The axolotl is the tadpole form of what creature found in Mexico and the USA. It is unusual in that it attains maturity and reproduces in the tadpole, or larval, stage of amphibian metamorphosis?
"to the salamander. This discovery was the starting point of research about neoteny. It is not certain that ""Ambystoma velasci"" specimens were not included in the original shipment. Vilem Laufberger in Prague used thyroid hormone injections to induce an axolotl to grow into a terrestrial adult salamander. The experiment was repeated by Englishman Julian Huxley, who was unaware the experiment had already been done, using ground thyroids. Since then, experiments have been done often with injections of iodine or various thyroid hormones used to induce metamorphosis. Today, the axolotl is still used in research as a model organism, and large"
"into mobile adolescent form before the breeding pool dries up. The tadpoles are carnivores and cannibalistic at the time of hatching and have nearly adult jaws. They sexually mature in about a year. It is commonly observed in Paraguay and Bolivia, and less frequently in Argentina. Its natural habitats are the dry and wet Chaco. Breeding may take place in shallow temporary pools and artificial ponds. It is in some areas threatened by habitat loss but there is a large total population size. The species is listed as Least Concern in view of its relatively wide distribution, presumed large population,"
"Tadpole A tadpole (also called a pollywog) is the larval stage in the life cycle of an amphibian, particularly that of a frog or toad. They are usually wholly aquatic, though some species have tadpoles that are terrestrial. When first hatched from the egg they have a more or less globular body, a laterally compressed tail and internal or external gills. As they grow they undergo metamorphosis, during which process they grow limbs, develop lungs and reabsorb the tail. Most tadpoles are herbivorous and during metamorphosis the mouth and internal organs are rearranged to prepare for an adult carnivorous lifestyle."
"through a dramatic reorganization when transitioning from aquatic larvae to terrestrial adults, while others, such as the Axolotl, display paedomorphosis and never develop into terrestrial adults. Within the genus ""Ambystoma"", species have evolved to be paedomorphic several times, and paedomorphosis and complete development which can both occur in some species. In newts, there is no true metamorphosis because newt larvae already feed as predators and continue doing so as adults. Newts' gills are never covered by a gill sac and will be resorbed only just before the animal leaves the water. Just as in tadpoles, their lungs are functional early,"
"and deposits the now-fertilized eggs on vegetation. Large-scale captive breeding of tiger salamanders has not been accomplished, for unknown reasons. The larva is entirely aquatic, and is characterized by large external gills and a prominent caudal fin that originates just behind the head, similar to the Mexican axolotl. Limbs are fully developed within a short time of hatching. Some larvae, especially in seasonal pools and in the north, may metamorphose as soon as feasible. These are known as small morph adults. Other larvae, especially in ancestral pools and warmer climates, may not metamorphose until fully adult size. These large larvae"
"incarnation of the god Xolotl, brother of Quetzalcoatl. It has been studied due to its abilities to regenerate limbs and other body parts. It can also reach sexual maturity as a larva, which no other amphibian can do. While mostly aquatic, it does have limited ability to breathe air. As of 2003, there were only 600 axolotls known to exist in the wild. Most of the threat to the species is loss of habitat and pollution, but the introduction of non-native fish such as tilapia has also had disastrous effects on the population of this and other species. Conservation efforts"
"adults too. The tadpole is moderately flat (dorsoventrally compressed). The tail is twice the length of the body. The tail fin is low and ends in a pointed tip. The male of this species guard the tadpoles that hatch from the eggs laid on the ground. The male then carries the tadpoles on its back to water. Its natural habitats are lower montane and lowland forests. The tadpoles develop in small rain pools and quiet sections of small, slow moving streams. The habitat of this species is mostly well protected, although it can potentially be impacted by habitat loss. It"
"amphibians that usually live in the water, though a few tadpoles are semi-terrestrial (""Indirana beddomii"" and ""Thoropa miliaris"") and terrestrial (""Indirana semipalmata"" and ""Adenomera andreae""). During the tadpole stage of the amphibian life cycle, most respire by means of autonomous external or internal gills. They do not usually have arms or legs until the transition to adulthood, and typically have a large, flattened tail with which they swim by lateral undulation, similar to most fish. As a tadpole matures, it most commonly metamorphosizes by gradually growing limbs (usually the back legs first, followed by the front legs) and then (most"
"tadpole undergoes metamorphosis in which its appearance and internal organs are rearranged. After this it is able to leave the water as a miniature, air-breathing frog. Two main types of reproduction occur in frogs, prolonged breeding and explosive breeding. In the former, adopted by the majority of species, adult frogs at certain times of year assemble at a pond, lake or stream to breed. Many frogs return to the bodies of water in which they developed as larvae. This often results in annual migrations involving thousands of individuals. In explosive breeders, mature adult frogs arrive at breeding sites in response"
"The largest tadpoles (Gosner stage 37) measure in body length and in total length. ""Ptychohyla acrochorda"" occurs in mesic cloud forests at elevations of above sea level. Males call perched on branches or bushes along streams. The tadpoles develop in streams. The habitat of this species is threatened by habitat loss caused by small-scale farming and wood extraction; chytridiomycosis is also a potential threat. Ptychohyla acrochorda Ptychohyla acrochorda is a species of frogs in the family Hylidae. It is endemic to Mexico and known from the Atlantic slopes of the Sierra Juárez in Oaxaca. Before being described as a new"
"events. Developmental processes are very evident during the process of metamorphosis. This occurs in various types of animal. Well-known are the examples of the frog, which usually hatches as a tadpole and metamorphoses to an adult frog, and certain insects which hatch as a larva and then become remodeled to the adult form during a pupal stage. All the developmental processes listed above occur during metamorphosis. Examples that have been especially well studied include tail loss and other changes in the tadpole of the frog ""Xenopus"", and the biology of the imaginal discs, which generate the adult body parts of"
"does in humans. Unlike some other neotenic salamanders (sirens and ""Necturus""), axolotls can be induced to metamorphose by an injection of iodine (used in the production of thyroid hormones) or by shots of thyroxine hormone. The adult form resembles a terrestrial plateau tiger salamander, but has several differences, such as longer toes, which support its status as a separate species. Six adult axolotls (including a leucistic specimen) were shipped from Mexico City to the in Paris in 1863. Unaware of their neoteny, Auguste Duméril was surprised when, instead of the axolotl, he found in the vivarium a new species, similar"
"the pet trade, especially white/pink animals with pink eyes that are double homozygous mutants for both the albino and leucistic trait. Axolotls also have some limited ability to alter their color to provide better camouflage by changing the relative size and thickness of their melanophores. The axolotl is only native to Lake Xochimilco and Lake Chalco in the Valley of Mexico. Lake Chalco no longer exists, as it was artificially drained to avoid periodic flooding, and Lake Xochimilco remains a remnant of its former self, existing mainly as canals. The water temperature in Xochimilco rarely rises above , though it"
"39 to 45 days, and tadpoles require about 80 days to attain metamorphosis. Oviposition generally takes place in densely vegetated, shallow portions of wetlands with little current, and in unusual cases, egg masses have been observed in water up to 500 cm in depth. Breeding sites can be either permanent or temporary, with inundation usually necessary into June for successful metamorphosis. The June date is based on Oregon conditions; in Northern California, metamorphosis occurs in late May or early June. Breeding is initiated when water temperatures exceed about 6°C (usually in January), but can be as late as March in"
"areas around the edge of water bodies, after rain or when water levels are high, during spring to autumn. Breeding occurs mostly after heavy rain and eggs are laid in a floating foamy mass, often attached to vegetation. Eggs and tadpoles are generally found in slow moving or still waters Tadpoles can reach up to 69 mm and as an opportunistic breeder metamorphosis can occur at any time of the year. The tadpoles are very similar to ""Limnodynastes tasmaniensis"" and cannot be readily distinguished until metamorphosis. In Australia, this species may be kept in captivity with a license. Although the"
"are laid and are stuck to water weeds or placed beneath underwater stones. When the tadpoles hatch, they feed on vegetable matter and take about three months before they undergo metamorphosis into juvenile frogs. These are about long. Males become mature when they are about in length and females when they are rather larger. The Iberian frog is threatened by habitat loss through agriculture, deforestation, and the planting of non-native woodlands. Tourist development and recreational use of the land may cause disturbances. Introduced fish species and the presence of the American mink (""Neovison vison""), escaped from fur farms, may also"
"are subtropical or tropical dry forests, intermittent rivers, intermittent freshwater marshes, water storage areas, and ponds. It is not considered a threatened species by the IUCN. Breeding takes place near ponds and swamps. The eggs are laid in clumps above the water on foliage. The tadpoles fall into the water after hatching. Mexican leaf frog The Mexican leaf frog, Pachymedusa dacnicolor, is a species of frog in the family Hylidae. It belongs to the monotypic genus Pachymedusa in the subfamily Phyllomedusinae. This frog is endemic to Mexico. The adult grows up to 100 mm in length, with an overall dorsal"
"carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. Young of the Cuban tree frog (""Osteopilus septentrionalis"") can occasionally be cannibalistic, the younger tadpoles attacking a larger, more developed tadpole when it is undergoing metamorphosis. At metamorphosis, rapid changes in the body take place as the lifestyle of the frog changes completely. The spiral‐shaped mouth with horny tooth ridges is reabsorbed together with the spiral gut. The animal develops a large jaw, and its gills disappear along with its gill sac. Eyes and legs grow quickly, and a tongue is formed. There are associated changes in the neural"
"species will often breed in temporary water. Its call is a short, high pitched, wr-e-e-ek ip-ip, repeated three or four times. They emit their calls from a single submandibular vocal sac. The males call during the spring and summer seasons, often before and after heavy rain. About 200-300 eggs are laid at each amplexus, and clumps of spawn contain up to 35 eggs. The minimum tadpole lifespan is 118 days, at a consist temperature of 20 °C. Metamorphosis occurs from January to March, the metamorphs resemble the adults and are very small, only 9–13 mm in length. This species is"
"the late Pliocene in Entre Ríos Province, Argentina. Water opossum The water opossum (""Chironectes minimus""), also locally known as the yapok (), is a marsupial of the family Didelphidae. It is the only living member of its genus, Chironectes. This semiaquatic creature is found in and near the freshwater streams and lakes in Mexico, Central, South America to Argentina and is the most aquatic living marsupial (the lutrine opossum also has aquatic habits). It is also the only living marsupial in which both sexes have a pouch. The thylacine, commonly referred to as the Tasmanian tiger, also exhibited this trait,"
"°C range, but from this point on, growth was significantly hindered at 18 °C. At the beginning of the metamorphing stage, all limbs are present and developed, along with a tail. During this phase, the tail is resorbed, and the only other visible change is the spiracle closing. Metamorphing tadpoles typically have a SVL of 22–28 mm, and will complete metamorphosis between two and 11 months, depending on the temperature of the water and available food. The process is slowed at low temperatures, but generally takes between three and eight days after the tadpole stage is complete. Breeding occurs in"
"four years to metamorphose in the cool, fast-moving mountain streams. Thermal tolerance range in adults is exceptionally low relative to other North American anurans. Adults have been observed to exhibit extreme philopatry, however, movements and migrational habits in ""Ascaphus"" have not been well documented. Adults forage primarily terrestrially along stream banks, but also occasionally feed underwater. A wide variety of food items is taken, including both aquatic and terrestrial larval and adult insects, other arthropods (especially spiders), and snails. Tadpoles consume small quantities of filamentous green algae and desmids. Large quantities of conifer pollen are consumed seasonally by tadpoles. During"
"tubercular folds, resulting in a wavy outline of the limbs. The tooth row formula of tadpoles is 2/3, with the A2 tooth row broadly separated in the center. Its natural habitats are tropical moist lowland forests and rivers; it is mostly found in riparian vegetation. In the northern part of its range (south to the Isthmus of Panama approximately) it is found on the Atlantic side of the American Cordillera; on the Pacific side, it is found from Costa Rica southwards. It occurs up to 960 meters ASL in the northern parts of its range, but apparently only up to"
"of the tadpole. The species description is based on a single adult male and series of tadpoles, one of them reared past metamorphosis. The adult male measures in snout–vent length. The head is broad but much narrower than body. The snout is rounded. The eyes are small. Skin is shagreen, and the occipital fold is complete. The fingers and toes have rounded tips and narrow fringes. Webbing is basal between the fingers and more developed between the toes. The dorsum is tan and mottled with dark brown. The venter is black with bluish-white flecks. The tadpoles grow to in length."
"way for explosive evolution to follow."" A paper by (Page ""et al."" 2010) have written that the Mexican axolotl (""Ambystoma mexicanum"") could be classified as a hopeful monster as it exhibits an adaptive and derived mode of development that has evolved rapidly and independently among tiger salamanders. According to the paper there has been an interest in aspects of the hopeful monster hypothesis in recent years: Goldschmidt proposed that mutations occasionally yield individuals within populations that deviate radically from the norm and referred to such individuals as ""hopeful monsters"". If the novel phenotypes of hopeful monsters arise under the right"
"urban locations. Its altitudinal range is between about . Much of its habitat consists of seasonally flooded areas in the Araguaia, Tocantins, Xingu and Parnaíba river systems. Breeding takes place around October in flooded grassland and flooded gallery forest habitats. Males call from still-water sites such as at the edges of ponds, often from near aquatic vegetation or fallen trees. Cattle dams are also used as breeding sites. Tadpoles have been found in large accumulations, sometimes swimming around a female floating in the water. On several occasions, a female was observed to ""gather"" tadpoles around her and move the group"
"Whether this is due to an actual lack of tadpole stage or taphonomy (many diadectomorphs were upland creatures where tadpoles would have a poor probability of being fossilized) is uncertain. Alfred Romer indicated that the anamniote/amniote divide might not have been very sharp, leaving the question of the actual mode of reproduction of these large animals unanswered. Possible reproductive modes include full amphibian spawning with aquatic tadpoles, internal fertilization with or without ovoviviparity, aquatic eggs with direct development or some combination of these. The reproductive mode might also have varied within the group. Diadectomorpha Diadectomorpha are a clade of large"
"pustules. The venter is pale blue-green, with dark chocolate brown mottling. The tadpoles are ""gastromyzophorous"", that is, torrent-adapted tadpoles that bear an abdominal sucker. They resemble those of another bufonid genus, ""Atelopus"", although the adults are different. The suctorial disc is large, extending about three-fourths length of body. The coloration is black with gold markings. The largest tadpoles are about in total length. A newly metamorphosed juvenile with a tail stub measured in snout–vent length. Its natural habitats are premontane and lower montane wet forests at elevations of above sea level. The tadpoles develop in mountain streams, clinging to rocks"
"Larva A larva (plural: ""larvae"" ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The larva's appearance is generally very different from the adult form (""e.g."" caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. Larvae are frequently adapted to environments separate from adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments, but can live outside water"
"surface of the first manual digit. Breeding males also develop – somewhat hair-like – dermal papillae that extend along the flanks and thighs. These contain arteries and are thought to increase the surface area for the purpose of absorbing oxygen (comparably to external gills of the aquatic stage), which is useful as the male stays with his eggs for an extended period of time after they have been laid in the water by the female. The species is terrestrial, but returns to the water for breeding, where egg masses are laid onto rocks in streams. The quite muscular tadpoles are"
"childhood (such as accelerated brain growth in humans), is also extended throughout this period. Neoteny has been implicated as a developmental cause for a number of behavior changes, as a result of increased brain plasticity and extended childhood. Progenesis (or paedogenesis) can be observed in the axolotl (""Ambystoma mexicanum""). Axolotls reach full sexual maturity while retaining their fins and gills (in other words, still in the juvenile form of their ancestors).They will remain in aquatic environments in this truncated developmental form, rather than moving onto land as other sexually mature salamander species. This is thought to be a form of"
"hatch, the adults transport the tadpoles on their backs to ponds, where the tadpoles complete their development. Ecuador poison frog The Ecuador poison frog (""Ameerega bilinguis"") is a species of frogs in the family Dendrobatidae found in Colombia, Ecuador, and possibly Peru. Its natural habitats are subtropical or tropical moist lowland forests, rivers, intermittent rivers, freshwater marshes, and intermittent freshwater marshes. It is threatened by habitat loss. The flashy and brilliant colors of this species constitutes a warning for its potential predators that its skin produces poison, a feature that makes it an undesirable food source. It is very common"
"risk of many predators such as dragonfly and beetle larvae, turtles, and most fish. The tadpole stage lasts six to eight weeks, before the tadpoles metamorphose. For the frog to mature completely it requires about two months. ""Hyperolius nitidulus"" inhabit margins of swamps, rivers and lakes in savanna, grassland and bushland habitats. It is a very adaptable species that also occurs in many human-modified areas, such as cultivated land, towns, and gardens. ""Hyperolius nitidulus"" live in an environment with a wet season that can be cold and humid, and an extremely hot and dry season. During the hot and dry"