Lizard

From Wikipedia, the free encyclopedia

Jump to: navigation, search

For other uses, see Lizard (disambiguation).

Lizards Fossil range: 199–0 Ma PreЄ Є O S D C P T J K Pg N Jurassic- Present
Central bearded dragon, Pogona vitticeps
Scientific classification
Domain: Eukarya Kingdom: Animalia Phylum: Chordata Superclass: Tetrapoda Class: Reptilia Order: Squamata Suborder: Lacertilia* Günther, 1867
Families
Many, see text.

Lizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria (reptiles with overlapping scales) which are neither sphenodonts (i.e., Tuatara) nor snakes. While the snakes are recognized as falling phylogenetically within the anguimorph lizards from which they evolved, the sphenodonts are the sister group to the squamates, the larger monophyletic group which includes both the lizards and the snakes.

Lizards typically have limbs and external ears, while snakes lack both these characteristics. However, because they are defined negatively as excluding snakes, lizards have no unique distinguishing characteristic as a group. Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodonts which have a more primitive and solid diapsid skull. Many lizards can detach their tails in order to escape from predators, an act called autotomy, but this trait is not shared by all lizards. Vision, including color vision, is particularly well developed in most lizards, and most communicate with body language or bright colors on their bodies as well as with pheromones. The adult length of species within the suborder ranges from a few centimeters for some chameleons and geckos to nearly three meters (9 feet, 6 inches) in the case of the largest living varanid lizard, the Komodo Dragon. Some extinct varanids reached great size. The extinct aquatic mosasaurs reached 17.5 meters, and the giant monitor Megalania prisca is estimated to have reached perhaps seven meters.

Contents [hide] 1 Physiology 2 Evolution and relationships 2.1 Lizard diversification 2.1.1 Iguania 2.1.2 Gekkota 3 Relationship with humans 4 Classification 5 References

[edit] Physiology

A feral Jackson's Chameleon from a population introduced to Hawaii in the 1970s.

Sight is quite important for most lizards, both for locating prey and for communication, and as such, many lizards have highly acute color vision. Most lizards rely heavily on body language, using specific postures, gestures and movements to define territory, resolve disputes, and entice mates. Some species of lizard also utilize bright colors, such as the iridescent patches on the belly of Sceloporus. These colors would be highly visible to predators, so are often hidden on the underside or between scales and only revealed when necessary.

A particular innovation in this respect is the dewlap, a brightly colored patch of skin on the throat, usually hidden between scales. When a display is needed, the lizards erect the hyoid bone of their throat, resulting in a large vertical flap of brightly colored skin beneath the head which can be then used for communication. Anoles are particularly famous for this display, with each species having specific colors, including patterns only visible under ultraviolet light, as lizards can often see UV.

[edit] Evolution and relationships

The fossil mosasaur Prognathodon, a varanid.

The retention of the basic 'reptilian' amniote body form by lizards makes it tempting to assume any similar animal, alive or extinct, is also a lizard. However, this is not the case, and lizards as squamates are part of a well-defined group.

The earliest "lizard" was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc (termed Anapsid). Turtles retain this skull form. Early anapsids later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles. Those with a single hole, the Synapsids, gave rise to the superficially lizard-like Pelycosaurs which include Dimetrodon and the Therapsids, including the Cynodonts, from which would evolve the modern mammals.

The Diapsids, possessing one temporal fenestra before the eye and one behind it, continued to diversify. One branch, the Archosaurs, retained the basic Diapsid skull, and gave rise to a bewildering array of animals, most famous being the crocodilians, the pterosaurs, the dinosaurs and their descendants, birds. The Ichthyosaurs and Plesiosaurs radiated from the same basal Diapsid group.

The smaller Lepidosaurs which would give rise to the lizards began to reduce the skull bones, making the skull lighter and more flexible. The modern Tuatara retains the basic Lepidosaur skull, distinguishing it from true lizards in spite of superficial similarities. Squamates, including snakes and all true lizards, further lightened the skull by eliminating the lower margin of the lower skull opening.

[edit] Lizard diversification

Within the Lacertilia are found four generally recognized suborders, Iguania, Gekkota, Amphisbaenia and Autarchoglossa, with the "blind skinks" in the family Dibamidae having an uncertain position. While traditionally excluded from the lizards, the snakes are usually classified as a clade with a similar subordinal rank.^[1]

[edit] Iguania

Anoles mating, Gainesville, FL

The suborder Iguania, found in Africa, south Asia, Australia, the New World, and with iguanas colonizing the islands of the west Pacific, form the sister group to the remainder of the squamata. They are largely arboreal, and have primitively fleshy, non-prehensile tongues, but this condition is obviously highly modified in the chameleons. This clade includes the following families:

Carp

From Wikipedia, the free encyclopedia

Jump to: navigation, search

For other uses, see Carp (disambiguation).

Carp
Common carp, Cyprinus carpio
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Cypriniformes Family: Cyprinidae
Genera
Abramis Aristichthys Barbodes Carassius Cirrhinus Ctenopharyngodon Cyprinus Epalzeorhynchos Henicorhynchus Hypophthalmichthys Labeo Mylopharyngodon and others

Carp is a common name for various species of an oily^[1] freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. Some consider all cyprinid fishes carp, and the family Cyprinidae itself is often known as the carp family. In colloquial use, however, carp usually refers only to several larger cyprinid species such as Cyprinus carpio (common carp), Carassius carassius (Crucian carp), Ctenopharyngodon idella (grass carp), Hypophthalmichthys molitrix (silver carp), and Hypophthalmichthys nobilis (bighead carp). Carp have long been an important food fish to humans, as well as popular ornamental fishes such as the various goldfish breeds and the domesticated common carp variety known as koi. As a result, carp have been introduced to various locations, though with mixed results.All species of carp are listed as invasive species by http://www.invasivespeciesinfo.gov/aquatics/asiancarp.shtml and http://www.dnr.state.mn.us/invasives/aquaticanimals/commoncarp/index.html. Worldwide billions are spent each year on common and bighead and silver carp control worldwide

Contents [hide] 1 Aquaculture 2 As ornamental fish 3 As sport fish 4 Types of carp 5 See also 6 References 7 External links

[edit] Aquaculture

Carp can be very harmful to other types of freshwater fish. They may feed on the oxygen-producing vegetation in a body of water, thus making it difficult for other species to live there. In areas that are distant from the sea, carp may be the most common fish eaten^{[citation needed]}; although the prevalence of inexpensive frozen fish products have made them less important.

Various species of carp have been domesticated and reared as food fish across Europe and Asia for thousands of years. These various species appear to have been domesticated independently, as the various domesticated carp species are native to different parts of Eurasia. For example, the Common carp Cyprinus carpio are originally from Central Europe.^[2] Several carp species (collectively known as Asian carps) were domesticated in East Asia. Carp that are originally from South Asia, for example catla (Gibelion catla), rohu (Labeo rohita) and mrigal (Cirrhinus cirrhosus), are known as Indian carps. Their hardiness and adaptability have allowed domesticated species to be propagated all around the world.

[edit] As ornamental fish

An unusual goldfish breed: An oranda-type variegated pearlscale.

Carp, along with many of their cyprinid relatives, are popular ornamental aquarium and pond fish. The two most notable ornamental carps are goldfish and koi. Goldfish and koi have advantages over most other ornamental fishes, in that they are tolerant of cold (they can survive in water temperatures as low as 4 degrees Celsius), can survive at low oxygen levels, and can tolerate low water quality.

Six different colored koi and a smaller goldfish.

Goldfish (Carassius auratus) were originally domesticated from the Prussian carp (Carassius gibelio), a dark greyish brown carp native to Asia. They were first bred for color in China over a thousand years ago. Due to selective breeding, goldfish have been developed into many distinct breeds and are found in various colors, color patterns, forms and sizes far different from those of the original carp. Goldfish were kept as ornamental fish in China for hundreds of years before being introduced to Japan in the 15th century, and to Europe in the late 17th century.

Koi are a domesticated variety of common carp (Cyprinus carpio) that have been selectively culled for color. The common carp was introduced from China to Japan, where selective breeding of the common carp in the 1820s in the Niigata region resulted in koi.^[3] In Japanese culture, koi are treated with affection, and seen as good luck. They are popular in other parts of the world as outdoor pond fish.

[edit] As sport fish

This section needs references that appear in reliable third-party publications. Primary sources or sources affiliated with the subject are generally not sufficient for a Wikipedia article. Please add more appropriate citations from reliable sources. (June 2009)

An angler with 17 kg mirror carp (Cyprinus carpio)

Main article: Carp fishing

Izaak Walton said about carp in The Compleat Angler, "The Carp is the queen of rivers; a stately, a good, and a very subtil fish; that was not at first bred, nor hath been long in England, but is now naturalised."

Carp are variable in terms of angling value.

• In Europe, even when not fished for food, they are eagerly sought by anglers, being considered highly prized coarse fish that are difficult to hook.^[4] The UK has a thriving carp angling market.
• In the United States, the carp is also classified as a rough fish as well as damaging naturalized exotic species but with sporting qualities. Many states' departments of natural resources are beginning to view the carp as an angling fish instead of a maligned pest. Groups such as the Carp Anglers Group and American Carp Society promote the sport and work with fisheries departments to educate.

[edit] Types of carp

Carp swarm in great numbers to eat feed thrown by tourists in Urfa, Turkey.

• Genus Abramis
  • Carp bream (Abramis brama)
• Genus Barbodes:
  • Carnatic carp (Barbodes carnaticus)
• Genus Carassius:
  • Crucian carp (Carassius carassius )
  • Prussian carp or Gibel carp (Carassius gibelio)
  • Goldfish (Carassius auratus)
• Genus Cirrhinus:
  • Chinese mud carp (Cirrhinus chinensis)
  • Deccan white carp (Cirrhinus fulungee)
  • Hora white carp (Cirrhinus macrops)
  • Small scale mud carp (Cirrhinus microlepis)
  • Mud carp (Cirrhinus molitorella)
  • Man carp (Cirrhinus saprian)
• Genus Ctenopharyngodon:
  • Grass carp (Ctenopharyngodon idellus)
• Genus Culter:

Polar bear

From Wikipedia, the free encyclopedia

Jump to: navigation, search

For other uses, see Polar bear (disambiguation).

Polar Bear
Conservation status
Vulnerable (IUCN 3.1)[1]
Scientific classification
Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Ursidae Genus: Ursus Species: U. maritimus
Binomial name
Ursus maritimus Phipps, 1774[2]
Polar bear range
Synonyms
Ursus eogroenlandicus Ursus groenlandicus Ursus jenaensis Ursus labradorensis Ursus marinus Ursus polaris Ursus spitzbergensis Ursus ungavensis Thalarctos maritimus

The polar bear (Ursus maritimus) is a bear native largely within the Arctic circle encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest carnivore species found on land. It is also the largest bear, together with the omnivore Kodiak bear which is approximately the same size.^[3] An adult male weighs around 350–680 kg (770–1,500 lb),^[4] while an adult female is about half that size. Although it is closely related to the brown bear, it has evolved to occupy a narrow ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet.^[5] Although most polar bears are born on land, it spends most of its time at sea, hence its name meaning "maritime bear", and can hunt consistently only from sea ice, spending much of the year on the frozen sea.

The polar bear is classified as a vulnerable species, with 5 of the 19 polar bear subpopulations in decline.^[6][7] For decades, unrestricted hunting raised international concern for the future of the species; populations have rebounded after controls and quotas began to take effect. For thousands of years, the polar bear has been a key figure in the material, spiritual, and cultural life of Arctic indigenous peoples, and the hunting of polar bears remains important in their cultures.

The IUCN now lists global warming as the most significant threat to the polar bear, primarily because the melting of its sea ice habitat reduces its ability to find sufficient food. The IUCN states, "If climatic trends continue polar bears may become extirpated from most of their range within 100 years."^[1] On May 14, 2008, the United States Department of the Interior listed the polar bear as a threatened species under the Endangered Species Act.

Contents [hide] 1 Naming and etymology 2 Taxonomy and evolution 3 Population and distribution 4 Habitat 5 Biology and behavior 5.1 Physical characteristics 5.2 Hunting and diet 5.3 Behavior 5.4 Reproduction and lifecycle 5.4.1 Maternity denning and early life 5.4.2 Later life 5.5 Ecological role 6 Hunting 6.1 Indigenous people 6.2 History of commercial harvest 6.3 Contemporary regulations 6.3.1 Russia 6.3.2 Greenland 6.3.3 Canada and the United States 7 Conservation status, efforts and controversies 7.1 Global warming 7.1.1 Observations linked to global warming 7.2 Pollution 7.3 Oil and gas development 7.3.1 Predictions 7.4 Controversy over species protection 7.5 U.S. endangered species legislation 7.6 Canadian endangered species legislation 8 In culture 8.1 Indigenous folklore 8.2 Symbols and mascots 8.3 Literature 9 See also 10 References 11 Notes 12 External links

Naming and etymology

Constantine John Phipps was the first to describe the polar bear as a distinct species.^[1] He chose the scientific name Ursus maritimus, the Latin for 'maritime bear',^[8] due to the animal's native habitat. The Inuit refer to the animal as nanook,^[9] (transliterated as nanuuq in the Inupiaq language,^[10] and nanuuk in Siberian Yupik.^{[citation needed]}) The bear is umka in the Chukchi language. In Russian, it is usually called бе́лый медве́дь (bélyj medvédj, the white bear), though an older word still in use is ошку́й (Oshkúj, which comes from the Komi oski, "bear").^[11] In Quebec French, the polar bear is referred to as Ours polaire.^[12] In the Norwegian administered Svalbard archipelago, the polar bear is referred to as Isbjørn ("ice bear").

The polar bear was previously considered to be in its own genus, Thalarctos.^[13] However, evidence of hybrids between polar bears and brown bears, and of the recent evolutionary divergence of the two species, does not support the establishment of this separate genus, and the accepted scientific name is now therefore Ursus maritimus, as Phipps originally proposed.^[14]

Taxonomy and evolution

Polar bears depend on sea ice as a platform for hunting seals. Large feet and short, stocky claws are adaptations to this environment.

The bear family, Ursidae, is believed to have split off from other carnivorans about 38 million years ago. The Ursinae subfamily originated approximately 4.2 million years ago. According to both fossil and DNA evidence, the polar bear diverged from the brown bear, Ursus arctos, roughly 200,000 years ago. The oldest known polar bear fossil is less than 100,000 years old. Fossils show that between ten to twenty thousand years ago, the polar bear's molar teeth changed significantly from those of the brown bear. Polar bears are thought to have diverged from a population of brown bears that became isolated during a period of glaciation in the Pleistocene.^[15]

More recent genetic studies have shown that some clades of brown bear are more closely related to polar bears than to other brown bears,^[16] meaning that the polar bear is not a true species according to some species concepts.^[17] In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids,^[15][18] indicating that they have only recently diverged and are genetically similar.^[19] However, as neither species can survive long in the other's ecological niche, and with distinctly different morphology, metabolism, social and feeding behaviors, and other phenotypic characteristics, the two bears are generally classified as separate species.^[19]

When the polar bear was originally documented, two subspecies were identified: Ursus maritimus maritimus by Constantine J. Phipps in 1774, and Ursus maritimus marinus by Peter Simon Pallas in 1776.^[20] This distinction has since been invalidated.

One fossil subspecies has been identified. Ursus maritimus tyrannus—descended from Ursus arctos—became extinct during the Pleistocene. U.m. tyrannus was significantly larger than the living subspecies.^[15]

Polar bears investigate the submarine USS Honolulu 280 miles (450 km) from the North Pole.

Population and distribution

The polar bear is found throughout the Arctic Circle and adjacent land masses . Due to the absence of human development in its remote habitat, it retains more of its original range than any other extant carnivore.^[21] While they are rare north of 88°, there is evidence that they range all the way across the Arctic, and as far south as James Bay in Canada. They can occasionally drift widely with the sea ice, and there have been anecdotal sightings as far south as Berlevåg on the Norwegian mainland and the Kuril Islands in the Sea of Okhotsk. It is difficult to estimate a global population of polar bears as much of the range has been poorly studied, however biologists use a working estimate of about 20,000-25,000 polar bears worldwide.^[6]

There are 19 generally recognized discrete subpopulations.^[6][7] The subpopulations display seasonal fidelity to particular areas, but DNA studies show that they are not reproductively isolated.^[22] The thirteen North American subpopulations range from the Beaufort Sea south to Hudson Bay and east to Baffin Bay in western Greenland and account for about 70% of the global population. The Eurasian population is broken up into the eastern Greenland, Barents Sea, Kara Sea, Laptev Sea, and Chukchi Sea subpopulations, though there is considerable uncertainty about the structure of these populations due to limited mark and recapture data.

Polar bears play-fighting

The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, US (Alaska) and Canada. These five nations are the signatories of the 1973 International Agreement for the Conservation of Polar Bears, which mandates cooperation on research and conservations efforts throughout the polar bear's range.

Modern methods of tracking polar bear populations have been implemented only since the mid-1980s, and are expensive to perform consistently over a large area.^[23] The most accurate counts require flying a helicopter in the Arctic climate to find polar bears, shooting a tranquilizer dart at the bear to sedate it, and then tagging the bear.^[23] In Nunavut, some Inuit have reported increases in bear sightings around human settlements in recent years, leading to a belief that populations are increasing. Scientists have responded by noting that hungry bears may be congregating around human settlements, leading to the illusion that populations are higher than they actually are.^[23] The Polar Bear Specialist Group of the IUCN takes the position that "estimates of subpopulation size or sustainable harvest levels should not be made solely on the basis of traditional ecological knowledge without supporting scientific studies."^[24]

Of the 19 recognized polar bear subpopulations, 8 are declining, 3 are stable, 1 is increasing, and 7 have insufficient data.^[6][7

Swordfish

From Wikipedia, the free encyclopedia

Jump to: navigation, search

This article is about a type of fish. For other uses, see Swordfish (disambiguation).

Swordfish Fossil range: 33.9–0 Ma PreЄ Є O S D C P T J K Pg N Early Oligocene to Present[1]
Conservation status
Data Deficient (IUCN 2.3)[2]
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Perciformes Family: Xiphiidae Genus: Xiphias Species: X. gladius
Binomial name
Xiphias gladius Linnaeus, 1758

Swordfish (Xiphias gladius), also known as Broadbill in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. They reach a maximum size of 177 in. (455 cm) and 1,400 lb (650 kg). The International Game Fish Association's all-tackle angling record for a swordfish was a 1,182 lb (536.15 kg) specimen taken off Chile in 1953.

They are the sole member of their family Xiphiidae.

Contents [hide] 1 Physiology 2 Reproduction 3 Harvest 4 Conservation status 5 Recreational importance 6 References 7 External links

[edit] Physiology

The swordfish is named after its sharp beak resembling a sword (Latin gladius), which together with its streamlined physique allows it to cut through the water with great ease and agility. Contrary to belief the "sword" is not used to spear, but instead may be used to slash at its prey in order to injure the prey animal, to make for an easier catch. Mainly the swordfish relies on its great speed, capable of reaching speeds up to 50 mph (80 km/h), and agility in the water to catch its prey. One possible defensive use for the sword-like bill is for protection from its few natural predators. The shortfin mako shark is one of the rare sea creatures big enough and fast enough to chase down and kill an adult swordfish, but they don't always win. Sometimes in the struggle with a shark a swordfish can kill it by ramming it in the gills or belly.

Females grow larger than males, with males over 300 lb (135 kg) being rare. Females mature at 4–5 years of age in northwest Pacific while males mature first at about 3 to 4 years. In the North Pacific, batch spawning occurs in water warmer than 24 °C from March to July and year round in the equatorial Pacific. Adult swordfish forage includes pelagic fish including small tuna, dorado, barracuda, flying fish, mackerel, forage fish as well as benthic species of hake and rockfish. Squid are important when available. Swordfish are thought to have few predators as adults although juveniles are vulnerable to predation by large pelagic fish.

Swordfish skeleton at the National Museum of Natural History, Washington, DC

While swordfish are cold blooded animals, they have special organs next to their eyes to heat their eyes and also their brain. Temperatures of 10 to 15 °C above the surrounding water temperature have been measured. The heating of the eyes greatly improves the vision, and subsequently improves their ability to catch prey. Out of the 25 000+ species of bony fish, only about 22 are known to have the ability to heat selected body parts above the temperature of the surrounding water. These include the swordfish, marlin, and tuna.

Swordfish are not schooling fish. They swim alone or in very loose aggregations, separated by as much as 10 meters from a neighboring swordfish. They are frequently found basking at the surface, airing their first dorsal fin. Boaters report this to be a beautiful sight, as is the powerful jumping for which the species is known. This jumping, also called breaching, is thought by some researchers to be an effort to dislodge pests, such as remora or lampreys. It could also be a way of surface feeding by stunning small fish as they jump out of the water, making the fish more easily captured for food.

Swordfish feed daily, most often at night when they rise to surface and near-surface waters in search of smaller fish. They have been observed moving through schools of fish, thrashing their swords to kill or stun their prey and then quickly turning to consume their catch. In the western North Atlantic, squid is the most popular food item consumed. But fish, such as menhaden, mackerel, bluefish, silver hake, butterfish, and herring also contribute to the swordfish diet.

Swordfish are vigorous, powerful fighters. When hooked or harpooned, they have been known to dive so quickly that they have impaled their swords into the ocean bottom up to their eyes. Although there are no reports of unprovoked attacks on humans, swordfish can be very dangerous when harpooned. They have run their swords through the planking of small boats when hurt.

The adults have few natural enemies, with the exception of large sharks, sperm whales, and orcas. They are easily frightened by small boats, yet paradoxically, large craft are often able to draw very near without scaring them. This makes swordfish easy to harpoon.

The swordfish is often mistaken for other billfish (like marlin), but upon examination their physiology is quite different.

[edit] Reproduction

Swordfish have also been observed spawning in the Atlantic Ocean, in water less than 250 ft (75 m) deep. Estimates vary considerably, but females may carry from 1 million to 29 million eggs in their gonads. Solitary males and females appear to pair up during the spawning season. Spawning occurs year-round in the Caribbean Sea, Gulf of Mexico, the Florida coast and other warm equatorial waters, while it occurs in the spring and summer in cooler regions. The most recognized spawning site is in the Mediterranean, off the coast of Italy. The height of this well-known spawning season is in July and August, when males are often observed chasing females. The pelagic eggs are buoyant, measuring 1.6–1.8 mm in diameter. Embryonic development occurs during the 2 ½ days following fertilization. As the only member of its family, the swordfish has unique-looking larvae. The pelagic larvae are 4 mm long at hatching and live near the surface. At this stage, the body is only lightly pigmented. The snout is relatively short and the body has many distinct, prickly scales. With growth, the body narrows. By the time the larvae reach half an inch long (12 mm), the bill is notably elongated, but both the upper and lower portions are equal in length. The dorsal fin runs the length of the body. As growth continues, the upper portion of the bill grows proportionately faster than the lower bill, eventually producing the characteristic prolonged upper bill. Specimens up to approximately 9 inches (23 cm) in length have a dorsal fin that extends the entire length of the body. With further growth, the fin develops a single large lobe, followed by a short portion that still reaches to the caudal peduncle. By approximately 20 inches (52 cm), the second dorsal fin has developed, and at approximately 60 inches (150 cm), only the large lobe remains of the first dorsal fin.