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| − | {{otheruses}}
| + | <noinclude><translate></noinclude> |
| − | {{Taxobox | color = pink
| + | ===Frogs=== <!--T:1--> |
| − | | name = Litoria
| + | [[Image:Frogspawn closeup.jpg|190px|thumb|Frogspawn]] |
| − | | image = Caerulea3 crop.jpg
| + | [[Image:Tadpoles 10 days.jpg|190px|thumb||10 days: Tadpoles]] |
| − | | image_width = 240px
| + | [[Image:Frog-Zhe.jpg||190px|thumb|8–12 weeks: Froglet]] |
| − | | image_caption = [[White's Tree Frog]] (''Litoria caerulea'')
| + | [[Image:Green-leopard-frog-in-swamp.jpg||190px|thumb|12–16 weeks: Adult frog]] |
| − | | regnum = [[Animal]]ia
| + | The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviors that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying. |
| − | | phylum = [[Chordate|Chordata]] | |
| − | | classis = [[Amphibia]] | |
| − | | ordo = [[Anura]]
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| − | | ordo_authority = [[Blasius Merrem| Merrem]], [[1820]] | |
| − | | subdivision_ranks = Suborders | |
| − | | subdivision = [[Archaeobatrachia]]<br/> | |
| − | [[Mesobatrachia]]<br/> | |
| − | [[Neobatrachia]] <br/> - <br/> | |
| − | [[Anura (family list)| Full list of families]]
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| − | }}
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| − | '''Frog''' is the common name for [[amphibian]]s in the order Anura. A distinction based on appearance is often made between frogs and [[toad]]s, but this actually has no scientific basis. The only family exclusively given the common name "toad" is [[Bufonidae]], but many species from various other families are also called "toads". "[[True frog]]s" are of the family Ranidae.
| + | <!--T:2--> |
| | + | The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week. |
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| − | ==Characteristics==
| + | <!--T:3--> |
| − | {{main|Frog zoology}}
| + | Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma. |
| − | Because of the great diversity of frogs (over 4000 species), many characteristics are not shared by all of the species. However, there are some general characteristics that distinguish them from other amphibians. Frogs are generally well suited to jumping, and have long hind legs, with elongated ankle bones. They have a short vertebral column, with no more than ten free vertebrae, followed by a fused tail bone, usually resulting in a frog without a tail.
| + | Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for breathing and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (''Alytes obstetricans'') and the Common Spadefoot (''Pelobates fuscus''). |
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| − | Frogs range in size from 10mm (''[[Psyllophryne didactyla]]'' of [[Brazil]] and ''[[Eleutherodactylus iberia]]'' of [[Cuba]]) to 300mm ([[Goliath frog]], ''Conraua goliath'', of [[Cameroon]]).
| + | <!--T:4--> |
| | + | At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail. |
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| − | The skin is unkeratinized and hangs loosely on the body because of the lack of [[loose connective tissue]], and can be smooth, warty or have skin folds. Frogs have three eyelid membranes: one transparent to protect the eyes underwater, and two which are translucent to opaque. They have a [[tympanum]] on each side of their head, which is involved in hearing, and is covered by skin in some species.
| + | <!--T:5--> |
| − | | + | After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals. |
| − | ===Call===
| + | <br style="clear:both"> |
| − | [[Image:Rana_skeleton.png|thumb|Skeleton of ''Rana'']]
| + | <noinclude></translate></noinclude> |
| − | The males of most [[species]] of frogs will call for a variety of reasons. It will call by passing air through the [[larynx]], in the throat. In most calling frogs, the sound is amplified by the vocal sac(s). The vocal sac is a membrane of skin under the throat or on the cheeks which distends during the amplification of the call. Each call is unique to a species.
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| − | The main reason for calling is for the male to attract a mate. Males will either call in a group, called a chorus, or individually. A male frog will emit a different call when mounted by another male. Many species also have a territorial call that is used to chase away other males. All of these calls are emitted with the mouth of the frog closed.
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| − | A distress call is emitted by some frogs when they are in a position of danger. This is done with the mouth open, and usually results in a higher pitched call. The effectiveness of the call is unknown, however it is suspected the call intrigues the predator, until another animal is attracted, distracting them enough for its escape.
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| − | Many species of frog have deep calls, or croaks. Frog noise tends to be spelt (for English speakers) as "crrrrk" in [[Britain]] and "ribbit" in the [[USA]]. This difference is due to the different species within each region (for example, [[Common frog]] (''Rana temporaria'') in Britain and [[Leopard frog]] (''Rana pipiens'') in the USA). The croak of the [[bullfrog| American bullfrog]] (''Rana catesbiana'') is sometimes spelt "jug o' rum".
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| − | ===Poison===
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| − | Some species of frog secrete [[toxin]]s from their skin. These toxins deter predatory animals from eating them, and some are extremely poisonous to humans. Generally the frog obtains the poison from the insects or animals they eat. The Australian [[Corroboree frog]]s, ''Pseudophryne corroboree'' and ''Pseudophryne pengilleyi'', have been discovered to be able to manufacture a unique [[alkaloid]] which is not derived from their diet (Daly). Some natives of the [[Amazon_Rainforest|Amazon]] area extract poison from the [[poison dart frog]] and put it on their [[dart]]s when hunting. It was previously a misconception that the poison was placed on arrows rather than darts. The name of the frog was changed from [[Poison arrow frog]] to Poison dart frog in the early 1980's. Poisonous frogs tend to advertise their toxicity with bright colours.
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| − | ==Distribution and status==
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| − | Frogs are found nearly worldwide, but they do not occur in [[Antarctica]] and are not present on many oceanic islands.
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| − | In many parts of the world, the [[Decline in frog populations|frog populations have declined]] drastically since the 1950s. Many environmental scientists feel that amphibians, and frogs in particular, may be excellent biological [[indicator species|indicators]] of ecosystem function because of their location on the food web, their permeable skins and their typically bi-phasic life (in both water and on land). The decline in frog diversity may also be to do with particular species having specialised on particular kinds of prey, such as certain kinds of [[earthworm]]s that are themselves indicator species due to their close dependence on soil chemistry.
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| − | Although habitat loss is certainly one of the most important features of most declines; pollutants, climate change, introduction of non-indigenous predators/competitors, and infectious diseases (see [[Chytrid|Chytrid fungus]]) have also been implicated.
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| − | [[Image:Dscn1922-frog.jpg|thumb|right|Frog skeleton]]
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| − | ==Life cycle==
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| − | The life cycle of frogs contains many stages. Typically, the male frogs of a species will assemble at a still water source. They will then call, collectively becoming a chorus of frogs. The call is unique to the species, and will attract females of that species. Some species have satellite males who do not call but intercept females approaching one of the calling males.
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| − | The male and female frog, will then undergo [[amplexus]]. This involves the male mounting the female. The female then releases her eggs, which the male frog covers with a sperm solution before the eggs make contact with the water. Once the eggs come in contact with the water, they will swell, and form a protective coating. The eggs are typically brown or black, with a clear, gelatine-like, covering.
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| − | The eggs will hatch after a short time, releasing [[tadpoles]]. The tadpoles are entirely aquatic, and undergo the most development in the life cycle. They will undergo [[metamorphosis]], in which they will develop legs, and lungs, to become a froglet, resembling an adult but retaining a vestigial tail. The final stage of development from froglet to adult frog involves [[apoptosis]] (programmed cell death) of the tail. Typically, tadpoles are [[herbivore]]s, feeding mostly on [[alga]]e, whereas juvenile and adult frogs are rather voracious [[carnivore]]s.
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| − | Most temperate species of frog reproduce in the period between late autumn to early spring. In the [[UK]] most common frog populations produce frogspawn in February although there is wide variation in timing. Water temperatures at this time of year are relatively low and typically between four and 10 degrees Celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time.
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| − | <gallery>
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| − | Image:Frogspawn closeup.JPG|Frogspawn
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| − | Image:Tadpoles 10 days.JPG|10 days: Tadpoles
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| − | Image:Frog-Zhe.jpg|8–12 weeks: Froglet
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| − | Image:Green-leopard-frog-in-swamp.jpg|12–16 weeks: Adult frog
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| − | </gallery>
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| − | ===Diversity of reproductive behaviours===
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| − | Many species of frog deviate from the life cycle outlined above in one or several ways. Some species lay eggs on leaves above ponds, with a coating designed to retain moisture. The tadpoles drop into the water upon hatching. Other species exhibit brood care and will carry the eggs and tadpoles on their hind legs or back (e.g. the [[midwife toad]], ''Alytes spp.''), in special folds on their backs, or in their stomachs (e.g. the [[gastric brooding frog]]s, ''Rheobatrachus spp.'').
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| − | In yet other species, the tadpoles overwinter and hence metamorphose at a much larger size.
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| − | ==Diet and Predators==
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| − | All adult frogs are [[carnivore]]s, and usually eat invertebrates such as: [[insect]]s, [[worm]]s and [[spider]]s. However, a few of the larger species may eat larger prey, such as small [[mammal]]s, [[fish]] and smaller frogs. Some frogs use their sticky tongues effectively in catching fast-moving prey, while others capture their prey, and force it into their mouth with their hands.
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| − | Most tadpoles are [[herbivore]]s, eating moss, or filtering small plant particles through their [[gill]]s. During the process of metamorphosis, their intestine will shorten to accommodate a carnivorous diet. Some species of frogs are carnivorous at the tadpole stage, and will usually eat small larvae and small fish.
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| − | Many animals eat frogs. These include [[birds]], large fish, [[snake]]s, [[otter]]s, [[fox]]es, [[badger]]s, [[coati]]s etc. Tadpoles and eggs are predated by fish, newts, predatory diving beetles, and birds such as [[kingfisher]]s. [[Cannibalism]] has also been observed among tadpoles.
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| − | ==Taxonomy==
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| − | ===Distinction of frogs and toads===
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| − | A problem commonly associated with Anurans, is the distinction between frogs and toads. This distinction has no scientific basis, and only refers to the common name of a species. Most frogs in the Ranidae family (true frogs) and Hylidae family (tree frogs) are considered frogs, whereas all those within the Bufonidae family (true toads) are considered toads. However, many families, and even genera, have a mixture of frogs and toads, so there is no taxonomic basis.
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| − | The distinction between frogs and toads usually given to the Anurans is; frogs are smooth and moist skinned, while toads have dry, warty skin. An exception can be made for the [[Fire-bellied toad]] (''Bombina bombina''). While its skin is slightly warty, it prefers a watery habitat.
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| − | ===Hybridisation===
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| − | Many Anurans readily [[hybrid]]ise. For instance, the [[Edible Frog]] (''Rana esculenta'') is a hybrid of the [[Pool Frog]] (''R. lessonae'') and the [[Marsh Frog]] (''R. ridibunda''). ''Bombina bombina'' and ''Bombina variegata'' similarly form hybrids, although these are less fertile, giving rise to a [[hybrid zone]].
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| − | ==Evolution==
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| − | The earliest well-known amphibian, [[Ichthyostega]], was found in Late [[Devonian]] deposits in [[Greenland]], dating back about 363 million years. The earliest amphibian discovered to date is [[Elginerpeton]], found in Late Devonian rocks of [[Scotland]] dating to approximately 368 million years ago. The later [[Paleozoic]] saw a great diversity of amphibians, ranging from small legless swimming forms ([[Aïstopoda]]) to bizarre "horned" forms ([[Nectridea]]). These first amphibians are thought to have evolved from bony fish of the Class [[Osteichthyes]] which was widespread during the period that amphibia emerged. There is however, substantial debate over what type of bony fish was the amphibian precursor. Suggestions include the lung-fish and the [[Actinopterygii]] as the forerunners to modern amphibia.
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| − | The earliest known (proto)frog is †''[[Triadobatrachus massinoti]]'', from the Early [[Triassic]] of [[Madagascar]]. It is about 250 million years old, and had not yet evolved the full combination of features currently being associated with frogs. The skull is frog-like being broad with large eye sockets, but the fossil has a number of other features differing to modern amphibia. These include a different [[ilium]], a longer body with more [[vertebrae]], the lack of a [[urostyle]] and vertebrae in its tail. The [[tibia]] and [[fibula]] bones are unfused and separate, making it probable that Triadobatrachus was not a very efficient leaper.
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| − | Another fossil frog, discovered in Arizona and called ''[[Prosalirus bitis]]'', was uncovered in 1985, and dates from roughly the same time as ''Triadobatrachus''. Like ''Triadobatrachus'', ''Prosalirus'' did not have greatly enlarged legs, but possessed the typical three-pronged [[pelvic]] structure. Unlike ''Triadobatrachus'', ''Prosalirus'' had already lost nearly all of its tail.
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| − | The earliest true frog is †''[[Vieraella herbsti]]'', from the Early [[Jurassic]] (188-213 mya). It is known only from the [[dorsal]] and [[ventral]] impressions of a single animal and was estimated to be 33 mm in snout-vent length. †''[[Notobatrachus degiustoi]]'' from the Middle Jurassic is just a bit younger, about 155-170 million years old. It seems likely that the evolution of modern anura was completed by the Jurassic period. The main evolutionary changes involved shortening of the body and loss of the tail.
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| − | Frog fossils have been found on all continents, including [[Antarctica]].
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| − | Chris Harvey species has recently been discovered.
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| − | ==Uses==
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| − | *[[Frog legs]] are a delicacy in [[China]], [[France]], and in many parts of the [[American South]], especially [[Louisiana]]. The French custom of eating frog legs is the source of the English use of the derogatory nickname "frogs" for French people.
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| − | *Dead frogs are often used for [[dissection]]s in high school and university anatomy classes, because their internal organs are relatively odourless and can easily be injected with coloured plastics to enhance the contrast between different [[organ (anatomy)|organ]]s.
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| − | *The behavior of frogs illustrating nonaction is a [[myth]]. ("Take a pot of hot water and a frog. Throw the frog into the pot. What do you think will happen? The obvious, of course: the frog will jump out. Who likes hanging around in a pot of hot water? Now ... [t]ake a pot of cold water, put the frog in it, and place the pot on the stove. Turn on the heat. This time something different will occur. The frog, because of the incremental change in temperature, will not notice that it is slowly being boiled." (from "Life and Death in the Executive Fast Lane" by Manfred Kets de Vries) Professor Doug Melton, Harvard University Biology Department, says, "If you put a frog in boiling water, it won't jump out. It will die. If you put it in cold water, it will jump before it gets hot -- they don't sit still for you." [http://www.fastcompany.com/online/01/frog.html] A frog put anywhere that doesn't kill it will jump, "they don't sit still for you."
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| − | yhklihdsflvhslvhaklgvhkSHJv;akshgL'Khglav
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| − | ==References==
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| − | * Holman, J.A. (2004). ''Fossil Frogs and Toads of North America'', Indiana University Press. ISBN 0253342805 .
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| − | * Estes, R., and O. A. Reig. 1973. "The early fossil record of frogs: a review of the evidence." pp. 11-63 In J. L. Vial (Ed.), ''Evolutionary Biology of the Anurans: Contemporary Research on Major Problems''. University of Missouri Press, Columbia.
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| − | ==External links==
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| − | {{commons|Frog}}
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| − | {{cookbook}}
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| − | * [http://www-itg.lbl.gov/ITG.hm.pg.docs/Whole.Frog/Whole.Frog.html The Whole Frog Project] - Virtual frog dissection and anatomy
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| − | * ''[http://raysweb.net/specialplaces/pages/frogsdecline.html Disappearance of toads, frogs has some scientists worried]'' - ''San Francisco Chronicle'', April 20, 1992
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| − | * [http://www.xenbase.org/ Xenbase] - A ''Xenopus laevis'' and ''tropicalis'' Web Resource
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| − | * [http://tolweb.org/tree?group=Salientia Tree of Life (Salientia)]
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| − | * [http://amphibiaweb.org Amphibia Web]
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| − | * [http://markus.nolf.org/blog.php?p=160 Time-lapse video showing the egg's development until hatching]
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| − | * [http://www.midwestfrogs.com Frogs]Short video clips of calling frogs and interviews with scientists about frog issues, including declining and malformed frog causes
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| − | * [http://www.dartden.com Dart Den] - Dart frog resource and forums
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| − | *[http://www.thelilypad.org/ The Lily Pad] - Frog information, care, and culture
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| − | * [http://www.lacueva.cl/ Frog Forum] - The popular Frog forum in Chile
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| − | * [http://www.racingfrogs.org Racing Frogs Game] - Create, Train, Motivate and Feed your own little froggy friend
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| − | * [http://www.bbc.co.uk/nature/animals/wildbritain/springwatch/ Record UK Frogspawn sightings here] - Springwatch 2006
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| − | [[Category:Frogs|*]]
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Frogs
The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviors that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying.
The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week.
Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma.
Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for breathing and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (Alytes obstetricans) and the Common Spadefoot (Pelobates fuscus).
At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail.
After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals.
