Cirrus octopus
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Cirrus octopus ( Eledone cirrhosa ) |
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| ( Lamarck , 1798) |
The cirrus octopus ( Eledone cirrhosa ) is a cephalopod from the genus Eledone . It lives in the north-eastern Atlantic, from Norway , Iceland and the British Isles southwards to the Mediterranean .
features
The cirrus octopus is a medium-sized species of octopus . The dorsal octopus is mainly colored from yellow to orange to reddish brown and ventrally white with a greenish tinge, but the animal can adapt its color to its surroundings. The cirrus octopus is characterized by the very fine and dense grain of its skin with warts in between. It becomes up to 50 cm long, the coat length of large specimens reaches 160, in exceptional cases up to 175 millimeters.
The coat is relatively short and egg-shaped, the head significantly narrower than the coat. There is a cirrus above each eye. Its slim and quite short tentacles, which are finely tapered distally, reach about two and a half to three times the length of the mantle. They are connected to one another by a membrane that reaches about 40 percent of the arm's length, but narrows like a seam and continues almost to the tip of the tentacles. The arms only have a row of suction cups, in larger females around 120 to 140 per arm, they are rolled up at rest. They are almost the same length as one another, the ventral pair is slightly shorter. The third arm of the male on the right has been modified as a hectocotylus for mating, it is shorter than the others. Its ligula is very short, a calamus (a conical extension of the arm at the base of the ligula) is missing.
The outer hem of the coat is framed by a low, pale colored bead. The animal is yellowish or reddish orange to reddish brown on the back with diffuse rust-brown spots and white on the belly.
In the southern distribution area, the cirrus octopus can reach a body mass of up to 1 kg, while in the north it can weigh up to 2 kg.
distribution and habitat
The cirrus octopus is widespread in the northeast Atlantic from Norway (north to the Trondheimfjord ) and the south of Iceland across the North Sea and the English Channel , along the east Atlantic coast south to the coast of Morocco , including the coasts of Great Britain and Ireland . He also lives throughout the Mediterranean , including the Adriatic and the Marmara Sea . The distribution area ranges from 66 to 67 degrees up to 33 degrees north latitude .
It lives in different water depths (eurybathically) from shallow water up to 700, occasionally up to 770 meters water depth. Commercial catches mostly come from a depth of 50 (60) to 300 meters in the shelf sea. The species is predominantly soil-living ( benthic ) and prefers soft substrates such as sand and mud, but occasionally also occurs on hard substrates. Seasonally, far more females than males can be observed in shallow water, which is explained by migration in shallow sea areas for reproduction. However, the species is considered to be relatively little mobile and localized. It often disguises itself by digging in the sand until only the eyes are visible.
At the beginning of the 21st century, the number of cirrus octopuses in the North Sea increased, which is associated with the heavy fishing and the resulting decimation of large predatory fish such as the Atlantic cod ( Gadus morhua ). As a result, problems arose for the shrimp and lobster producers, as the cirrus octopus easily penetrated the vessels in order to prey on the crabs that were used as bait or caught here.
nutrition
The cirrus octopus feeds mainly on large decapods and fish . A serological analysis of octopuses from Moray Firth and Sound of Jura indicated that the main prey animals were species in the genus Liocarcinus , Nephrops norvegicus , Cancer pagurus , Crangon crangon and Carcinus maenas , although many individuals ate other prey. For some economically important cancers such as Homarus gammarus , Nephrops norvegicus and Cancer pagurus , it is an important predator, which the cancers often prey on from human-set traps. The octopus drills a hole in the chitin cuticle of the preyed cancer with its radula and paralyzes it by injecting toxins through the hole into the victim's body. Injected digestive enzymes loosen the meat from the chitin cuticle so that the octopus can easily detach it from the carapace.
Life cycle
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The cirrus octopus is around 1 to 5 years old and reaches sexual maturity at around 1 year of age, with the female being around 12 to 40 cm long with a body mass of 400 to 1000 g and the male being somewhat smaller. However, females weighing 1000 to 1200 g have also been observed which showed no signs of mature ovaries. Mating with internal fertilization takes place as with other octopuses with a heterocotylus . On average, a female lays around 1,000 to 5,000 eggs. The males can weigh a little over 600 g and usually have fully developed gonads with a body mass of 200 g.
Most animals reproduce only once in a lifetime ( semelpar ) and die shortly after reproduction. Young animals usually do not reach reproductive maturity until they are two years old, i.e. they live to be two years old. A small proportion (less than ten percent in the Mediterranean) does not reproduce in the second year and is three, very rarely more than three years old. Animals from the north of the distribution area tend to be older than those in the south.
The cirrus octopus reproduces in the north, especially in the months from July to September, so that there are numerous young animals in October. In the south the breeding season is earlier, in the western Mediterranean in early summer and in the eastern in late summer. The hatchlings that emerge from the eggs have a rounded to conical and slightly elongated body with a mantle length of 3.7 to 4.0 mm and a length of the not quite identical tentacles of 2.5 to 2.8 mm. The arms have 8 suction cups and 8 to 11 chromatophores in a row. The funnel has 2 chromatophores on the side of the lip. The mantle is densely covered both ventrally and dorsally with over 50 chromatophores each, but these may be missing in the area above the midgut gland . The dorsal surface of the midgut gland shows 13 visceral chromatophores. On the dorsal part of the head there are over 6 chromatophores in an arrangement of 2 and 4, while each eye has at least 8 chromatophores and is surrounded by silver-colored iridophores. In young animals with a coat length of 12 mm, the somewhat unequal arms are 16 mm long and have at least 28 suction cups in a row, while the number and arrangement of the chromatophores corresponds to those in hatchlings.
Predators
Studies of the stomach contents of stranded round-headed dolphins ( Grampus griseus ) on the coast of Scotland revealed that their main prey was cirrus octopus.
Economical meaning
The species is intensively fished and has regional economic importance, especially in the western Mediterranean. In the Atlantic, so the lobster -Fisheries against Scotland, they are, however, rarely used and thrown as an unwanted "bycatch" back into the sea. The species is mainly fished with trawling , using bottom trawls . The species is fished almost all year round, with maximum catches from July to December. Two size classes are used in the Mediterranean. In addition to the adult octopuses, there is a specialized fishery for juveniles, which are called "popets" in Catalonia and "moscardini" in Tuscany.
The catches are difficult to indicate. Although the species is listed in the FAO's FishStat database, the majority of the catches are not broken down by species but are thrown together in a collective category with other octopus species, so that reliable figures are only available for Eledone cirrhosa , Eledone moschata and Octopus vulgaris together . However, it is assumed that the catches of E.cirrhosa against E.moschata predominate. For the year 2005 catches of 9600 tonnes for both Eledone species together are given for the Mediterranean .
Taxonomy
The species was first described in 1798 by the French zoologist Jean-Baptiste Lamarck . A common synonym is Octopus aldrovandi Montfort, 1802.
literature
- Sven Gehrmann: The fauna of the North Sea - lower animals & vertebrates. Epubli, 2011. p. 211.
- PJ Hayward, JS Ryland: Handbook of the Marine Fauna of North-West Europe. Oxford University Press, Oxford 1995. Eledone cirrhosa , p. 628.
Web links
Individual evidence
- ↑ a b Patrizia Jereb, Clyde FE Roper, Mark D. Norman, Julian K. Finn: Cephalopods of the world. An annotated and illustrated catalog of cephalopod species known to date. Volume 3: Octopods and Vampire Squids. FAO Food and Agriculture Organization of the United Nations, Rome 2016. ISBN 978-92-5-107989-8 . Eledone cirrhosa on pages 117–118.
- ↑ a b c d e f Patrizia Jereb, A. Louise Allcock, Evgenia Lefkaditou, Uwe Piatkowski, Lee C. Hastie, Graham J. Pierce (editors): Cephalopod biology and fisheries in Europe: II. Species Accounts. ICES Cooperative Research Report no.325. ICES International Council for the Exploration of the Sea, June 2015. 360 pages. ISBN 978-87-7482-155-7 . Eledone cirrhosa, Horned Octopus on pages 29–41.
- ↑ Emily Wilson: Eledone cirrhosa, Curled octopus. In: H. Tyler-Walters, K. Hiscock (Eds.): Marine Life Information Network , Biology and Sensitivity Key Information Reviews. Marine Biological Association of the United Kingdom , Plymouth 2008.
- ^ Report of the Working Group on Cephalopod Fisheries and Life History (WGCEPH). SICICOM Steering Group on Ecosystem Functions (SSGEF), International Council for the Exploration of the Sea , 2013.
- ↑ a b C. D. MacLeod, MB Santos, GJ Pierce: Can habitat modeling for the octopus Eledone cirrhosa help identify key areas for Risso's dolphin in Scottish waters? ( Memento of December 24, 2016 in the Internet Archive ). Scottish Natural Heritage Commissioned Report No. 530. Scottish Natural Heritage, Inverness 2014.
- ↑ PR Boyle, MS Grisley, G. Robertson (1986): Crustacea in the Diet of Eledone cirrhosa (Mollusca: Cephalopoda) deterministic mined by Serological Methods. Journal of the Marine Biological Association of the United Kingdom 66 (4), pp. 867-879. doi : 10.1017 / s0025315400048499
- ^ PR Boyle (1986): A Descriptive Ecology of Eledone cirrhosa (Mollusca: Cephalopoda) in Scottish Waters. Journal of the Marine Biological Association of the United Kingdom 66, pp. 855-865. doi = 10.1017 / S0025315400048487
- ^ NW Runham, CJ Bailey, M. Carr, CA Evans, S. Malham (1997): Hole drilling in crab and gastropod shells by Eledone cirrhosa (Lamarck, 1798). Scientia Marina 61, Supplement 2, pp. 67-76.
- ^ PR Boyle, Daniela Knobloch (1983): The female reproductive cycle of the octopus, Eledone cirrhosa. Journal of the Marine Biological Association of the United Kingdom 63 (1), pp. 71-83. doi = 10.1017 / s002531540004981x
- ^ PR Boyle (1984): Male reproductive maturity in the octopus, Eledone cirrhosa (Cephalopoda: Octopoda). Journal of the Marine Biological Association of the United Kingdom 64 (3), pp. 573-579. doi = 10.1017 / s0025315400030265
- ↑ Frances Dipper (2017): Wildlife Reports: Marine Life. British Wildlife 29 (2), pp. 135-137.
- ↑ M. van Couwelaar: Eledone cirrhosa (Lamarck, 1798). Zooplankton and Micronekton of the North Sea, Marine Species Identification Portal, accessed June 25, 2018.