Manila Ocean Park
The Manila Ocean Park is an oceanarium in Manila, Philippines. It is owned by China Oceanis Philippines Inc. a subsidiary of China Oceanis Inc. a Singaporean-registered firm. It is located behind the Quirino Grandstand at Rizal Park; the construction involved the erecting of structural pillars at the beachfront, the construction of the platform that would serve as the basis of the foundation of the entire building. The base structure and platform was completed but laid idle and served a secondary purpose as a promenade walkway until construction of the actual park continued. By April 2007, the Manila Ocean Park is under construction, it was set to open in December 15, 2007 but the opening date was moved to February 24, 2008. The facility opened in March 2008. E. R. Hitosis and Associates was involved in the construction management of the Manila Ocean Park; the main attraction of Manila Ocean Park is the Oceanarium which houses 14,000 sea creatures from about 277 species all of, indigenous in Southeast Asia.
The Oceanarium contains 3,000 cubic meters of sea water. Its main feature is the 25 meters 220° curved walkway tunnel after a 55-meter walkthrough inside the Oceanarium; the water used in the Oceanarium is derived from the Manila Bay, filtered to be suitable to marine life. It has an educational activity area, function rooms for events, shark and stingray viewing area situated in two levels; the Jellies Exhibit, a separate attraction hosts jellyfishes. The Back of the House features information on the operation of the facility itself; the Manila Ocean Park hosts the Trails to Antarctica, the first penguin park facility in the country, which features Humboldt penguins. Through the years, their breeding program for the penguins have been successful; as of May 2017, they have a total of 13 baby penguins that hatched inside the park. They have the Birds of Prey Kingdom which features Brahminy kites and the World of Creepy Crawlies which exhibits frogs, insects and worms. Services were offered to patrons such as the Mermaid Swim Experience where visitors are taught to swim while wearing a costume mermaid tail, Underwater diving, Fish Spa, rides on a boat with a glass bottom.
Shows such as the Sea Lion Show and All Star Bird Show is performed inside the Manila Ocean Park and seats up to 1,900 pax per show. As part of their banner CSR program called "I Love My Ocean Planet", the show brings valuable information on environmental conservation and close interaction with the birds and sea lions; the Symphony is a performance involving fountains that shoots water 40 meters high supplemented with multimedia effects is among the attractions of the Manila Ocean Park. The Manila Ocean Park hosts a hotel on top of the Oceanarium dubbed as Hotel H2O; the hotel itself has spa and meeting rooms. The Makansutra Asian Food Village hosts dining outlets for its patrons. Hotel H2O hosts areas for events which covers a total area of 3,500 square metres and has a total capacity of 1,000 people. Official website
The American lobster is a species of lobster found on the Atlantic coast of North America, chiefly from Labrador to New Jersey. It is known as Atlantic lobster, Canadian lobster, true lobster, northern lobster, Canadian Reds, or Maine lobster, it can reach a body length of 64 cm, a mass of over 20 kilograms, making it not only the heaviest crustacean in the world, but the heaviest of all living arthropod species. Its closest relative is the European lobster Homarus gammarus, which can be distinguished by its coloration and the lack of spines on the underside of the rostrum. American lobsters are bluish green to brown with red spines, but several color variations have been observed. Homarus americanus is distributed along the Atlantic coast of North America, from Labrador in the north to Cape Hatteras, North Carolina in the south. South of New Jersey, the species is uncommon, landings in Delaware, Maryland and North Carolina make up less than 0.1% of all landings. A fossil claw assigned to Homarus americanus was found at Nantucket.
In 2013, an American lobster was caught at the Farallon Islands off the coast of California. Homarus americanus reaches 8–24 inches long and weighs 1–9 pounds in weight, but has been known to weigh as much as 44 lb, making this the heaviest crustacean in the world. Together with Sagmariasus verreauxi, it is the longest decapod crustacean in the world; the longest American lobsters have a body 64 cm long. According to Guinness World Records, the heaviest crustacean recorded was an American lobster caught off Nova Scotia, weighing 44.4 lb. The closest relative of H. americanus is the European lobster, Homarus gammarus. The two species are similar, can be crossed artificially, although hybrids are unlikely to occur in the wild since their ranges do not overlap; the two species can be distinguished by several characteristics: The rostrum of H. americanus bears one or more spines on the underside, which are lacking in H. gammarus. The spines on the claws of H. americanus are red or red-tipped, while those of H. gammarus are white or white-tipped.
The underside of the claw of H. americanus is orange or red, while that of H. gammarus is creamy white or pale red. The antennae measure split into Y-shaped structures with pointed tips; each tip exhibits. These hairs are covered with multiple nerve cells. Larger, thicker hairs found along the edges control the flow of water, containing odor molecules, to the inner sensory hairs; the shorter antennules provide a further sense of smell. By having a pair of olfactory organs, a lobster can locate the direction a smell comes from, much the same way humans can hear the direction a sound comes from. In addition to sensing smells, the antennules can judge water speed to improve direction finding. Lobsters have two urinary bladders, located on either side of the head. Lobsters use scents to communicate what and where they are, those scents are in the urine, they project long plumes of urine 1–2 meters in front of them, do so when they detect a rival or a potential mate in the area. The first pair of pereiopods is armed with a asymmetrical pair of claws.
The larger one is the "crusher", has rounded nodules used for crushing prey. The normal coloration of Homarus americanus is redder on the body and claws, greener on the legs; this coloration is produced by mixing yellow and red pigments that occur in the shell. Despite the rarity of strangely colored lobsters, many more of them are reported being caught, it is unclear as to whether this is an artifact of social media making reporting and sharing more accessible, or if it is due to a drop in predator populations. The lobsters mentioned below get media coverage due to their "rarity" and eye appeal. Mating only takes place shortly after the female has molted, her exoskeleton is still soft; the female releases a pheromone which causes the males to become less aggressive and to begin courtship, which involves a courtship dance with claws closed. The male inserts spermatophores into the female's seminal receptacle using his first pleopods; the female releases eggs through her oviducts, they pass the seminal receptacle and are fertilized by the stored sperm.
They are attached to the female's pleopods using an adhesive, where they are cared for until they are ready to hatch. The female cleans the eggs and fans them with water to keep them oxygenated; the large telolecithal eggs may resemble the segments of a raspberry, a female carrying eggs is said to be "in berry". Since this period lasts 10–11 months, berried females can be found at any time of year. In the waters off New England, the eggs are laid in July or August, hatch the following May or June; the developing embryo passes through several molts within the egg, before hatching as a metanauplius larva. When the eggs hatch, the female releases them by waving her tail in the water, setting batches of larvae free; the metanauplius of H. americanus is 1⁄3 in long, with large eyes and a long spine projecting from its head. It molts, the next three stages are similar, but larger; these molts take 10 -- 20 days.
Japan is an island country in East Asia. Located in the Pacific Ocean, it lies off the eastern coast of the Asian continent and stretches from the Sea of Okhotsk in the north to the East China Sea and the Philippine Sea in the south; the kanji that make up Japan's name mean "sun origin", it is called the "Land of the Rising Sun". Japan is a stratovolcanic archipelago consisting of about 6,852 islands; the four largest are Honshu, Hokkaido and Shikoku, which make up about ninety-seven percent of Japan's land area and are referred to as home islands. The country is divided into 47 prefectures in eight regions, with Hokkaido being the northernmost prefecture and Okinawa being the southernmost one; the population of 127 million is the world's tenth largest. 90.7 % of people live in cities. About 13.8 million people live in the capital of Japan. The Greater Tokyo Area is the most populous metropolitan area in the world with over 38 million people. Archaeological research indicates; the first written mention of Japan is in Chinese history texts from the 1st century AD.
Influence from other regions China, followed by periods of isolation from Western Europe, has characterized Japan's history. From the 12th century until 1868, Japan was ruled by successive feudal military shōguns who ruled in the name of the Emperor. Japan entered into a long period of isolation in the early 17th century, ended in 1853 when a United States fleet pressured Japan to open to the West. After nearly two decades of internal conflict and insurrection, the Imperial Court regained its political power in 1868 through the help of several clans from Chōshū and Satsuma – and the Empire of Japan was established. In the late 19th and early 20th centuries, victories in the First Sino-Japanese War, the Russo-Japanese War and World War I allowed Japan to expand its empire during a period of increasing militarism; the Second Sino-Japanese War of 1937 expanded into part of World War II in 1941, which came to an end in 1945 following the Japanese surrender. Since adopting its revised constitution on May 3, 1947, during the occupation led by SCAP, the sovereign state of Japan has maintained a unitary parliamentary constitutional monarchy with an Emperor and an elected legislature called the National Diet.
Japan is a member of the ASEAN Plus mechanism, UN, the OECD, the G7, the G8, the G20, is considered a great power. Its economy is the world's third-largest by nominal GDP and the fourth-largest by purchasing power parity, it is the world's fourth-largest exporter and fourth-largest importer. Japan benefits from a skilled and educated workforce. Although it has renounced its right to declare war, Japan maintains a modern military with the world's eighth-largest military budget, used for self-defense and peacekeeping roles. Japan is a developed country with a high standard of living and Human Development Index, its population enjoys the highest life expectancy and third lowest infant mortality rate in the world, but is experiencing issues due to an aging population and low birthrate. Japan is renowned for its historical and extensive cinema, influential music industry, video gaming, rich cuisine and its major contributions to science and modern technology; the Japanese word for Japan is 日本, pronounced Nihon or Nippon and means "the origin of the sun".
The character nichi means "sun" or "day". The compound therefore means "origin of the sun" and is the source of the popular Western epithet "Land of the Rising Sun"; the earliest record of the name Nihon appears in the Chinese historical records of the Tang dynasty, the Old Book of Tang. At the end of the seventh century, a delegation from Japan requested that Nihon be used as the name of their country; this name may have its origin in a letter sent in 607 and recorded in the official history of the Sui dynasty. Prince Shōtoku, the Regent of Japan, sent a mission to China with a letter in which he called himself "the Emperor of the Land where the Sun rises"; the message said: "Here, I, the emperor of the country where the sun rises, send a letter to the emperor of the country where the sun sets. How are you". Prior to the adoption of Nihon, other terms such as Yamato and Wakoku were used; the term Wa is a homophone of Wo 倭, used by the Chinese as a designation for the Japanese as early as the third century Three Kingdoms period.
Another form of Wa, Wei in Chinese) was used for an early state in Japan called Nakoku during the Han dynasty. However, the Japanese disliked some connotation of Wa 倭, it was therefore replaced with the substitute character Wa, meaning "togetherness, harmony"; the English word Japan derives from the historical Chinese pronunciation of 日本. The Old Mandarin or early Wu Chinese pronunciation of Japan was recorded by Marco Polo as Cipangu. In modern Shanghainese, a Wu dialect, the pronunciation of characters 日本; the old Malay word for Japan, Japun or Japang, was borrowed from a southern coastal Chinese dialect Fukienese or Ningpo – and this Malay word was encountered by Portuguese traders in Southeast Asia in the 16th century. These Early Portuguese traders brought the word
Crabs are decapod crustaceans of the infraorder Brachyura, which have a short projecting "tail" entirely hidden under the thorax. They live in all the world's oceans, in fresh water, on land, are covered with a thick exoskeleton and have a single pair of pincers. Many other animals with similar names – such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs, crab lice – are not true crabs. Crabs are covered with a thick exoskeleton, composed of mineralized chitin, armed with a single pair of chelae. Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 metres. About 850 species of crab are terrestrial or semi-terrestrial species, they were thought to be a monophyletic group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World. The earliest unambiguous crab fossils date from the Jurassic, although Carboniferous Imocaris, known only from its carapace, may be a primitive crab.
The radiation of crabs in the Cretaceous and afterward may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, crabs' main predators. Crabs show marked sexual dimorphism. Males have larger claws, a tendency, pronounced in the fiddler crabs of the genus Uca. In fiddler crabs, males have one claw, enlarged and, used for communication for attracting a mate. Another conspicuous difference is the form of the pleon; this is. Crabs attract a mate through chemical, acoustic, or vibratory means. Pheromones are used by most aquatic crabs, while terrestrial and semiterrestrial crabs use visual signals, such as fiddler crab males waving their large claws to attract females; the vast number of brachyuran crabs have mate belly-to-belly. For many aquatic species, mating takes place just after the female is still soft. Females can store the sperm for a long time before using it to fertilise their eggs; when fertilisation has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material.
In this location, they are protected during embryonic development. Females carrying eggs are called "berried"; when development is complete, the female releases the newly hatched larvae into the water, where they are part of the plankton. The release is timed with the tides; the free-swimming tiny zoea larvae can take advantage of water currents. They have a spine, which reduces the rate of predation by larger animals; the zoea of most species must find food, but some crabs provide enough yolk in the eggs that the larval stages can continue to live off the yolk. Each species has a particular number of zoeal stages, separated by moults, before they change into a megalopa stage, which resembles an adult crab, except for having the abdomen sticking out behind. After one more moult, the crab is a juvenile, living on the bottom rather than floating in the water; this last moult, from megalopa to juvenile, is critical, it must take place in a habitat, suitable for the juvenile to survive. Most species of terrestrial crabs must migrate down to the ocean to release their larvae.
After living for a short time as larvae in the ocean, the juveniles must do this migration in reverse. In many tropical areas with land crabs, these migrations result in considerable roadkill of migrating crabs. Once crabs have become juveniles, they will still have to keep moulting many more times to become adults, they are covered with a hard shell. The moult cycle is coordinated by hormones; when preparing for moult, the old shell is softened and eroded away, while the rudimentary beginnings of a new shell form under it. At the time of moulting, the crab takes in a lot of water to expand and crack open the old shell at a line of weakness along the back edge of the carapace; the crab must extract all of itself – including its legs, mouthparts and the lining of the front and back of the digestive tract – from the old shell. This is a difficult process that takes many hours, if a crab gets stuck, it will die. After freeing itself from the old shell, the crab is soft and hides until its new shell has hardened.
While the new shell is still soft, the crab can expand it to make room for future growth. Crabs walk sideways, because of the articulation of the legs which makes a sidelong gait more efficient. However, some crabs walk forwards or backwards, including raninids, Libinia emarginata and Mictyris platycheles; some crabs, notably the Portunidae and Matutidae, are capable of swimming, the Portunidae so as their last pair of walking legs is flattened into swimming paddles. Crabs are active animals with complex behaviour patterns, they can communicate by waving their pincers. Crabs tend to be aggressive towards one another, males fight to gain access to females. On rocky seashores, where nearly all caves and crevices
Malacostraca is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crabs, crayfish, krill, amphipods, mantis shrimp and many other, less familiar animals, they have colonised freshwater and terrestrial habitats. They are segmented animals, united by a common body plan comprising 20 body segments, divided into a head and abdomen; the name Malacostraca was coined by a French zoologist Pierre André Latreille in 1802. He was curator of the arthropod collection at the National Museum of Natural History in Paris; the name comes from the Greek roots μαλακός and ὄστρακον. The name is misleading, since the shell is only soft after moulting, is hard. Malacostracans are sometimes contrasted with entomostracans, a name applied to all crustaceans outside the Malacostraca, named after the obsolete taxon Entomostraca; the class Malacostraca includes about 40,000 species, "arguably... contains a greater diversity of body forms than any other class in the animal kingdom".
Its members are characterised by the presence of three tagmata – a five-segmented head, an eight-segmented thorax and an abdomen with six segments and a telson, except in the Leptostraca, which retain the ancestral condition of seven abdominal segments. Malacostracans have abdominal appendages, a fact that differentiates them from all other major crustacean taxa except Remipedia; each body segment bears a pair of jointed appendages. The head bears two pairs of antennae, the first of, biramous and the second pair bear exopods which are flattened into antennal scales known as scaphocerites; the mouthparts consist of pairs each of mandibles and maxillae. A pair of stalked compound eyes is present, although in some taxa the eyes are unstalked, reduced or lost. Up to three thoracic segments may be fused with the head to form a cephalothorax. A carapace may be absent, present or secondarily lost, may cover the head, part or all of the thorax and some of the abdomen, it is variable in form and may be fused dorsally with some of the thoracic segments or be in two parts, hinged dorsally.
Each of the thoracic appendages is biramous and the endopods are the better developed of the branches, being used for crawling or grasping. Each endopod consist of seven articulating segments. In decapods, the claw is formed by the articulation of the dactylus against an outgrowth of the propodus. In some taxa, the exopods are lost and the appendages are uniramous. There is the six or seven-segmented abdomen. In most taxa, each abdominal segment except the last carries a pair of biramous pleopods used for swimming, gas exchange, creating a current or brooding eggs; the first and second abdominal pleopods may be modified in the male to form gonopods. The appendages of the last segment are flattened into uropods, which together with the terminal telson, make up the "tail fan", it is the sudden flexion of this tail fan that provides the thrust for the rapid escape response of these crustaceans and the tail fan is used in steering. In Leptostraca, the appendages on the telson instead form caudal rami.
The digestive tract is straight and the foregut consists of a short oesophagus and a two-chambered stomach, the first part of which contains a gizzard-like "gastric mill" for grinding food. The walls of this have chitinous ridges and calcareous ossicles; the fine particles and soluble material are moved into the midgut where chemical processing and absorption takes place in one or more pairs of large digestive caeca. The hindgut is concerned with water reclamation and the formation of faeces and the anus is situated at the base of the telson. Like other crustaceans, malacostracans have an open circulatory system in which the heart pumps blood into the hemocoel where it supplies the needs of the organs for oxygen and nutrients before diffusing back to the heart; the typical respiratory pigment in malacostracans is haemocyanin. Structures that function as kidneys are located near the base of the antennae. A brain exists in the form of ganglia close to the antennae, there are ganglia in each segment and a collection of major ganglia below the oesophagus.
Sensory organs include compound eyes, ocelli and sensory bristles. The naupliar eye is a characteristic of the nauplius larva and consists of four cup-shaped ocelli facing in different directions and able to distinguish between light and darkness. Malacostracans live in a wide range of marine and freshwater habitats, three orders have terrestrial members: Amphipoda and Decapoda, they are abundant in all marine ecosystems, most species are scavengers, although some, such as the porcelain crabs, are filter feeders, some, such as mantis shrimps, are carnivores. Most species of malacostracans have distinct sexes; the female genital openings or gonopores are located on the sixth t
Kagoshima Prefecture is a prefecture of Japan located on the island of Kyushu. The capital is the city of Kagoshima. Kagoshima Prefecture corresponds to the ancient Japanese provinces Ōsumi and Satsuma, including the northern part of the Ryukyu Islands; this region played a key role in the Meiji Restoration, the city of Kagoshima was an important naval base during Japan's 20th century wars and the home of admiral Tōgō Heihachirō. More recent incidents are the sinking of a North Korean spy ship in 2001 by the Coast Guard, salvaged and exhibited in Tokyo, the abduction of an office clerk from a Kagoshima beach in 1978 by agents from the same country; this became known only under the Koizumi administration. Kagoshima Prefecture is located at the southwest tip of Kyushu on the Satsuma Peninsula and Ōsumi Peninsula; this prefecture includes a chain of islands stretching further to the southwest of Kyushu for a few hundred kilometers. The most important group is the Amami Islands. Surrounded by the East China Sea to the west, Okinawa Prefecture in the south, Kumamoto Prefecture to the north, Miyazaki Prefecture to the east, it has 2,632 km of coastline.
It has a bay called Kagoshima Bay, sandwiched by two peninsulas, Satsuma and Ōsumi. Its position made it a'gateway' to Japan at various times in history. While Kyushu has about 13 million people, there are less than 2 million in this prefecture; the prefecture boasts a chain of active and dormant volcanoes, including the great Sakurajima, which towers out of the Kagoshima bay opposite Kagoshima city. A steady trickle of smoke and ash emerges from the caldera, punctuated by louder mini-eruptions on an daily basis. On active days in Kagoshima city an umbrella is advisable to ward off the ash. Sakurajima is one of Japan's most active volcanoes. Major eruptions occurred in 1914, when the island mountain spilled enough material to become permanently connected to the mainland, a lesser eruption in 1960. Volcanic materials in the soil make Sakurajima a source for record daikon radishes the size of a basketball. Many beaches around the Kagoshima Bay are littered with well-worn pumice stones. A crater lake in the southwestern tip of the prefecture, near the spa town of Ibusuki, is home to a rare species of giant eel.
As of March 31, 2008, 9% of the total land area of the prefecture was designated as Natural Parks, namely the Kirishima-Yaku and Unzen-Amakusa National Parks. Most of the economic sector is focused in Kagoshima City and the surrounding area, corresponding to the extent of the former Satsuma Province; the eastern part of the prefecture, the former Ōsumi Province, is rural and shows a general population decline. The prefecture has strong agricultural roots, which are reflected in its most well-known exports: green tea, sweet potato, Pongee rice, Satsuma ware and Berkshire pork. Kagoshima prefecture's production of bonito flakes is second only to that of Shizuoka. In addition it produces Japan's largest volume of unagi eels; the Japan Aerospace Exploration Agency has several facilities within the prefecture, including the country's main launch facility on Tanegashima and the Uchinoura Space Center. The prefecture's gross domestic product is 4.834 trillion yen. The following is a list of Kagoshima Prefecture's cities, its administrative districts with their constituent towns and villages: Nineteen cities are located in Kagoshima Prefecture: Kagoshima These are the towns and villages in each district: Kagoshima Rebnise, a professional basketball team, was founded in 2003 and competes in the second division of the national B.
League. Kagoshima United FC, a soccer team, competes in the J3 League. Although no major professional baseball teams are based in the prefecture, a number of Kagoshima's ballparks have hosted the spring training camps of Nippon Professional Baseball teams: Kamoike Ballpark, previous camp home of the Chiba Lotte Marines and Lotte Giants. Hosts regular season games. Kamoike Citizen Stadium Ibusuki Municipal Ballpark, camp home of the Kokutesu Swallows Yunomoto Ballpark, camp home of the Yakult Atoms Kagoshima Kamoike Stadium, camp home of Júbilo Iwata and Toshiba Brave Lupus Kagoshima Fureai Sportsland, camp home of Sagan Tosu The Kirishima-Yaku National Park is located in Kagoshima Prefecture. Kagoshima University National Institute of Fitness and Sports in Kanoya The International University of Kagoshima Kagoshima Immaculate Heart University Daiichi Institute of Technology Shigakukan University Kagoshima Prefectural College Kagoshima Immaculate Heart College Kagoshima Women's Junior College Daiichi Junior College of Infant Education Tanegashima Space Center Uchinoura Space Center Bansei Tokkō Peace Museum Chiran Peace Museum for Kamikaze Pilots Museum of the Meiji Restoration Reimeikan, Kagoshima Prefectural Center for Historical Material Uenohara site JR Kyushu Kyushu Shinkansen Kagoshima Line Nippō Main Line Ibusuki Makurazaki Line Hisatsu Line Kitto Line Hisatsu Orange Railway Kagoshima City Tram Kyushu Expressway Miyazaki Expressway Ibusuki Toll Road Minamikyushu Expressway Higashikyushu Expressway National Route 3 National Route 10 National Route 58 Route 220 (Miyazaki-Nichinan-Shibushi-Kanoya
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids and crustaceans; the term Arthropoda as proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora. Arthropods are characterized by their jointed limbs and cuticle made of chitin mineralised with calcium carbonate; the arthropod body plan consists of each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton; some species have wings. Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments, they have over a million described species, making up more than 80 per cent of all described living animal species, some of which, unlike most other animals, are successful in dry environments. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab.
Arthropods' primary internal cavity is a haemocoel, which accommodates their internal organs, through which their haemolymph – analogue of blood – circulates. Like their exteriors, the internal organs of arthropods are built of repeated segments, their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, their brains are formed by fusion of the ganglia of these segments and encircle the esophagus; the respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong. Their vision relies on various combinations of compound eyes and pigment-pit ocelli: in most species the ocelli can only detect the direction from which light is coming, the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey.
Arthropods have a wide range of chemical and mechanical sensors based on modifications of the many setae that project through their cuticles. Arthropods' methods of reproduction and development are diverse; the evolutionary ancestry of arthropods dates back to the Cambrian period. The group is regarded as monophyletic, many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall, the basal relationships of Metazoa are not yet well resolved; the relationships between various arthropod groups are still debated. Aquatic species use either external fertilization. All arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother. Arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and undergo a total metamorphosis to produce the adult form; the level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. Arthropods contribute to the human food supply both directly as food, more indirectly as pollinators of crops.
Some species are known to spread severe disease to humans and crops. The word arthropod comes from the Greek ἄρθρον árthron, "joint", πούς pous, i.e. "foot" or "leg", which together mean "jointed leg". Arthropods are invertebrates with jointed limbs; the exoskeleton or cuticles consists of a polymer of glucosamine. The cuticle of many crustaceans, beetle mites, millipedes is biomineralized with calcium carbonate. Calcification of the endosternite, an internal structure used for muscle attachments occur in some opiliones. Estimates of the number of arthropod species vary between 1,170,000 and 5 to 10 million and account for over 80 per cent of all known living animal species; the number of species remains difficult to determine. This is due to the census modeling assumptions projected onto other regions in order to scale up from counts at specific locations applied to the whole world. A study in 1992 estimated that there were 500,000 species of animals and plants in Costa Rica alone, of which 365,000 were arthropods.
They are important members of marine, freshwater and air ecosystems, are one of only two major animal groups that have adapted to life in dry environments. One arthropod sub-group, insects, is the most species-rich member of all ecological guilds in land and freshwater environments; the lightest insects weigh less than 25 micrograms. Some living crustaceans are much larger; the embryos of all arthropods are segmented, built from a series of repeated modules. The last common ancestor of living arthropods consisted of a series of undifferentiated segments, each with a pair of appendages that functioned as limbs. However, all known living and fossil arthropods have grouped segments into tagmata in which segments and their limbs are specialized in various ways; the three-