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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 the olm, have both lungs and gills as adults. [8]
Some species of cave salamanders are neotenic, and keep their larval gills even as adults. Gills are absent in all other adult plethodontids. [13] Plethodontids possess costal grooves on the trunk of their bodies. These help keep the skin moist via water transport over the surface of the body. [14]
Their external gills resemble ostrich plumes and their size depends on the oxygen levels present in the water. In stagnant water, mudpuppies have larger gills, whereas in running streams where oxygen is more prevalent, they have smaller gills. [4] The distal portions of the gills are very filamentous and contain many capillaries. [7]
External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes. Instead, the respiratory organs are set on a frill of stalks protruding from the sides of an animal's head.
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Adult salamanders often have an aquatic phase in spring and summer, and a land phase in winter. For adaptation to a water phase, prolactin is the required hormone, and for adaptation to the land phase, thyroxine. External gills do not return in subsequent aquatic phases because these are completely absorbed upon leaving the water for the first ...
These folds help increase the animals' surface area, allowing them to absorb more oxygen from the water as the adults lacks gills and have poorly developed lungs. Like in the majority of salamander species, there are four toes on the fore limbs and five on the hind limbs. They have paedomorphic traits, meaning their metamorphosis from the ...
Amphiuma possess relatively ancestral forms of lungs compared to some of the other groups of salamanders that live terrestrially today. [ 17 ] [ 18 ] Their lungs are long organs, extending over half of the body length, with dense capillary networks and large surface area that suggest the utilization of the entire lung for respiration while the ...