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| − | {{AIDcur}}
| + | <noinclude><translate></noinclude> |
| − | {{otheruses}}
| + | ===Frogs=== <!--T:1--> |
| − | {{Taxobox | color = pink
| + | [[Image:Frogspawn closeup.jpg|190px|thumb|Frogspawn]] |
| − | | name = Frogs
| + | [[Image:Tadpoles 10 days.jpg|190px|thumb||10 days: Tadpoles]] |
| − | | image = Caerulea3 crop.jpg
| + | [[Image:Frog-Zhe.jpg||190px|thumb|8–12 weeks: Froglet]] |
| − | | image_width = 240px
| + | [[Image:Green-leopard-frog-in-swamp.jpg||190px|thumb|12–16 weeks: Adult frog]] |
| − | | image_caption = [[White's Tree Frog]] (''Litoria caerulea'')
| + | 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. |
| − | | regnum = [[Animal]]ia | |
| − | | phylum = [[Chordate|Chordata]] | |
| − | | classis = [[Amphibia]]
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| − | | ordo = [[Anura]] | |
| − | | ordo_authority = [[Blasius Merrem| Merrem]], [[1820]] | |
| − | | range_map = Frog distribution.png
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| − | | range_map_width = 240px | |
| − | | range_map_caption = Distribution of frogs (in black) | |
| − | | subdivision_ranks = Suborders | |
| − | | subdivision = [[Archaeobatrachia]]<br/> | |
| − | [[Mesobatrachia]]<br/> | |
| − | [[Neobatrachia]] <br/> - <br/>
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| − | [[Anura (family list)| Full list of families]]
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| − | }}
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| − | '''Frog''' is the common name for [[amphibian|amphibians]] in the order Anura. Adult frogs are characterised by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Frogs and [[toad]]s, are often differentiated based on appearance, but this 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.
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| | + | 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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| − | Most frogs have a semi-aquatic lifestyle, and their larvae, called [[tadpole]]s, have [[gill]]s and develop in water. Some frogs are poisonous and have [[aposematism|warning colouration]]; others are well camouflaged. Their distribution ranges from tropic to subarctic regions, with most of the species found in tropical rainforests.
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| | + | 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''). |
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| − | ==Characteristics==
| + | <!--T:4--> |
| − | Because of the great diversity of frogs (approximately 5250 described 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 usually 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, normally resulting in a tailless frog.
| + | 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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| − | Frogs range in size from 10mm (''[[Psyllophryne didactyla]]'' of [[Brazil]] and ''[[Eleutherodactylus iberia]]'' of [[Cuba]]) to 300mm ([[Goliath frog]], ''Conraua goliath'', of [[Cameroon]]).
| + | <!--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. |
| − | The skin hangs loosely on the body because of the lack of [[loose connective tissue]]. Skin texture varies: it can be smooth, warty or folded. Frogs have three eyelid membranes: one is transparent to protect the eyes underwater, while the two others vary from being translucent to opaque. They have a [[tympanum]] on each side of the head, which is involved in hearing, and is covered by skin in some species.
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| − | frog originated from the amniotic fluids of horses
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| − | The internal organs of frogs are relatively odourless. Hence, dead frogs are often used for [[dissection]]s in high school and university anatomy classes, often after being injected with coloured plastics to enhance the contrast between different [[organ (anatomy)|organ]]s.
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| − | ===Feet and legs===
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| − | [[Image:L tyleri.jpg|thumb|230px|right|[[Tyler's Tree Frog]] (''Litoria tyleri''), illustrating large toe pads and webbed feet.]]
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| − | The feet and legs of frogs are some of the most varied structures within the order Anura(Tailless Amphibians) because frogs can be found in a wide range of habitats (terrestrial, aquatic, and arboreal).
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| − | An aquatic lifestyle for a frog demands that a frog be able to move through the water quickly. To achieve this, frogs have evolved a structure similar to most semi-aquatic animals - webbed feet. The degree to which a frog is aquatic correlates with the amount of webbing on their feet. For example, the [[African dwarf frog]] (''Hymenochirus sp.'') is completely aquatic and its feet are fully webbed, whereas [[White's tree frog]] is arboreal, so its feet are only half or one-quarter webbed.
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| − | [[Tree frogs|Arboreal frogs]] have toe pads on the end of their toes to help grip vertical surfaces. The toe discs do not work by suction. Rather, the cells on the pads are interlocking, with gaps between each cell. The pressure from the frog interlocks any irregularities on a surface, and therefore grips the surface. On smooth surfaces, the gaps drain away excess moisture, to produce a thin layer of moisture. Capillarity then maintains the grip . For this reason, wet frogs cannot grip to smooth surfaces.Also these frogs possess a warty belly, helping to cling to the surface. {{ref|Emerson}}
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| − | Tree frogs also have a small structure called the "intercalary structure" in their toes. This aids in creating the greatest surface area touching the substrate, by applying even pressure to the toes.
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| − | Since hopping through trees can be dangerous, many arboreal frogs have hips which allow both hopping and walking.
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| − | Ground-dwelling frogs do not have many specific adaptations other than the lack of the adaptations of aquatic and arboreal frogs. They will usually have reduced toe pads (if any at all), and some webbing. Some of the burrowing frogs possess an extension on their toes called a metatarsal tubercle.This helps these frogs in burrowing. These belong to the type Microhylidae (or narrow mouthed frogs). The hind legs of ground-dwellers are more muscular than those of the aoueous and tree dwelling frogs.
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| − | ===Call===
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| − | [[Image:Rana_skeleton.png|thumb|Skeleton of ''Rana'']]
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| − | The call of a frog is unique to its species. Frogs call by passing air through the [[larynx]] in the throat. In most calling frogs, the sound is amplified by the vocal sac(s), a membrane of skin under the throat or on the corner of the mouth which distends during the amplification of the call.
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| − | Some frogs lack vocal sacs, such as those from the genera ''Heleioporus'' and ''Neobatrachus'', but even these can still produce a loud call. Their buccal cavity is enlarged and dome shaped, acting as a [[resonance chamber]] that amplifies their call. Species of frog which do not have vocal sacs and do not have a loud call tend to inhabit areas close to flowing water. The noise of flowing water overpowers any call so they must communicate by other means.
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| − | The main reason for calling is for the male to attract a mate. Males will call either individually or in a group called a "chorus." Females of many frog species, e.g. ''Polypedates leucomystax'', produce calls reciprocal to the males' which act as the catalyst for the enhancement of reproductive activity in the breeding colony (Roy, 1997). 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, emitted by some frogs when they are in danger, is produced with the mouth open, resulting 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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| − | ===Moisture retention===
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| − | Many frogs are able to absorb water directly through their skin, especially that around the pelvic area. However, the permeability of a frog's skin also results in water loss. Many frogs, such as [[tree frogs]], have adapted behaviors that conserve water. Some tree frogs reduce water loss with a waterproof layer of skin. Some species will use behavioral traits to reduce water loss. These include engaging in [[nocturnal]] activity and resting in a water conserving position. This position involves the frog lying with its toes and fingers tucked under its body and chin respectively, with no gap between the body and substrate. These adaptations only reduce water loss enough for a predominately arboreal existence, and are not suitable for arid conditions.
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| − | Frogs that live in arid areas such as deserts, where water may not be easily accessible, must rely on other adaptations. The Australia genus ''Cyclorana'', and American genus ''Pternohyla'' will dig underground, create a water-impervious cocoon and [[hibernate]] during dry periods. Once it rains, they emerge, find a temporary pond and breed. The egg and tadpole development is very fast in comparison to most other frogs, so the pond does not dry up before breeding is complete.
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| − | ===Respiration===
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| − | Just as frogs are able to absorb water through their skin, they are also able to breathe through their skin. There are a number of blood vessels near the surface of the skin. When a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream. On land, adult frogs use their lungs to breathe. Their lungs are similar to those of humans, but the chest muscles are not involved in respiration, and there are no [[rib]]s or [[diaphragm]] to support breathing. Frogs can breathe by simply opening the mouth and letting air flow into the [[trachea]]. They can also breathe with their mouths closed by taking air in through the nostrils (causing the throat to puff out), and then compressing the floor of the mouth, which forces the air into the lungs.
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| − | ===Camouflage===
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| − | [[Image:Crinia signifera.jpg|thumb|230px|right|[[Common Eastern Froglet]] (''Crinia signifera'') camouflaged against leaf litter.]]
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| − | [[Camouflage]] is a common defensive mechanism in frogs. Most camouflaged frogs are [[nocturnal]], which adds to their ability to hide. Nocturnal frogs will usually find the ideal camouflaged position during the day to sleep. Some frogs have the ability to change colour. However, this is usually restricted to shades of one or two colours. For example, [[White's tree frog]] (''Litoria caerulea'') varies in shades of green and brown. Features such as warts or skin folds are usually found on ground-dwelling frogs, where a smooth skin would not disguise them effectively. Arboreal frogs usually have smooth skin, enabling them to disguise themselves as leaves.
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| − | Certain frogs change colour between night and day, as light and moisture stimulate the pigment cells and cause them to expand or contract.
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| − | ===Poison===
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| − | All toads have poison glands(called the parotid gland).However, not all frogs have poison glands. Some, such as the poison-arrow frog, are however especially [[toxin|toxic]]. The chemical makeup of these toxins varies from irritants to [[hallucinogen]]s, [[convulsant]]s, nerve poisons, and [[vasoconstrictor]]s (which act to narrow the blood vessels). Many predators of frogs have adapted to tolerate high levels of these poisons. Others, including humans, may be severely affected and hence deterred by them.
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| − | Generally the frog obtains the poison from the insects and other animals it eats, although the Australian [[Corroboree Frog]]s, (''Pseudophryne corroboree'' and ''Pseudophryne pengilleyi''), can manufacture an [[alkaloid]] not derived from their diet {{ref|Smith}}. 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 thus changed from Poison Arrow Frog to Poison Dart Frog in the early [[1980s]]. Poisonous frogs tend to advertise their toxicity with bright colours. There are also at least two nonpoisonous species of frogs in South America which mimic poisonous frog’s colors to protect itself.
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| − | ==Life cycle==
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| − | The life cycle of frogs contains two main stages, the adult and the tadpole.
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| − | Frogs start life as [[tadpole]]s. Tadpoles are typically [[herbivore|herbivorous]], feeding mostly on [[alga]]e, including [[diatom]]s that are filtered from the water through the [[gill]]s. Some species are carnivorous at the tadpole stage, usually eating small larvae and fish. Tadpoles are entirely aquatic, and are vulnerable to predation by fish, [[newt]]s, predatory [[diving beetle]]s, and birds such as [[kingfisher]]s. [[Cannibalism]] has also been observed among tadpoles. As tadpoles grow, they undergo [[metamorphosis]], in which they develop legs and lungs, have their intestines shorten to accommodate a carnivorous diet, to become a froglet. The final stage of development from froglet to adult frog involves [[apoptosis]] (programmed cell death) of the tail. Most species complete their development within about three months, while others, such as the [[midwife toad]] ''Alytes obstetricans'' and the Common Spadefoot (''Pelobates fuscus''), [[hibernate]] as tadpoles and complete their development the following spring.
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| − | All juvenile and adult frogs are [[carnivore]]s, eating invertebrates such as [[insect]]s, [[worm]]s and [[spider]]s. 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 to catch fast-moving prey, while others capture their prey, and force it into their mouth with their hands.
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| − | Frogs are themselves predated by [[birds]], large [[fish]], [[snake]]s, [[otter]]s, [[fox]]es, [[badger]]s, [[coati]]s, and other animals. Frogs are also eaten by people. [[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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| − | The life cycle continues with male frogs of a species assembling 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 and gripping her tightly. 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. The eggs will hatch after a short time, releasing tadpoles.
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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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| − | The egg and tadpole stage of a frog's life cycle is usually the most dangerous due to easy [[predation]]. Frogs have evolved many techniques to protect the survival of the next generation.
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| − | The most common adaptation is mass laying of eggs. The female will lay thousands of eggs in one laying. A majority of the offspring will usually die due to predation, disease or competition with other tadpoles. However, there is a greater chance some will survive than a laying of smaller numbers. One way in which some species avoid the predation and pathogens eggs are exposed to in ponds is to lay eggs on leaves above the pond, with a coating designed to retain moisture. The tadpoles drop into the water upon hatching.
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| − | Poisonous tadpoles and/or eggs is an adaptation also present in frogs. Some tadpoles will advertise their toxicity, usually poison dart frogs, to warn potential prey. Other poisonous species will not, such as the [[Cane Toad]] (''Bufo marinus''). Although the Cane Toad, and similar species, do not advertise their toxicity the offspring still survive in large numbers. They will lay the eggs en masse, and any predator within the region will die once they eat the egg or tadpole. This reduces the number of predators, and therefore increases the number of surviving offspring.
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| − | Although brood care is much less common, there is a great diversity of such behaviours. Some species of poison dart frogs will lay eggs on the forest floor, and protect them until hatching. This protection involves guarding the eggs from predation, and keeping the eggs moist. The frog will urinate if they become too dry. After hatching, a parent (sex depending upon the species) will move them, on its back, to a water-holding [[bromeliad]]. The parent will then feed it through laying unfertilised eggs into the bromeliad, until the young have metamorphosed. Other frogs will carry the eggs and tadpoles on their hind legs or back (e.g. the [[midwife toad]]s, ''Alytes spp.'').
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| − | Many frogs protect their offspring inside their own body. The male Australian pouched frog (''Assa darlingtoni'') has pouches along its side. The tadpoles will reside in the pouch until the end of metamorphosis. The female [[Gastric-brooding Frog]]s (genus: ''Rheobatrachus'') from [[Australia]] swallows its tadpoles which develop in the stomach. To do this, the Gastric-brooding Frog must stop secreting [[stomach acid]] and suppress [[peristalsis]] (contractions of the stomach). [[Darwin's Frog]] (''Rhinoderma darwinii'') from [[Chile]] puts the tadpoles in its vocal sac for development.
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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 caused by the specialization of particular species 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 one of the most important causes of frog population decline, pollutants, climate change, introduction of non-indigenous predators/competitors, and infectious diseases (see [[Chytrid|Chytrid fungus]]) have also been implicated.
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| − | ==Taxonomy==
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| − | [[Image:Bombina bombina 1 (Marek Szczepanek) tight crop.jpg|thumb|190px|[[European Fire-bellied Toad]] (''Bombina bombina'')]]
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| − | The order Anura contains some 5250 species in 33 families, whereof the Leptodactylidae (1100 spp.), Hylidae (800 spp.) and Ranidae (750 spp.) are the most speciose.
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| − | The use of the common names "frog" and "toad" has no real taxonomic justification. From a taxonomic perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads." The use of the term "frog" in common names usually refers to species which are aquatic or semi-aquatic with smooth or moist skins, and the use of the term "toad" generally refers to species that tend to be terrestrial with 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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| − | Frogs and toads are broadly classified into three suborders: [[Archaeobatrachia]], [[Mesobatrachia]] and [[Neobatrachia]] - old, intermediate and new frogs respectively. This classification is based on the perceived possession of derived features of the three groups and refers to a fairly deep phylogenetic split, with the newest group, the Neobatrachia, having some 5,000 species. However, this distinction is far from universally accepted, especially because there are few features that are unique to any group.
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| − | Many Anurans [[hybrid]]ise readily. 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 amphibian discovered to date is [[Elginerpeton]], found in Late Devonian rocks of [[Scotland]] dating to approximately 368 million years ago. The earliest well-known amphibian, [[Ichthyostega]], was found in Late [[Devonian]] deposits in [[Greenland]], dating back about 363 million years. 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 were widespread during the period that amphibia emerged. There is, however, substantial debate over what type of bony fish was the precursor to amphibians. 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 associated with frogs. The skull is frog-like, being broad with large eye sockets, but the fossil has a number of other features diverging from 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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| − | ==See also==
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| − | *[[Frog zoology]]
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| − | *[[Frogs in popular culture]]
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| − | ==Notes==
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| − | #{{note|Emerson}}Emerson, S.B. and Diehl, D. (1980). "Toe pad morphology and mechanisms of sticking in frogs." ''Biol. J. Linn. Soc.'' '''13'''(3): 199-216.
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| − | #{{note|Smith}} Smith B. P., Tyler M. J., Kaneko T., Garraffo H. M., Spande T. F., Daly J. W. (2002). "Evidence for biosynthesis of pseudophrynamine alkaloids by an Australian myobatrachid frog (pseudophryne) and for sequestration of dietary pumiliotoxins." ''J Nat Prod'' '''65'''(4): 439-47.
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| − | ==References==
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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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| − | * Holman, J. A. (2004). ''Fossil Frogs and Toads of North America'', Indiana University Press. ISBN 0253342805.
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| − | * Roy, Debjani. (1997) "Communication signals and sexual selection in amphibians." ''Current Science'' '''72''', 923-927.
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| − | * Tyler, M. J. (1994). ''Australian Frogs A Natural History''. Reed Books ISBN 0730104680.
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| − | * 2004. ''Encyclopedia of Reptiles & Amphibians Second Edition''. Fog City Press. ISBN 1877019690.
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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.bbc.co.uk/nature/animals/wildbritain/springwatch/ Record UK Frogspawn sightings here] - Springwatch 2006
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| − | [[Category:Frogs|*]]
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