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The Mexican tetra (Astyanax mexicanus) is a freshwater fish of the characin family (family Characidae) of order Characiformes.[1] [2] The type species of its genus, it is native to the Nearctic ecozone, originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas as well as the central and eastern parts of Mexico. Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ...
Animalia redirects here. ...
Typical Classes See below Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. ...
Orders See text The Actinopterygii are the ray-finned fish. ...
Families Acestrorhynchidae Anostomidae - Headstanders Characidae - Characins and tetras Citharinidae Ctenoluciidae - Pike-characids Curimatidae Erythrinidae - Trahiras Gasteropelecidae - Freshwater hatchetfishes Hemiodontidae Hepsetidae Lebiasinidae The Characiformes are an order of ray-finned fish, comprising the characins and their allies. ...
Genera Subfamily Alestiinae - African tetras Alestes (or Brycinus) Hydrocynus Micralestes Phenacogrammus Rhabdalestes and 13 other genera Subfamily Characidiinae 8 genera Subfamily Characinae Acestrorhynchus - Pike characins Aphyocharax Boehlkea Chalceus Charax Cynodo Exodon Hasemania Hydrolycus Nematobrycon Petitella Priocharax Rhaphiodon Roeboides Thayeria ... Subfamily Crenuchinae Crenuchus Poecilocharax Subfamily Glandulocaudinae 16 genera Subfamily Iguanodectinae Iguanodectes...
Species Categories: Animal stubs | Characins ...
In biology, binomial nomenclature is the formal method of naming species. ...
1853 was a common year starting on Saturday (see link for calendar). ...
For the village on the Isle of Wight, see Freshwater, Isle of Wight. ...
A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ...
Families Acestrorhynchidae Anostomidae - Headstanders Characidae - Characins and tetras Citharinidae Ctenoluciidae - Pike-characids Curimatidae Erythrinidae - Trahiras Gasteropelecidae - Freshwater hatchetfishes Hemiodontidae Hepsetidae Lebiasinidae The Characiformes are an order of ray-finned fish, comprising the characins and their allies. ...
In biological classification, family (Latin: familia, plural familiae) is 1) a rank or 2) a taxon in that rank. ...
Genera Subfamily Alestiinae - African tetras Alestes (or Brycinus) Hydrocynus Micralestes Phenacogrammus Rhabdalestes and 13 other genera Subfamily Characidiinae 8 genera Subfamily Characinae Acestrorhynchus - Pike characins Aphyocharax Boehlkea Chalceus Charax Cynodo Exodon Hasemania Hydrolycus Nematobrycon Petitella Priocharax Rhaphiodon Roeboides Thayeria ... Subfamily Crenuchinae Crenuchus Poecilocharax Subfamily Glandulocaudinae 16 genera Subfamily Iguanodectinae Iguanodectes...
In scientific classification used in biology, the order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). ...
Families Acestrorhynchidae Anostomidae - Headstanders Characidae - Characins and tetras Citharinidae Ctenoluciidae - Pike-characids Curimatidae Erythrinidae - Trahiras Gasteropelecidae - Freshwater hatchetfishes Hemiodontidae Hepsetidae Lebiasinidae The Characiformes are an order of ray-finned fish, comprising the characins and their allies. ...
Type specimens When a new species is discovered, more important than creating a new and unique name for the species is developing a reasonably detailed description. ...
For other uses of the word, please see Genus (disambiguation). ...
The Nearctic is one of the eight terrestrial ecozones dividing the Earths land surface. ...
An ecozone or biogeographic realm is the largest scale biogeographic division of the earths surface based on the historic and evolutionary distribution patterns of plants and animals. ...
RÃo Bravo redirects here. ...
The Nueces River is a river in the U.S. state of Texas, approximately 315 mi (507 km) long. ...
The Pecos River rises in northern New Mexico, USA, and flows for 926 miles (1,480 km) through the eastern portion of that state and neighboring Texas before it empties into the Rio Grande near Del Rio. ...
Official language(s) No Official Language See languages of Texas Capital Austin Largest city Houston Area Ranked 2nd - Total 261,797 sq mi (678,051 km²) - Width 773 miles (1,244 km) - Length 790 miles (1,270 km) - % water 2. ...
Growing to a maximum overall length of 12 cm (4.7 in), the Mexican tetra is of typical characin shape, with unremarkable, drab coloration. Its blind cave form, however, is notable for having no eyes and being albino, that is, completely devoid of pigmentation; it has a pinkish-white color to its body. This article is being considered for deletion in accordance with Wikipedias deletion policy. ...
An inch (plural: inches; symbol or abbreviation: in or, sometimes, ″ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ...
Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ...
This fish is reasonably popular among aquarists. This is especially true of the blind cave form. For other uses, see Aquarium (disambiguation). ...
A. mexicanus is a peaceful species that spends most of its time in the mid-level of the water above the rocky and sandy bottoms of pools and backwaters of creeks and rivers of its native environment. Coming from a subtropical climate, it prefers water with 6.0–7.8 pH, a hardness of up to 30 dGH, and a temperature range of 20 to 25 °C (68 to 77 °F). In the winter it migrates to warmer waters. Its natural diet consists of crustaceans, insects, and annelids, although in captivity it is omnivorous. Subtropical (or semitropical) areas are those adjacent to the tropics, usually roughly defined as the ranges 23. ...
The correct title of this article is . ...
The title given to this article is incorrect due to technical limitations. ...
The degree Celsius (symbol: °C) is an SI derived unit of temperature. ...
Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ...
Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The nauplius larva of a dendrobranchiate Porcellio scaber, the common rough woodlouse, a terrestrial crustacean Pollicipes polymerus, the gooseneck barnacle Glyphea pseudastacus, a fossil glypheoid The crustaceans (Crustacea) are...
{{Taxobox | color = pink | name = Insects | fossil_range = Carboniferous - Recent | image = European honey bee extracts nectar. ...
Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata* Oligochaeta - earthworms, etc. ...
Omnivores are organisms that consume both plants and animals. ...
The Mexican tetra has been treated as a subspecies of A. fasciatus, the banded tetra, but this is not widely accepted.[1]
Blind cave form
A. mexicanus is famous for its blind cave form, which is known by such names as blind cave tetra, blind tetra, and blind cavefish. Some thirty distinct populations of Mexican tetras live in deep caves and have lost the power of sight and even their eyes. These fish can still, however, find their way around by means of their lateral lines, which are highly sensitive to fluctuating water pressure. Lechuguilla Cave, New Mexico A cave is a natural underground void large enough for a human to enter. ...
Visual perception is one of the senses, consisting of the ability to detect light and interpret (see) it as the perception known as sight or naked eye vision. ...
// A human eye. ...
In fish, the lateral line is a sense organ used to detect movement in the surrounding water. ...
Water pressure is the pressure in any system for supplying water, usually a domestic water system, although the term is used in other contexts as well, such as a municipal water system. ...
The eyed and eyeless forms of A. mexicanus, being members of the same species, are closely related and can interbreed. Astyanax jordani, however, is another blind cave fish, independently and recently evolved from the sighted surface form, which is sometimes confused with the cave form of A. mexicanus. However, when born, the cave dwelling form of A. mexicanus has eyes. As they grow older, skin just grows over them and the eyes degenerate completely, because there is no need for sight in the pitch-black world of a cave.[3] Binomial name Astyanax jordani (Hubbs and Innes, 1936) Astyanax jordani is a freshwater fish of the characin family (family Characidae) of order Characiformes, native to Mexico. ...
In the aquarium A. mexicanus only grows to a length of 12 cm (4.7 in) in the recommended minimum of 30 US gallons. The blind cave tetra is a fairly hardy species, but is in no way a beginner's fish. They are not picky on food, as they will eat anything from standard flakes to sinking carnivore pellets. Their lack of sight does not hinder their ability to get any and all food before it hits the bottom. They prefer subdued lighting with a rocky substrate, like gravel. It is recommended that the tank mimic their natural environment, so artificial or natural rock is highly appreciated. They become semi-aggressive as they age but are by nature, schooling fish, and a group of at least three is a good idea. However, it isn't imperative, as they can be kept as a single specimen. As stated earlier, they can get to their food rather swiftly, even more so than fish with the ability to see, so they aren't really good for a community, but one is OK for a semi-aggressive community. They are also incredibly fast, so catching them with the net is a chore in itself while conducting maintenance. They are very personable fish and will respond to a given name. If you call their name before every feeding, they will eventually associate that sound with food and come when called.
Evolution research The surface and cave forms of the Mexican tetra have proven popular subjects for scientists studying evolution. This article is about evolution in biology. ...
A recent study suggests that there are at least two distinct genetic lineages among the blind populations, arguing that these represent a case of convergent evolution.[4] In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ...
In one experiment studying eye development, University of Maryland scientists transplanted lenses from the eyes of sighted surface-form embryos into blind cave-form embryos, and vice versa. In the cave form, lens development begins within the first 24 hours of embryonic development, but quickly aborts, the lens cells dying; most of the rest of the eye structures never develop. Researchers found that the lens seemed to control the development of the rest of the eye, as the surface-form tetras which received cave-form lenses failed to develop eyes, while cave-form tetras which received surface-form lenses grew eyes with pupils, corneas, and irises. (It is not clear whether they possessed sight, however.)[5] [6] The University of Maryland, College Park (also known as UM, UMD, or UMCP) is a public university located in the city of College Park, in Prince Georges County, Maryland, just outside Washington, D.C., in the United States. ...
Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ...
It has been suggested that embryology be merged into this article or section. ...
The human eye The pupil is the central transparent area (showing as black). ...
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ...
The human iris The iris is the green/grey/brown area. ...
Blind cave tetras and creationism The blind form of the Mexican tetra is different from the surface-dwelling form in a number of ways, including having unpigmented skin, having a better olfactory sense by having taste buds all over its head, and by being able to store four times more energy as fat allowing it to deal with irregular food supplies more effectively.[7] However, it is the lack of eyes that has been at the centre of discussion of the Mexican cave tetras among creationists. Young boy smelling a flower Olfaction, which is also known as Olfactics is the sense of smell, and the detection of chemicals dissolved in air. ...
Taste buds (or lingual papillae) are small structures on the upper surface of the tongue that provide information about the taste of food being eaten. ...
Creationism is the belief that humanity, life, the Earth, and the universe were created in their entirety by a supernatural deity or deities (typically God), whose existence is presupposed. ...
Darwin said of sightless fish -
By the time that an animal had reached, after numberless generations, the deepest recesses, disuse will on this view have more or less perfectly obliterated its eyes, and natural selection will often have affected other changes, such as an increase in the length of antennae or palpi, as compensation for blindness. —Charles Darwin, Origin of Species (1859) Modern genetics has made clear that the lack of use does not, in itself, necessitate a feature's disappearance[1] - as seen in humans with useless evolutionary retentions such as wisdom teeth and the appendix. In this context, the positive genetic benefits for the 'degeneration' have to be considered, i.e., what advantages are obtained by cave-dwelling tetras by losing their eyes? Possible explanations include[2]: Wisdom teeth are third molars that usually appear between the ages of 17 and 24 (although they may appear when older, younger, or may not appear at all). ...
Look up appendix in Wiktionary, the free dictionary. ...
- not developing eyes allows the individual more energy for growth and reproduction[3]
- there remains less chance of accidental damage and infection, since the previously useless and exposed organ is sealed with a flap of protective skin
Among creationists the cave tetra is seen as evidence against evolution. One argument claims that this is an instance of "devolution" -- showing an evolutionary trend of decreasing complexity -- and that this is inconsistent with the main tenet of evolutionary theory, as it implies a loss of 'information'. Another argument, though representing a minor and controversial subset within creationists, maintains that such 'degeneration' is a product of a "fallen, cursed creation"[4]. Others see such 'degeneration' as an abnormal disability.[5] The creation-evolution controversy (also termed the creation vs. ...
The term devolution, which normally means a delegation of powers, is sometimes erroneously used to refer to the evolution of a species into more primitive forms. ...
From the scientific perspective, such arguments are based on a common misunderstanding of the theory. Mainstream evolution defines a non-directional process, and increased complexity is a common, but not necessarily inherent effect of it. Evolution does not dictate that an organism becomes more or less complex, but rather better suited to their environment.[8] The term devolution, which normally means a delegation of powers, is sometimes erroneously used to refer to the evolution of a species into more primitive forms. ...
References - ^ a b "Astyanax mexicanus". FishBase. Ed. Ranier Froese and Daniel Pauly. March 2006 version. N.p.: FishBase, 2006.
- ^ Astyanax mexicanus (TSN 162850). Integrated Taxonomic Information System. Accessed on 1 July 2006.
- ^ "Astyanax jordani". FishBase. Ed. Ranier Froese and Daniel Pauly. March 2006 version. N.p.: FishBase, 2006.
- ^ Dowling, T. E., D. P. Martasian, and W. R. Jeffrey (2002). "Evidence for Multiple Genetic Forms with Similar Eyeless Phenotypes in the Blind Cavefish, Astyanax mexicanus". Molecular Biology and Evolution 19: 446–55.
- ^ Yamamoto, Yoshiyuki, and William R. Jeffrey (2000). "Central Role for the Lens in Cave Fish Eye Degeneration". Science 289 (28 July): 631–3.
- ^ Pennisi, Elizabeth (2000). "Embryonic Lens Prompts Eye Development". Science 289 (28 July): 522–3.
- ^ Helfman G., Collette B., & Facey D.: The Diversity of Fishes, Blackwell Publishing, p 315, 1997, ISBN 0-86542-256-7
- ^ Dawkins, R.: Climbing Mount Improbable, W. W. Norton & Co, 1997, ISBN 0393316823
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