Antarctic giant octopus
| Antarctic giant octopus | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Megaledons | ||||||||||||
| Taki , 1961 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Megaleledons setebos | ||||||||||||
| ( Robson , 1932) |
The Antarctic giant octopus ( Megaleledon setebos ) is a cephalopod and the only species in the genus Megaledon . He lives in Antarctica . The species was first described by Guy Coburn Robson in 1932. The genus Megaledon was described in 1961 by Iwao Taki . The giant Antarctic octopus is probably the sister species of all deep-sea octopuses with suction cups arranged in a row.
features
anatomy
Megaledon setebos has an average mantle length of 28 centimeters and reaches a total length of 90 centimeters. The heaviest specimen to date had a total weight of 27 kilograms.
The webbing extends deep and covers 40% of the arm's length at the deepest point. It reaches deepest on the side arms. The webs are least developed on the back and the ventral arms. The edges expand to the tips of the tentacles. The tentacles reach two to three times the length of the mantle and are of different lengths. The dorsal arms are the shortest. The giant Antarctic octopus has comparatively thick limbs. The suction cups on each arm are arranged in a single row. Large animals have 40 to 69 suction cups on each tentacle. There are no enlarged suction cups. In male Megaledon setebos , the third right arm forms the Hectocotylus , the length of which is about 90 to 95% of the remaining arms. At the top is the ligula , which makes up three to four percent of the arm's length. The Calmus is of medium size with around 40% of the length of the ligula. The mating arm has only 35 to 40 suction cups.
The gills have 10 to 13 lamellae per demibranch . The funnel organ has a V-shaped appearance. The radula consists of nine elements, seven rows of teeth and tiny plates. The esophagus is only swollen with no visible goiter. An ink bag is provided and opens outward in front of the anus. Anal valves are present.
Appearance
The skin color of the Antarctic giant octopus varies on its upper side from pink and cream to gray and pink. The ventral skin surface is cream-colored. The body is speckled with pink spots. There are no ocelles , so-called false eye spots. The skin is loose and at large intervals covered with fine, rounded, wart-shaped structures called papillae. There are only small papillae above the eyes. The giant Antarctic octopus has a skin ridge around the lateral edge of the mantle.
Like all real octopuses, the Antarctic giant octopus can adapt its appearance to its surroundings through a combination of different chromatophores and a change in skin texture.
Poison
Like many real octopuses, Megaledon setebos has a poison with which it kills its prey and which is also effective at temperatures below freezing point. He injects this poison by drilling small holes in the shells of molluscs and pouring them into them. It is harmless to humans.
Way of life
habitat
The Antarctic Circumpolar Current forms the habitat of the species around the Antarctic. However , the species does not exist in the waters around the islands of the Subantarctic . The Antarctic giant octopus is a deep sea dweller and lives at depths between 32 and 850 meters below sea level on muddy and sandy surfaces made of gravel and rocks. There he preferably hides under sponges and moss animals .
Reproduction
The spermatophores are comparatively large at 150 to 235 millimeters. These are transmitted to the female with a special tentacle, the hectocotylus. The giant Antarctic octopus lays large eggs that can reach a diameter of up to 42 millimeters.
evolution
In 2008, as part of the cataloging of the Census of Marine Life (CoML), in which more than 80 nations participate, including biologists from the British Antarctic Survey (BAS) in Cambridge, numerous species living in Antarctica and in the deep sea were collected, whereupon one Group of predominantly Australian researchers compared their genetic makeup. In this study, Megaleledon setebos was the sister species of a clade of other species, all of which are distributed in the deep sea, with a distribution focus on the southern hemisphere. According to the methods of the molecular clock , the common clade is about 33 million years old. The data confirm a hypothesis according to which the deep-sea species could all be descended from an ancestor who, like megaleledons setebos, lived in the shelf sea of Antarctica today .
More recent studies by the same working group have shown that the common clade of the Antarctic and deep-sea inhabitants is not closely related to the genus Eledone . They therefore proposed a new family, Megaleledonidae, for these genera.
Historical systematics
The species was first named by Guy Coburn Robson as Graneledone setebos in 1932. Iwao Taki provisionally assigned the species to the newly established genus Megaleledon in 1961 , but could not make an exact classification because he did not have the type material . In 2003 it was shown that the species Megaledon senoi, newly described by Taki, is identical to Graneledon setebos . The species Takis was assigned to the genus, the validity of which, despite the synonymisation of the species, remained recognized. The type species of the genus is therefore Megaleledone senoi ( synonym for Megaledone setebos ).
confusion
Despite the same German name, the Antarctic giant octopus does not belong to the genus of giant octopus ( Enteroctopus ).
Individual evidence
- ↑ a b c World Register of Marine Species
- ↑ a b c d e f g Cephalopods of the world. An annotated and illustrated catalog of cephalopod species known to date (p. 85)
- ^ Octopuses in the Southern Ocean: a prominent role in the ecosystem
- ↑ Skin as superreflectors
- ↑ Octopodidae - Article at Tree of Life
- ↑ Antarctic octopuses found with cold-resistant venom
- ^ Jan M. Strugnell, Alex D. Rogers, Paulo A. Prodo, Martin A. Collins, A. Louise Allcock (2008): The thermohaline expressway: the Southern Ocean as a center of origin for deep-sea octopuses. Cladistics 24: 853-860. doi : 10.1111 / j.1096-0031.2008.00234.x
- ↑ Jan M. Strugnell, Mark D. Norman, Michael Vecchione, Michelle Guzik, A. Louise Allcock (2014): The ink sac clouds octopod evolutionary history. Hydrobiologia 725 (1): 215-235. doi : 10.1007 / s10750-013-1517-6
- ^ AL Allcock, FG Hochberg, TN Stranks (2003): Re-evaluation of Graneledone setebos (Cephalopoda: Octopodidae) and allocation to the genus Megaleledone. Journal of the Marine Biological Association of the United Kingdom 83: 319-328.