Architeuthis
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El calamar gigante, creída una criatura mítica, son calamares de la familia Architeuthidae, representados por ocho especies del género Architeuthis. Son animales de inmersión profunda, que crecen en dimensiones prodigiosas: recientes estimaciones dan un máximo de 10 m para machos y de 13 m para hembras
Los tentáculos llegan a 2 m en long. (más en hembras), y se han reclamado reportes de especímenes de más de 20 m, pero científicamente no han sido documentados. El 30 de septiembre de 2004, estudios del Museo Nacional de Ciencias de Japón y la Asociación de observadores de Ballenas de Ogasawara obtuvieron imágenes de un calamar gigante en su hábitat natural.[1] Se obtuvieron 556 fotos en 2006. Y el mismo equipo filmó un calamar gigante por primera vez el 4 de diciembre de 2006.[1]
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[editar] Biología
A pesar de su inmensidad, el calamar gigante no es particularmente pesado al compararlo con su principal predador, el cachalote, because the majority of their length is taken up by their eight arms and two tentacles. The weights of recovered specimens have been measured in hundreds, rather than thousands, of kg. Post-larval juveniles have been discovered in surface waters off New Zealand, and there are plans to capture more such juveniles and maintain them in an aquarium in an attempt to learn more about the creature's biology and habits.
Little is known regarding the reproductive cycle of the giant squid, but what has been learned is that the male of the species has a prehensile spermatophore-depositing tube, or penis, of over 9 dm) in length, which extends from inside the animal's mantle and apparently is used to inject sperm-containing packets into the female squid's arms — the means by which the sperm is transferred to the egg mass is a matter of much debate, but a recovery in Tasmania of a female specimen with a small subsidiary tendril attached to the base of each of its eight arms could be a vital clue to resolving the question. The giant squid lacks the hectocotylus used for reproduction in many other cephalopods.
Giant squid possess the largest eyes of any living creature—with the possible exception of those of the colossal squid—the eye being over 1 ft (30 cm) in diameter. The tentacles are equipped with hundreds of suction cups, each mounted on an individual "stalk" and equipped around its circumference with a ring of sharp teeth to aid the creature in capturing its prey by firmly attaching itself thereto by both suction and perforation. The size of the suction cups varies from 2 to 5 cm in diameter (1 to 2 in), and it is common to find their circular scars on the head area of sperm whales that have fed — or attempted to feed — upon giant squid. The only other known predator of the adult giant squid is the Pacific sleeper shark, found off Antarctica, but it is not yet known whether these sharks actively hunt the squid, or are simply scavengers of squid carcasses. Owing to the fact that sperm whales are skilled at locating giant squid, scientists have attempted to conduct
One of the more unusual aspects of giant squid (as well as some other species of large squid) is their reliance upon the low density of ammonia in relation to seawater to maintain neutral buoyancy in their natural environment, as they lack the gas-filled swim bladder that fish use for this function; instead, they use ammonia
As with all cephalopods, giant squid have special organs called statocysts to sense their orientation and motion in the water. The age of a giant squid can be determined by "growth rings" in the statocyst's "statolyth", analogous to determining the age of a tree by counting its rings. Much of what is known about giant squid is based upon estimates of the growth rings and from undigested beaks found in the stomachs of sperm whales.
[editar] Visión
El Architeuthis tiene los ojos más grandes del reino Animal. Hay algunos vertebrados más grandes que el Architeuthis, pero ninguno tienen los ojos de ese tamaño; 25 cm de diámetro.
Los cefalópodos se distinguen del resto de los invertebrados por poseer un complicado sistema visual. Tanto el sistema visual de los cefalópodos como el de los vertebrados son un ejemplo de evolución convergente. Esto significa que ambos grupos de animales son semejantes, pero su habilidad para ver se desarrolló por separado en cada grupo. De hecho, si comparamos los ojos de un calamar con los nuestros, encontramos notables diferencias en cuanto a su anatomía. Tanto los calamares como los humanos tienen ojos simples, con pupilas, iris y retina.
[editar] Tamaño
Giant squid size, and particularly total length, has often been misreported and exaggerated. Reports of specimens reaching or even exceeding 18 m (59 ft) in length are widespread, but no animals approaching this size have been scientifically documented. Such lengths were likely achieved by great lengthening of the two long feeding tentacles, analogous to stretching elastic bands.[2]
Based on the examination of 105 specimens as well as beaks recovered from Sperm Whales, the giant squid is not known to attain a mantle length (ML) in excess of 2.25 m (7.4 ft).[2] Including the head and arms, but excluding the tentacles, Architeuthis very rarely exceeds 5 m (16 ft) in length.[2] Maximum total length, when measured relaxed post mortem, is estimated at 13 m (43 ft) for females and 10 m (33 ft) for males from caudal fin to the tip of the two long tentacles.[2]
Giant squid exhibit sexual dimorphism. Maximum weight is estimated at 275 kg for females and 150 kg for males.[2]
[editar] Alimentación
Aunque el calamar gigante tiene ocho brazos, son los dos tentáculos más largos los que capturar las presas, pudiendo llegar a 12 m de largo. Cada tentáculo está equipado con ventosas, las cuales presentan una especie de anillo con dientes. Mientras que estos hacen succión, los dientes se clavan en la piel de la víctima, proporcionando así una mayor seguridad a la hora de acechar a sus presas. La boca de los calamares se parece bastante al pico de un loro. La lengua está equipada con un órgano llamado rádula, encargado de saborear la presa antes de que pase al esófago para que pueda ser digerida. En los estudios realizados de alimentación, en sus estómagos se han encontrado un alta porcentaje de bacaladilla. Las últimas necropsias también revelan restos de pequeños crustáceos.
[editar] Reproducción
Como los grandes mamíferos (elefantes, ballenas, gorilas), los calamares se pasan su vida creciendo para madurar y reproducirse. Para determinar la edad de un calamar se estudian los huesos del oído -los estatolitos-, los órganos del equilibrio, los cuales presentan una serie de anillos concéntricos como los que presentan los troncos de los árboles; lo único que hay que hacer es contar ese número de anillos para determinar la edad de un calamar. La edad máxima que puede alcanzar es de 5 años. La tasa de crecimiento de un calamar gigante es extraordinariamente rápida. Crecen 1 cm/día, son el animal con la tasa de crecimiento más rápida, de ahí que en pocos años tengan ese tamaño descomunal. Como muchos peces, los calamares tienen muchas limitaciones para poder reproducirse. Si las cosas van mal un año, ya bien sea por una mala salud, malas condiciones ambientales, etc. , en los siguientes años van a tener muchos problemas para poder reproducirse. Los calamares compensan esto poniendo grandes cantidades de huevos.
Los calamares gigantes, tanto del género Architeuthis Dux, como Taningea Danae, se caracterizan por tener un sistema reproductor bastante diferenciado de los demás cefalópodos. Por ello poseen un órgano copulador o pene, que puede llegar a alcanzar los 85 cm de longitud en el Taningea, y los 78 en el Architeuthis.
Según las últimas necropsias realizadas por Cepesma, estos órganos copuladores, supuestamente actúan mediante unos sistemas de presión (similares a los sistemas hidráulicos) por los cuales disparan los espermatóforos durante la cópula. En el primer ejemplar estudiado por Cepesma, se pueden observar estos espermatóforos incrustados en la masa muscular de los brazos del macho. En un principio, se supuso una relación sexual entre dos machos, descartándose al final, creyendo que se trata de una cópula con un una hembra en un cortejo con algún macho más.
En el caso del Taningea, no solamente posee un órgano reproductor, fácilmente visible, por encontrarse exteriorizado, teniendo este, una longitud tan larga como los brazos. También posee otro de similares características, aunque algo más pequeño (1/5 parte) dentro del manto.
[editar] Especies
The taxonomy of the giant squid, as with many cephalopod genera, has not been entirely resolved. Lumpers and splitters may propose as many as eight species or as few as one. The broadest list is:
- Architeuthis dux, "Calamr gigante del Atlántico"
- Architeuthis hartingii
- Architeuthis japonica
- Architeuthis kirkii
- Architeuthis martensi
- Architeuthis physeteris
- Architeuthis sanctipauli, "Calamar gigante del Sur"
- Architeuthis stockii
It is probable that not all of these are distinct species. No genetic or physical basis for distinguishing between the named species has been proposed, as evidenced by the placenames — of location of specimen capture — used to describe several of them. The rarity of observations of specimens and the extreme difficulty of observing them alive, tracking their movements, or studying their mating habits militates against a complete understanding.
In the 1984 FAO Species Catalogue of the Cephalopods of the World, C.F.E. Rope, M.J. Sweeney and C.F. Nauen wrote:
"Many species have been named in the sole genus of the family Architeuthidae, but they are so inadequately described and poorly understood that the systematics of the group is thoroughly confused."
Kir Nazimovich Nesis (1982, 1987) considers that only three species are likely to be valid.
In 1991, Frederick Aldrich of the Memorial University of Newfoundland wrote:
"I reject the concept of 20 separate species, and until that issue is resolved, I choose to place them all in synonymy with Architeuthis dux Steenstrup."
In a letter to Richard Ellis dated June 18, 1996, Martina Roeleveld of the South African Museum wrote:
"So far, I have seen nothing to suggest that there might be more than one species of Architeuthis."
In Cephalopods: A World Guide (2000), Mark Norman writes the following:
"The number of species of giant squid is not known although the general consensus amongst researchers is that there are at least three species, one in the Atlantic Ocean (Architeuthis dux), one in the Southern Ocean (A. sanctipauli) and at least one in the northern Pacific Ocean (A. martensi)."
[editar] Distribución
Se los encuentra en todos los océanos. Se han encontrado en el Atlántico Norte, Escocia, Irlanda, Sudáfrica, Nueva Zelanda y España, concretamente en el Caladero de Carrandi, entre las 18 y 30 millas (vertical de Colunga). Cepesma posee 21 calamares gigantes de distintas especies. Los Architeuthis expuestos van desde los 6 m a los 13 m de longitud. El primer ejemplar es una hembra inmadura de 1,5 años y 147 kg El segundo ejemplar pesa 140 kg y tiene tentáculos de 6,5 m de longitud. También ha ejemplares de 120, 114, 107 kg entre los más grandes.
[editar] Desplazamiento
El desplazamiento de los calamares gigantes del género Architeuthis Dux se efectúa mediante su sifón, algo parecido a un sistema de “propulsión a chorro”. Las dos pequeñas aletas que tienen en el manto les sirven como estabilizadores.
[editar] Línea del Tiempo
[editar] Mito
Es una criatura marina muy popular el calamar; basado en un espécimen de inmensas proporciones, con terribles y poderosos tentáculos, de ventosas, fuertes mandíbulas y ojos inmensos. Krake o kraken es una palabra noruega para “monstruo marino de fábula”. En 1755 se usó esa palabra para describir a una gran serpiente marina que nadaba cerca de un barco en la costa de Noruega, en 1746. De hecho, el Atlántico Norte ha acogido a un gran número de calamares gigantes, y no se trata de serpientes o de monstruos marinos, sino de calamares. Las leyendas de calamares son comunes entre marineros desde ancianos tiempos, estando la leyenda noruega del kraken, capaz de engullirse uan nave. Japetus Steenstrup, the describer of Architeuthis, suggested a giant squid was the species described as a sea monk to the Danish king Christian III c.1550. The Lusca of the Caribbean and Scylla in Greek mythology may also derive from giant squid sightings. However, it is thought to be impossible for a giant squid to lift its tentacles from the water. Eyewitness accounts of other sea monsters like the sea serpent are also thought to be mistaken interpretations of giant squid.
Steenstrup produced a number of papers on giant squid in the 1850s. He first used the term "Architeuthis" in a paper in 1857. A portion of a giant squid was secured by the French gunboat Alecton in 1861 leading to wider recognition of the species/genus in the scientific community. Between 1870 and 1880, large numbers of strandings occurred on the shores of Newfoundland. For example, a specimen washed ashore in Thimble Tickle Bay, Newfoundland on November 2, 1878 was 6.1 m (20 ft) long (mantle length), and one of its tentacles measured 10.7 m (35 ft) long and it was estimated as weighing 2.2 tonnes. In 1873 a squid "attacked" a minister and a young boy in a dory in Bell Island, Newfoundland.
Large numbers of strandings also occurred in New Zealand during the late nineteenth century. Although strandings continúe to occur sporadically throughout the world, the high frequency of strandings at Newfoundland and New Zealand in the late nineteenth century have not yet been repeated. It is not known exactly why giant squid become stranded on shore, but it is possible that a periodic though temporary alteration of the distribution of the deep, cold water where the squid live might be the cause. Many scientists who have studied squid mass strandings believe that they are cyclical and predictable, but the length of time between strandings is not yet known. A period of 90 years between mass strandings has been proposed by Frederick Aldrich, an Architeuthis specialist, who used this value to correctly predict a relatively small stranding that occurred between 1964 and 1966. By and large, however, squid strandings remain a mystery.
The search for a live Architeuthis specimen includes attempts to find live young, including larvae. Larval Architeuthis closely resemble larvae of Nototodarus and Moroteuthis, with distinctive characteristics being the shape of the mantle attachment by the head, the tentacle suckers, and the beaks. Approximately 65 specimens, one-fifth of all the giant squid ever found, have been found in the waters off Newfoundland; the last in December 2004.
El 30 de septiembre de 2004, Tsunemi Kubodera (National Science Museum of Japan) and Kyoichi Mori (Ogasawara Whale Watching Association) succeeded in taking history's first images of a live adult giant squid. Their teams had worked together for nearly two years to accomplish this. They used a five-ton fishing boat and only two crew members. The images were created on their third trip to a known Sperm Whale hunting ground 600 miles (970 km) south of Tokio, where they had dropped a 3,000 ft (900 m) line baited with squid and shrimp. The line also held a camera and a flash. After over twenty tries that day, a 26-foot (8 m) giant squid attacked the lure and snagged its tentacle. It took the squid over four hours to break free, during which time the camera took over 500 photos. These were the first photographs ever captured of a live giant squid in its natural habitat. The squid left behind, attached to the lure, an 18-foot (5.5 m) tentacle. Later DNA tests confirmed the animal as a giant squid.
El 27 de septiembre de 2005, Kubodera and Mori released the photos to the world. The photo sequence, taken at a depth of 900 m (nearly 3,000 ft) off Japan's Ogasawara Islands, shows the squid homing in on the baited line and enveloping it in "a ball of tentacles." The researchers were able to locate the likely general location of giant squid by closely tailing the movements of Sperm Whales. According to Kubodera, "we knew that they fed on the squid, and we knew when and how deep they dived, so we used them to lead us to the squid." Kubodera and Mori reported their observations in the journal Proceedings of the Royal Society.
Among other things, the observations demonstrate actual hunting behaviors of adult Architeuthis, a subject on which there had been much speculation. The photographs showed an aggressive hunting pattern by the baited squid, leading to it impaling a tentacle on the bait ball's hooks. This may disprove the theory that the giant squid is a drifter which eats whatever floats by, rarely moving so as to conserve energy. It seems that the species has a much more belligerent feeding technique.
In December 2005, the Melbourne Aquarium in Australia paid AUD$100,000 for the intact body of a giant squid, preserved in a giant block of ice, which had been caught by fishermen off the coast of New Zealand's South Island earlier in the year. [2]
In early 2006, another giant squid, later named "Archie", was caught off the coast of the Falkland Islands by a trawler. It measured 8.62 m (28 ft) and was then sent to the Natural History Museum in London for study and preservation. It was put on display on March 1, 2006 at the Darwin Centre.[3][4] [5]Most giant squid specimens tend to be those that have washed up dead on beaches, or been retrieved from the stomach of sperm whales; they tend to be in quite poor condition. The find of such a large, complete specimen is extremely rare.
Giant squid researchers undertook a painstaking process to preserve the giant creature, which is now on show in a 9 m (30 ft) long glass tank. The first stage was to defrost it, after it spent the trip back to England on ice aboard the trawler. This thawing took about four days. The major difficulty was then the body of the animal — or the mantle. Thawing the thick mantle took much longer than the comparatively thin tentacles. To prevent the tentacles from rotting, scientists bathed the mantle in water, while covering the tentacles in ice packs, after which they injected the squid with a formol-saline solution to prevent rotting.
The squid now resides in a glass tank, filled to the brim with preservative solution, and is one of 22 specimens that can be seen as part of the behind-the-scenes Darwin Centre tour of the Natural History Museum.
El 4 de diciembre de 2006, an adult giant squid was finally caught on video by Kubodera near the Ogasawara Islands, 1.000 km al sur de Tokio. It was a small female about 3,5 m long and weighing 50 kg. It was pulled aboard the research vessel but died in the process. [6]
As of 2004, almost 600 giant squid specimens had been reported.[3]
[editar] Calamares gigantes en la cultura
The elusive nature of the giant squid and its terrifying appearance have firmly established its place in the human imagination. Representations of the giant squid have been known from early legends of the Kraken through books such as Moby-Dick and Twenty Thousand Leagues Under the Sea to modern animated television programs.
In particular, the image of a giant squid locked in battle with a Sperm Whale is a common one, although the squid is, in fact, the whale's prey and not an equal combatant.
[editar] Referencias
- ↑ Kubodera, T. & K. Mori 2005. First-ever observations of a live giant squid in the wild.Plantilla:PDFlink Proceedings of the Royal Society B: Biological Sciences, 272(1581):2583-2586.
- ↑ a b c d e O'Shea, S. 2003. "Giant Squid and Colossal Squid Fact Sheet". The Octopus News Magazine Online.
- ↑ Guerra, A., A.F. González & F. Rocha 2004. Plantilla:PDFlink ICES Annual Science Conference 22–25 September 2004, Vigo, Spain.
- Ellis, R. 1998. The Search for the Giant Squid. Lyons Press (London).
- National Geographic Video: "Sea Monsters"
- Aldrich, F.A. & E.L. Brown 1967. The Giant Squid in Newfoundland. The Newfoundland Quarterly. Vol. LXV No. 3. p. 4–8.
- New giant squid predator found. Consultado el October 6de 2005.
- Holroyd, J. New squid on the (ice) block, The Age, 21 December 2005.
- Grann, D. The Squid Hunter. New Yorker, May 24, 2004.
- Foxnews.com: New giant squid predator found. Consultado el December 22de 2006.
[editar] Enlaces externos
Commons alberga contenido multimedia sobre Architeuthis.- Researchers catch giant squid
- BBC News Report
- Holy Squid! Photos Offer First Glimpse of Live Deep-Sea Giant
- TONMO.com's fact sheet for giant and colossal squids
- TONMO.com's giant squid reproduction article
- Reuters: Video of Giant Squid
- Encounters with Giant Squid
- 15 January, 2003, Giant squid 'attacks French boat'
- Cephalopod taxonomy (as PDF)
- Scientific report in Proceedings of the Royal Society
