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External Gills
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. This type of gill is most commonly observed on the aquatic larva of most species of salamanders, lungfish, and bichirs (which have only one large pair), and are retained by neotenic adult salamanders and some species of adult lungfish. They are present on non-transforming salamander species, such as most members of the family Proteidae (the olm and mudpuppies) and the family Sirenidae, which naturally never metamorphose into an air-breathing form. The embryos of frogs A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order Anura (coming from the Ancient Greek , literally 'without tail'). Frog s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gill
A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Branchia (: branchiae) is the zoologists' name for gills (from Ancient Greek ). With the exception of some aquatic insects, the filaments and lamella (surface anatomy), lamellae (folds) contain blood or Coelom#Coelomic fluid, coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body. Carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in various groups of aquatic animals, including Mollusc, molluscs, crustaceans, insects, fish, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pharynx
The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates, though its structure varies across species. The pharynx carries food to the esophagus and air to the larynx. The flap of cartilage called the epiglottis stops food from entering the larynx. In humans, the pharynx is part of the Digestion, digestive system and the conducting zone of the respiratory system. (The conducting zone—which also includes the nostrils of the Human nose, nose, the larynx, trachea, bronchus, bronchi, and bronchioles—filters, warms, and moistens air and conducts it into the lungs). The human pharynx is conventionally divided into three sections: the nasopharynx, oropharynx, and laryngopharynx (hypopharynx). In humans, two sets of pharyngeal muscles form the pharynx and determine the shape of its lumen (anatomy), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gill Slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head. The anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow. A modified slit, called a spiracle, lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks. Spiracles are reduced or missing in active pelagic sharks. While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishes
A fish (: fish or fishes) is an aquatic, anamniotic, gill-bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break to the long tradition of grouping all fish into a single class (Pisces), modern phylogenetics views fish as a paraphyletic group. Most fish are cold-blooded, their body temperature varying with the surrounding water, though some large active swimmers like white shark and tuna can hold a higher core temperature. Many fish can communicate acoustically with each other, such as during courtship displays. The study of fish is known as ichthyology. The earliest fish appeared during the Cambrian as small filter feeders; they continued to evolve through the Paleozoic, diversifying into many forms. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axolotl Portrait
The axolotl (; from ) (''Ambystoma mexicanum'') is a paedomorphic salamander, one that matures without undergoing metamorphosis into the terrestrial adult form; adults remain fully aquatic with obvious external gills. This trait is somewhat unusual among amphibians, though this trait is not unique to axolotls, and this is apparent as they may be confused with the larval stage or other neotenic adult mole salamanders (''Ambystoma spp.''), such as the occasionally paedomorphic tiger salamander ('' A. tigrinum'') widespread in North America; or with mudpuppies (''Necturus spp.''), which bear a superficial resemblance but are from a different family of salamanders. Axolotls originally inhabited a system of interconnected wetlands and lakes in the Mexican highlands; they were known to inhabit the smaller lakes of Xochimilco and Chalco, and are also presumed to have inhabited the larger lakes of Texcoco and Zumpango. These waterways were mostly drained by Spanish settlers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salamanders
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 a tail in both larvae and adults. All ten extant salamander families are grouped together under the order (biology), order Urodela, the sole surviving order from the group Caudata. ''Urodela'' is a scientific Latin term based on the Ancient Greek : ourà dēlē "conspicuous tail". ''Caudata'' is the Latin for "tailed ones", from : "tail". Salamander diversity is highest in eastern North America, especially in 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, d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lungfish
Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the tetrapods (which includes living amphibians, reptiles, birds and mammals). The mouths of lungfish typically bear tooth plates, which are used to crush hard shelled organisms. Today there are only six known species of lungfish, living in Africa, South America, and Australia, though they were formerly globally distributed. The fossil record of the group extends into the Early Devonian, over 410 million years ago. The earliest known members of the group were marine, while almost all post-Carboniferous representatives inhabit freshwater environments. Etymology Dipnoi is Modern Latin derived from the Greek δίπν ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bichir
Bichirs and the reedfish comprise Polypteridae , a family (biology), family of archaic Actinopterygii, ray-finned fishes and the only family in the order (biology), order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuary, estuaries. Cladistia, polypterids and their fossil relatives, are considered the sister group to all other extant ray-finned fishes (Actinopteri).Dai Suzuki, Matthew C. Brandley, Masayoshi Tokita: ''CORRECTION: The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes.'' BMC Evolutionary Biology. Bd. 10, Art.-Nr. 209, 2010, They likely diverged from Actinopteri at least 330 million ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neotenic
Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny in modern humans is more significant than in other primates. In progenesis or paedogenesis, sexual development is accelerated. Both neoteny and progenesis result in paedomorphism (as having the form typical of children) or paedomorphosis (changing towards forms typical of children), a type of heterochrony. It is the retention in adults of traits previously seen only in the young. Such retention is important in evolutionary biology, domestication, and evolutionary developmental biology. Some authors define paedomorphism as the retention of larval traits, as seen in salamanders.Schell, S. C. ''Handbook of Trematodes of North America North of Mexico'', 1985, pg. 22 History and etymology Julius Kollmann created the term "neoteny" in 1885 after he described the axolot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteidae
The family (biology), family Proteidae is a group of aquatic Salamander, salamanders found today in the Balkan Peninsula and North America. The range of the genus ''Necturus'' (commonly known as waterdogs or mudpuppies) runs from southern central Canada, through the midwestern United States, east to North Carolina and south to Georgia and Mississippi. The range of the olm, the only extant member of the genus ''Proteus'', is limited to the Western Balkans. The fossil record of the family extends back to the Late Cretaceous, with ''Paranecturus'' being known from the Maastrichtian of North America, and ''Bishara (salamander), Bishara'' from the Santonian-Campanian of Central Asia. Taxonomy Proteidae, is divided into two extant taxon, extant genera, ''Necturus'' with five North American species, and ''Olm, Proteus'' with one extant European species, the olm. A number of extinct genera are known extending back to the end of the Late Cretaceous. Family Proteidae * Genus ''Nectu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Necturus
''Necturus'' is a genus of aquatic salamanders in the family Proteidae. Species of the genus are native to the eastern United States and Canada. They are commonly known as waterdogs and mudpuppies. The common mudpuppy ''(N. maculosus)'' is probably the best-known species – as an amphibian with gill slits, it is often dissected in comparative anatomy classes. The common mudpuppy has the largest distribution of any fully aquatic salamander in North America. Taxonomy The genus ''Necturus'' is under scrutiny by herpetologists. The relationship between the species is still being studied. In 1991, Collins recommended ''N. maculosus louisianensis'' be elevated to full species status as ''N. louisianensis''. Originally described by Viosca as a species, it is usually considered a subspecies of the common mudpuppy (''N. maculosus''). However, the interpretation of Collins was not largely followed. Petranka, J.W. (1998). ''Salamanders of the United States and Canada''. Washington, D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sirenidae
Sirenidae, the sirens, are a family of neotenic aquatic salamanders. Family members have very small fore limbs, and lack hind limbs altogether. In one species, the skeleton in their fore limbs is made of only cartilage. In contrast to most other salamanders, they have external gills bunched together on the neck in both larval and adult states. Sirens are found only in the Southeastern United States and northern Mexico. Although they are primarily carnivorous, they are the only salamanders observed eating plant material.Hill, R. L., Mendelson, J. R. & Stabile, J. L. 2015. Direct observation and review of herbivory in Sirenidae (Amphibia: Caudata). Southeastern Naturalist 14, N5-N9. Description Sirens are quite distinct from other salamanders, and in some classifications they form their own suborder, Sirenoidea, or as a completely distinct order (Meantes or Trachystomata). Genetic analysis variously places them as the sister to other Salamandroidea or as sister to all other salam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
