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Mexican tetra

January 01, 1970

"Blind cave fish" redirects here. For cavefish in general, see cavefish.

The Mexican tetra (Astyanax mexicanus), also known as the blind cave fish, blind cave characin, and blind cave tetra, is a freshwater fish of the family Characidae of the order Characiformes.[3][4] The type species of its genus, it is native to the Nearctic realm, originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas, as well as the central and eastern parts of Mexico.[3][5][6]

Mexican tetra
Normal form (above) and blind cave form (below)
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. mexicanus
Binomial name
Astyanax mexicanus
(De Filippi, 1853)
Approximate range
Synonyms[2]
  • Tetragonopterus mexicanus De Filippi, 1853
  • Astyanax fasciatus mexicanus (De Filippi, 1853)
  • Tetragonopterus fulgens Bocourt, 1868
  • Tetragonopterus nitidus Bocourt, 1868
  • Tetragonopterus streetsii Cope, 1872

Growing to a maximum total length of 12 cm (4.7 in), the Mexican tetra is of typical characin shape, with silvery, unremarkable scalation.[3] Its blind cave form, however, is notable for having no eyes or pigment; it has a pinkish-white color to its body (resembling an albino).[7]

This fish, especially the blind variant, is reasonably popular among aquarists.[8]

A. mexicanus is a peaceful species that spends most of its time in midlevel 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 6.5–8 pH, a hardness of up to 30 dGH, and a temperature range of 20 to 25 °C (68 to 77 °F). In the winter, some populations migrate to warmer waters. Its natural diet consists of crustaceans, insects, and annelids, although in captivity it is omnivorous.[3][8]

The Mexican tetra has been treated as a subspecies of A. fasciatus, but this is not widely accepted.[3] Additionally, the hypogean blind cave form is sometimes recognized as a separate species, A. jordani, but this directly contradicts phylogenetic evidence.[7][9][10][11][12][13]

Blind cave form edit

 
Blind cave fish form

A. mexicanus is famous for its blind cave form, which is known by such names as blind cave tetra, blind tetra (leading to easy confusion with the Brazilian Stygichthys typhlops), blind cave characin and blind cavefish. Depending on the exact population, cave forms can have degenerated sight or have total loss of sight and even their eyes, due to down-regulation of the protein αA-crystallin and consequent lens cell death.[14] The fish in the Pachón caves have lost their eyes completely whilst the fish from the Micos cave only have limited sight.[15] Cave fish and surface fish are able to produce fertile offspring.[15]

These fish can still, however, find their way around by means of their lateral lines, which are highly sensitive to fluctuating water pressure.[16] Blindness in A. mexicanus induces a disruption of early neuromast patterning, which further causes asymmetries in cranial bone structure. One such asymmetry is a bend in the dorsal region of their skull, which is propounded to increase water flow to the opposite side of the face, functionally enhancing sensory input and spatial mapping in the dark waters of caves.[17] Scientists suggest that gene cystathionine beta synthase-a mutation restricts blood flow to cavefish eyes during a critical stage of growth so the eyes are covered by skin.[18]

Currently, about 30 cave populations are known, dispersed over three geographically distinct areas in a karst region of San Luis Potosí and far southern Tamaulipas, northeastern Mexico.[9][19][20] Among the various cave population are at least three with only full cave forms (blind and without pigment), at least eleven with cave, "normal" and intermediate forms, and at least one with both cave and "normal" forms but no intermediates.[19] Studies suggest at least two distinct genetic lineages occur among the blind populations, and the current distribution of populations arose by at least five independent invasions.[9] Furthermore, cave populations have a very recent origin (< 20,000 years) in which blindness or reduced vision evolved convergently after surface ancestors populated several caves independently and at different times.[21][22] This recent origin suggests that the phenotypic changes in cavefish populations, namely eye degeneration, arose as a result of the high fixation of genetic variants present in surface fish populations in a short period of time.[23]

The eyed and eyeless forms of A. mexicanus, being members of the same species, are closely related and can interbreed[24] making this species an excellent model organism for examining convergent and parallel evolution, regressive evolution in cave animals, and the genetic basis of regressive traits.[25] This, combined with the ease of maintaining the species in captivity, has made it the most studied cavefish and likely also the most studied cave organism overall.[19]

The blind and colorless cave form of A. mexicanus is sometimes recognized as a separate species, A. jordani, but this leaves the remaining A. mexicanus as a paraphyletic species and A. jordani as polyphyletic.[7][9][10][11][12][13] The Cueva Chica Cave in the southern part of the Sierra del Abra system is the type locality for A. jordani.[7] Other blind populations were initially also recognized as separate species, including antrobius described in 1946 from the Pachón Cave and hubbsi described in 1947 from the Los Sabinos Cave (both subsequently merged into jordani/mexicanus).[7] The most divergent cave population is the one in Los Sabinos.[7][26]

Another cave-adapted population of Astyanax, varying from blind and depigmented to individuals showing intermediate features, is known from the Granadas Cave, part of the Balsas River drainage in Guerrero, southern Mexico, but it is a part of A. aeneus (itself sometimes included in A. mexicanus).[7][20][27]

Evolution research edit

The surface and cave forms of the Mexican tetra have proven powerful subjects for scientists studying evolution.[24] When the surface-dwelling ancestors of current cave populations entered the subterranean environment, the change in ecological conditions rendered their phenotype—which included many biological functions dependent on the presence of light—subject to natural selection and genetic drift.[25][28] One of the most striking changes to evolve was the loss of eyes. This is referred to as a "regressive trait" because the surface fish that originally colonized caves possessed eyes.[24] In addition to regressive traits, cave forms evolved "constructive traits". In contrast to regressive traits, the purpose or benefit of constructive traits is generally accepted.[25] Active research focuses on the mechanisms driving the evolution of regressive traits, such as the loss of eyes, in A. mexicanus. Recent studies have produced evidence that the mechanism may be direct selection,[29] or indirect selection through antagonistic pleiotropy,[30] rather than genetic drift and neutral mutation, the traditionally favored hypothesis for regressive evolution.[28]

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.[31]

Darwin said of sightless fish:[32]

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 effected other changes, such as an increase in the length of antennae or palpi, as compensation for blindness.

— Charles Darwin, The Origin of Species (1859)

Modern genetics has made clear that the lack of use does not, in itself, necessitate a feature's disappearance.[33][34] In this context, the positive genetic benefits have to be considered, i.e., what advantages are obtained by cave-dwelling tetras by losing their eyes? Possible explanations include:

  • Not developing eyes allows the individual more energy for growth but not egg production.[14] However the species does use other methods to locate food and detect danger, which also consume energy that would be conserved if it had eyes or transparent eyelids.
  • There remains less chance of accidental damage and infection, since the previously useless and exposed organ is sealed with a flap of protective skin. It is unknown why this species did not develop transparent skin or eyelids instead, as some species of reptiles did.
  • The lack of eyes disables the "body clock", which is controlled by periods of light and dark, conserving energy. However sunlight does have minimal impact on the "body clock" in caves.[citation needed]

Another likely explanation for the loss of its eyes is that of selective neutrality and genetic drift; in the dark environment of the cave, the eyes are neither advantageous nor disadvantageous and thus any genetic factors that might impair the eyes (or their development) can take hold with no consequence on the individual or species. Because there is no selection pressure for sight in this environment, any number of genetic abnormalities that give rise to the damage or loss of eyes could proliferate among the population with no effect on the fitness of the population.

Among some creationists, the cave tetra is seen as evidence 'against' evolution. One argument claims this is an instance of "devolution"—showing an evolutionary trend of decreasing complexity. But evolution is a non-directional process, and while increased complexity is a common effect, there is no reason why evolution cannot tend towards simplicity if that makes an organism better suited to its environment.[35]

Inhibition of the HSP90 protein has a dramatic effect in the development of the blind tetra.[36]

In the aquarium edit

The blind cave tetras seen in the aquarium trade are all based on stock collected in the Cueva Chica Cave in the southern part of the Sierra del Abra system in 1936.[7] These were sent to an aquarium company in Texas, who soon started to distribute them to aquarists. Since then, these have been selectively bred for their troglomorphic traits.[7] Today large numbers are bred at commercial facilities, especially in Asia.[8]

The blind cave tetra is a hardy species.[7] Their lack of sight does not hinder their ability to get food. They prefer subdued lighting with a rocky substrate, like gravel, mimicking their natural environment. They become semi-aggressive as they age, and are by nature schooling fish.[37] Experiments have shown that keeping these fish in bright aquarium set-ups has no effect on the development of the skin flap that forms over their eyes as they grow.

See also edit

References edit

  1. ^ NatureServe (2013). "Astyanax mexicanus". IUCN Red List of Threatened Species. 2013: e.T62191A3109229. doi:10.2305/IUCN.UK.2013-1.RLTS.T62191A3109229.en.
  2. ^ Froese, R.; Reyes, R. D. (2023-04-21). Froese, R.; Pauly, D. (eds.). "Synonyms of Astyanax mexicanus (De Filippi, 1853)". FishBase. Retrieved 2023-04-21.
  3. ^ a b c d e Froese, Rainer; Pauly, Daniel (eds.) (2015). "Astyanax mexicanus" in FishBase. October 2015 version.
  4. ^ "Astyanax mexicanus". Integrated Taxonomic Information System. Retrieved 1 July 2006.
  5. ^ Borowsky, Richard (2018-01-22). "Cavefishes". Current Biology. 28 (2): R60–R64. doi:10.1016/j.cub.2017.12.011. ISSN 1879-0445. PMID 29374443. S2CID 235332375.
  6. ^ Palermo,LiveScience, Elizabeth. "Blind Cavefish Stops Its Internal Clock". Scientific American. Retrieved 2022-02-24.
  7. ^ a b c d e f g h i j Keene, A.; Yoshizawa, M.; McGaugh, S. (2016). Biology and Evolution of the Mexican Cavefish. Elsevier Science. pp. 68–69, 77–87. ISBN 978-0-12-802148-4.
  8. ^ a b c "Astyanax mexicanus". Seriously Fish. Retrieved 2 May 2017.
  9. ^ a b c d Gross, J.B. (June 2012). "The complex origin of Astyanax cave fish". BMC Evolutionary Biology. 12: 105. doi:10.1186/1471-2148-12-105. PMC 3464594. PMID 22747496.
  10. ^ a b Jeffery, W. (2009). "Regressive evolution in Astyanax cavefish". Annual Review of Genetics. 43: 25–47. doi:10.1146/annurev-genet-102108-134216. PMC 3594788. PMID 19640230.
  11. ^ a b Bradic, M.; Beerli, P.; Garcia-de Leon, F. J.; Esquivel-Bobadilla, S.; Borowsky, R. L. (2012). "Gene flow and population structure in the Mexican blind cavefish complex (Astyanax mexicanus)". BMC Evolutionary Biology. 12: 9. doi:10.1186/1471-2148-12-9. PMC 3282648. PMID 22269119.
  12. ^ a b Dowling, T. E.; Martasian, D. P.; Jeffery, W. R. (2002). "Evidence for multiple genetic forms with similar eyeless phenotypes in the blind cavefish, Astyanax mexicanus". Molecular Biology and Evolution. 19 (4). Oxford University Press (OUP) (Society for Molecular Biology and Evolution (smbe)): 446–455. doi:10.1093/oxfordjournals.molbev.a004100. PMID 11919286.
  13. ^ a b Strecker, U.; Faúndez, V. H.; Wilkens, H. (2004). "Phylogeography of surface and cave Astyanax (Teleostei) from Central and North America based on cytochrome b sequence data". Molecular Phylogenetics and Evolution. 33 (2). Academic Press: 469–481. doi:10.1016/j.ympev.2004.07.001. PMID 15336680.
  14. ^ a b Jeffery, W. R. (2005-01-13). "Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish". Journal of Heredity. 96 (3): 185–196. doi:10.1093/jhered/esi028. ISSN 1465-7333. PMID 15653557.
  15. ^ a b Moran, D.; Softley, R. & Warrant, E. J. (2015). "The energetic cost of vision and the evolution of eyeless Mexican cavefish". Science Advances. 1 (8): e1500363. Bibcode:2015SciA....1E0363M. doi:10.1126/sciadv.1500363. PMC 4643782. PMID 26601263.
  16. ^ Yoshizawa, M.; Yamamoto, Y.; O'Quin, K. E.; Jeffery, W. R. (December 2012). "Evolution of an adaptive behavior and its sensory receptors promotes eye regression in blind cavefish". BMC Biology. 10: 108. doi:10.1186/1741-7007-10-108. PMC 3565949. PMID 23270452.
  17. ^ Powers, Amanda K.; Berning, Daniel J.; Gross, Joshua B. (2020-02-06). "Parallel evolution of regressive and constructive craniofacial traits across distinct populations of Astyanax mexicanus cavefish". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 334 (7–8): 450–462. Bibcode:2020JEZB..334..450P. doi:10.1002/jez.b.22932. ISSN 1552-5007. PMC 7415521. PMID 32030873.
  18. ^ "Gene found that causes eyes to wither in cavefish". phys.org. Retrieved 2020-06-27.
  19. ^ a b c Romero, A. (2009). Cave Biology: Life in Darkness. Cambridge University Press. pp. 147–148. ISBN 978-0-521-82846-8.
  20. ^ a b Luis Espinasa; Patricia Rivas-Manzano; Héctor Espinosa Pérez (2001). "A New Blind Cave Fish Population of Genus Astyanax: Geography, Morphology and Behavior". Environmental Biology of Fishes. 62 (1): 339–344. doi:10.1023/A:1011852603162. S2CID 30720408.
  21. ^ Fumey, Julien; Hinaux, Hélène; Noirot, Céline; Thermes, Claude; Rétaux, Sylvie; Casane, Didier (2018-04-18). "Evidence for late Pleistocene origin of Astyanax mexicanus cavefish". BMC Evolutionary Biology. 18 (1): 43. doi:10.1186/s12862-018-1156-7. ISSN 1471-2148. PMC 5905186. PMID 29665771.
  22. ^ WILKENS, HORST; STRECKER, ULRIKE (2003-12-01). "Convergent evolution of the cavefish Astyanax (Characidae, Teleostei): genetic evidence from reduced eye-size and pigmentation". Biological Journal of the Linnean Society. 80 (4): 545–554. doi:10.1111/j.1095-8312.2003.00230.x. ISSN 0024-4066.
  23. ^ Fumey, Julien; Hinaux, Hélène; Noirot, Céline; Thermes, Claude; Rétaux, Sylvie; Casane, Didier (2016-12-16). "Evidence for Late Pleistocene origin of Astyanax mexicanus cavefish". BMC Evolutionary Biology. 18 (1): 43. bioRxiv 10.1101/094748. doi:10.1186/s12862-018-1156-7. PMC 5905186. PMID 29665771.
  24. ^ a b c Retaux, S.; Casane, D. (September 2013). "Evolution of eye development in the darkness of caves: adaptation, drift, or both?". Evodevo. 4 (1): 26. doi:10.1186/2041-9139-4-26. PMC 3849642. PMID 24079393.
  25. ^ a b c Soares, D.; Niemiller, M. L. (April 2013). "Sensory Adaptations of Fishes to Subterranean Environments". BioScience. 63 (4): 274–283. doi:10.1525/bio.2013.63.4.7.
  26. ^ Lyndon M. Coghill; C. Darrin Hulsey; Johel Chaves-Campos; Francisco J. García de Leon; Steven G. Johnson (2014). "Next Generation Phylogeography of Cave and Surface Astyanax mexicanus". Molecular Phylogenetics and Evolution. 79: 368–374. doi:10.1016/j.ympev.2014.06.029. PMID 25014568.
  27. ^ William R. Jeffery; Allen G. Strickler; Yoshiyuki Yamamoto (2003). "To See or Not to See: Evolution of Eye Degeneration in Mexican Blind Cavefish". Integrative and Comparative Biology. 43 (4). Oxford University Press (OUP) (Society for Integrative and Comparative Biology): 531–541. doi:10.1093/icb/43.4.531. PMID 21680461.
  28. ^ a b Wilkens, H (November 2012). "Genes, modules and the evolution of cave fish". Heredity. 105 (5): 413–422. doi:10.1038/hdy.2009.184. PMID 20068586.
  29. ^ Protas, M; Tabansky, I.; Conrad, M.; Gross, J. B.; Vidal, O.; Tabin, C. J.; Borowsky, R. (April 2008). "Multi-trait evolution in a cave fish, Astyanax mexicanus". Evolution & Development. 10 (2): 196–209. doi:10.1111/j.1525-142x.2008.00227.x. PMID 18315813. S2CID 32525015.
  30. ^ Jeffery, WR (2009). "Regressive Evolution in Astyanax Cavefish". Annual Review of Genetics. 43: 25–47. doi:10.1146/annurev-genet-102108-134216. PMC 3594788. PMID 19640230.
  31. ^ Helfman, G. S.; Collete, B. B.; Facey, D. E. (1997). The Diversity of Fishes. Malden, Massachusetts, USA: Blackwell Science. p. 315. ISBN 0-86542-256-7.
  32. ^ Darwin, Charles R. (2001) [As published 1909–1914, originally published 1859]. "Chapter 5: Laws of Variation, Effects of the Increased Use and Disuse of Parts, as Controlled by Natural Selection". In Eliot, Charles W. (ed.). The Origin of Species. The Harvard Classics. Vol. XI. New York: P.F. Collier and Son. Retrieved 8 February 2024 – via Bartleby.com.
  33. ^ Espinasa, L.; Espinasa, M. (June 2005). . FindArticles. Archived from the original on 2006-05-15. Retrieved 2007-02-13.
  34. ^ Espinasa, M.; Espinasa, L. (2008). "Losing Sight of Regressive Evolution". Evolution: Education and Outreach. 1 (S4): 509–516. doi:10.1007/s12052-008-0094-z.
  35. ^ Dawkins, R. (1997). Climbing Mount Improbable. New York: W. W. Norton. ISBN 0-393-31682-3.
  36. ^ Rohner, N.; Jarosz, D. F.; Kowalko, J. E.; Yoshizawa, M.; Jeffery, W. R.; Borowsky, R. L.; Lindquist, S.; Tabin, C. J. (2013). "Cryptic variation in morphological evolution: HSP90 as a capacitor for loss of eyes in cavefish". Science. 342 (6164): 1372–1375. Bibcode:2013Sci...342.1372R. doi:10.1126/science.1240276. hdl:1721.1/96714. PMC 4004346. PMID 24337296.
  37. ^ "Mexican Tetra (Astyanax mexicanus): Ultimate Care Guide". Fish Laboratory. August 5, 2022. Retrieved August 5, 2022.

January 01, 1970
mexican, tetra, blind, cave, fish, redirects, here, cavefish, general, cavefish, astyanax, mexicanus, also, known, blind, cave, fish, blind, cave, characin, blind, cave, tetra, freshwater, fish, family, characidae, order, characiformes, type, species, genus, n. Blind cave fish redirects here For cavefish in general see cavefish The Mexican tetra Astyanax mexicanus also known as the blind cave fish blind cave characin and blind cave tetra is a freshwater fish of the family Characidae of the order Characiformes 3 4 The type species of its genus it is native to the Nearctic realm originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas as well as the central and eastern parts of Mexico 3 5 6 Mexican tetra Normal form above and blind cave form below Conservation status Least Concern IUCN 3 1 1 Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Actinopterygii Order Characiformes Family Characidae Genus Astyanax Species A mexicanus Binomial name Astyanax mexicanus De Filippi 1853 Approximate range Synonyms 2 Tetragonopterus mexicanus De Filippi 1853Astyanax fasciatus mexicanus De Filippi 1853 Tetragonopterus fulgens Bocourt 1868Tetragonopterus nitidus Bocourt 1868Tetragonopterus streetsii Cope 1872 Growing to a maximum total length of 12 cm 4 7 in the Mexican tetra is of typical characin shape with silvery unremarkable scalation 3 Its blind cave form however is notable for having no eyes or pigment it has a pinkish white color to its body resembling an albino 7 This fish especially the blind variant is reasonably popular among aquarists 8 A mexicanus is a peaceful species that spends most of its time in midlevel 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 5 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 some populations migrate to warmer waters Its natural diet consists of crustaceans insects and annelids although in captivity it is omnivorous 3 8 The Mexican tetra has been treated as a subspecies of A fasciatus but this is not widely accepted 3 Additionally the hypogean blind cave form is sometimes recognized as a separate species A jordani but this directly contradicts phylogenetic evidence 7 9 10 11 12 13 Contents 1 Blind cave form 1 1 Evolution research 1 2 In the aquarium 2 See also 3 ReferencesBlind cave form edit nbsp Blind cave fish form A mexicanus is famous for its blind cave form which is known by such names as blind cave tetra blind tetra leading to easy confusion with the Brazilian Stygichthys typhlops blind cave characin and blind cavefish Depending on the exact population cave forms can have degenerated sight or have total loss of sight and even their eyes due to down regulation of the protein aA crystallin and consequent lens cell death 14 The fish in the Pachon caves have lost their eyes completely whilst the fish from the Micos cave only have limited sight 15 Cave fish and surface fish are able to produce fertile offspring 15 These fish can still however find their way around by means of their lateral lines which are highly sensitive to fluctuating water pressure 16 Blindness in A mexicanus induces a disruption of early neuromast patterning which further causes asymmetries in cranial bone structure One such asymmetry is a bend in the dorsal region of their skull which is propounded to increase water flow to the opposite side of the face functionally enhancing sensory input and spatial mapping in the dark waters of caves 17 Scientists suggest that gene cystathionine beta synthase a mutation restricts blood flow to cavefish eyes during a critical stage of growth so the eyes are covered by skin 18 Currently about 30 cave populations are known dispersed over three geographically distinct areas in a karst region of San Luis Potosi and far southern Tamaulipas northeastern Mexico 9 19 20 Among the various cave population are at least three with only full cave forms blind and without pigment at least eleven with cave normal and intermediate forms and at least one with both cave and normal forms but no intermediates 19 Studies suggest at least two distinct genetic lineages occur among the blind populations and the current distribution of populations arose by at least five independent invasions 9 Furthermore cave populations have a very recent origin lt 20 000 years in which blindness or reduced vision evolved convergently after surface ancestors populated several caves independently and at different times 21 22 This recent origin suggests that the phenotypic changes in cavefish populations namely eye degeneration arose as a result of the high fixation of genetic variants present in surface fish populations in a short period of time 23 The eyed and eyeless forms of A mexicanus being members of the same species are closely related and can interbreed 24 making this species an excellent model organism for examining convergent and parallel evolution regressive evolution in cave animals and the genetic basis of regressive traits 25 This combined with the ease of maintaining the species in captivity has made it the most studied cavefish and likely also the most studied cave organism overall 19 The blind and colorless cave form of A mexicanus is sometimes recognized as a separate species A jordani but this leaves the remaining A mexicanus as a paraphyletic species and A jordani as polyphyletic 7 9 10 11 12 13 The Cueva Chica Cave in the southern part of the Sierra del Abra system is the type locality for A jordani 7 Other blind populations were initially also recognized as separate species including antrobius described in 1946 from the Pachon Cave and hubbsi described in 1947 from the Los Sabinos Cave both subsequently merged into jordani mexicanus 7 The most divergent cave population is the one in Los Sabinos 7 26 Another cave adapted population of Astyanax varying from blind and depigmented to individuals showing intermediate features is known from the Granadas Cave part of the Balsas River drainage in Guerrero southern Mexico but it is a part of A aeneus itself sometimes included in A mexicanus 7 20 27 Evolution research edit The surface and cave forms of the Mexican tetra have proven powerful subjects for scientists studying evolution 24 When the surface dwelling ancestors of current cave populations entered the subterranean environment the change in ecological conditions rendered their phenotype which included many biological functions dependent on the presence of light subject to natural selection and genetic drift 25 28 One of the most striking changes to evolve was the loss of eyes This is referred to as a regressive trait because the surface fish that originally colonized caves possessed eyes 24 In addition to regressive traits cave forms evolved constructive traits In contrast to regressive traits the purpose or benefit of constructive traits is generally accepted 25 Active research focuses on the mechanisms driving the evolution of regressive traits such as the loss of eyes in A mexicanus Recent studies have produced evidence that the mechanism may be direct selection 29 or indirect selection through antagonistic pleiotropy 30 rather than genetic drift and neutral mutation the traditionally favored hypothesis for regressive evolution 28 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 31 Darwin said of sightless fish 32 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 effected other changes such as an increase in the length of antennae or palpi as compensation for blindness Charles Darwin The Origin of Species 1859 Modern genetics has made clear that the lack of use does not in itself necessitate a feature s disappearance 33 34 In this context the positive genetic benefits have to be considered i e what advantages are obtained by cave dwelling tetras by losing their eyes Possible explanations include Not developing eyes allows the individual more energy for growth but not egg production 14 However the species does use other methods to locate food and detect danger which also consume energy that would be conserved if it had eyes or transparent eyelids There remains less chance of accidental damage and infection since the previously useless and exposed organ is sealed with a flap of protective skin It is unknown why this species did not develop transparent skin or eyelids instead as some species of reptiles did The lack of eyes disables the body clock which is controlled by periods of light and dark conserving energy However sunlight does have minimal impact on the body clock in caves citation needed Another likely explanation for the loss of its eyes is that of selective neutrality and genetic drift in the dark environment of the cave the eyes are neither advantageous nor disadvantageous and thus any genetic factors that might impair the eyes or their development can take hold with no consequence on the individual or species Because there is no selection pressure for sight in this environment any number of genetic abnormalities that give rise to the damage or loss of eyes could proliferate among the population with no effect on the fitness of the population Among some creationists the cave tetra is seen as evidence against evolution One argument claims this is an instance of devolution showing an evolutionary trend of decreasing complexity But evolution is a non directional process and while increased complexity is a common effect there is no reason why evolution cannot tend towards simplicity if that makes an organism better suited to its environment 35 Inhibition of the HSP90 protein has a dramatic effect in the development of the blind tetra 36 In the aquarium edit The blind cave tetras seen in the aquarium trade are all based on stock collected in the Cueva Chica Cave in the southern part of the Sierra del Abra system in 1936 7 These were sent to an aquarium company in Texas who soon started to distribute them to aquarists Since then these have been selectively bred for their troglomorphic traits 7 Today large numbers are bred at commercial facilities especially in Asia 8 The blind cave tetra is a hardy species 7 Their lack of sight does not hinder their ability to get food They prefer subdued lighting with a rocky substrate like gravel mimicking their natural environment They become semi aggressive as they age and are by nature schooling fish 37 Experiments have shown that keeping these fish in bright aquarium set ups has no effect on the development of the skin flap that forms over their eyes as they grow See also editList of freshwater aquarium fish speciesReferences edit NatureServe 2013 Astyanax mexicanus IUCN Red List of Threatened Species 2013 e T62191A3109229 doi 10 2305 IUCN UK 2013 1 RLTS T62191A3109229 en Froese R Reyes R D 2023 04 21 Froese R Pauly D eds Synonyms of Astyanax mexicanus De Filippi 1853 FishBase Retrieved 2023 04 21 a b c d e Froese Rainer Pauly Daniel eds 2015 Astyanax mexicanus in FishBase October 2015 version Astyanax mexicanus Integrated Taxonomic Information System Retrieved 1 July 2006 Borowsky Richard 2018 01 22 Cavefishes Current Biology 28 2 R60 R64 doi 10 1016 j cub 2017 12 011 ISSN 1879 0445 PMID 29374443 S2CID 235332375 Palermo LiveScience Elizabeth Blind Cavefish Stops Its Internal Clock Scientific American Retrieved 2022 02 24 a b c d e f g h i j Keene A Yoshizawa M McGaugh S 2016 Biology and Evolution of the Mexican Cavefish Elsevier Science pp 68 69 77 87 ISBN 978 0 12 802148 4 a b c Astyanax mexicanus Seriously Fish Retrieved 2 May 2017 a b c d Gross J B June 2012 The complex origin of Astyanax cave fish BMC Evolutionary Biology 12 105 doi 10 1186 1471 2148 12 105 PMC 3464594 PMID 22747496 a b Jeffery W 2009 Regressive evolution in Astyanax cavefish Annual Review of Genetics 43 25 47 doi 10 1146 annurev genet 102108 134216 PMC 3594788 PMID 19640230 a b Bradic M Beerli P Garcia de Leon F J Esquivel Bobadilla S Borowsky R L 2012 Gene flow and population structure in the Mexican blind cavefish complex Astyanax mexicanus BMC Evolutionary Biology 12 9 doi 10 1186 1471 2148 12 9 PMC 3282648 PMID 22269119 a b Dowling T E Martasian D P Jeffery W R 2002 Evidence for multiple genetic forms with similar eyeless phenotypes in the blind cavefish Astyanax mexicanus Molecular Biology and Evolution 19 4 Oxford University Press OUP Society for Molecular Biology and Evolution smbe 446 455 doi 10 1093 oxfordjournals molbev a004100 PMID 11919286 a b Strecker U Faundez V H Wilkens H 2004 Phylogeography of surface and cave Astyanax Teleostei from Central and North America based on cytochrome b sequence data Molecular Phylogenetics and Evolution 33 2 Academic Press 469 481 doi 10 1016 j ympev 2004 07 001 PMID 15336680 a b Jeffery W R 2005 01 13 Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish Journal of Heredity 96 3 185 196 doi 10 1093 jhered esi028 ISSN 1465 7333 PMID 15653557 a b Moran D Softley R amp Warrant E J 2015 The energetic cost of vision and the evolution of eyeless Mexican cavefish Science Advances 1 8 e1500363 Bibcode 2015SciA 1E0363M doi 10 1126 sciadv 1500363 PMC 4643782 PMID 26601263 Yoshizawa M Yamamoto Y O Quin K E Jeffery W R December 2012 Evolution of an adaptive behavior and its sensory receptors promotes eye regression in blind cavefish BMC Biology 10 108 doi 10 1186 1741 7007 10 108 PMC 3565949 PMID 23270452 Powers Amanda K Berning Daniel J Gross Joshua B 2020 02 06 Parallel evolution of regressive and constructive craniofacial traits across distinct populations of Astyanax mexicanus cavefish Journal of Experimental Zoology Part B Molecular and Developmental Evolution 334 7 8 450 462 Bibcode 2020JEZB 334 450P doi 10 1002 jez b 22932 ISSN 1552 5007 PMC 7415521 PMID 32030873 Gene found that causes eyes to wither in cavefish phys org Retrieved 2020 06 27 a b c Romero A 2009 Cave Biology Life in Darkness Cambridge University Press pp 147 148 ISBN 978 0 521 82846 8 a b Luis Espinasa Patricia Rivas Manzano Hector Espinosa Perez 2001 A New Blind Cave Fish Population of Genus Astyanax Geography Morphology and Behavior Environmental Biology of Fishes 62 1 339 344 doi 10 1023 A 1011852603162 S2CID 30720408 Fumey Julien Hinaux Helene Noirot Celine Thermes Claude Retaux Sylvie Casane Didier 2018 04 18 Evidence for late Pleistocene origin of Astyanax mexicanus cavefish BMC Evolutionary Biology 18 1 43 doi 10 1186 s12862 018 1156 7 ISSN 1471 2148 PMC 5905186 PMID 29665771 WILKENS HORST STRECKER ULRIKE 2003 12 01 Convergent evolution of the cavefish Astyanax Characidae Teleostei genetic evidence from reduced eye size and pigmentation Biological Journal of the Linnean Society 80 4 545 554 doi 10 1111 j 1095 8312 2003 00230 x ISSN 0024 4066 Fumey Julien Hinaux Helene Noirot Celine Thermes Claude Retaux Sylvie Casane Didier 2016 12 16 Evidence for Late Pleistocene origin of Astyanax mexicanus cavefish BMC Evolutionary Biology 18 1 43 bioRxiv 10 1101 094748 doi 10 1186 s12862 018 1156 7 PMC 5905186 PMID 29665771 a b c Retaux S Casane D September 2013 Evolution of eye development in the darkness of caves adaptation drift or both Evodevo 4 1 26 doi 10 1186 2041 9139 4 26 PMC 3849642 PMID 24079393 a b c Soares D Niemiller M L April 2013 Sensory Adaptations of Fishes to Subterranean Environments BioScience 63 4 274 283 doi 10 1525 bio 2013 63 4 7 Lyndon M Coghill C Darrin Hulsey Johel Chaves Campos Francisco J Garcia de Leon Steven G Johnson 2014 Next Generation Phylogeography of Cave and Surface Astyanax mexicanus Molecular Phylogenetics and Evolution 79 368 374 doi 10 1016 j ympev 2014 06 029 PMID 25014568 William R Jeffery Allen G Strickler Yoshiyuki Yamamoto 2003 To See or Not to See Evolution of Eye Degeneration in Mexican Blind Cavefish Integrative and Comparative Biology 43 4 Oxford University Press OUP Society for Integrative and Comparative Biology 531 541 doi 10 1093 icb 43 4 531 PMID 21680461 a b Wilkens H November 2012 Genes modules and the evolution of cave fish Heredity 105 5 413 422 doi 10 1038 hdy 2009 184 PMID 20068586 Protas M Tabansky I Conrad M Gross J B Vidal O Tabin C J Borowsky R April 2008 Multi trait evolution in a cave fish Astyanax mexicanus Evolution amp Development 10 2 196 209 doi 10 1111 j 1525 142x 2008 00227 x PMID 18315813 S2CID 32525015 Jeffery WR 2009 Regressive Evolution in Astyanax Cavefish Annual Review of Genetics 43 25 47 doi 10 1146 annurev genet 102108 134216 PMC 3594788 PMID 19640230 Helfman G S Collete B B Facey D E 1997 The Diversity of Fishes Malden Massachusetts USA Blackwell Science p 315 ISBN 0 86542 256 7 Darwin Charles R 2001 As published 1909 1914 originally published 1859 Chapter 5 Laws of Variation Effects of the Increased Use and Disuse of Parts as Controlled by Natural Selection In Eliot Charles W ed The Origin of Species The Harvard Classics Vol XI New York P F Collier and Son Retrieved 8 February 2024 via Bartleby com Espinasa L Espinasa M June 2005 Why do cave fish lose their eyes A Darwinian mystery unfolds in the dark FindArticles Archived from the original on 2006 05 15 Retrieved 2007 02 13 Espinasa M Espinasa L 2008 Losing Sight of Regressive Evolution Evolution Education and Outreach 1 S4 509 516 doi 10 1007 s12052 008 0094 z Dawkins R 1997 Climbing Mount Improbable New York W W Norton ISBN 0 393 31682 3 Rohner N Jarosz D F Kowalko J E Yoshizawa M Jeffery W R Borowsky R L Lindquist S Tabin C J 2013 Cryptic variation in morphological evolution HSP90 as a capacitor for loss of eyes in cavefish Science 342 6164 1372 1375 Bibcode 2013Sci 342 1372R doi 10 1126 science 1240276 hdl 1721 1 96714 PMC 4004346 PMID 24337296 Mexican Tetra Astyanax mexicanus Ultimate Care Guide Fish Laboratory August 5 2022 Retrieved August 5 2022 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