Giant squid: Difference between revisions
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==References== |
==References== |
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Revision as of 13:45, 4 July 2006
| Giant squid | |
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| Family: | Architeuthidae Pfeffer, 1900
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| Genus: | Architeuthis Steenstrup, 1857b
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Architeuthis dux | |
Giant squid, once believed to be mythical creatures, are squid of the Architeuthidae family, represented by as many as eight species of the genus Architeuthis. They are deep-ocean dwelling squid that can grow to a tremendous size: recent estimates put the maximum size at 10 m (34 ft) for males and 13 m (44 ft) for females from caudal fin to the tip of the two long tentacles (second only to the Colossal Squid at an estimated 14 m, one of the largest living organisms). The mantle length, though, is only about 2 m (7 ft) in length (more for females, less for males), and the length of the squid excluding its tentacles is about 5 m (16 ft). There were reported claims of specimens of up to 20 m (66 ft), but none had been scientifically documented. On September 30, 2004, researchers from the National Science Museum of Japan and the Ogasawara Whale Watching Association took the first images of live giant squid in their natural habitat. The photos were released a year later.
The Natural History Museum in London put a preserved specimen on display on 1st March 2006 at their Darwin Centre [1][2] [3].
Biology
Despite their great length, giant squid are not particularly heavy when compared to their chief predator, the Sperm Whale, 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 kilograms. 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.
The reproductive cycle of the giant squid is still a great mystery, but what has been learned so far is both bizarre and fascinating; male giant squid are equipped with a prehensile spermatophore-depositing tube, or penis, of over 3 feet (90 cm) 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 — how exactly the sperm then is transferred to the egg mass is a matter of much debate, but the recent recovery in Tasmania of a female specimen having a small subsidiary tendril attached to the base of each of its eight arms could be a vital clue in the solution of this enigma. The giant squid lacks the hectocotylus used for reproduction in many other cephalopods.
Giant squid possess the largest eyes of any living creature, over 1 foot (30 cm) in diameter, and their arms are equipped with hundreds of suction cups in total; each is 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 to it both by suction and perforation. The size of these suction cups can vary from 2 to 5 cm in diameter (one to two inches), and it is not uncommon 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. Because sperm whales are skilled at locating giant squid, scientists have attempted to conduct in-depth observations of sperm whales in order to study squid.
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 (in the form of ammonium chloride) in the fluid of their flesh throughout their bodies, making it taste not unlike salmiakki. This makes the giant squid unattractive for general human consumption, although sperm whales seem to be attracted by (or are at least tolerant of) its taste.
Like all cephalopods they use special organs called statocysts to sense their orientation and motion in the water. The age of giant squids can be estimated by "growth rings" in the statocyst's "statolyth" much like counting tree rings. Much of what is known about these animals come from estimates based on these, and from undigested beaks found in sperm whale stomachs.
Species
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, "Atlantic Giant Squid"
- Architeuthis hartingii
- Architeuthis japonica
- Architeuthis kirkii
- Architeuthis martensi
- Architeuthis physeteris
- Architeuthis sanctipauli, "Southern Giant Squid"
- 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.
Nesis (1982, 1987) considers that only three species are likely to be valid.
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. santipauli) and at least one in the northern Pacific Ocean (A. martensi)."
Timeline
Tales of giant squid have been common among mariners since ancient times, and may have led to the Norwegian legend of the kraken, a tentacled sea monster as large as an island capable of engulfing and sinking any ship. 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 Glover's Harbour, 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 continue 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.
On September 30, 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 giant squid. Their teams had worked together for nearly two years to make the accomplishment. 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 grounds 600 miles south of Tokyo, where they had dropped a 3,000 foot line baited with squid and shrimp. The line also held a camera and a flash. After over twenty tries that day, a 26-foot 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 tentacle. Later DNA tests confirmed the animal as a Giant squid.
On September 27, 2005, Kubodera and Mori released the photos to the world. The photo sequence, taken at a depth of 900 m (nearly 3000 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. [4]
Giant squid researchers, including Prof. Adam Siefkas of the Southern Illinois University Carbondale, 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, (having spent the trip back to England on ice abord 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.
More recently in early 2006 another giant squid was caught off the coast of the Falkland Islands by a trawler. It measured 8.62 m (28 ft). Most giant squid tend to be washed up dead on beaches, or retrieved from the stomach of sperm whales, so they tend to be in quite poor condition, as a result, finding such a large, complete specimen is extremely rare. It was then sent to the Natural History Museum in London for study and preservation.
Giant squid in culture
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 often seen, although it is now known that the squid is the whale's prey and not an equal combatant.
See also
References
- Ellis, R. (1998) The Search for the Giant Squid. Lyons Press. London.
- National Geographic Video: "Sea Monsters"
- Aldrich, F. A., and Brown, E. L. 1967. The Giant Squid in Newfoundland. The Newfoundland Quarterly. Vol. LXV No. 3. p. 4–8.
- "New giant squid predator found". Retrieved October 6.
{{cite web}}: Check date values in:|accessdate=(help); Unknown parameter|accessyear=ignored (|access-date=suggested) (help) - Holroyd, Jane. New squid on the (ice) block, The Age, 21 December 2005.
External links
- Face to face at last with Captain Nemo's old foe
- japanese photo link
- 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
- Encounters with Giant Squid
- 15 January, 2003, Giant squid 'attacks French boat'
- Cephalopod taxonomy (as PDF)
- Scientific report in Proceedings of the Royal Society
- Slate: Giant Squid, Where Are You?
- CephBase: Architeuthis
- Smithsonian squid exhibit