151-540: Plethodontidae , or lungless salamanders , are a family of salamanders . With over 500 species, lungless salamanders are by far the largest family of salamanders in terms of their diversity. Most species are native to the Western Hemisphere , from British Columbia to Brazil. Only two extant genera occur in the Eastern Hemisphere : Speleomantes (native to Sardinia and mainland Europe south of
302-550: A broad number of terrestrial habitats which is a testament to the high success and proliferation of Plethodontidae. Despite the absence of lungs, some can grow rather large. The largest species of lungless salamanders, Bell's false brook salamander , can reach lengths of 36 cm (14 in). Many species have a projectile tongue and hyoid apparatus , which they can fire almost a body length at high speed to capture prey. Measured in individual numbers, they are very successful animals where they occur. In some places, they make up
453-413: A concealed site in flowing water, and these are usually guarded by an adult, normally the female. Many of the tropical climbing salamanders ( Bolitoglossa ) and lungless salamanders (Plethodontinae) lay a small number of large eggs on land in a well-hidden spot, where they are also guarded by the mother. Some species such as the fire salamanders ( Salamandra ) are ovoviviparous , with the female retaining
604-586: A flash of warning hue on its underside. The red eft, the brightly colored terrestrial juvenile form of the eastern newt ( Notophthalmus viridescens ), is highly poisonous. It is avoided by birds and snakes, and can survive for up to 30 minutes after being swallowed (later being regurgitated). The red salamander ( Pseudotriton ruber ) is a palatable species with a similar coloring to the red eft. Predators that previously fed on it have been shown to avoid it after encountering red efts, an example of Batesian mimicry . Other species exhibit similar mimicry. In California,
755-416: A hissing sound, while the sirens sometimes produce quiet clicks, and can resort to faint shrieks if attacked. Similar clicking behaviour was observed in two European newts Lissotriton vulgaris and Ichthyosaura alpestris in their aquatic phase. Vocalization in salamanders has been little studied and the purpose of these sounds is presumed to be the startling of predators. Respiration differs among
906-438: A lateral row. This may provide an aposematic signal that makes the spines more visible. When the danger has passed, the ribs retract and the skin heals. Although many salamanders have cryptic colors so as to be unnoticeable, others signal their toxicity by their vivid coloring . Yellow, orange, and red are the colors generally used, often with black for greater contrast. Sometimes, the animal postures if attacked, revealing
1057-665: A long body, a laterally flattened tail with dorsal and ventral fins and in some species limb-buds or limbs. Pond-type larvae may have a pair of rod-like balancers on either side of the head, long gill filaments and broad fins. Stream-type larvae are more slender with short gill filaments—in Rhyacotriton and Onychodactylus, and some species in Batrachuperus, the gills and gill rakers are extremely reduced, narrower fins and no balancers, but instead have hind limbs already developed when they hatch. The tadpoles are carnivorous and
1208-417: A lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum . The left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula . Its name means "little tongue". The lingula on the left lung serves as an anatomic parallel to the middle lobe on
1359-517: A minute fragment of skin is deadly. In feeding trials, fish, frogs, reptiles, birds, and mammals were all found to be susceptible. Mature adults of some salamander species have "nuptial" glandular tissue in their cloacae , at the base of their tails, on their heads or under their chins. Some females release chemical substances , possibly from the ventral cloacal gland, to attract males, but males do not seem to use pheromones for this purpose. In some plethodonts , males have conspicuous mental glands on
1510-609: A reasonable size. Large species such as the Japanese giant salamander ( Andrias japonicus ) eat crabs, fish, small mammals, amphibians, and aquatic insects. In a study of smaller dusky salamanders ( Desmognathus ) in the Appalachian Mountains , their diet includes earthworms , flies , beetles , beetle larvae, leafhoppers , springtails , moths , spiders , grasshoppers , and mites . Cannibalism sometimes takes place, especially when resources are short or time
1661-447: A right lung and a left lung. They are situated within the thoracic cavity of the chest . The right lung is bigger than the left, the left lung shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles , and which receive air breathed in via
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#17327760184441812-485: A right lung with only two lobes, or a left lung with three lobes. A variation in the airway branching structure has been found specifically in the central airway branching. This variation is associated with the development of COPD in adulthood. The development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth. The larynx , trachea , bronchi and lungs that make up
1963-433: A second. In some species, the tongue is attached anteriorly to the floor of the mouth, while in others, it is mounted on a pedicel. It is rendered sticky by secretions of mucus from glands in its tip and on the roof of the mouth. High-speed cinematography shows how the tiger salamander ( Ambystoma tigrinum ) positions itself with its snout close to its prey. Its mouth then gapes widely, the lower jaw remains stationary, and
2114-678: A short period of time and involves the closing of the gill slits and the loss of structures such as gills and tail fins that are not required as adults. At the same time, eyelids develop, the mouth becomes wider, a tongue appears, and teeth are formed. The aqueous larva emerges onto land as a terrestrial adult. Not all species of salamanders follow this path. Neoteny , also known as paedomorphosis, has been observed in all salamander families, and may be universally possible in all salamander species. In this state, an individual may retain gills or other juvenile features while attaining reproductive maturity. The changes that take place at metamorphosis are under
2265-514: A simplified retinal structure, and in cave dwellers such as the Georgia blind salamander , they are absent or covered with a layer of skin. In amphibious species, the eyes are a compromise and are nearsighted in air and farsighted in water. Fully terrestrial species such as the fire salamander have a flatter lens which can focus over a much wider range of distances. To find their prey, salamanders use trichromatic color vision extending into
2416-407: A small lizard, having a basal tetrapod body form with a cylindrical trunk, four limbs, and a long tail. Except in the family Salamandridae, the head, body, and tail have a number of vertical depressions in the surface which run from the mid-dorsal region to the ventral area and are known as costal grooves . Their function seems to be to help keep the skin moist by channeling water over the surface of
2567-514: A tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata . Urodela is a scientific Latin term based on the Ancient Greek οὐρά δήλη : ourà dēlē "conspicuous tail". Caudata is the Latin for "tailed ones", from cauda : "tail". Salamander diversity is highest in eastern North America , especially in
2718-408: A tail-straddle walk in which the female orients her head at the base of the male's tail while also straddling the tail with her body. The male will twist his body around and deposit a sperm capsule, known as the spermatophore, on the substrate in front of the female's snout. As the male leads the female over the spermatophore with his tail, the female lowers her cloaca onto the spermatophore and lodges
2869-437: A top predator since the introduction of locally exotic species such as Nile tilapia and carp. Tilapia and carp directly compete with axolotls by consuming their eggs, larvae, and juveniles. Climate change has also immensely affected axolotls and their populations throughout the southern Mexico area. Due to its proximity to Mexico City , officials are currently working on programs at Lake Xochimilco to bring in tourism and educate
3020-626: Is North America, with oldest of the European members of the family known from the Middle Miocene of Slovakia. The family Plethodontidae consists of two extant subfamilies and about 516 to 520 species divided among 29 genera, making up the majority of known salamander species: Following a major revision in 2006, the genus Haideotriton was found to be a synonym of Eurycea , while the genus Lineatriton were made synonyms of Pseudoeurycea . A single hemidactyliine ( Palaeoplethodon )
3171-520: Is advanced into the salamander's mouth, the teeth tips relax and bend in the same direction, encouraging movement toward the throat, and resisting the prey's escape. Many salamanders have patches of teeth attached to the vomer and the palatine bones in the roof of the mouth, and these help to retain prey. All types of teeth are resorbed and replaced at intervals throughout the animal's life. A terrestrial salamander catches its prey by flicking out its sticky tongue in an action that takes less than half
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#17327760184443322-414: Is also responsible for the elastic recoil needed. Elastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions. The connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance. The alveoli have interconnecting air passages in their walls known as the pores of Kohn . All of the lower respiratory tract including
3473-566: Is another large, long-lived species with dwindling numbers and fewer juveniles reaching maturity than previously. Another alarming finding is the increase in abnormalities in up to 90% of the hellbender population in the Spring River watershed in Arkansas. Habitat loss, silting of streams, pollution and disease have all been implicated in the decline and a captive breeding programme at Saint Louis Zoo has been successfully established. Of
3624-459: Is being undertaken to assess the status of these salamanders, and to better understand the factors involved in their population declines, with a view to taking action. Ambystoma mexicanum , an aquatic salamander, is a species protected under the Mexican UMA (Unit for Management and conservation of wildlife) as of April 1994. Another detrimental factor is that the axolotl lost their role as
3775-421: Is correlated with changes in the developmental characteristics of plethodontids compared to other families of salamanders including increases in egg size and duration of embryonic development. Additionally, the evolutionary loss of the aquatic larval stage is related to a diminishing dependence on aquatic habitats for reproduction. The lift of this constraint allowed widespread colonization and diversification within
3926-422: Is divided into three lobes by a horizontal fissure , and an oblique fissure . The left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung. In the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe. The lower, oblique fissure separates the lower lobe from the middle and upper lobes. Variations in
4077-475: Is driven by different muscular systems in different species. Mammals, reptiles and birds use their musculoskeletal systems to support and foster breathing. In early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping , a mechanism still seen in amphibians. In humans, the primary muscle that drives breathing is the diaphragm . The lungs also provide airflow that makes vocalisation including speech possible. Humans have two lungs,
4228-401: Is held in the fluid-filled amniotic sac and so they do not function to breathe. Blood is also diverted from the lungs through the ductus arteriosus . At birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire. The lungs only fully develop in early childhood. In humans the lungs are located in the chest on either side of
4379-624: Is internal. As a general rule, salamanders with internal fertilization have indirect sperm transfer, but in species like the Sardinian brook salamander , the Corsican brook salamander , the Caucasian salamander and the Pyrenean brook salamander , the male transfer his sperm directly into the female cloaca. For the species with indirect sperm transfer, the male deposits a spermatophore on
4530-518: Is known from Miocene fossil remains preserved in Dominican amber , marking the only record of salamanders in the Caribbean . Salamander Cryptobranchoidea Salamandroidea Salamanders are a group of amphibians typically characterized by their lizard -like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of
4681-417: Is larger than that of the female, is used during the amplexus embrace to propel the mating couple to a secluded location. In terrestrial species, the tail moves to counterbalance the animal as it runs, while in the arboreal salamander and other tree-climbing species, it is prehensile . The tail is also used by certain plethodontid salamanders that can jump, to help launch themselves into the air. The tail
Plethodontidae - Misplaced Pages Continue
4832-435: Is likely related to the absence of lungs in these salamanders. Though some lunged salamanders do exhibit similar structures, they are reduced in size and are not arranged near the nostrils (i.e. nares) in the same fashion as plethodontids. Due to the fact that plethodontids cannot generate air pressure via expulsion of air from the lungs and through the nares, they are presented with the challenge of removing water and debris from
4983-427: Is likely to be made up of between 30 and 50 primary lobules. The lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles. The respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch. Each lobule is enclosed by an interlobular septum. Each acinus is incompletely separated by an intralobular septum. The respiratory bronchiole gives rise to
5134-435: Is limited. Tiger salamander tadpoles in ephemeral pools sometimes resort to eating each other, and are seemingly able to target unrelated individuals. Adult blackbelly salamanders ( Desmognathus quadramaculatus ) prey on adults and young of other species of salamanders, while their larvae sometimes cannibalise smaller larvae. Most species of salamander have small teeth in both their upper and lower jaws. Unlike frogs , even
5285-465: Is not just limited to limbs but extends to vital organs such as the heart, jaw, and parts of the spinal cord, showing their uniqueness compared to different types of vertebrates. This ability is most remarkable for occurring without any type of scarring. This has made salamanders an invaluable model organism in scientific research aimed at understanding and achieving regenerative processes for medical advancements in human and animal biology. Members of
5436-626: Is not limited by ventilation. Oxygen uptake is identical in water and air, assuming the partial pressure of oxygen is the same. Oxygenated and non-oxygenated blood are mixed together in the venous system, which causes the partial pressure of oxygen within cardiac blood to typically be low. Plethodontids can tolerate hypoxia for prolonged periods by reducing their metabolic rate instead of by relying on anaerobic cutaneous respiration, as initially theorized. Plethodontids have been observed to develop rudimentary lungs as embryos. The lung rudiment develops similarly to that of non-plethodontid salamanders for
5587-455: Is restricted to the slightly cooler and wetter conditions in north-facing cove forests in the southern Appalachians, and to higher elevations above 900 m (3,000 ft), while the former is more adaptable, and would be perfectly able to inhabit these locations, but some unknown factor seems to prevent the two species from co-existing. One species, the Anderson's salamander , is one of
5738-435: Is the part of the lung distal to the respiratory bronchiole. Thus, it includes the alveolar ducts, sacs, and alveoli but not the respiratory bronchioles. The unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule . This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid. The secondary pulmonary lobule
5889-413: Is used in courtship and as a storage organ for proteins and lipids. It also functions as a defense against predation, when it may be lashed at the attacker or autotomised when grabbed. Unlike frogs, an adult salamander is able to regenerate limbs and its tail when these are lost. The skin of salamanders, in common with other amphibians, is thin, permeable to water, serves as a respiratory membrane, and
6040-407: Is well-supplied with glands. It has highly cornified outer layers, renewed periodically through a skin shedding process controlled by hormones from the pituitary and thyroid glands. During moulting, the skin initially breaks around the mouth, and the animal moves forward through the gap to shed the skin. When the front limbs have been worked clear, a series of body ripples pushes the skin toward
6191-706: The Alaska Panhandle . They had an exclusively Laurasian distribution until Bolitoglossa invaded South America from Central America, probably by the start of the Early Miocene , about 23 million years ago. They also lived on the Caribbean Islands during the early Miocene epoch, confirmed by the discovery of Palaeoplethodon hispaniolae , found trapped in amber in the Dominican Republic . Vertebrae fossils recovered from
Plethodontidae - Misplaced Pages Continue
6342-588: The Appalachian Mountains ; most species are found in the Holarctic realm , with some species present in the Neotropical realm . Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to
6493-943: The Holarctic and Neotropical regions, not reaching south of the Mediterranean Basin , the Himalayas , or in South America the Amazon Basin . They do not extend north of the Arctic tree line , with the northernmost Asian species, Salamandrella keyserlingii , which can survive long-term freezing at −55 °C, occurring in the Siberian larch forests of Sakha and the most northerly species in North America, Ambystoma laterale , reaching no farther north than Labrador and Taricha granulosa not beyond
6644-618: The Murgon fossil site have been tentatively attributed to that of a Salamander, though its true identity is disputed. If the vertebrae truly belong to a Salamander, they would represent the only Salamanders in Australia . There are about 760 living species of salamander. One-third of the known salamander species are found in North America. The highest concentration of these is found in the Appalachian Mountains region, where
6795-449: The amphiumas , metamorphosis is incomplete, and they retain one pair of gill slits as adults, with fully functioning internal lungs. Some species that lack lungs respire through gills. In most cases, these are external gills, visible as tufts on either side of the head. Some terrestrial salamanders have lungs used in respiration, although these are simple and sac-like, unlike the more complex organs found in mammals . Many species, such as
6946-425: The carina where the trachea divides into the two main bronchi. The cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart. Both lungs have a central recession called the hilum , where the blood vessels and airways pass into the lungs making up the root of the lung . There are also bronchopulmonary lymph nodes on the hilum. The lungs are surrounded by
7097-470: The circulation , and carbon dioxide diffuses from the blood into the lungs to be breathed out . Estimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being "the size of a tennis court", it is actually less than half the size of a singles court . The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open
7248-401: The cloud forests of Guatemala and Mexico during the 1970s were found by 2009 to be rare. Few data have been gathered on population sizes over the years and, by intensive surveying of historic and suitable new locations, it has been possible to locate individuals of other species, such as Parvimolge townsendi , which had been thought to be extinct . Currently, the major lines of defense for
7399-523: The conducting zone . These divide until air reaches microscopic alveoli , where gas exchange takes place. Together, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac of two pleurae which allows the inner and outer walls to slide over each other whilst breathing takes place, without much friction. The inner visceral pleura divides each lung as fissures into sections called lobes. The right lung has three lobes and
7550-438: The esophagus behind the hilum and the pulmonary ligament , and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart. The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb). The left lung is divided into two lobes, an upper and
7701-495: The family Salamandridae are mostly known as newts and lack the costal grooves along the sides of their bodies typical of other groups. The skin of some species contains the powerful poison tetrodotoxin ; these salamanders tend to be slow-moving and have bright warning coloration to advertise their toxicity. Salamanders typically lay eggs in water and have aquatic larvae, but great variation occurs in their lifecycles . Some species in harsh environments reproduce while still in
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#17327760184447852-418: The heart in the rib cage . They are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm . The apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib . The lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from
8003-676: The immune system . They remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels. There is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis. The microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD . For example significant changes can take place in COPD following infection with rhinovirus . Fungal genera that are commonly found as mycobiota in
8154-594: The lens or retina of the eye. Within only a few weeks of losing a piece of a limb, a salamander perfectly reforms the missing structure. Salamanders split off from the other amphibians during the mid- to late Permian, and initially were similar to modern members of the Cryptobranchoidea . Their resemblance to lizards is the result of symplesiomorphy , their common retention of the primitive tetrapod body plan, but they are no more closely related to lizards than they are to mammals. Their nearest relatives are
8305-638: The olm , have both lungs and gills as adults. In the Necturus , external gills begin to form as a means of combating hypoxia in the egg as egg yolk is converted into metabolically active tissue. Molecular changes in the mudpuppy during post-embryonic development primarily due to the thyroid gland prevent the internalization of the external gills as seen in most salamanders that undergo metamorphosis. The external gills seen in salamanders differs greatly from that of amphibians with internalized gills. Unlike amphibians with internalized gills which typically rely on
8456-427: The pulmonary pleurae . The pleurae are two serous membranes ; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid . Middle Lower Lingula Lower Each lung is divided into sections called lobes by
8607-409: The respiratory system in many animals, including humans. In mammals and most other tetrapods , two lungs are located near the backbone on either side of the heart . Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange . Respiration
8758-502: The ultraviolet range, based on three photoreceptor types that are maximally sensitive around 450, 500, and 570 nm. The larvae, and the adults of some highly aquatic species, also have a lateral line organ, similar to that of fish, which can detect changes in water pressure. All salamanders lack middle ear cavity, eardrum and eustachian tube , but have an opercularis system like frogs, and are still able to detect airborne sound. The opercularis system consists of two ossicles:
8909-468: The 20 species of minute salamanders ( Thorius spp.) in Mexico, half are believed to have become extinct and most of the others are critically endangered. Specific reasons for the decline may include climate change, chytridiomycosis, or volcanic activity, but the main threat is habitat destruction as logging, agricultural activities, and human settlement reduce their often tiny, fragmented ranges. Survey work
9060-475: The Alps) and Karsenia (native to South Korea). Adult lungless salamanders have four limbs, with four toes on the fore limbs, and usually with five on the hind limbs. Within many species, mating and reproduction occur solely on land. Accordingly, many species also lack an aquatic larval stage, a phenomenon known as direct development in which the offspring hatch as fully-formed, miniature adults. Direct development
9211-500: The California newt has many large poison glands in its skin, is diurnal, and is avoided by snakes. Some salamander species use tail autotomy to escape predators. The tail drops off and wriggles around for a while after an attack, and the salamander either runs away or stays still enough not to be noticed while the predator is distracted. The tail regrows with time, and salamanders routinely regenerate other complex tissues, including
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#17327760184449362-517: The Plethodontidae are thought to have originated in mountain streams. Here, vegetation zones and proximity to water are of greater importance than altitude. Only species that adopted a more terrestrial mode of life have been able to disperse to other localities. The northern slimy salamander ( Plethodon glutinosus ) has a wide range and occupies a habitat similar to that of the southern gray-cheeked salamander ( Plethodon metcalfi ). The latter
9513-401: The abraded spot which are secreted from a pad of tissue called the mental gland located underneath the male's chin. Courtship pheromones greatly increase male mating success for a variety of reasons. Overall, the pheromone secretions increase female receptivity to courtship and sperm transfer. This not only increases the likelihood of successful mating with a specific female, but also shortens
9664-473: The airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration. The lungs have a dual blood supply provided by a bronchial and a pulmonary circulation . The bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta . There are usually three arteries, two to
9815-399: The airways. The bronchioles have no cartilage and are surrounded instead by smooth muscle . Air is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone. Particles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance . Pulmonary stretch receptors in the smooth muscle of
9966-464: The alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli. The walls of the alveoli are extremely thin allowing a fast rate of diffusion . The alveoli have interconnecting small air passages in their walls known as the pores of Kohn . Alveoli consist of two types of alveolar cell and an alveolar macrophage . The two types of cell are known as type I and type II cells (also known as pneumocytes). Types I and II make up
10117-474: The alveolar septa which separate each alveolus. The septa consist of an epithelial lining and associated basement membranes . Type I cells are not able to divide, and consequently rely on differentiation from Type II cells. Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant . Type II cells are able to divide and differentiate to Type I cells. The alveolar macrophages have an important role in
10268-462: The alveoli. The four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4 . FGF10 is seen to have the most prominent role. FGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10. The development of
10419-405: The animal of an approaching predator. Salamanders are usually considered to have no voice and do not use sound for communication in the way that frogs do. Before mating, they communicate by pheromone signaling; some species make quiet ticking, clicking, squeaks or popping noises, perhaps by the opening and closing of valves in the nose. Most salamanders lack vocal cords, but a larynx is present in
10570-422: The animal slippery and more difficult for predators to catch. Granular glands scattered on the upper surface, particularly the head, back, and tail, produce repellent or toxic secretions. Some salamander toxins are particularly potent. The rough-skinned newt ( Taricha granulosa ) produces the neurotoxin tetrodotoxin , the most toxic nonprotein substance known. Handling the newts does no harm, but ingestion of even
10721-404: The axolotl does not account for the overall lack of diversity. Evidence points toward a historical bottlenecking of Ambystoma that contributes to the variation issues and no longer a large genetic pool for it to pull from, thus raising concern for inbreeding due to lack of gene flow. One way researchers are looking into maintaining genetic diversity within the population is via cryopreservation of
10872-410: The base of the lung. By standard reference range , the weight of the left lung is 110–675 g (0.243–1.488 lb) in men and 105–515 g (0.231–1.135 lb) in women. The lungs are part of the lower respiratory tract , and accommodate the bronchial airways when they branch from the trachea. The bronchial airways terminate in alveoli which make up the functional tissue ( parenchyma ) of
11023-402: The body. Some aquatic species, such as sirens and amphiumas , have reduced or absent hind limbs, giving them an eel -like appearance, but in most species, the front and rear limbs are about the same length and project sideward, barely raising the trunk off the ground. The feet are broad with short digits, usually four on the front feet and five on the rear. Salamanders do not have claws, and
11174-416: The branch. In the development of the lungs (as in some other organs) the epithelium forms branching tubes. The lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus. Each bronchus branches into bronchioles. The branching is a result of the tip of each tube bifurcating. The branching process forms the bronchi, bronchioles, and ultimately
11325-478: The breeding season. Cave species dwelling in darkness lack pigmentation and have a translucent pink or pearlescent appearance. Salamanders range in size from the minute salamanders , with a total length of 27 mm ( 1 + 1 ⁄ 8 in), including the tail, to the Chinese giant salamander which reaches 1.8 m (6 ft) and weighs up to 65 kg (145 lb). All the largest species are found in
11476-402: The bronchus and bronchioles, and increases the secretions from glands. The lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation . The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem , along the phrenic nerve from the cervical plexus to
11627-455: The changing of pressures within the buccal and pharyngeal cavities to ensure diffusion of oxygen onto the gill curtain, neotenic salamanders such as Necturus use specified musculature, such as the levatores arcuum, to move external gills to keep the respiratory surfaces constantly in contact with new oxygenated water. Salamanders are opportunistic predators . They are generally not restricted to specific foods, but feed on almost any organism of
11778-457: The chin which are pressed against the females' nostrils during the courtship ritual. They may function to speed up the mating process, reducing the risk of its being disrupted by a predator or rival male. The gland at the base of the tail in Plethodon cinereus is used to mark fecal pellets to proclaim territorial ownership. Olfaction in salamanders plays a role in territory maintenance,
11929-472: The cloacae of females. The results of this research may be used in captive-breeding programmes for endangered species. The order name Urodela comes from the name Urodèles given by André Marie Constant Duméril in 1805, it is derived from the Greek words οὐρά ourā́ "tail" and δῆλος dēlos "visible, conspicuous" because of their "persistent" tails. Disagreement exists among different authorities as to
12080-424: The columella (equivalent to the stapes of higher vertebrates ) which is fused to the skull, and the operculum. An opercularis muscle connects the latter to the pectoral girdle, and is kept under tension when the animal is alert. The system seems able to detect low-frequency vibrations (500–600 Hz), which may be picked up from the ground by the fore limbs and transmitted to the inner ear. These may serve to warn
12231-533: The composition of which is tightly regulated and determines how well mucociliary clearance works. Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 percent of the total epithelial population. PNECs are innervated airway epithelial cells that are particularly focused at airway junction points. These cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products. Cytoplasmic processes from
12382-617: The conservation of Salamanders includes both in situ and ex situ conservation methods. There are efforts in place for certain members of the Salamander family to be conserved under a conservation breeding program (CBP) but there should be research done ahead of time to determine if the Salamander species is actually going to value from the CBP, as researchers have noted that some species of amphibians completely fail in this environment. Various conservation initiatives are being attempted around
12533-498: The control of thyroid hormones and in obligate neotenes such as the axolotl ( Ambystoma mexicanum ), the tissues are seemingly unresponsive to the hormones. In other species, the changes may not be triggered because of underactivity of the hypothalamus-pituitary-thyroid mechanism which may occur when conditions in the terrestrial environment are too inhospitable. This may be due to cold or wildly fluctuating temperatures, aridity, lack of food, lack of cover, or insufficient iodine for
12684-512: The definition of the terms Caudata and Urodela. Some maintain that the Urodela should be restricted to the crown group , with the Caudata being used for the total group. Others restrict the name Caudata to the crown group and use Urodela for the total group. The former approach seems to be most widely adopted and is used in this article. Lung The lungs are the primary organs of
12835-423: The diaphragm. The lobes of the lung are subject to anatomical variations . A horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases. An accessory fissure was also found in 14% and 22% of left and right lungs, respectively. An oblique fissure was found to be incomplete in 21% to 47% of left lungs. In some cases a fissure is absent, or extra, resulting in
12986-603: The different species of salamanders, and can involve gills, lungs, skin, and the membranes of mouth and throat. Larval salamanders breathe primarily by means of gills , which are usually external and feathery in appearance. Water is drawn in through the mouth and flows out through the gill slits. Some neotenic species such as the mudpuppy ( Necturus maculosus ) retain their gills throughout their lives, but most species lose them at metamorphosis . The embryos of some terrestrial lungless salamanders, such as Ensatina , that undergo direct development, have large gills that lie close to
13137-756: The dominant biomass of vertebrates. An estimated 1.88 billion individuals of the southern redback salamander inhabit just one district of Mark Twain National Forest alone, about 1,400 tons of biomass. Due to their modest size and low metabolism, they are able to feed on prey such as springtails , which are usually too small for other terrestrial vertebrates. This gives them access to a whole ecological niche with minimal competition from other groups. Plethodontids exhibit highly stereotyped and complex mating behaviors and courtship rituals that are not present in any other salamander family. Mating behavior tends to be uniform among all plethodontids and typically involves
13288-411: The duration of courtship which is important because it minimizes the chance of the male being interrupted by other competing males. In scientific literature discussing the variations between the mental glands of plethodontid salamanders, it was discovered that male plethodontids had minor variations in height and diameter of the simple tubular glands, and major variation was found in the diameter of
13439-406: The egg's surface. When present in adult salamanders, lungs vary greatly among different species in size and structure. In aquatic, cold-water species like the torrent salamanders ( Rhyacotriton ), the lungs are very small with smooth walls, while species living in warm water with little dissolved oxygen, such as the lesser siren ( Siren intermedia ), have large lungs with convoluted surfaces. In
13590-755: The eggs are laid. In the Asiatic salamanders , the giant salamanders and Sirenidae , which are the most primitive groups, the fertilization is external. In a reproductive process similar to that of typical frogs, the male releases sperm onto the egg mass. These salamanders also have males that exhibit parental care , which otherwise only occur in females with internal fertilization. Three different types of egg deposition occur. Ambystoma and Taricha spp. spawn large numbers of small eggs in quiet ponds where many large predators are unlikely. Most dusky salamanders ( Desmognathus ) and Pacific giant salamanders ( Dicamptodon ) lay smaller batches of medium-sized eggs in
13741-437: The eggs inside her body until they hatch, either into larvae to be deposited in a water body, or into fully formed juveniles. In temperate regions, reproduction is usually seasonal and salamanders may migrate to breeding grounds. Males usually arrive first and in some instances set up territories . Typically, a larval stage follows in which the organism is fully aquatic. The tadpole has three pairs of external gills, no eyelids,
13892-530: The few species of living amphibians to occur in brackish or salt water. Many salamanders do not use vocalisations, and in most species the sexes look alike, so they use olfactory and tactile cues to identify potential mates, and sexual selection occurs. Pheromones play an important part in the process and may be produced by the abdominal gland in males and by the cloacal glands and skin in both sexes. Males are sometimes to be seen investigating potential mates with their snouts. In Old World newts, Triturus spp.,
14043-490: The first three weeks of development and then begins to regress through apoptosis . A paralogue of the SFTPC gene, which is expressed exclusively in the lungs in other vertebrates, is in lungless salamanders expressed in the larval integument instead. When going through metamorphosis, it disappears from the integument and appears in the buccopharynx in adults. It is suggested the gene facilitate extrapulmonary respiration through
14194-460: The fissures are fairly common being either incompletely formed or present as an extra fissure as in the azygos fissure , or absent. Incomplete fissures are responsible for interlobar collateral ventilation , airflow between lobes which is unwanted in some lung volume reduction procedures. The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of
14345-481: The formation of thyroid hormones. Genetics may also play a part. The larvae of tiger salamanders ( Ambystoma tigrinum ), for example, develop limbs soon after hatching and in seasonal pools promptly undergo metamorphosis. Other larvae, especially in permanent pools and warmer climates, may not undergo metamorphosis until fully adult in size. Other populations in colder climates may not metamorphose at all, and become sexually mature while in their larval forms. Neoteny allows
14496-406: The four families giant salamanders , sirens , Congo eels and Proteidae , who are all aquatic and obligate paedomorphs. Some of the largest terrestrial salamanders, which goes through full metamorphosis, belongs to the family of Pacific giant salamanders , and are much smaller. Most salamanders are between 10 and 20 cm (4 and 8 in) in length. An adult salamander generally resembles
14647-704: The frogs and toads, within Batrachia . The oldest known total-group ( Caudata ) salamander is Triassurus from the Triassic of Kyrgyzstan . Further salamander fossils are known from the Middle Jurassic of England , Scotland , China , and Kazakhstan . The oldest known crown-group salamander ( Urodela ) remains uncertain but recent analyses suggest it is Valdotriton from the Late Jurassic of Spain . Salamanders are found only in
14798-449: The future. Skin secretions of the tiger salamander ( Ambystoma tigrinum ) fed to rats have been shown to produce aversion to the flavor, and the rats avoided the presentational medium when it was offered to them again. The fire salamander ( Salamandra salamandra ) has a ridge of large granular glands down its spine which are able to squirt a fine jet of toxic fluid at its attacker. By angling its body appropriately, it can accurately direct
14949-437: The ground or in the water according to species, and the female picks this up with her vent. The spermatophore has a packet of sperm supported on a conical gelatinous base, and often an elaborate courtship behavior is involved in its deposition and collection. Once inside the cloaca, the spermatozoa move to the spermatheca , one or more chambers in the roof of the cloaca, where they are stored for sometimes lengthy periods until
15100-406: The hilum, is a well-marked curved groove for the aortic arch , and a groove below it for the descending aorta . The left subclavian artery , a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein . The esophagus may sit in a wider shallow impression at
15251-413: The infoldings of the visceral pleura as fissures. Lobes are divided into segments, and segments have further divisions as lobules. There are three lobes in the right lung and two lobes in the left lung. The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion. The right lung
15402-403: The larvae of salamanders possess these teeth. Although larval teeth are shaped like pointed cones, the teeth of adults are adapted to enable them to readily grasp prey. The crown , which has two cusps (bicuspid), is attached to a pedicel by collagenous fibers. The joint formed between the bicuspid and the pedicel is partially flexible, as it can bend inward, but not outward. When struggling prey
15553-404: The larval stage may last from days to years, depending on species. Sometimes this stage is completely bypassed, and the eggs of most lungless salamanders (Plethodontidae) develop directly into miniature versions of the adult without an intervening larval stage. By the end of the larval stage, the tadpoles already have limbs and metamorphosis takes place normally. In salamanders, this occurs over
15704-619: The larval state. The word salamander comes from Old French salamandre from Latin salamandra from Greek σαλαμάνδρα : salamándra, of uncertain, possibly, pre-Greek origin. The Greek word is used for the fire salamander . The skin lacks scales and is moist and smooth to the touch, except in newts of the Salamandridae, which may have velvety or warty skin, wet to the touch. The skin may be drab or brightly colored, exhibiting various patterns of stripes, bars, spots, blotches, or dots. Male newts become dramatically colored during
15855-829: The last few decades of the 20th century, although no direct link between the fungus and the population decline has yet been found. The IUCN made further efforts in 2005 as they established the Amphibian Conservation Action Plan (ACAP), which was subsequently followed by Amphibian Ark (AArk), Amphibian Specialist Group (ASG), and finally the umbrella organization known as the Amphibian Survival Alliance (ASA). Researchers also cite deforestation , resulting in fragmentation of suitable habitats, and climate change as possible contributory factors. Species such as Pseudoeurycea brunnata and Pseudoeurycea goebeli that had been abundant in
16006-628: The left has two. The lobes are further divided into bronchopulmonary segments and lobules. The lungs have a unique blood supply, receiving deoxygenated blood sent from the heart for the purposes of receiving oxygen (the pulmonary circulation ) and a separate supply of oxygenated blood (the bronchial circulation ). The tissue of the lungs can be affected by a number of respiratory diseases , including pneumonia and lung cancer . Chronic diseases such as chronic obstructive pulmonary disease and emphysema can be related to smoking or exposure to harmful substances. Diseases such as bronchitis can also affect
16157-458: The left lung and one to the right, and they branch alongside the bronchi and bronchioles. The pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body. The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system. This quantity can easily fluctuate from between one-half and twice
16308-738: The local population on the restoration of the natural habitat of these creatures. This proximity is a large factor that has impacted the survival of the axolotl, as the city has expanded to take over the Xochimilco region in order to make use of its resources for water and provision and sewage. It is farmed for use in research facilities and so may one day return to its natural habitat. The recent decline in population has substantially impacted genetic diversity among populations, making it difficult to further progress scientifically. Some genetic indiversity due to paedeomorphism in Ambystoma species such as
16459-420: The lower part of the trachea to the diaphragm. The left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this. The front and outer sides of the lungs face the ribs, which make light indentations on their surfaces. The medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels , and
16610-495: The lung, and veins, arteries, nerves, and lymphatic vessels . The trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa. The smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli. The lungs are supplied with the largest lymphatic drainage system of any other organ in the body. Each lung is surrounded by a serous membrane of visceral pleura , which has an underlying layer of loose connective tissue attached to
16761-415: The lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments . Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply . Segments for the left and right lung are shown in the table. The segmental anatomy is useful clinically for localising disease processes in
16912-410: The lungless salamanders ( family Plethodontidae and the clawed salamanders in the family of Asiatic salamanders ), no lungs or gills are present, and gas exchange mostly takes place through the skin, known as cutaneous respiration , supplemented by the tissues lining the mouth. To facilitate this, these salamanders have a dense network of blood vessels just under the skin and in the mouth. In
17063-419: The lungs. A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue. The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal. The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near
17214-471: The males are sexually dimorphic and display in front of the females. Visual cues are also thought to be important in some Plethodont species. Except for terrestrial species in the three families Plethodontidae , Ambystomatidae , and Salamandridae , salamanders mate in water. The mating varies from courtship between a single male and female to explosive group breeding. In the clade Salamandroidea , which makes up about 90% of all species, fertilization
17365-409: The microbiota include Candida , Malassezia , Saccharomyces , and Aspergillus . The lower respiratory tract is part of the respiratory system , and consists of the trachea and the structures below this including the lungs. The trachea receives air from the pharynx and travels down to a place where it splits (the carina ) into a right and left primary bronchus . These supply air to
17516-515: The mudpuppy (Necturus) and some other species, and the Pacific giant salamanders and a few others have a large larynx and bands known as plicae vocales. The California giant salamander can produce a bark or rattle, and a few species can squeak by contracting muscles in the throat. The arboreal salamander can squeak using a different mechanism; it retracts its eyes into its head, forcing air out of its mouth. The ensatina salamander occasionally makes
17667-401: The nasal passages which has the potential to significantly limit olfactory processes. As such, the nasolabial grooves are structured in a way that maximizes drainage from the nose. The groove is deeper and more narrow directly around the nares and the orifices of the glands are slightly elevated both of which aid in the gravitational flow of fluid from the nares and nasal depression. Additionally,
17818-512: The nasolabial glands around the margins of the nares secrete a fatty film which further encourages the removal of water from the nasal passages due to differences in polarity between water and the lipid secretions. Plethodontidae are estimated to have split from their sister group Amphiumidae around the K-Pg boundary , and to have diversified during the Paleogene . The origin region of the family
17969-416: The normal volume. Also, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation. The lungs are supplied by nerves of the autonomic nervous system . Input from the parasympathetic nervous system occurs via the vagus nerve . When stimulated by acetylcholine , this causes constriction of the smooth muscle lining
18120-543: The palatable yellow-eyed salamander ( Ensatina eschscholtzii ) closely resembles the toxic California newt ( Taricha torosa ) and the rough-skinned newt ( Taricha granulosa ), whereas in other parts of its range, it is cryptically colored. A correlation exists between the toxicity of Californian salamander species and diurnal habits: relatively harmless species like the California slender salamander ( Batrachoseps attenuatus ) are nocturnal and are eaten by snakes, while
18271-406: The posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage ; on the mediastinal surface it may be traced back to the hilum . The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung. The mediastinal surface of
18422-579: The prey, which is then swallowed. Though frequently feeding on slow-moving animals like snails , shrimps and worms , sirenids are unique among salamanders for having developed herbivory speciations, such as beak-like jaw ends and extensive intestines. They feed on algae and other soft-plants in the wild, and easily eat offered lettuce . Salamanders have thin skins and soft bodies, move rather slowly and might appear vulnerable to opportunistic predation, but have several effective lines of defense. Mucus coating on damp skin makes them difficult to grasp, and
18573-427: The production of pulmonary surfactant-like secretions. Another distinctive feature is the presence of a vertical slit between the nostril and upper lip, known as the "nasolabial groove". The groove is lined with glands, and enhances the salamander's chemoreception which is correlated with a higher degree of olfactory lobe and nasal mucous membrane development in plethodontids. The presence of this specialized structure
18724-467: The pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas. In the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open. Bronchioles are too narrow to support cartilage and their walls are of smooth muscle , and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium. The absence of cartilage in
18875-488: The rear. The hind limbs are extracted and push the skin farther back, before it is eventually freed by friction as the salamander moves forward with the tail pressed against the ground. The animal often then eats the resulting sloughed skin. Glands in the skin discharge mucus which keeps the skin moist, an important factor in skin respiration and thermoregulation. The sticky layer helps protect against bacterial infections and molds, reduces friction when swimming, and makes
19026-410: The recognition of predators, and courtship rituals, but is probably secondary to sight during prey selection and feeding. Salamanders have two types of sensory areas that respond to the chemistry of the environment. Olfactory epithelium in the nasal cavity picks up airborne and aquatic odors, while adjoining vomeronasal organs detect nonvolatile chemical cues, such as tastes in the mouth. In plethodonts,
19177-404: The respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut . The respiratory tract has a branching structure, and is also known as the respiratory tree. In the embryo this structure is developed in the process of branching morphogenesis , and is generated by the repeated splitting of the tip of
19328-404: The respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων "lung") as in pneumonia. In embryonic development , the lungs begin to develop as an outpouching of the foregut , a tube which goes on to form the upper part of the digestive system . When the lungs are formed the fetus
19479-429: The right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles . These in turn supply air through alveolar ducts into the alveoli , where the exchange of gases take place. Oxygen breathed in , diffuses through the walls of the alveoli into the enveloping capillaries and into
19630-403: The right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein , and above this is a wide groove for the superior vena cava and right brachiocephalic vein ; behind this, and close to the top of the lung is a groove for the brachiocephalic artery . There is a groove for
19781-425: The right lung, with both areas being predisposed to similar infections and anatomic complications. There are two bronchopulmonary segments of the lingula: superior and inferior. The mediastinal surface of the left lung has a large cardiac impression where the heart sits. This is deeper and larger than that on the right lung, at which level the heart projects to the left. On the same surface, immediately above
19932-480: The salamander family. Research is being done on the environmental cues that have to be replicated before captive animals can be persuaded to breed. Common species such as the tiger salamander and the mudpuppy are being given hormones to stimulate the production of sperm and eggs, and the role of arginine vasotocin in courtship behaviour is being investigated. Another line of research is artificial insemination , either in vitro or by inserting spermatophores into
20083-524: The secretory granules. This is attributed to the fact that males can mate throughout all months of the year, while females oviposit seasonally. A number of features distinguish the plethodontids from other salamanders. Most significantly, they lack lungs , conducting respiration through their skin, and the tissues lining their mouths. Some species of cave salamanders are neotenic, and keep their larval gills even as adults. Gills are absent in all other adult plethodontids. Plethodontids possess costal grooves on
20234-448: The sensory epithelium of the vomeronasal organs extends to the nasolabial grooves , which stretch from the nostrils to the corners of the mouth. These extended areas seem to be associated with the identification of prey items, the recognition of conspecifics , and the identification of individuals. The eyes of most salamanders are adapted primarily for vision at night. In some permanently aquatic species, they are reduced in size and have
20385-462: The shape of the foot varies according to the animal's habitat. Climbing species have elongated, square-tipped toes, while rock-dwellers have larger feet with short, blunt toes. The tree-climbing salamander ( Bolitoglossa sp.) has plate-like webbed feet which adhere to smooth surfaces by suction, while the rock-climbing Hydromantes species from California have feet with fleshy webs and short digits and use their tails as an extra limb. When ascending,
20536-429: The slimy coating may have an offensive taste or be toxic. When attacked by a predator, a salamander may position itself to make the main poison glands face the aggressor. Often, these are on the tail, which may be waggled or turned up and arched over the animal's back. The sacrifice of the tail may be a worthwhile strategy, if the salamander escapes with its life and the predator learns to avoid that species of salamander in
20687-458: The species to survive even when the terrestrial environment is too harsh for the adults to thrive on land. A general decline in living amphibian species has been linked with the fungal disease chytridiomycosis . A higher proportion of salamander species than of frogs or caecilians are in one of the at-risk categories established by the IUCN . Salamanders showed a significant diminution in numbers in
20838-426: The sperm mass inside while leaving the base of the spermatophore on the ground. Within many species of plethodontidae, the courtship ritual is often accompanied by transfer of male pheromones during the tail-straddling walk. During the breeding period, males will grow enlarged anterior teeth used to scratch the female's skin on her head as a part of the courtship ritual. Subsequently, the male will rub pheromones onto
20989-432: The spermatophores from the male axolotl. It is a safe and non-invasive method that requires the collection of the spermatophores and places them into a deep freeze for preservation. Most importantly, they have found that there is only limited damage done to the spermatophores upon thawing and thus it is a viable option. As of 2013, it is a method that is being used to save not only the axolotl but also numerous other members of
21140-439: The spray for a distance of up to 80 cm (30 in). The Iberian ribbed newt ( Pleurodeles waltl ) has another method of deterring aggressors. Its skin exudes a poisonous, viscous fluid and at the same time, the newt rotates its sharply pointed ribs through an angle between 27 and 92°, and adopts an inflated posture. This action causes the ribs to puncture the body wall, each rib protruding through an orange wart arranged in
21291-441: The substance of the lung. The connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls. Elastin is the key protein of the extracellular matrix and is the main component of the elastic fibres . Elastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance . It
21442-406: The tail props up the rear of the body, while one hind foot moves forward and then swings to the other side to provide support as the other hind foot advances. In larvae and aquatic salamanders, the tail is laterally flattened, has dorsal and ventral fins, and undulates from side to side to propel the animal through the water. In the families Ambystomatidae and Salamandridae, the male's tail, which
21593-467: The terminal bronchioles gives them an alternative name of membranous bronchioles . The conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles. This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs , and alveoli. An acinus measures up to 10 mm in diameter. A primary pulmonary lobule
21744-413: The throat, assisted by depression of the eyeballs into the roof of the mouth. Many lungless salamanders of the family Plethodontidae have more elaborate feeding methods. Muscles surrounding the hyoid bone contract to store elastic energy in springy connective tissue, and actually "shoot" the hyoid bone out of the mouth, thus elongating the tongue. Muscles that originate in the pelvic region and insert in
21895-431: The tongue are used to reel the tongue and the hyoid back to their original positions. An aquatic salamander lacks muscles in the tongue, and captures its prey in an entirely different manner. It grabs the food item, grasps it with its teeth, and adopts a kind of inertial feeding. This involves tossing its head about, drawing water sharply in and out of its mouth, and snapping its jaws, all of which tend to tear and macerate
22046-487: The tongue bulges and changes shape as it shoots forward. The protruded tongue has a central depression, and the rim of this collapses inward as the target is struck, trapping the prey in a mucus-laden trough. Here it is held while the animal's neck is flexed, the tongue retracted and jaws closed. Large or resistant prey is retained by the teeth while repeated protrusions and retractions of the tongue draw it in. Swallowing involves alternate contraction and relaxation of muscles in
22197-451: The trachea, bronchi, and bronchioles is lined with respiratory epithelium . This is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus , ciliated cells, basal cells , and in the terminal bronchioles – club cells with actions similar to basal cells, and macrophages . The epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL),
22348-486: The trunk of their bodies. These help keep the skin moist via water transport over the surface of the body. Plethodontid salamanders are almost entirely reliant on cutaneous respiration. Approximately 83%–93% of oxygen uptake is through this method. Plethodontid salamander respiration rates are constrained by their SA:V , and higher SA:Vs are correlated to warmer, wetter climates. Plethodontids are constantly exposed to air or water, which allows for constant gas exchange that
22499-464: The walls and alveolar septa . Type I cells provide 95% of the surface area of each alveoli and are flat (" squamous "), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape. Despite this, cells occur in a roughly equal ratio of 1:1 or 6:4. Type I are squamous epithelial cells that make up the alveolar wall structure. They have extremely thin walls that enable an easy gas exchange. These type I cells also make up
22650-455: The water intermittently, and others are entirely terrestrial as adults. This group of amphibians is capable of regenerating lost limbs as well as other damaged parts of their bodies. Researchers hope to reverse engineer the regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery. The remarkable ability of salamanders to regenerate
22801-481: The world. The Chinese giant salamander , at 1.8 m (6 ft) the largest amphibian in the world, is critically endangered , as it is collected for food and for use in traditional Chinese medicine . An environmental education programme is being undertaken to encourage sustainable management of wild populations in the Qinling Mountains and captive breeding programmes have been set up. The hellbender
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