Cutaneous Respiration

Adaptations for cutaneous respiration include intraepidermal blood vessels in cryptobranchid salamanders (hellbenders and giant salamanders) (Supplemental Fig. e7) and development of elaborate skin folds that increase surface expanse for gas substitution (eastward.yard., the Lake Titicaca Frog).

From: Pathology of Wildlife and Zoo Animals , 2018

AIR-BREATHING FISHES | Respiratory Adaptations for Air-Breathing Fishes

J.B. Graham , in Encyclopedia of Fish Physiology, 2011

Skin

Cutaneous respiration is documented for most of the major fish groups and only a few differences distinguish the air-animate species ( see too GAS Substitution | Respiration: An Introduction). Many developing fishes breathe exclusively through their skin prior to gill development. Larval Monopterus respire through extensive subepithelial capillary networks. Posthatch Neoceratodus have a ciliated respiratory epithelium covering their body surface.

Fish peel is a less constructive gas-exchange organ than either the gills or ABO because of its greater thickness, the added diffusion barriers of scales and fungus, and low perfusion and ventilation potentials. Amongst species shown to have cutaneous respiration, water–blood diffusion distances range from fifty to 400   μm, and at that place is no consequent relationship betwixt features such as scales, epidermal thickness, or amount of vascularization, and the rate of cutaneous Oii transfer. For instance, a cutaneous V ˙ O 2 of 32% of total V ˙ O 2 was measured for the heavily scaled Erpetoichthys calabaricus. Fish peel is metabolically active; the epidermis contains a living epithelium as well every bit sensory and secretory cells, all of which receive diet via dermal capillaries. Cutaneous respiration may serve the pare but not deeper aerobic requirements. Such a function would, however, be limited in hypoxic or brackish water, which minimizes diffusion.

Specializations for peel respiration in amphibious air-breathing fishes include the presence of epidermal capillaries (reduce air–claret diffusion altitude) along the dorsal torso surface (this area is readily exposed to air and makes less contact with the substrate). In mudskippers, which obtain near one-half of their O2 via the peel, air–blood diffusion distances tin be less than v   μm forth the dorsal-trunk surface merely as much as 150–200   μm at other sites. In Kryptolebias (= Rivulus) marmoratus, which is totally reliant on skin respiration in air, capillaries on its dorsal body surface are inside 1   μm of the torso surface. Among aquatic air breathers, the most dramatic awarding of cutaneous respiration occurs in the eleotrid, Dormitator latifrons. In hypoxic h2o, this fish hyperinflates its physoclistous gas bladder and becomes positively buoyant, thus emerging its forehead to betrayal a dense capillary network that is engorged with blood and functions for aerial respiration ( Figure thirteen ).

Figure thirteen. Overhead view of a large number of Dormitator latifrons aggregated at a dam in Panama. Each fish is positively buoyant and has its aerial-respiratory frontal pare patch exposed to air.

 Reproduced from Fig. ii.9 in Graham JB (1997) Air Breathing Fishes: Evolution, Multifariousness and Adaptation. San Diego, CA: Academic Press, with permission from Elsevier.

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Water Balance and Gas Exchange

Laurie J. Vitt , Janalee P. Caldwell , in Herpetology (Fourth Edition), 2013

Skin

The highly permeable skin of amphibians is a major site of gas exchange in terrestrial, semiaquatic, and aquatic species. Cutaneous respiration accounts for some gas exchange in certain species of reptiles ( Fig. 6.xx). Commutation of respiratory gases occurs by diffusion and is facilitated by a relatively thin layer of keratin and a rich supply of capillaries in the pare. Exchange of gases across the peel in water is limited past the same physical factors as exchange across other respiratory surfaces.

Figure 6.20. Cutaneous exchange of gases in amphibians and reptiles. Orange bars betoken uptake of oxygen; green bars indicate excretion of carbon dioxide. Values represent the percentage of total gas exchange occurring through the skin.

 Adjusted from Kardong, 2006.

Ventilation of skin, as with gills and other respiratory surfaces, is required to disrupt the purlieus layer that tin can develop. Xenopus has been observed to remain submerged longer and to move less frequently in moving compared to still h2o. Most plethodontid salamanders have neither lungs nor gills and are largely terrestrial (Fig. half dozen.21). The majority of their gas exchange occurs through the pare. In these salamanders, in dissimilarity to others, in that location is no partial separation of the oxygenated and venous blood in the middle. Many species of this various group, because of their mode of respiration, are express to cool, oxygenated habitats and to nonvigorous activity. Their oxygen uptake is only one-third that of frogs under similar conditions. Plethodontids that inhabit tropical habitats where temperatures tin be high, such as Bolitoglossa in tropical rainforests, are active primarily on rainy nights. Waterproof frogs cede their ability to undergo cutaneous respiration in exchange for the skin resistance to water loss.

FIGURE six.21. Plethodontid salamanders, like this Plethodon angusticlavius, accept no lungs. All respiration occurs across other skin surfaces. Consequently, all alive in wet or moist habitats, most are secretive and/or nocturnal, and most are small in body size (L. J. Vitt).

Some amphibians increase their chapters for cutaneous respiration past having capillaries that penetrate into the epidermal layer of pare. This modification is carried to an extreme in Trichobatrachus robustus, the "hairy frog," which has dense epidermal projections on its thighs and flanks. These projections increase the surface expanse for gaseous exchange. Hellbenders, Cryptobranchus alleganiensis, live in mount streams in the eastern Usa. These large salamanders have all-encompassing highly vascularized folds of peel on the sides of the trunk, through which ninety% of oxygen uptake and 97% of carbon dioxide release occurs. Lungs are used for buoyancy rather than gas exchange. The Titicaca frog, Telmatobius culeus, which inhabits deep waters in the high-pinnacle Lake Titicaca in the southern Andes, has reduced lungs and does not surface from the depths of the lake to breathe. The highly vascularized skin hangs in great folds from its body and legs (Fig. 6.22). If the oxygen content is very depression, the frog ventilates its skin by bobbing. Other genera of frogs, salamanders, and caecilians (typhlonectines) have epidermal capillaries that facilitate gas exchange.

Effigy 6.22. The Titicaca frog Telmatobius culeus (Ceratophryidae) lives at dandy depths in Lake Titicaca and does non surface to breathe. The large folds of peel profoundly increment the surface area of the peel, facilitating cutaneous respiration (V. H. Hutchison).

Gas exchange in tadpoles occurs across the skin to some degree in all species. Tadpole skin is highly permeable, similar to that of adults. Gas exchange across the skin is prevalent in bufonids and some torrent-dwelling species that do not develop lungs until metamorphosis. Microhylids, some leptodactylids, and some pipids have reduced gills, thus increasing their reliance on cutaneous respiration.

Contempo studies prove that some reptiles, once thought not to substitution gases through the peel, may use cutaneous respiration for as much equally 20–30% of total gas commutation. In some aquatic species, such every bit Acrochordus and Sternotherus, gas substitution beyond the skin is especially significant for carbon dioxide (Fig. six.20). Even in terrestrial taxa such as Lacerta and Boa, measurable amounts of gas exchange occur cutaneously. A body of water serpent, Pelamis platurus, frequently dives and remains submerged. During these dives, oxygen uptake equals 33% of the total, and 94% of the carbon dioxide loss is through the pare. Exchange does not occur through scales but rather through the skin at the interscalar spaces.

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Operant Learning in Invertebrates

Romuald Nargeot , Laura Puygrenier , in Reference Module in Life Sciences, 2019

ii.3.one Accommodation of breathing behavior

The fresh water snail Lymnaea stagnalis is a bi-modal breather in that it can breathe direct through the skin (cutaneous respiration), or through the pneumostome, a respiratory orifice that conveys air into a lung (aerial respiration) ( Lukowiak et al., 2006). To perform aerial respiration, the snail moves to the h2o surface and when the pneumostome is in contact with the atmosphere, it opens fully. Then, the mantle muscles contract and expel gas from the lung. Subsequent muscle relaxation allows passive re-inflation of the lung. This cycle of expiration/inspiration is repeated several times before the pneumostome closes once more, signaling the terminate of an aerial respiratory bout. The animal emits several successive bouts of aerial respiration before submerging. In eumoxic atmospheric condition, information technology essentially performs cutaneous respiration and expresses simply 1–2 aerial respirations per hour. However, this beliefs tin can be motivated by hypoxic h2o conditions. In these atmospheric condition, which are not harmful to the snail, the expression of aerial respiration strongly increases. This motivated beliefs is easily observable and quantifiable in terms of pneumostome openings (i.e., number of breaths) and total time the pneumostome is open up (i.east., duration of breath). Moreover, the essential neurons for generating pneumostome opening and closing take been identified, allowing this system to assist uncover causal neuronal and molecular processes of operant conditioning, memory formation and their regulation by factors such as forgetting and stress.

In an operant workout process in a hypoxic N2–rich environment, each spontaneous attempt at pneumostome opening was associated with delivery of a punisher; a tactile stimulation applied with a wooden applicator to the pneumostome (Lukowiak et al., 1996, 2003). This aversive stimulus triggers pneumostome closure. Repeated associations between this operant and the punisher reduce both the number of aerial breaths and the total breathing time. Yoked-command animals that receive the tactile stimulus independently of their own behavior, merely in temporal correlation with animate in a trained snail, do not change their respiratory behavior. This preparation protocol is equanimous of 1 or ii successive sessions of 30 or 45 min. Memory of the penalization is tested by comparing the number of pneumostome opening at different periods after the last training session. The behavioral changes were establish to exist consolidated into intermediate- (lasting two–3 h) and long-term (lasting up to half dozen h after training) memories depending on the number of, or interval between, the grooming sessions. A more elementary procedure, based on a single grooming trial, also forms long-term memory. In this prototype, every bit shortly as the animal opens its pneumostome, it is placed for 30 s into a watch drinking glass containing a punisher equanimous of a high concentration of potassium chloride. The animal is and so transferred into a eumoxic aquarium. Yoked-control animals permit testing the contribution of this operant/punisher association. These animals are placed in the high potassium chloride solution regardless of their behavior. Additional control animals are set into like drinking glass-watches merely containing fresh-water. None of these two control groups expressed a alter in their aerial respiratory behavior.

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Learning Theory and Behaviour

D. Eisenhardt , N. Stollhoff , in Learning and Memory: A Comprehensive Reference, 2008

ane.27.ii.2.1 Lymnaea stagnalis: The operant aeriform respiration paradigm

Lymnaea stagnalis is an aquatic pulmonate snail ( Figure 5 ). Information technology is a bimodal sabbatical and can breathe via its skin (cutaneous respiration) or through a simple lung (aerial respiration). When the creature stays in stagnant water where the oxygen content is low, it becomes hypoxic. And then the snail comes to the water surface for aerial respiration. Information technology opens and closes its respiratory orifice, the pneumostome, and breathes through the lung ( Figure 6(a) ). This behavior past the snail is used in the operant aeriform respiration paradigm (Lukowiak et al., 1996). Here the snails are put in beakers of h2o, which is made hypoxic by bubbling Nii through it. When the animal attempts to open its pneumostome as a reaction to the hypoxic water, it receives a gentle tactile stimulus to the pneumostome area, reducing its aeriform respiration, without affecting cutaneous respiration. The number of openings is recorded during grooming periods and retention tests. Learning takes identify if the number of attempted pneumostome openings is significantly decreased between the kickoff and the last grooming trial. It is important to note that in this paradigm memory retrieval and retention tests consist of the same procedure equally the training sessions. They are only designated differently for the reader's convenience.

Figure 5. The snail Lymnaea stagnalis The snail Lymnaea stagnalis sinks from the water surface to the footing of the swimming. Photograph by Kathrin Spöcker.

Figure 6. The snail Lymnaea stagnalis: Neuronal network underlying respiratory behavior. (a) Lymnaea stagnalis with opened pneumostome (pointer). From Lukowiak M, Sangha Due south, Scheibenstock A, et al. (2003) A molluscan model organization in the search for the engram. J. Physiol. 69–76. (b) Schematic drawing of the central pattern generator (CPG). A chemosensory stimulus (here hypoxia) activates sensory neurons (SNs) in the pneumostome expanse, which in turn provide excitatory input (greenish line) to the right pedal dorsal 1 interneuron (RPeD1). Once stimulated, RPeD1 activates the input3 interneuron (IP3) via a biphasic outcome (inhibition followed by excitation) (bluish line) and inhibits visceral dorsal four interneuron (VD4) (cerise line). IP3 in turn excites both RPeD1 and the I/J motor neurons involved in pneumostome openings (O). IP3 likewise produces an inhibitory effect on VD4, and after release from this inhibition, VD4 fires, resulting in pneumostome closure (C). Tactile stimulation of the pneumostome area evokes closure of the pneumostome, and the aerial respiratory behavior stops. Adjusted from Figure 1 in Sangha Due south, Varshney North, Fras M, et al. (2004) Retentiveness, reconsolidation and extinction in Lymnaea require the soma of RPeD1. Adv. Exp. Med. Biol. 551: 311–318. Syed NI Winlow W (1991) Coordination of locomotor and cardiorespiratory networks of Lymnaea stagnalis by a pair of identified interneurones. J. Exp. Biol. 158: 37–62.

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Biology and Diseases of Amphibians

Dorcas P. O'Rourke DVM, MS, DACLAM , Matthew D. Rosenbaum DVM, MS, DACLAM , in Laboratory Animal Medicine (Third Edition), 2015

3 Respiratory System

Larval amphibians breathe primarily through gills. Adult amphibians may retain and utilize gills, lose gills and develop lungs, breathe with both gills and lungs, or accept neither and utlize cutaneous respiration mechansims. X. laevis tadpoles and axolotls accept both gills and lungs and will gulp air at the water'due south surface. Axolotls flex their external gills to move fresh water over the filaments; this behavior increases when animals are housed in warm h2o with decreased oxygen content (Gresens, 2004). Developed plethodontids (lungless salamanders) lack both lungs and gills, and rely on cutaneous respiration. Skin, in fact, is the chief respiratory surface in about amphibians and must be kept moist. In species that utilize lungs for respiration, air is forced in and out of the lungs by motion of the buccopharyngeal flooring (Zug, 1993). Lungs lack alveoli and are very fragile and easily ruptured (Wright, 1996) (Fig. eighteen.5). In many frog species, the trachea is brusque, and bifurcation occurs close to the glottis; this anatomic feature must exist taken into account when performing endotracheal intubation.

Effigy xviii.5. Amphibian lungs lack alveoli and are very fragile.

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Caudata (Urodela)

Eric J. Baitchman , Timothy A. Herman , in Fowler's Zoo and Wild Animal Medicine, Volume eight, 2015

Special Physiology

Mechanisms of respiratory substitution in Amphibia are remarkable for the taxa every bit a whole and may occur via four routes: branchial, buccopharyngeal, cutaneous, or pulmonary. The Caudata are unique in the extent to which different families have adapted to dissimilar primary routes. Branchial respiration is present in all amphibians as larvae, whereas only some neotenic salamander species retain this means of respiration as a primary route through adulthood. Cutaneous respiration is likewise employed by all amphibians to various degrees, although to a greater extent in caudates than in anurans. In anurans, cutaneous respiration occurs primarily as a means of carbon dioxide exchange, with the majority of oxygen substitution occurring in the lungs. 21,31 Nearly caudates, by comparison, take up almost of their oxygen through cutaneous respiration, even in species that possess lungs. 58 Respiratory capillaries are concentrated in the skin in taxa that rely on the cutaneous road as the primary site for gas exchange, as in the lungless Plethodontidae and aquatic Cryptobrachidae. The cryptobranchids also use modified skinfolds to increase surface area and vascularization to raise respiratory exchange underwater. 31

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AMPHIBIANS

Natalie Mylniczenko , in Manual of Exotic Pet Exercise, 2009

RESPIRATORY System

At that place are four forms of respiration in caudates, and they are species dependent: branchial, cutaneous, buccopharyngeal, and pulmonic. Animals with gills may have short or long filaments depending on their natural environment. Animals with short gills are typically located in stream areas and thus accept higher requirements for dissolved oxygen. Cutaneous respiration can occur in these animals because of a loftier surface expanse on the skin and a low metabolic rate; additionally, anaerobic glycolysis tin can occur. Behavioral responses, such every bit rocking, allow a current to run into the skin, optimizing contact with dissolved oxygen in the water. Most salamanders possess two lungs, with either single lobes (aquatic) or sacculated lobes (terrestrial). There is a lungless salamander. Costal grooves (skin folds forth the ribs) also increment the integumentary area. Buccopharyngeal respiration technically is cutaneous respiration occurring within the oral cavity. The trachea of caudates is very short and should prompt the clinician to exercise caution when performing procedures like intubation and tracheal washes.

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Biology and Diseases of Amphibians

Dorcas P. O'Rourke , Terry Wayne Schultz , in Laboratory Animal Medicine (Second Edition), 2002

3. Respiratory System

Larval amphibians breathe primarily through gills. Adults tin can retain and apply gills, lose gills and develop lungs, breathe with both gills and lungs, or have neither (Fig. 8 ). Developed plethodontids (lungless salamanders) lack both lungs and gills, and rely on cutaneous respiration. Peel, in fact, is the primary respiratory surface in most amphibians and must be kept moist. In species that use lungs for respiration, air is forced in and out of the lungs by motion of the buccopharyngeal floor ( Zug, 1993). Lungs lack alveoli and are very delicate and hands ruptured (Wright, 1996). In many frog species, the trachea is short, and bifurcation occurs close to the glottis; this anatomic characteristic must be taken into account when performing endotracheal intubation.

Fig. viii. Axolotls are large, aquatic, neotenous salamanders that respire through feathery external gills.

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Anesthesia and Analgesia in Amphibians

Dorcas P. O'Rourke , Audrey L. Jenkins , in Anesthesia and Analgesia in Laboratory Animals (Second Edition), 2008

II. Full general CONSIDERATIONS

Amphibians are poikilothermic and therefore rely on external heat sources to generate adequate body temperatures for metabolic processes. Like reptiles, each amphibian species has a preferred temperature range. There is, even so, considerable variation among species, and amphibians tin be constitute in a wide variety of temperate and tropical habitats (Table xx-1). Preferred temperature ranges for a given species should be obtained if at all possible. If this information is unavailable, temperate frogs tin can be kept at approximately 20–25°C and tropical frogs at 25–xxx°C (Raphael, 1993). Many salamander species alive under leaf litter in cool environments, or in cool water streams in mountainous regions. These temperate species prefer ranges of 10–xvi°C (Jaeger, 1992). Tropical salamanders may be kept at 15–xx°C (Raphael, 1993).

TABLE 20-1. GENERAL TEMPERATURE RANGES

Temperate Tropical
Frog/toad a 20–25°C 25–30°C
(68–77°F) (77–86°F)
Salamander a,b ten–16°C 15–xx°C
(50–threescore.8°F) (59–68°F)
a
Raphael, B.L. (1993). Amphibians. Vet. Clin. North Am. Small Anim. Pract. 23, 1271–1286.
b
Jaeger, R.Thousand. (1992). Housing, treatment and diet of salamanders. In "The Intendance and Use of Amphibians, Reptiles and Fish in Inquiry." (D.O. Schaeffer, Yard.Yard. Kleinow, and 50. Krulisch, eds.), pp 25–29. S.C.A.Due west.

Amphibian respiratory anatomy is as variable as temperature preference. Virtually amphibians begin life as aquatic larvae, with gills as the primary organ for oxygen exchange. Some larvae (for instance, Xenopus tadpoles and Ambystoma tigrinum larvae) have lungs too as gills, and swim to the water's surface to gulp air (Fig. twenty-one ). Many salamander larvae too utilize cutaneous respiration for a significant portion of oxygen exchange. Adult frogs accept paired lungs; in some species, cartilage reinforces the lungs. Adult salamanders may have lungs, gills, both lungs and gills, or neither ( Fig. 20-2). One group of salamanders, the plethodontid salamanders, lack lungs and exhale solely through cutaneous respiration. The buccopharyn-geal cavity is highly vascular and is also used for respiration. In species that breathe through lungs, inspiration begins by contraction of throat muscles, which depress the floor of the buccal crenel. This has the upshot of pulling air through the nostrils and filling buccal cavity with air. Consequently, closure of the nostrils, opening of the glottis, and elevation of the buccal cavity floor then force air into the lungs. To remove air from the lungs, the buccal floor is depressed while the nares are closed and the glottis is open. Then the nares are opened, the glottis is closed, and the buccal floor is elevated to forcefulness air out of the rima oris (Duellman and Trueb, 1986). The trachea of most amphibians is extremely curt, and circumspection must exist taken if intubation is attempted (Wright, 2001). Both low oxygen and elevated carbon dioxide levels stimulate respiration in virtually amphibians (Van Vliet and W, 1992). High oxygen levels inhibit respiratory movements in amphibians.

Fig. xx-ane. In improver to breathing through gills, Xenopus tadpoles will gulp air at the water's surface.

Fig. xx-2. The axolotl is a salamander that breathes through feathery external gills.

Amphibian pare is highly glandular. There are two bones types of skin glands: mucous and granular. Mucous glands are numerous and establish over the unabridged trunk surface. They secrete a slimy mucus, which serves to keep skin moist and facilitate cutaneous respiration (Fig. 20-3). Fungus also protects the pare from abrasive trauma and inhibits pathogen entry. Granular glands are less abundant than mucous glands, and may be scattered over the torso or amassed. The parotoid glands of toads, which appear equally raised areas behind the eyes, are examples of clustered granular glands. Parotoid glands secrete cardiotoxins designed to deter predators. Other toxins secreted by granular glands include hallucinogens and neurotoxins. Different types of granular glands can secrete a diverseness of substances, including pheromones and antimicrobial compounds (Clarke, 1997).

Fig. twenty-3. Mucous glands encompass the entire trunk of the amphibian.

While hematologic and serum biochemical information are limited, Tabular array xx-2 provides values for a few of the more than common species used in inquiry.

Table 20-2. HEMATOLOGIC AND SERUM BIOCHEMICAL VALUES

Measurements African clawed frog (Xenopus laevis) a Bullfrog (Rana catesbeiana) b Leopard Frog (Rana pipiens) c Japanese Newt (Cynops pyrrhogaster) d Axolotl (Ambystoma mexicanum) eastward
Hematology
PCV (%) − 30.1 (25–39) 24.6(31–39.9) 40.0(38.1–41.ix) −
Hgb (g/dl) 14.86 6.8 (five.12–eleven.06) 26.75 (2.iv–ix.6) − −
WBC (xiii/μl) 8.two 20.5 (11.6–32.vii) − − −
Neutro/heter (%) 8.0 (6.9–ix.1) 60.9 (forty.0–86.ane) 26.five (eleven–48) 28.0 (26.4–30.6) lx.9 (57.three–64.5)
Lymphocytes (%) 65.3 (62.vi–68.0) 26.8 (sixteen.3–39.8) 53.four (29–75) iii.0 (2.6–3.four) 26.4 (24.half-dozen–28.2)
Monocytes (%) 0.5 2.9 (1.0–5.0) xi.0 (5–24) half-dozen.0 (5.0–7.0) −
Eosinophils (%) − v.8 (2.0–11.9) seven.3 (4–xi) 4.0 (3.3–4.7) half-dozen.i (4.two–8.0)
Basophils (%) 8.5 (7.1–9.9) iii.v (0.6.0) 4.4 (0.9) 57.0 (three.8–60.two) 0.1 (0.0–0.two)
− −
Chemistries
Sodium (mEq/L) − 118.6 (99–144) − − −
Potassium (mEq/Fifty) − 3.62 (1.92–5.84) − − −
Chloride (mEq/L) − 108.half-dozen (1.0–116) − − −
Albumin (g/dl) − ane.58 (one.02–ii.67) − − −
Calcium (mg/dl) − 8.31 (6.0–eleven.2) − − −
Creatinine (mg/dl) − iv.83 (1.07–12.iii) − − −
AST (IU/50) − 48.ane (23–fourscore) − − −
ALT (IU/L) − 12.iv (seven–xx) − − −
LDH (IU/L) − 117 (l–260) − − −
Phosphorus (mg/dl) − 8.83 (four.1–13.vii) − − −
Magnesium (mEq/L) − 2.41 (one.33–4.09) − − −
Uric acid (mg/dl) − 13.4 (1.3–30.two) − − −
Urea (mg/dl) − 84.ii (xxx.one–180) − − −
Glucose (g/50) − 0.5 (0.ane–0.98) − − −
a
Carpenter, J.W. (2005). Exotic fauna formulary, ed 3, WB Saunders, St Louis.
b
Coppo, J.A., Mussart, N.B., and Fioranelli, A. (2005). Blood and urine physiological values in subcontract-cultured Rana catesbeiana (Anura: Ranidae) In Argentina. Rev. Biol. Trop. (Int. J. Trop. Biol) 53(three–4), 545.
c
Rouf, M. A. Hematology of the leopard frog, rana pipiens. Copeia, Vol. 1969, No. 4. (December. 5, 1969), pp. 682–687.
d
Pfeiffer, C.J. Pyle, H. and Asashima, M. (1990). Blood cell morphology and counts in the Japanese newt (Cynops pyrrhogaster). J Zoo Wildlife Med. 21(i), 56–64.
eastward
Ussing, A.P. and Rosenkilde, P. (1995). Effect of Induced Metamorphosis on the Immune System of the Axolotl, Ambystoma mexicanum General and Comparative Endocrinology 97(3), 308–319.

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Tetrapod Relationships and Evolutionary Systematics

Laurie J. Vitt , Janalee P. Caldwell , in Herpetology (Fourth Edition), 2014

Mod Amphibians—The Lissamphibia

About recent analyses indicate that mod amphibians (Lissamphibia) are monophyletic (i.e., share a mutual ancestor). Numerous patterns of human relationship have been proposed, only the contempo discovery of Gerobatrachus hottoni from the Permian and a reanalysis of existing data signal that frogs and salamanders had a mutual ancestor almost 290   Ma. Gerobatrachus is a salamander-like amphibian with a skull and other features of the head that are similar to those of frogs. Thus caecilians, which are much older, are sister to the frog–salamander clade. The Lower Triassic frog, Triadobatrachus massinoti, from Madagascar, shows a possible link to the dissorophid temnospondyls. T. massinoti shares with them a large lacuna in the squamosal bone that may have housed a tympanum. Neither salamanders nor caecilians have tympana, although they have profoundly reduced eye ears, suggesting contained loss of the outer ear structures.

A number of other unique traits argue strongly for the monophyly of the Lissamphibia. All share a reliance on cutaneous respiration, a pair of sensory papillae in the inner ear, ii audio transmission channels in the inner ear, specialized visual cells in the retina, pedicellate teeth, the presence of two types of skin glands, and several other unique traits.

Three structures, gills, lungs, and skin, serve as respiratory surfaces in lissamphibians; two of them frequently function simultaneously. Aquatic amphibians, specially larvae, use gills; terrestrial forms use lungs. In both air and h2o, the skin plays a major role in transfer of oxygen and carbon dioxide. One group of terrestrial amphibians, the plethodontid salamanders, has lost lungs, and some aquatic taxa likewise accept lost lungs or take greatly reduced ones; these amphibians rely entirely on cutaneous respiration. All lunged species use a force–pump mechanism for moving air in and out of the lungs. Ii types of peel glands are present in all living amphibians: mucous and granular (poison) glands. Mucous glands continuously secrete mucopolysaccharides, which proceed the skin surface moist for cutaneous respiration. Although structure of the poisonous substance glands is identical in all amphibians, the toxicity of the diverse secretions produced is highly variable, ranging from barely irritating to lethal to predators.

The auditory organisation of amphibians has ane channel that is common to all tetrapods, the stapes–basilar papilla aqueduct. The other aqueduct, the opercular–amphibian papilla, allows the reception of low-frequency sounds (<thou   Hz). The possession of 2 types of receptors may non seem peculiar for frogs because they are vocal animals. For the largely mute salamanders, a dual hearing organization seems peculiar and redundant. Salamanders and frogs have light-green rods in the retina; these structures are presumably absent in the degenerate-eyed caecilians. Greenish rods are establish simply in amphibians, and their particular function remains unknown.

The teeth of modern amphibians are two-role structures: an elongate base (pedicel) is anchored in the jawbone and a crown protrudes above the glue. Each tooth is usually constricted where the crown attaches to the pedicel. As the crowns wear downwards, they break complimentary at the constriction and are replaced past a new crown emerging from within the pedicel. Few living amphibians lack pedicellate teeth. Among extinct "amphibians," pedicellate teeth occur in only a few dissorophids.

Living amphibians share other unique traits. All have fat bodies that develop from the germinal ridge of the embryo and retain an association with the gonads in adults. Frogs and salamanders are the merely vertebrates able to raise and lower their eyes. The bony orbit of all amphibians opens into the roof of the mouth. A special muscle stretched across this opening elevates the middle. The ribs of amphibians do not encircle the body.

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