AcharyaChanakya/simple-wikipedia huggingface dataset:
Relatives of the modern land snails are rare before the Cretaceous period. The familiar "Helix" first appeared in that period.
In rocks of the Mesozoic era gastropods are more common as fossils and their shell is often well preserved. Their fossils occur in beds of both freshwater and marine environments. The Purbeck Marble of the Jurassic period and the Sussex Marble of the early Cretaceous, which both occur in southern England, are limestones containing the tightly packed remains of the pond snail "Viviparus".
Rocks of the Cainozoic era have very large numbers of gastropod fossils in them. Many of these fossils are closely related to modern living forms. The diversity of the gastropods increased markedly at the beginning of this era, along with that of the bivalves.
Gastropods are one of the groups that record the changes in fauna caused by the advance and retreat of the Ice Sheets during the Pleistocene epoch.
These pages illustrate the variety of gastropod forms.
Abalone;
conch;
cowry;
limpet;
nudibranch;
sea slug;
slug;
snail;
whelk.
The name Limpet is used for many marine and freshwater gastropod species which have a simple conical shell. The phrase "true limpets" is used only for marine limpets in the ancient clade Patellogastropoda. This article is mainly about the true limpets.
True limpets are small marine gastropod molluscs with flattened, cone-shaped shells. They live throughout the intertidal zone, attached to rocks or other hard ground. They attach themselves using mucus and a muscular "foot", which seals them against the rock and protects them from desiccation during low tide, and from high-energy waves action.
Limpets eat by grazing on algae found on rock surfaces. They scrape films of algae from the rock with a radula, a ribbon-like tongue with rows of teeth. Limpets move by rippling the muscles of their foot in a wave-like motion. Most limpets are less than 3in (8cm) long, but a West Mexican Limpet grows to be 8in (20 cm).
Some key-hole limpets have a hole at the top, through which gas exchange can occur (they are not true limpets).
There are many limpets in the Paleozoic fossil record, from the lower Cambrian, but none can be placed with certainty in the Patellogastropoda. Some might be Monoplacophorans, which is a separate mollusc class with a similar life-style. The earliest patellogastropod verified by shell microstructure is from the Triassic of Italy, but it is in the Upper Cretaceous and Cainozoic periods that many of the living forms make their first appearance.
The life-style of limpets is sessile: they stick fast to rocks or other hard substrates.
Some species of limpets return to the same spot on the rock known as a "home scar" just before the tide ebbs. It is thought that they follow chemical trails. In such species, the shape of their shell often grows to precisely match the contours of the rock surrounding the scar. This behaviour permits a better seal to the rock. It is thought that they follow a mucus trail left as they move.
Where the limpets eat the algae, off bare rocks, it causes places where other organisms can grow and thrive. Some species, such as "Lottia gigantea" "garden" a patch of algae around their home scar. They push other organisms out of this patch by ramming with their shell, allowing their patch of algae to grow for their own grazing.
Limpets are prey for starfish, shore-birds, fish, seals, and humans. They have a two main defences; fleeing (letting go in the water) or clamping their shells against the surface they are on. The defence response can be adjusted to the type of predator, which can often be detected chemically by the limpet.
Limpets can be long lived, with tagged specimens surviving for more than 10 years. If the limpet lives on bare rock, it grows at a slower rate but can live for up to 20 years.
Limpets found on sheltered shores (limpets that are less frequently in contact with wave action, and thus less frequently in contact with water) have a greater risk of desiccation because of the effects of sunlight, water evaporation and the wind. To avoid drying out they will clamp to the rock they inhabit, minimizing water-loss from the rim around their base. As this occurs chemicals are released that promote the vertical growth of the shell.
Limpets are hermaphrodites (producing both male and female reproductive cells) and undergo sex change during life. They become male at about 9 months, but after a couple of years they change sex to become female. Spawning occurs once a year, usually during winter, and is triggered by rough seas which disperse the eggs and sperm. Larvae are pelagic for a couple of weeks before settling onto a hard substrate.
Abalone
Abalone (from Spanish "Abulón") are shellfish, a genus of gastropods.
Abalone are known by their colorful "pearlescent" inside shell. This is also called ear-shell, "ormer" in Guernsey, "abalone" in South Africa, and "pāua" in New Zealand.
The meat of this shellfish is thought to be delicious in some parts of Latin America (especially Chile), South East Asia, and East Asia (especially in China, Japan, and Korea).
Abalones live all over the world, They can be seen along the waters of every continent, except the Atlantic coast of South America, the Caribbean, and the East Coast of the United States. Most abalones are found in cold waters, along the coasts of New Zealand, South Africa and Australia, and Western North America and Japan in the Northern Hemisphere. In the Chilean Pacific coast, the species called loco ("Concholepas concholepas") has a hard, black shell, and is eaten by many people.
Abalone have unique features: the shell is round, with two to three spirals. The last spiral is grown into a large "ear"-like shape, which explains the name 'ear-shell'. The inside of the shell is shiny, from silvery white to green-red mother-of-pearl.
Abalones can start to give birth at a small size. Their fertility is high and increases with size (from 10,000 to 11 million eggs at a time).
Young albalones, called larvae, feed on plankton. The adults eat plants and feed on algae. They like to eat red algae. Their size can be as small as 20 mm to as big as 200 mm.
The shell of the abalone is known for being very strong. It is made of very tiny calcium carbonate tiles stacked like bricks. Between the layers of tiles is a sticky protein substance. Allergic skin reactions and asthma attacks can happen when breathing the dust made when these tiles are broken down.
The colorful inside part of the abalone shell can be used for decorative inlays, in guitars, for example.
Sport harvesting of red abalone is allowed with a California fishing license and an abalone stamp card. Abalone may only be taken using breath-hold techniques: freediving or shorepicking. SCUBA diving for abalone is strictly not allowed. Abalone harvesting is not allowed south of the mouth of the San Francisco Bay. There is a size minimum of seven inches measured across the shell and a limit of three per day and 24 per year that can be taken. Abalone may only be taken in April, May, June, August, September, October and November, but they may not be taken in July, December, January, February or March. Transportation of abalone is only legal while the abalone is still attached to the shell. Sale of sport-caught abalone is illegal, including the shell. Only red abalone may be taken; black, white, pink, and flat abalone are protected by law.
Abalone divers normally use a very thick wetsuit, including a hood, booties, and gloves. They also wear a mask, snorkel, weight belt, abalone iron, and abalone gauge. It is common to take abalone in water a few inches up to 10 m/28' deep. Fewer freedivers can work deeper than that. Abalone are normally found on rocks near food sources (kelp). An abalone iron is used to pry the abalone from the rock before it can fully clamp down. Visibility is normally five to ten feet. Divers commonly dive out of boats, kayaks, tube floats or directly off the shore. An eight-inch abalone is considered a good catch, a nine-inch would be very good, and a ten-inch plus (250 mm) abalone would be an excellent catch. Rock- or shore-picking is a different method from diving where the rock picker feels below rocks during low tides for abalone.
There has been a trade in diving to catch abalones off parts of the United States coast from before 1939. In World War II, many of these abalone divers were recruited into the United States armed forces and trained as frogmen.
There is a worldwide black market in the collection and export of abalone meat. In New Zealand, where abalone is called pāua in the Māori language, this can be a particular problem. The right to harvest pāua can be granted legally under Māori customary rights. When such permits are overused, it is difficult to police. The legal daily limit is 10 pāua per diver with a minimum shell length of 125 mm. The limit is strictly enforced by many Ministry of Fisheries officers with the help of the police. Pāua 'poaching' is a major industry in New Zealand with many thousands of abalones being taken illegally, mostly undersized. Convictions have caused removal of diving gear, boats and motor vehicles as well as fines and in rare cases; imprisonment. The Ministry of Fisheries expects in the year 2004/05, nearly 1000 tons of pāua will be poached, with 75% of that being undersized.
Highly polished New Zealand pāua shells are extremely popular as gifts with their striking blue, green and purple iridescence. Transporting unprocessed abalone shells out of New Zealand is illegal.
The largest abalone in South Africa, "Haliotis midae", can be found along about two-thirds of the country’s coastline. Abalone-diving has been a recreational activity for many years, but stocks are currently being threatened by illegal commercial harvesting.
Ormers ("Haliotis tuberculata") are considered a delicacy in the Channel Islands and are looked after with great eagerness by the locals. Unfortunately, this has led to a huge decrease in numbers since the second half of the 19th century, and 'ormering' is now strictly regulated in order to keep stocks. The taking of ormers is now restricted to a number of 'ormering tides', from the January 1 to April 30, which happen on the full or new moon and two days after that. No ormers may be taken from the beach that are under 8 cm in shell length. Gatherers are not allowed to wear wetsuits or even put their heads underwater. Any breach of these laws is illegal and can lead to a large fine. The demand for ormers is so big that it started the world's first underwater arrest, when Mr. Kempthorne-Leigh of Guernsey was arrested by a police officer in full diving gear while illegally diving for ormers.
White Abalone are going extinct because of their delicious tender meat, jewlery, and beautiful shell.
There have been a number of attempts to artificially grow (farm) abalone for the purpose of consumption.
Shellfish is a culinary term for some aquatic invertebrates used as food: molluscs, crustaceans, and echinoderms. It is not a scientific term, and its use may vary from place to place.
Both saltwater and freshwater invertebrates are considered shellfish. Molluscs commonly used as food include the clam, mussel, oyster, winkle, and scallop.
Some crustaceans commonly eaten are the shrimp, prawn, lobster, crayfish, and crab.
Echinoderms are not eaten as commonly as molluscs and crustaceans. In Asia, sea cucumber and sea urchins are eaten.
Edible cephalopods such as squid, octopus, and cuttlefish and terrestrial snails, though all molluscs, are sometimes considered to be shellfish and sometimes not.
The term "finfish" is sometimes used to distinguish ordinary (vertebrate) fish from shellfish.
Jewish and Islamic dietary laws forbid the eating of shellfish (those that live on the land, and in the water).
In Japanese cuisine, chefs often use shellfish and their roe. Sushi and sashimi feature both raw and cooked shellfish.
Alban Berg
Alban Berg (born Vienna, 9 February 1885; died Vienna 24 December 1935) was an Austrian composer. Alban Berg and Anton Webern were both pupils of Arnold Schoenberg. All three composers in their own way changed the style of musical composition in the early 20th century. They grew up at a time when most composers were still writing Romantic music, but Schoenberg and his pupils started to write atonal music (music which is not in any key) and then twelve-tone music in which all 12 notes in an octave are of the same importance. Although Berg wrote a lot of twelve-tone music he still managed to make it sound quite Romantic at times, more so than Schoenberg or Webern. His most important works are his two operas "Wozzeck" and "Lulu" and his "Violin Concerto".
Berg was brought up in the centre of Vienna. His family had plenty of money, but when Berg’s father died in 1900 life became much harder for them. He did not do very well at school. He also had a love affair with a kitchenmaid, with whom he had a daughter.
He was interested in music, played the piano and had started to compose, but he had not done well enough in his school exams to get into the music conservatory. He was not interested in business like his father had been. He got an unpaid job. Then, in 1904, he started to study with Schoenberg. This was the first time he had been given proper music lessons. Two years later, his mother inherited some money, and Berg was then able to give up his unpaid job and concentrate on music.
Schoenberg taught him harmony, counterpoint and music theory, all the things one needs to know to compose well. Berg had lessons from him from 1904 until 1911. His first proper pieces include a Piano Sonata and a String quartet. Here he had already found the modern style which suited him. He wrote harmonies which seemed to float. He often wrote pieces with several movements which are all linked by a common theme. He also liked themes which are heard upside down, or palindromes, where the tune sounds the same forwards as backwards. He met a girl called Helene and they married in 1910.
Berg liked to listen to all kinds of music. In this way he was different to Schoenberg or Webern. Berg was interested in French composers such as Debussy, as well as jazz. He liked the modern theatre and the political works of the playwright Bertolt Brecht and the composer Kurt Weill.
Berg was very grateful to Schoenberg for all that he had learned from him, but he still continued to be quite afraid of him. Schoenberg wrote many letters to him asking him to do things for him (e.g. making piano arrangements of his orchestral pieces) and often criticising him. Only in the 1920s, when Berg had become well-known, did Schoenberg start writing to him more like an equal friend.
Berg wrote "Five Orchestral Pieces". It is one of the first important works he wrote without Schoenberg’s help. The music has some modern chords which must have sounded very shocking to the Viennese audience. On 31 March 1913 Schoenberg conducted a concert in Vienna which included some songs by Berg. People in the audience started to fight and the police had to be called. When Schoenberg wrote to Berg criticising his music, Berg lost all his self-confidence. Slowly he started to get more confidence again. He wrote "Three Orchestral Pieces" op 6. The music sounds quite like Mahler. There are a lot of musical ideas which grow into one another and make a rich sound.
During World War I Berg spent some time in an army training camp. This experience must have been in his mind when he wrote his opera "Wozzeck". This opera became very famous. There were a lot of new ideas in it. It is not about a great hero, but about a simple man who is mistreated by people. The music, too, is very different from opera music up to that time. Although it was so modern it was a great success and made Berg world-famous. It gave him more money which, together with a little teaching, allowed him to spend most of his time composing.
"Wozzeck" has a little twelve tone music in it, but in his next works the twelve tone system is much more important. He wrote "Lyrical Suite" for String Quartet and a "Kammerkonzert" ("Chamber Concerto") in which the form is made up by mathematical rules. He liked to hide things in his music e.g. favourite numbers or letters from people’s names. These are like secret codes and, in later years, musicians have spent a lot of time trying to work out what Berg was trying to do.
In 1928 Berg started work on his second and last opera: "Lulu". He had thought about the opera for many years. He had seen a play called "Die Büchse des Pandora" "(Pandora’s Box)" in 1905. Wedekind had played the part of Jack the Ripper. People thought the play was obscene, but it still became very popular, especially after 1918 when there was no more censorship in Germany. He worked on the opera until 1934. He then stopped work on it to write his "Violin Concerto". When he heard about the sad death from poliomyelitis of a young girl he knew called Manon Gropius, he dedicated the concerto to her memory. He wrote: “To the memory of an angel”. Manon’s mother, Alma, had been the wife of Gustav Mahler.
Soon after he had finished the Violin Concerto, Berg was stung by an insect. This formed an abscess and he was rushed to hospital but he died. The concerto had not yet been performed. He had not finished "Lulu". The third act was only sketched in short score (showing the main notes, but not exactly what each instrument plays). When the opera was first performed, Act III was just acted out in mime while some other music by Berg was played. Berg’s widow Helene did not want anyone else to finish the opera, so Act III was never performed until after Helene died in 1976. It was finished by Friedrich Cerha and performed in 1977, although a court action had tried to stop it from being performed.
Herefordshire
Herefordshire (known as County of Herefordshire) is a county in the West Midlands region of England. It borders the English counties of Shropshire to the north, Worcestershire to the east, Gloucestershire to the south east and the Welsh counties of Gwent to the south west and Powys to the west. It is not to be confused with Hertfordshire, a county north of London.
It is pronounced (i.e. first syllable as in "herring", and -e- a separate syllable).
The county town of Herefordshire is the cathedral city of Hereford.
Historically, the Rivers Wye and Lugg were navigable but the wide seasonal variations in water levels mean that few craft larger than canoes and coracles are now used. There are canoe centres at The Boat House, Glasbury-on-Wye, the Hereford Youth Service and Kerne Bridge Ross-on-Wye, as well as a rowing club in Hereford.
The early nineteenth century saw the construction of two canals, The Hereford & Gloucester Canal and The Leominster & Stourport Canal but these were never successful and there are now few remains to be seen.
A conch is a sea-dwelling mollusc. It is a marine gastropod. The ch at the end of 'conch' may be pronounced hard or soft.
Many other gastropods have common names with "conch" in them. They are however not true conches, in the family
Strombidae. One such example is the Horse Conch ("Pleuroploca gigantea"). The genus Strombus is made up of the true conches.
While most Strombid species are extinct, at least 65 species still exist. Of these, most are in the Indo-Pacific Oceans while six are in the greater Caribbean region. Living true conch species include the Queen Conch, "Strombus gigas", and the West Indian Fighting Conch ("Strombus pugilis").
Many conch, such as the Queen Conch, are found among beds of sea grass in warm tropical waters.
"Strombus gigas" is included in Appendix II of the UNEP's CITES list of endangered species and international trade is heavily restricted.
Conches have spirally constructed shells. Depending on species (or aberrant growth patterns), shell growth can be sinistral (left-handed) or dextral (right-handed).
Conches have long eye stalks, a long and narrow aperture, and a siphonal canal with an indentation near the anterior end. This indentation is called a stromboid notch. They also have a foot ending in a pointed, sickle-shaped, horny operculum. They grow a flared lip on their shells upon reaching sexual maturity.
Conches have a characteristic leaping motion, using their pointed, sickle-shaped, horny operculum to propel themselves forward. They lay eggs in long, gelatinous strands.
The animal inside the shell is eaten, either raw, as in salads, or cooked, as in fritters, chowders, gumbos, and burgers. In East Asian cuisines, the meat is often cut into thin slices and then steamed or stir-fried. Conch meat is also often confused with Scungilli, which is more accurately whelk meat.
Conch shells are sometimes used as decoration, as decorative planters, and in cameo-making. As with other mollusk shells, they are ground up into an ingredient in porcelain. In classic Mayan art, conches are shown being utilized in many ways including as paint and ink holders for elite scribes, as bugle or trumpet, and as hand weapons (held by combatants by inserting their hands in the aperture).
In some countries, cleaned Queen Conch ("Strombus gigas") shells or polished fragments are sold, mainly to tourists, as souvenirs or in jewelry. Without a permit however, export is a breach of CITES regulations and may lead to arrest . This is most likely to occur on return to the tourist's home country while clearing customs. In the UK conch shells are the 9th most seized import.
Conch shells are occasionally used as a building material, either in place of bricks or as bulk for landfill.
It is also believed to be used as a weapon by the earliest Caribbean natives.
Conch shells are sometimes made into crude bugles by removing the small tip of the shell to form a mouthpiece. Such instruments are used in the Pacific Islands as well as in many parts of Asia. While lacking the range capabilities and tonal quality of brass instruments, the conch shell is still an interesting instrument to play. As it has no mouthpiece or valves, the embouchure in shell playing is critical. Most shells will only naturally play one note, but with pitch manipulations, multiple sounds can be achieved. The insertion of the hand and the placement of the fingers will also change the pitch of the shell. The conch shell is said to be the musical instrument of mermaids and mermen. Steve Turre is the leading innovator of the shell. It is sometimes found in classical works, such as the symphony piece "La Noche de Los Mayas", or "Night of the Mayas", which was premiered in 1939 with Jacob Watkins on percussion and conch.
The conch shell is a major Hindu article of prayer, used as a trumpeting announcement of all sorts. The God of Preservation, Vishnu, is said to hold a special conch, Panchajanya, that represents life as it has come out of life-giving waters. In the story of Dhruva the divine conch plays a special part. The warriors of ancient India would blow conch shells to announce battle, such as is famously represented in the beginning of the war of Kurukshetra in the Mahabharata, the famous Hindu epic. The conch shell is a deep part of Hindu symbolic and religious tradition. To this very day, many Hindus use the conch as a part of their religious practices, blowing it during worship at specific points, accompanied by ceremonial bells.
See also: Krishna
Buddhism also has incorporated the conch into its symbolism. See: Buddhist symbolism.
William Golding's "Lord of the Flies" features frequent references to "The Conch". In the novel, a conch shell is blown to call the other boys together. It is held by whoever is speaking at meetings, symbolically representing democracy and order. When Roger, Jack's lieutenant, smashes the shell, it is a sign that civilized order has collapsed and Jack's domination has begun.
Gloucestershire
Gloucestershire (pronounced ; "GLOSS-ter-sher") is a county in South West England. The county includes part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean.
The county town is Gloucester, and other principal towns include Cheltenham, Stroud, Cirencester, and Tewkesbury.
Gloucestershire borders the county of Gwent in Wales, and in England the counties of Herefordshire, Worcestershire, Warwickshire, Oxfordshire, Wiltshire, Somerset and Bristol.
This is a chart of trend of regional gross value added of Gloucestershire at current basic prices published (pp.240-253) by "Office for National Statistics" with figures in millions of British Pounds Sterling.
Cowry
Cowry shells (or cowrie), are marine snails of the family Cypraeidae.
They are found chiefly in tropical regions. There are about 200 different species of cowry.
The shell itself is almost always very smooth and shiny. They have with a long, narrow, slit-like opening. All varieties have a porcelain-like shine and many have colorful patterns. In life the shell is covered by the slippery mantle.
Shell sizes range from 5 mm (1/5") for some tropical species to 15 cm (6") for the tiger cowry, "Cypraea tigris".
The slippery shell is very difficult for most animals to grip. The very narrow toothed aperture of the cowry shell makes it difficult for predators to reach into. However cowries are still vulnerable to predation:
For nearly 200 years, every species in the family Cypraeidae was placed in one genus, "Cypraea", but in 2002 the cowries were divided into many different genera.
Cowries (esp. "Cypraea moneta") were used as a currency in Africa (Ghanaian cedi in Ghana named after cowry shells) and elsewhere, such as in China where the shell or copies of the shell were in theory used as a means of exchange. They are also worn as jewelry or otherwise used as ornaments or charms, as they are viewed as symbols of womanhood, fertility, birth and wealth. Many find the shiny, porcelain-like shells pleasing to look at.
Cowry shells are sometimes used in a way similar to dice, e.g., in board games like Pachisi, or in divination (cf. Ifá and the annual customs of Dahomey).
A number of shells (6 or 7 in Pachisi) are thrown, with those landing aperture upwards indicating the actual number rolled.
Cowries have also been used in the recent past as a frame over which sock heels were stretched for darning. The cowry ridges allowed the needle to get under the cloth more easily.
The Ojibway aboriginal people in North America used the cowry shells in ceremonies, and the Whiteshell Provincial Park in Manitoba, Canada is named after this type of shell. There is some debate about how they traded for or found these shells so far inland, away from the natural sources. Oral stories and birch bark scrolls seem to indicate that they were found in the ground, and/or washed up on the shores of lakes or rivers. The cowry shells so far inland may indicate the use of them by an earlier tribe or group in the area, and an extensive trade network in the ancient past.
The typewritten postage stamps of 1895 Uganda also are called "Cowries".
Wiltshire (short: "Wilts") is an English county. It borders the counties of Hampshire, Dorset, Somerset, Gloucestershire, Oxfordshire and Berkshire, and contains the unitary authority of Swindon. The county town is Trowbridge, in the west of the county at . The county covers 858,931 acres (3476 km²)
Notable towns and cities in Wiltshire are:
A full list of settlements is at List of places in Wiltshire.
Notable places of interest in Wiltshire are:
Notable areas of countryside in Wiltshire are:
Notable routes through Wiltshire are:
Wiltshire is "Mid-Wessex" in the novels of Thomas Hardy
West Midlands (county)
The County of West Midlands is a metropolitan county in western central England with a population of around 2,600,000 people. The county contains three major cities, these being Birmingham, Coventry and Wolverhampton. Other large settlements in the county include Sutton Coldfield, Solihull, and the Black Country towns of Dudley, Walsall and West Bromwich.
The name "West Midlands" is also used for the much larger West Midlands region, which sometimes causes confusion.
The West Midlands borders the counties of Warwickshire to the east, Worcestershire to the south, and Staffordshire to the north.
The West Midlands is one of the most heavily urbanised counties in the UK. Birmingham, Wolverhampton, the Black Country and Solihull together form the largest conurbation in the UK outside London, with a combined population of around 2.27 million.
The West Midlands is not entirely urban; Coventry is separated from the Birmingham urban area, by stretch of green belt land roughly 15 miles across known as the "Meriden Gap", which retains a strongly rural character.
A smaller piece of green belt between Birmingham, Walsall and West Bromwich includes Barr Beacon and the Sandwell Valley.
The West Midlands contains 6 universities;
Though Warwick and Birmingham are considered the most prestigious of the universities in the area, all have a large intake of students from around the country.
A conurbation is an urban area that includes a number of cities, towns and villages which, through population growth and expansion, have physically merged to form one continuous built up area. It is a sort of agglomeration.
A metropolitan area usually combines one or several conurbations.
Dunkirk (, pronounced or ; ) is a harbour city in the northernmost part of France, 10 km (6 mi) from the Belgian border.
The population of the whole metropolitan area was of 265,974 at the 1999 census.
Until the middle of the 20th century the city was in the Dutch language area; today the local Dutch dialect still can be heard but has largely given way to French.
Dunkirk was first mentioned in 1067 as "Dunkerk" ().
In World War II, heavy fighting took place around Dunkirk during the German invasion in 1940 (Battle of Dunkirk), but a lull in the action unexpectedly allowed a large number of French and British soldiers to escape to England. The British evacuation of Dunkirk through the English Channel was codenamed "Operation Dynamo".
During the war, Dunkirk was largely destroyed by bombing.
On 14 December 2002, the Norwegian auto carrier "Tricolor" collided with the Bahamian-registered "Kariba" and sank off Dunkirk harbour, causing a hazard to navigation in the English Channel.
Dunkirk has the third largest harbour in France, after those of Le Havre and Marseille. It is also an industrial city, heavily dependent on the steel, food processing, oil refining, ship building and chemical industries.
Dunkirk has a ferry connection with Dover in England.
Dunkirk is twinned with:
Dunkirk has cooperation agreements with:
Limburg-Weilburg
Limburg-Weilburg is a Landkreis (rural district) in the west of Hesse, Germany.
1867 the "Oberlahnkreis" with the capital Weilburg was created. In 1886 "Limburg an der Lahn" district was set up, with the capital Limburg. In 1974 both districts were joined together.
The district is located between the two mountain areas Westerwald and Taunus. The main river is the Lahn.
Elz, Hesse
Elz is a municipality and a village in Hessen, Germany. It is part of the Landkreis Limburg-Weilburg. It is along the river Lahn. It has 8,088 inhabitants (2004).
The elevation is between 110m and 291m above sea level. Elz is in a valley called "Limburger Becken", which surrounds the town of Limburg. Elz is also in the valley of the "Elbbach", which flows into the river Lahn after passing Elz.
The municipality of Elz borders the municipalities of Hundsangen, Hambach, Görgeshausen, Niedererbach, Obererbach and the towns of Hadamar and Limburg.
The municipality of Elz consists of two villages: The village of Elz (7,743 inhabitants) and the village of Malmeneich (345 inhabitants).
Average temperatures are 10.5 °C in Elz and 9.9 °C in Malmeneich. Though this sounds quite moderate, temperatures can vary between -20 °C in winter and 40 °C in summer. In an average year there are 600mm of rain in Elz and 720mm in Malmeneich.
Elz was first mentioned in a document from 933 AD, which does not exist any more. Political importance resulted from its position at the Hohe Straße, the former most important road between Frankfurt am Main and Cologne, which still exists and is now part of the "Bundesstraße 8", which can be translated with Interstate 8.
Elz got the town privileges in 1442. Soon a wall around the town was constructed but knocked down later.
The council consists of 31 members. 19 members are from the Christian Democrats, seven are from the Social Democratic Party, four from the Free Voters' Community and one is from the Green Party. The mayor Horst Kaiser is a Christian Democrat and was elected in 2005 with 84.8% of all votes.
In Elz thaere are more than 600 businesses with much more than 2,000 jobs. The industrial area is at the B8 between Elz and Malmeneich.
Elz is not only at the B8,which goes from the Dutch border to Passau, but also at the Autobahn 3, which connects Würzburg,Frankfurt am Main and Cologne.
In Elz there is a big outdoor swimming pool, two gyms, several sport and tennis fields and two old people's homes.
There are three kindergartens, two primary schools and one "Haupt- und Realschule" (part of the German secondary education).
Cephalopod
The Cephalopoda (Greek meaning "head-foot") is an important mollusc class. They have bilateral symmetry, a head, and arms or tentacles. Teuthology, a branch of malacology, is the study of cephalopods.
The class has two living subclasses. In the Coleoidea, the mollusc shell has become smaller, or is not there at all; this subclass has the octopus, squid, and cuttlefish. The "Nautiloidea" have a shell; "Nautilus" is its only living genus.
There are at least 800 different living species of Cephalopods. Two important extinct taxa are the Ammonites, and the Belemnites (order "Belemnoidea", of class Coleoidea). Cephalopods are found in all the oceans of the world and at all pelagic levels. None of them can live in freshwater (water with no salt in it), but a few species live in brackish (partly salty) water.
There are still discoveries of new species of cephalopods:
There are many more fossil species. It is thought there are around 11,000 extinct taxa.
Cephalopods are the most intelligent invertebrates and have good senses and large brains. The nervous system of cephalopods is the most complex of the invertebrates, and their brain to body mass ratio falls between that of warm and cold blooded vertebrates. The giant nerve fibers of the cephalopod mantle have been a favourite experimental material for many years; their large diameter makes them easier to study.
Most cephalopods have chromatophores – that is, cells with different colours – which they can use in a number of surprising ways. As well as blending with their background, some cephalopods bioluminesce, shining light downwards to hide their shadows from any attackers. The bioluminescence is made by bacterial symbionts; the host cephalopod is able to find the light made by these animals. Bioluminescence may also be used to attract prey, and some species use colourful shows to get mates, amaze predators, or even signal to one another.
Colouration can be changed in milliseconds as they adjust to their environment, and the pigment cells can expand or contract. Rapid colour change is usually more common in near-shore species than those living in the open ocean. Those in open ocean mostly use camouflage to make their body outline less easy to see.
Evidence of original colouration has been found in cephalopod fossils as far back as the Silurian; certain straight-shelled species had lines round their shell, which are thought to have used as camouflage of their body outline. Devonian cephalopods bear more complex colour patterns, whose function may be more complex.
Cephalopods usually move by jet propulsion (squirting water). This uses a lot of energy to travel compared to the tail propulsion used by fish. They use jet propulsion because they do not have fins or flippers. The efficiency of jet propulsion goes down with larger animals. This is probably the reason why many species use their fins or arms for moving if possible.
Oxygenated water is taken into the mantle cavity to the gills. By contracting the mantle's muscles, the water is pushed out through the siphon, made by a fold in the mantle. Motion of the cephalopods is usually backward as water is forced out forwards, but the siphon can be pointed in different directions. Some cephalopods can adjust their body shape to move through the water more easily.
Some octopus species are also able to walk along the sea bed. Squids and cuttlefish can move short distances in any direction by moving a flap of muscle around the mantle.
With the exception of the Nautilidae and the species of octopus of the suborder Cirrina, all known cephalopods have an ink sac, which can be used to push out a cloud of dark ink to confuse predators.
Like most molluscs, cephalopods use haemocyanin, a copper-containing protein, rather than haemoglobin to transport oxygen. As a result, their blood is colourless when deoxygenated and turns blue when placed in air.
With a few exceptions, Coleoideans live short lives with fast growth. Most of the energy from their food is used for growing. The penis in most male Coleoidea is a long and muscular end of the vas deferens (tube for sperms) used to transfer spermatophores (sperm packages) to a modified arm called a hectocotylus. That in turn is used to transport the spermatophores to the female. In species where the hectocotylus is missing, the penis is long and able to extend beyond the mantle cavity and transfers the spermatophores directly to the female. The females lay many small eggs in one batch, and die afterwards. The Nautiloidea, on the other hand make a few large eggs in each batch, and live for a long time.
The class developed during the late Cambrian and were the most common and varied marine life forms during the Palaeozoic and Mesozoic eras. "Tommotia", an early cephalopod, had squid-like tentacles but also a snail-like foot it used to move across the sea floor. Early cephalopods were at the top of the food chain.
The old (cohort Belemnoidea) and modern (cohort Neocoleoidea) coleoids, as well as the ammonoids, all diverged (evolved away from) from the external shelled nautiloids during the middle Paleozoic Era, between 450 and 300 million years ago. Most ancient varieties had protective shells. These shells at first were conical but later developed into the curved shapes seen in modern nautilus species. Shells inside the body still exist in many living cephalopod groups, such as cuttlefish. The most famous group with external shells, the ammonites, became extinct at the end of the Cretaceous period.
Cuttlefish are marine Cephalopod molluscs. They belong to the same class as squid, octopodes and the nautilus.
Cuttlefish have an internal shell (called a cuttlebone), large eyes, and eight arms and two tentacles furnished with finely toothed suckers, with which they grab their prey.
Cuttlefish eat small molluscs, crabs, shrimp, fish and other cuttlefish. Various sharks and fish prey on them. They live about 1 to 2 years.
Cuttlefish have an internal cuttlebone, made of calcium carbonate. It is porous, full of small holes, The buoyancy of the cuttlebone can change, allowing the cuttlefish to go lower or higher by changing the amount of gas and liquid in its chambers. The cuttlebone of each species has a distinct shape, size, and pattern of ridges or texture. Cuttlebones are used by jewellers and silversmiths as moulds for casting small objects. They are probably better known today as the material given to pet birds as a source of calcium. The cuttlebone is only found in cuttlefish, and is one of the features that makes them different from squid and other molluscs.
Cuttlefish are sometimes called the chameleon of the sea because they are able to change their skin color. Their skin can flash a colorful pattern in order to communicate with other cuttlefish and to camouflage them from predators. This color-changing function is produced by groups of red, yellow, brown, and black pigmented chromatophores above a layer of reflective iridophores and leucophores. These are all in the cuttlefish's skin, and work together to change its colour. There are up to 200 of these special pigment cells per square millimeter.
The pigmented chromatophores have a sac of pigment and a large membrane that is folded when retracted. There are 6-20 small muscle cells on the sides which can contract to squash the elastic sac into a disc against the skin.
Iridophores are plates of chitin or protein, which can reflect light. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. All of these cells can be used in combinations. As well as being able to influence the colour of the light that reflects off their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other animals which sense polarization.
Cuttlefish eyes are among the most developed in the animal kingdom. The way cephalopod eyes develop is fundamentally different from that of vertebrates like humans, but the way they work is rather similar. The similarity between cephalopod and vertebrate eyes is an examples of convergent evolution. Although they cannot see color, they can perceive the polarization of light, which improves their ability to see contrast. They have two spots of concentrated sensor cells on their retina (known as fovea), one to look more forward, and one to look more backwards. The lenses, instead of being reshaped as they are in humans, are instead pulled around by reshaping the entire eye in order to change focus.
The blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein haemocyanin to carry oxygen instead of the red iron-containing protein haemoglobin that is found in vertebrates. This is similar to the blood of arthropods. Haemocyanin is not so good at carrying oxygen as is haemoglobin. The blood is pumped by three separate 'hearts'. Two of these are used for pumping blood to the cuttlefish's pair of gills (one heart for each gill), and the third for pumping blood around the rest of the body.
Cuttlefish have inks like squid and octopuses. As with squid, the ink is a defensive tool, squirted out to cover its retreat in the case of danger. This ink was formerly an important dye, called sepia. Today artificial (not natural) dyes have replaced natural sepia.
Cuttlefish are caught for food in Mediterranean, and East Asian cultures. Although squid is more popular as a restaurant dish all over the world, in East Asia dried cuttlefish is highly popular.
Cuttlefish is popular in Italy and Croatia, where it is used in "Risotto Nero". "Nero" means 'black', which is the colour the rice turns because of the cuttlefish ink. Spanish cuisine often uses cuttlefish and squid ink for cooking due to the marine flavor and smoothness that it provides to the meals and it is included in dishes such as rice, pasta and fish stews.
Cuttlefish made their most important literary appearance in the title of Eugenio Montale's collection of poetry called Cuttlefish Bones ("Ossi di seppia"), published in Turin in 1925. Montale was awarded the Nobel Prize for Literature in 1975.
There are over 120 species of living cuttlefish, in 5 genera. Sepiadariidae contains seven species and two genera; all the rest are in the Sepiidae.
Nautilus is the common name for cephalopods of the family Nautilidae. They are the only living members of the subclass Nautiloidea. In appearance, they have not changed much in millions of years. The term "chambered nautilus" is also used for any species of the Nautilidae.
Many biologists see them as 'living fossils', because they are the only living descendents of the group which gave rise to the ammonites in the Palaeozoic era.
Today, there are six living species in two genera. The species "Nautilus pompilius", from Western Australia is the largest and best known. It get up to 27 cm in diameter. However, most other nautiluses never exceed 20 cm. The Bellybutton nautilus, "Nautilus macromphalus", is the smallest species, usually measuring only 16 cm.
The radula is wide and has exactly nine teeth. There are two pairs of gills.
Nautiluses are the only cephalopods who have an external shell. This is an ancestral or basal, feature. The animal can withdraw completely into its shell. It can the close the opening with a leathery hood formed from two specially folded tentacles. The shell is coiled and calcareous, with mother-of-pearl lining. It is pressure resistant, but will implode at a depth of about 800 m. The nautilus shell is made of two layers: the outer layer is a dull white, while the inner layer is a striking white with iridescence. The innermost portion of the shell is pearlescent, blue-gray. A osmena pearl is not a pearl, but a jewellery product got from this part of the shell.
The shell is internally divided into chambers. All the walls between chambers ('septa') are pierced in the middle by a duct, the siphuncle. Through this the animal can change the air pressure in the chambers. As the nautilus matures its body moves forward, sealing each chamber in turn with a new "septum" (wall). The last fully open chamber, the largest one, is used as the living chamber. The number of chambers increases from around four at the moment of hatching to thirty or more in adults.
The shell colour keeps the animal hidden in the water. When seen from the top, the shell is darker in color and marked with irregular stripes, which makes it blend into the darkness of the water below. The underside is almost completely white, making the animal indistinguishable from brighter waters near the ocean surface. This mode of camouflage is called "countershading".
The nautilus shell is one of the finest natural examples of a logarithmic spiral.
In order to swim, the nautilus draws water into and out of the living chamber and makes use of jet propulsion. When water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood. When water is pumped out, the animal adjusts its buoyancy with the gas contained in the chamber. Buoyancy can be controlled by the pumping of gas and fluid into or from the chambers using the siphuncle. The control of buoyancy like this limits the nautilus; they cannot operate under extreme pressure.
In the wild, nautilus usually lives in depths of about 300 m, rising to around 100 m at night for feeding, mating and egg laying. The shell of the nautilus cannot withstand depths greater than approximately 800 m.
Nautiluses are predators and feed mainly on shrimp, small fish and crustaceans, which are captured by the tentacles. However, due to the very little energy they devote to swimming, they need only eat once a month. Unlike other cephalopods, they do not have good vision; their eye structure is highly developed but lacks a solid lens. They have a simple "pinhole" lens through which water can pass. Instead of vision, the animal is thought to use olfaction as the primary sensory means during foraging, locating or identifying potential mates.
Fossil records indicate that nautiloids have not changed much (at least in their body form) for the last 500 million years. Nautiloids were much more common and varied 200 million years ago. Many of the early ones were straight-shelled, as in the extinct genus "Lituites". They developed in the Cambrian and became a significant sea predator in the Ordovician period. Some species reached over 2.5 meters in size. The other cephalopod subclass, Coleoidea, diverged from the Nautilidae long ago and the nautilus has remained relatively unchanged since. Extinct relatives of the nautilus include ammonites, which were very important for many millions of years. Other groups were the baculites and goniatites.
Nautiluses are sexually dimorphic and reproduce by laying eggs. Attached to rocks in shallow waters, the eggs take twelve months to develop before hatching out at around 30 mm long. Females spawn once per year and regenerate their gonads, making nautiluses the only cephalopods to repeat reproduction. The lifespan of nautiluses is about 20 years, which is exceptionally long for a cephalopod.
Nautiluses are only found in the tropical Indian and Pacific Oceans, from 30° N to 30° S latitude and 90° to 185° W longitude. They live on the deep slopes of coral reefs.
Logarithmic spiral
A logarithmic spiral, equiangular spiral or growth spiral is a special kind of spiral curve which often appears in nature. The logarithmic spiral was first described by Descartes and later extensively investigated by Jakob Bernoulli, who called it "Spira mirabilis", "the marvelous spiral".
In polar coordinates ("r", θ) the curve can be written as
hence the name "logarithmic". In parametric form, the curve is
with real numbers "a" and "b".