East Pacific Rise.[2]
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.[3]V. hydrothermalis has been shown to exhibit feeding that relies on the coordination of their arms to entrap their prey.[4] 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.[5]
Vulcanoctopus hydrothermalis lives along theEast Pacific Rise which borders thePacific,Cocos, andNazca Plates. The vent octopus is found near colonies ofgiant tube worms,[2] 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.[2] 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 onlycephalopod endemic to this environment. The vent octopus has been observed to congregate around vents, but isolated elsewhere.[6] It is because of this close proximity thatV. hydrothermalis are thought to be more prone to infections by the parasiteGenesis vulcanoctopusi, which is described further in Host-Parasite Relationships.[4]
The morphology ofVulcanoctopus 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 anink sac. Additionally, itsdorsalarms are longer than theventral arms and featurebiserial suckers. Overall,V. hydrothermalis has a mean total length of 184 mm (7.2 in).[3]
The first femaleV. hydrothermalis was discovered at the Gromit hydrothermal vent site in 2004 and captured for comparison against the male species.[5] The ratio of recovered individuals is skewed towards males, indicating fewer females or spatial segregation by sex.[6] The female was found to have similar external characteristics to males, but differed in its reproductive and digestive systems.[5] Unlike the digestive systems of this male vent octopus, the females lacked the appearance of dark swelling. Females also lack spermathecae, which internally holdsspermatophores.[5]
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 usejet propulsion. One specimen exhibited “tactile feeding,” using its dorsal arms to sense prey while crawling on theseabed. 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.[6]
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 itshectocotylus. The transparency of their skin allowed the observers to note their sexual maturity without specimens being gathered.[6]
Its confirmed prey consist of theamphipod andcrab, which are thought to be their primary food sources.[1] Analyzing the materials within the digestive tracts ofVulcanoctopus hydrothermalis, researchers believe that these vent octopuses engage in a foraging behavior and feed on large aggregates of amphipods.[4] At 2,620 meters depth, theHOV Alvin has captured video evidence ofV. hydrothermalis wrapping their arms around thesebathypelagic 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 thatsulfide spires located along the hydrothermal vent may serve to benefitV. 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.[4]
Genesis vulcanoctopusi, acopepod parasite, is described fromVulcanoctopus hydrothermalis. Anendoparasitic relationship is characterized by the presence of all copepodid stages, found within the connective tissue beneath the epithelium ofV. hydrothermalis ' head and mantle.[7] The parasitism leads to structural integrity loss in theV. hydrothermalis' tissue, with signs of compression, deformation, and mechanical disruption due to the copepods' presence, which causes significant cell-mediated immune response by cephalopodamoebocytes.[7]