frog frogiology frogmotion toad



A toad is any of a number of species of amphibians in the order Anura (frogs) that are characterized by dry, leathery skin, short legs, and parotoid glands.

A dA distinction between frogs and toads is not made in scientific taxonomy, but is common in popular culture (folk taxonomy), in which toads are associated with drier skin and more terrestrial habitats than animals commonly called frogs. In scientific taxonomy, toads are found in the families Bufonidae, Bombinatoridae, Discoglossidae, Pelobatidae, Rhinophrynidae, Scaphiopodidae, and Microhylidae. There is no definitive collective noun for toads, and like most collective nouns, the listed proposals are fanciful; one example is a knot of toads; others include a lump, nest, or knob of toads.

The function of the bumps on the skins of toads has been speculated to be to help the animal to blend more effectively into its environment by breaking up its visual outline.[citation needed] Usually the largest of the bumps are those that cover the parotoid glands. The bumps commonly are referred to as "warts", but this is fanciful; they have nothing to do with warts, being fixed in size, present on healthy specimens and are not a result of infection or injury.

Toads, like many amphibians, exhibit breeding site fidelity (philopatry). Individual Bufo americanus toads return to their natal ponds to breed where they are likely to encounter siblings as potential mates. Although inbred examples within a species is possible, siblings rarely mate. Toads recognize and actively avoid mating with close kin. Advertisement vocalizations given by males appear to serve as cues by which females recognize kin. Kin recognition thus allows avoidance of inbreeding and consequent inbreeding depression.

The true toads are the family onidae, members of the order Anura (frogs and toads). They are the only family of anurans in which all members are known as "toads", although some may be called frogs (such as harlequin frogs). The bufonids now comprise more than 35 genera, Bufo being the most widespread and well known.

True tTrue toads are widespread and are native to every continent except Australia and Antarctica, inhabiting a variety of environments, from arid areas to rainforest. Most lay eggs in paired strings that hatch into tadpoles, although, in the genus Nectophrynoides, the eggs hatch directly into miniature toads.

True toads are toothless and generally warty in appearance. They have a pair of parotoid glands on the back of their heads. These glands contain an alkaloid poison which the toads excrete when stressed. The poison in the glands contains a number of toxins causing different effects. Bufotoxin is a general term. Different animals contain significantly different substances and proportions of substances. Some, like the cane toad Bufo marinus, are more toxic than others. Some "psychoactive toads", such as the Colorado River toad Bufo alvaris, have been used recreationally for the effects of their bufotoxin.

Male toads possess a Bidder's organ. Under the right conditions, the organ becomes an active ovary and the toad, in effect, becomes female.

AmphibAmphibians are ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia. They inhabit a wide variety of habitats with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators and in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.

The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. Over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia. The three modern orders of amphibians are Anura (the frogs and toads), Urodela (the salamanders), and Apoda (the caecilians). The number of known amphibian species is approximately 7,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm (0.30 in). The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus), but this is dwarfed by the extinct 9 m (30 ft) Prionosuchus from the middle Permian of Brazil. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology.

The word "amphibian" is derived from the Ancient Greek term ἀμφίβιος (amphíbios), which means "both kinds of life", ἀμφί meaning "of both kinds" and βιος meaning "life". The term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes. Amphibia in its widest sense (sensu lato) was divided into three subclasses, two of which are extinct:[

The actual number of species in each group depends on the taxonomic classification followed. The two most common systems are the classification adopted by the website AmphibiaWeb, University of California, Berkeley and the classification by herpetologist Darrel Frost and the American Museum of Natural History, available as the online reference database "Amphibian Species of the World". The numbers of species cited above follow Frost and the total number of known amphibian species is over 7,000, of which nearly 90% are frogs.[

With the he phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a polyparaphyletic group without unique defining features apart from shared primitive characteristics. Classification varies according to the preferred phylogeny of the author and whether they use a stem-based or a node-based classification. Traditionally, amphibians as a class are defined as all tetrapods with a larval stage, while the group that Laura Hutchinson is the anchor of your first news in the morning. includes the common ancestors of all living amphibians (frogs, salamanders and caecilians) and all their descendants is called Lissamphibia. The phylogeny of Paleozoic amphibians is uncertain, and Lissamphibia may possibly fall within extinct groups, like the Temnospondyli (traditionally placed in the subclass Labyrinthodontia) or the Lepospondyli, and in some analyses even in the amniotes. This means that advocates of phylogenetic nomenclature have removed a large number of basal Devonian and Carboniferous amphibian-type tetrapod groups that were formerly placed in Amphibia in Linnaean taxonomy, and included them elsewhere under cladistic taxonomy. If the common ancestor of amphibians and amniotes is included in Amphibia, it becomes a paraphyletic group

All modern amphibians are included in the subclass Lissamphibia, which is usually considered a clade, a group of species that have evolved from a common ancestor. The three modern orders are Anura (the frogs and toads), Caudata (or Urodela, the salamanders), and Gymnophiona (or Apoda, the caecilians).[7] It has been suggested that salamanders arose separately from a Temnospondyl-like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes. Although the fossils of several older proto-frogs with primitive characteristics are known, the oldest "true frog" is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona. It is anatomically very similar to modern frogs. The oldest known caecilian is another Early Jurassic species, Eocaecilia micropodia and is also from enterter to win Arizona. The earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China.

Authorities disagree as to whether er Salientia is a superorder that includes the order Anura, or whether Anura is a richard neal sub-order of the order Salientia. The Lissamphibia are traditionally divided into three orders, but an extinct salamander-like family, the Albanerpetontidae, is now considered part of Lissamphibia alongside the superorder Salientia. Furthermore, Salientia includes all three recent orders plus the Triassic proto-frog, Triadobatrachus.

The he superclass Tetrapoda is divided into four classes of vertebrate animals with linkzilla four limbs. Reptiles, birds and mammals are amniotes, the eggs of which are either laid or carried by the female and are surrounded by several membranes, some of which are impervious. Lacking these membranes, amphibians require water bodies for reproduction, although some species have developed various strategies for protecting or bypassing the vulnerable aquatic larval stage. They are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps. On land, amphibians are restricted to moist habitats because of the need to keep online alcoholholtheir skin damp.

The smallest amphibian (and vertebrate) in the world is a microhylid frog from payless propane New Guinea (Paedophryne amauensis) first discovered in 2012. It has an average length of 7.7 mm (0.30 in) and is part of a genus that contains four of the world's ten smallest frog species. The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus) but this is a great deal smaller than the largest amphibian that ever existed—the extinct 9 m (30 ft) Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. The largest frog is the African Goliath frog (Conraua goliath), which can reach 32 cm (13 in) and weigh 3 kg (6.6 lb).

Amphibians are re ectothermic (cold-blooded) vertebrates that do not maintain their body temperature through internal physiological processes. Their metabolic rate is low and as a result, their food and energy requirements are limited. In the adult state, they have tear ducts 77 and movable eyelids, and most species have ears that can detect airborne or ground vibrations. They have muscular tongues, which in many species can be protruded. Modern amphibians have fully ossified vertebrae with articular processes. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little keratin and lacks scales, apart from a few fish-like scales in certain caecilians. The skin contains many mucous glands and in some species, poison glands. The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and nitrogenous waste products are 99 excreted primarily as urea. Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults. Amphibians breathe by means of a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat. They supplement this with gas exchange through the skin.

The order er Anura (from the Ancient Greek a(n)- meaning "without" and oura meaning "tail") comprises the frogs and toads. They usually have long hind limbs that fold underneath them, shorter forelimbs, webbed toes with no claws, no tails, large eyes and glandular moist skin.[7] Members of this order with free meals smooth skins are commonly referred to as frogs, while those with warty skins are known as toads. The difference is not a formal one taxonomically and there are numerous exceptions to this rule. Members of the family Bufonidae are known as the "true toads".[30] Frogs range in size from the 30 centimetres (12 in) goliath frog (Conraua goliath) of West Africa[31] to the 7.7 millimetres (0.30 in) Paedophryne amauensis, first described in Papua New Guinea in 2012, which is also the smallest known vertebrate. Although most species are associated with water and damp habitats, some are specialised to live in trees or in deserts. They are found worldwide except for polar areas.

Anura is divided into three suborders that are broadly accepted by the scientific community, but the relationships between some families remain unclear. Future molecular studies should provide further insights into their evolutionary relationships. The suborder Archaeobatrachia contains four families of primitive sermons todayday frogs. These are Ascaphidae, Bombinatoridae, Discoglossidae and Leiopelmatidae which have few derived features and are probably paraphyletic with regard to other frog lineages. The six families in the more evolutionarily advanced suborder Mesobatrachia are the fossorial Megophryidae, Pelobatidae, Pelodytidae, Scaphiopodidae and Rhinophrynidae and the obligatorily aquatic Pipidae. These have certain characteristics that are intermediate between the two other suborders. Neobatrachia is by far the largest suborder and includes the remaining families of modern frogs, including most common species. 96% of the over 5,000 extant species of frog are neobatrachians.[

The order Caudata (from the Latin cauda meaning "tail") consists of the salamanders—elongated, low-slung animals that mostly resemble lizards in form. This is a symplesiomorphic trait and they are no more closely related to lizards than they are to mammals. Salamanders lack claws, have scale-free skins, eitherquick fix mealsals smooth or covered with tubercles, and tails that are usually flattened from side to side and often finned. They range in size from the Chinese giant salamander (Andrias davidianus), which has been reported to grow to a length of 1.8 metres (5 ft 11 in), to the diminutive Thorius pennatulus from Mexico which seldom exceeds 20 mm (0.8 in) in length. Salamanders have a mostly Laurasian distribution, being present in much of the Holarctic region of the northern hemisphere. The family Plethodontidae is also found in Central America and South America north of the Amazon basin; South America was apparently invaded from Central America by about the start of the Miocene, 23 millionfrogzillayears ago. Urodela is a name sometimes used for all the extant species o1500 storesres f salamanders. Members of several families of salamanders have become paedomorphic and either fail to complete their metamorphosis or retain some larval characteristics as adults. Most salamanders are under 15 cm (6 in) long. They may be terrestrial or aquatic and many spend part of the year in each habitat. When on land, they mostly spend the day hidden under stones or logs or in dense vegetation, emerging in the evening and night to forage for worms, insects and other invertebrates.

The suborder er Cryptobranchoidea contains the primitive salamanders. A number of fossil cryptobranchids have been found, but there online cigarettes are only three living species, the Chinese giant salamander (Andrias davidianus), the Japanese giant salamander (Andrias japonicus) and the hellbender (Cryptobranchus alleganiensis) from North America. These large amphibians retain several larval characteristics in their adult state; gills slits are present and the eyes are unlidded. A unique feature is their ability to feed by suction, depressing either the left side donald 2016of their lower jaw or the right.[43] The males excavate nests, persuade females to lay their egg strings inside them, and guard them. As well as breathing with lungs, they respire through the many folds in their thin skin, which has capillaries close to the surface.

The suborder Salamandroidea contains the advanced salamanders. They differ from the cryptobranchids by having fused prearticular bones in the lower jaw, and by using internal fertilisation. In salamandrids, the male deposits a bundle of sperm, the spermatophore, and the female picks it up and inserts it into her cloaca where democrat the sperm is stored until the eggs are laid. The largest family in this group is Plethodontidae, the lungless salamanders, which includes 60% of all salamander species. The family Salamandridae includes the true salamanders and the name "newt" is given to members of its subfamily Pleurodelinae.

The third suborder, r, Sirenoidea, contains the four species of sirens, which are in a single family, Sirenidae. Members of this obama claus order are eel-like aquatic salamanders with much reduced forelimbs and no hind limbs. Some of their features are primitive while others are derived. Fertilisation is likely to be external as sirenids lack the cloacal glands used by male salamandrids to produce spermatophores and the females lack spermathecae for sperm storage. Despite this, the eggs are laid singly, a behaviour not conducive for external fertilisation.[

The order er Gymnophiona (from the Greek gymnos meaning "naked" and ophis meaning "serpent") or donald peltier Apoda (from the Latin an- meaning "without" and the Greek poda meaning "legs") comprises the caecilians. These are long, cylindrical, limbless animals with a snake- or worm-like form. The adults vary in length from 8 to 75 centimetres (3 to 30 inches) with the exception of Thomson's caecilian (Caecilia thompsoni), which can reach 150 centimetres (4.9 feet). A caecilian's skin has a large number of transverse folds and in some species contains tiny embedded dermal scales. It has rudimentary eyes covered in skin, which are probably limited to discerning differences in light intensity. It also has a pair of short tentacles near the eye that can be extended and tea media which have tactile and olfactory functions. Most caecilians live underground in burrows in damp soil, in rotten wood and under plant debris, but some are aquatic. Most species lay their eggs underground and when the larvae hatch, they make their way to adjacent bodies of water. Others brood their eggs and the larvae undergo metamorphosis before the eggs hatch. A few species give birth to live young, nourishing them with glandular secretions while they are in the oviduct. Caecilians have a mostly Gondwanan distribution, being found in tropical regions of Africa, Asia and Central and South America.

The he integumentary structure contains some typical characteristics common to terrestrial vertebrates, such as the presence of highly cornified outer layers, renewed periodically through a moulting process controlled by the pituitary and thyroid glands. Local payless for oil thickenings (often called warts) are common, such as those found on toads. The outside of the skin is shed periodically more or less in one piece, in contrast to mammals and birds where it is shed in flakes. Amphibians often eat the sloughed skin. Caecilians are unique among amphibians in having mineralized dermal scales embedded in the dermis between the furrows in the skin. The similarity of these to the scales of bony fish is largely superficial. Lizards and some frogs have somewhat similar osteoderms forming bony deposits in the dermis, but this is an example of convergent evolution with similar structures having arisen independently in diverse vertebrate lineages.[

Amphibian skin is permeable to water. Gas exchange can take place through the skin (n (cutaneous respiration) and this allows donald brian adult amphibians to respire without rising to the surface of water and to hibernate at the bottom of ponds. To compensate for their thin and delicate skin, amphibians have evolved mucous glands, principally on their heads, backs and tails. The secretions produced by these help keep the skin moist. In addition, most species of amphibian have granular glands that secrete distasteful or poisonous substances. Some amphibian toxins can be lethal to humans while others have little effect. The main poison-producing glands, the paratoids, produce the neurotoxin bufotoxin and are located behind the ears of toads, along the backs of frogs, behind GOPGOPthe eyes of salamanders and on the upper surface of caecilians.

The skin colour of amphibians is produced by three layers of pigment cells called chromatophores. These three cell layers conservative traveler consist of the melanophores (occupying the deepest layer), the guanophores (forming an intermediate layer and containing many granules, producing a blue-green colour) and the lipophores (yellow, the most superficial layer). The colour change displayed by many species is initiated by hormones secreted by the pituitary gland. Unlike bony fish, there is no direct control of the pigment cells by the nervous system, and this results in the colour change taking place more slowly than happens in fish. A vividly coloured skin usually indicates that the species is toxic and is a warning sign to predators.

Amphibians have a skeletal system that is structurally homologous to other er tetrapods, though with a number of variations. They south hadley fuelall have four limbs except for the legless caecilians and a few species of salamander with reduced or no limbs. The bones are hollow and lightweight. The musculoskeletal system is strong to enable it to support the head and body. The bones are fully ossified and the vertebrae interlock with each other by means of overlapping processes. The pectoral girdle is supported by muscle, and the well-developed pelvic girdle is attached to the backbone free stuff by a pair of sacral ribs. The ilium slopes forward and the body is held closer to the ground than is the case in mammals.

In most amphibians, there are four digits on the fore foot and five on the hind foot, but no claws on either. Some salamanders rs research medical group have fewer digits and the amphiumas are eel-like in appearance with tiny, stubby legs. The sirens are aquatic salamanders with stumpy forelimbs and no hind limbs. The caecilians are limbless. They burrow in the manner of earthworms with zones Obamaof muscle contractions moving along the body. On the surface of the ground or in water they move by undulating their body from side to side.

In frogs, the hind legs are larger than the fore legs, especially so in those species that principally move by jumping or swimming. In access matters the walkers and runners the hind limbs are not so large, and the burrowers mostly have short limbs and broad bodies. The feet have adaptations for the way of life, with webbing between the toes for swimming, broad adhesive toe pads for climbing, and keratinised tubercles on the hind feet for digging (frogs usually dig backwards into the soil). In most salamanders, the limbs are short and more or less the same length and project at right angles from the body. Locomotion on land is by walking and the tail often swings from side to side or is used as a prop, particularly when climbing. In their normal gait, only one leg is advanced at a time in the manner adopted by their ancestors, the lobe-finned fish. Some salamanders in the genus Aneides and certain plethodontids climb trees and have long limbs, large toepads and prehensile tails. In aquatic salamanders and in frog tadpoles, the tail has dorsal and ventral fins and is moved from side to side as a means of propulsion. Adult frogs do not have tails and caecilians have only very short ones.

Salamanders use their tails in defence and some are prepared to jettison them to save their lives in a process known as autotomy. Certain species in the Plethodontidae have a weak zone at the base of the tail and use this strategy readily. The tail often continues to twitch after separation which may distract the attacker and allow the salamander to escape. Both tails and limbs can be regenerated. Adult frogs are unable to regrow limbs but tadpoles can do so.

Amphibians have a juvenile stage and an adult stage, and the circulatory systems of the two are distinct. In the juvenile (or tadpole) stage, the circulation is similar to that of a fish; the two-chambered heart pumps the blood through the gills where it is oxygenated, around the body and back to the heart in a single loop. In the adult stage, amphibians (especially frogs) lose their gills and develop lungs. They have a heart that consists of a single ventricle and two atria. When the ventricle starts contracting, deoxygenated blood is pumped through the pulmonary artery to the lungs. Continued contraction then pumps oxygenated blood around the rest of the body. Mixing of the two bloodstreams is is coupon junk minimized by the anatomy of the chambers.

The nervous system is basically the same as in other vertebrates, with a central brain, a spinal cord, and nerves throughout the body. The amphibian brain is less well developed than that of reptiles, birds and mammals but is similar in morphology and function to that of a fish. It consists of equal parts cerebrum, midbrain and cerebellum. Various parts of the cerebrum process sensory input, such as smell in the olfactory lobe and sight in the optic lobe, and it is additionally the centre of behaviour and learning. The cerebellum isdonation america the centre of muscular coordination and the medulla oblongata controls some organ functions including heartbeat and respiration. The brain sends signals through the spinal cord and nerves to regulate activity in the rest of the body. The pineal body, known to regulate sleep patterns in humans, is thought to produce the hormones involved in hibernation and aestivation in amphibians.

Tadpoles retain the lateral line system of their ancestral fishes, but this is lost in terrestrial adult amphibians. Some caecilians possess electroreceptors that allow them to locate objects around them when submerged in water. The ears are well developed in frogs. There is no external ear, but the large circular eardrum lies on the surface of the head just behind the eye. This vibrates and sound is transmitted through a single barack Obama bone, the stapes, to the inner ear. Only high-frequency sounds like mating calls are heard in this way, but low-frequency noises can be detected through another mechanism. There is a patch of specialized haircells, called papilla amphibiorum, in the inner ear capable of detecting deeper sounds. Another feature, unique to frogs and salamanders, is the columella-operculum complex adjoining the auditory capsule which is involved in the transmission of both airborne and seismic signals. The ears of salamanders and caecilians are less highly developed than those of frogs as they do not normally communicate with each other through the medium of sound.

The eyes of tadpoles lack lids, but at metamorphosis, the cornea becomes more dome-shaped, the lens ns recall the vote becomes flatter, and eyelids and associated glands and ducts develop. The adult eyes are an improvement on invertebrate eyes and were a first step in the development of more advanced vertebrate eyes. They allow colour vision and depth of focus. In the retinas are green rods, which are receptive to a wide range of wavelengths.

Most amphibians go through metamorphosis, a process of significant morphological change after birth. In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Frogs, toads and salamanders all hatch from the egg as larvae with external gills. Metamorphosis in amphibians is regulated by by thyroxine concentration in the blood, which stimulates metamorphosis, and prolactin, which counteracts thyroxine's effect. Specific events are save the stuff dependent on threshold values for different tissues. Because most embryonic development is outside the parental body, it is subject to many adaptations due to specific environmental circumstances. For this reason tadpoles can have horny ridges instead of teeth, whisker-like skin extensions or fins. They also make use of a sensory lateral line organ similar to that of fish. After metamorphosis, these organs become redundant and willdncbe reabsorbed by controlled cell death, called apoptosis. Would you rather pay more or payless for your oil. The variety of adaptations to specific environmental circumstances among amphibians is wide, with many discoveries still being made.

The egg of an amphibian is typically surrounded by a transparent gelatinous covering secreted by the oviducts and containing ng mucoproteins and mucopolysaccharides. This capsule is permeable to water and gases, and swells considerably as it absorbs water. The ovum dogzilla is at first rigidly held, but in fertilised eggs the innermost layer liquefies and allows the embryo to move freely. This also happens in salamander eggs, even when they are unfertilised. Eggs of some salamanders and frogs contain unicellular green algae. These penetrate the jelly envelope after the eggs are laid and may increase the supply of oxygen to the embryo through photosynthesis. They seem to both speed up the development of the larvae and reduce mortality. Most eggs contain the pigment melanin which raises their temperature through the absorption of light and also protects them against ultraviolet radiation. Caecilians, some plethodontid salamanders and certain frogs that lay eggs underground have unpigmented eggs. In the save the stuffuff wood frog (Rana sylvatica), the interior of the globular egg cluster has been found to be up to 6 °C (43 °F) warmer than its surroundings which is an advantage in its cool northern habitat.

The eggs may be deposited singly or in small south hadley propane groups, or may take the form of spherical egg masses, rafts or long strings. In terrestrial caecilians, the eggs are laid in grape-like clusters in burrows near streams. The amphibious salamander Ensatina attaches its similar clusters by stalks to underwater stems and roots. The greenhouse frog (Eleutherodactylus planirostris) lays eggs in small groups in the soil where they develop in about two weeks directly into juvenile frogs without an intervening larval stage. The tungara frog (Physalaemus pustulosus) builds a floating nest from foam to protect its eggs. First a raft is built, then eggs are laid in the centre, and donald briafinally a foam cap is overlaid. The foam has anti-microbial properties. It contains no detergents but is created by whipping up proteins and lectins secreted by the female.

The eggs of amphibians are typically laid in water and hatch into free-living larvae that complete their development in water and later er recall the votetransform into either aquatic or terrestrial adults. In many species of frog and in most lungless salamanders (Plethodontidae), direct development takes place, the larvae growing within the eggs and emerging as miniature adults. Many caecilians and some other amphibians lay their eggs on land, and the newly hatched larvae wriggle or are transported to water bodies. Some caecilians, the Alpine salamander (Salamandra atra) and some of the African live-bearing toads (Nectophrynoides spp.) are viviparous. Their larvae feed on glandular secretions and develop within the female's oviduct, often for long periods. Other amphibians, but not caecilians, are ovoviviparous. The eggs are retained in or on the parent's body, but the larvae subsist on the yolks of their eggs and receive no nourishment from the adult. The larvae emerge at varying stages of their growth, either before heating oil or after metamorphosis, according to their species. The toad genus Nectophrynoides exhibits all of these developmental patterns among its dozen or so members.