Astyanax argentatus

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Astyanax argentatus
Astyanax argentatus illustration (1859).jpg
1859 illustration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. argentatus
Binomial name
Astyanax argentatus
Baird & Girard, 1854

Astyanax argentatus is a small freshwater fish native to northern Central America and southern North America. Given its native range, it is also known as the Texan tetra. Little has been published regarding the feeding habits or behavior of A. argentatus, but it is known to have the northernmost distribution of any member of the genus Astyanax.

Contents

There is debate regarding its status as a species, as it was considered a synonym of the Mexican tetra (A. mexicanus) for 20 years, but it has recently come back into favor as its own distinct entity. Various morphological specifics indicate their separation, though some resources still consider them synonymous. It also has visual similarities to various other members of the genus; its silver scales, single humeral spot, and yellowish or reddish fins are not uncommon features therein.

Taxonomy

Astyanax argentatus was originally the type species of the genus Astyanax , proposed by American scientists Spencer F. Baird and Charles Girard in 1854. [2] In a period from 1900 to roughly 1920, it was momentarily renamed to Tetragonopterus argentatus, and briefly synonymized with Tetragonopterus mexicanus (which is now Astyanax mexicanus). [3] By 1921, ichthyologist Carl H. Eigenmann had undone this, then synonymized two genera under Astyanax - Poecilurichthys and Zygogaster - and labeled them as subgenera; [4] these are still considered valid, along with subgenus Astyanax itself. [5] In its 2017 redescription, A. argentatus was designated a member of subgenus Astyanax, based on a complete predorsal series of scales. [6]

Astyanax is a large and speciose genus that is unlikely to be monophyletic - that is, there is probably more than one distinct lineage in the group, as opposed to a single lineage with a single shared ancestor. There are two currently proposed clades. One is the Astyanax bimaculatus clade, which is itself unlikely to be monophyletic. The other is the Astyanax argentatus clade, which includes A. argentatus itself and the majority of Central and North American congeners, suggesting a closer relationship between the species therein than to others of the genus. [7] This clade is noted as well-supported across various phyletic analyses. [8]

There is ongoing debate as to whether or not A. argentatus should be considered synonymous with congener A. mexicanus. Scientists from 1997 to 2017 marked the two as identical in the phyletic sense. [6] Sources such as the World Register of Marine Species [9] and OBIS [10] still consider the two synonymous, while others cite A. argentatus as valid on its own, such as FishBase, [11] the IUCN, [1] and the Harvard Museum of Comparative Zoology. [12] Amongst the institutions including it as valid is the University of Texas, located in the state from whence A. argentatus was originally described. [13] Given that the resurrection of A. argentatus from synonymy is a relatively recent event, this discrepancy is not surprising.

Etymology

Though the meaning of the scientific name of A. argentatus is understood, the precise reason for such nomenclature was not made clear in the original text. [2] The specific epithet "argentatus", meaning "silver", is almost certainly a simple reference to the large, silvery scales; the genus name "Astyanax" is from Homer's Iliad, wherein Astyanax was a Trojan warrior, the son of prince Hector. Why this name was chosen is a mystery, but it may again originate in the scales, which could be compared to armor or a shield. [14]

Because of its type locality and its native range, A. argentatus is sometimes colloquially referred to as the Texan tetra. [1] [11]

Description

Astyanax argentatus reaches a maximum length of 11.4 cm (4.5 in) standard length (SL). The body is slender, at a mean of 34% SL, and there are between 19 and 23 anal-fin rays, most often 20. [11] There are 10 soft rays in the dorsal fin, and 11–13 rays in each pectoral fin. The head is short, from 23–26% SL, and the eye is large, taking up around a quarter of the head (16–34% of the head's length, with a mean of 28%). There are 32–37 scales in the lateral line, usually 33. [15] The caudal and anal fins are notably long. [2]

The back is darker than the rest of the body, the sides are silver, and the belly is tinted slightly red. Most fins are a faint orange or red-yellow color, and there is a black spot on the caudal peduncle that continues onto the central caudal rays. [6] The anal fin is unpigmented. There is a single humeral spot that demonstrates variation; it can be rectangular, triangular, or indistinct. [15]

Though A. argentatus is visually similar to congener A. mexicanus (the Mexican tetra) in many ways, there are various morphometric differences between the two. These include fewer anal-fin rays in A. argentatus (21–25, modally 23 in A. mexicanus), a more slender body (37% SL in A. mexicanus), and a longer anal fin (14% SL or longer, mean 16% in A. argentatus, vs. 15% SL or shorter, mean 13% in A. mexicanus). [16]

Sexual Dimorphism

On the anal-fin rays of mature males, there are small fleshy protrusions or spines sometimes referred to as nuptial tubercles. In other species of the genus, these are present in different ways; for instance, on Astyanax acatlanensis , some of these tubercles are bifid (vs. all simple in A. argentatus), and they are only present on the pelvic fin of Astyanax rioverde . [11]

Distribution and ecology

The type locality of A. argentatus was reported as the upper tributaries of the Nueces River, in the U.S. state of Texas. [2] Further specimens have been collected from Aramberri, a municipality in the Mexican state of Nuevo León. [15] It remains the northernmost species within the genus Astyanax. [1] It has been described as "a Nearctic representative of a Neotropical clade". [6]

The Nueces River is in a region of low rainfall, but it is fed by various springs and aquifers, which means that it is largely composed of clear and cool water. [17] The riparian vegetation of the region is healthy; [18] little is known about the feeding habits of A. argentatus, but other members of Astyanax near robust riparian zones feed on the resulting plentiful allochthonous material, and are otherwise flexible omnivores. [19]

Conservation status

The IUCN considers A. argentatus a species of least concern. Despite a fragmented population, it is often one of the most frequent species when it is present at surveyed sites, and appears to be adaptable enough for high survivability. [1]

Though the species itself is healthy, some of the habitats of A. argentatus are at minor risk due to human recreational use; for instance, small-scale pollution from nearby hiking trails and campgrounds affects the Nueces River. However, protections have been passed to prevent the usage of personal vehicles, such as ATVs, in various areas relevant to the watershed, which shields the riparian zone and prevents contamination from fuel and exhaust fumes. [18]

Related Research Articles

<i>Astyanax</i> (fish) Genus of fishes

Astyanax is a genus of freshwater fish in the family Characidae of the order Characiformes. Some of these fish, like many of their relatives, are kept as aquarium pets and known collectively as tetras. With around 150 described species and new ones being described yearly, this genus is among the largest of the entire order; Hyphessobrycon also has more than 145 species and which one is larger at any one time depends on whether more species have been recently described in one or the other. The blind and colorless cave tetra of Mexico is a famous member of the genus, but its taxonomic position is disputed: Some recognize it as part of the Mexican tetra and this is supported by phylogenetic evidence, but others recognize the cave form as a separate species, A. jordani.

<i>Carlastyanax</i> Genus of fishes

Carlastyanax aurocaudatus is a small species of freshwater fish in the family Characidae native to the Río Cauca in Colombia. It is the only member of the monotypic genus Carlastyanax, which was named in 1972 specifically for the species by Jacques Géry. Upon description, it was named Astyanax aurocaudatus by Carl H. Eigenmann. There has been debate concerning whether or not the genus should be recognized, but C. aurocaudatus is currently considered a valid species.

<i>Astyanax acatlanensis</i> Species of fish

Astyanax acatlanensis, sometimes called the Acatlán tetra, is a small species of fish from the rivers of Mexico. It is a relatively hardy species that is able to tolerate a variety of water conditions, but is only found in freshwater, never brackish or marine. It is known only from the Río Acatlán, which is its type locality, and the Río Jía, which is a small, unknown river in the Oaxaca region.

<i>Astyanax aeneus</i> Species of fish

Astyanax aeneus, the banded tetra, is a small species of fish native to southern Central America and northern South America. It can be found in a variety of environments, including lakes, rivers, ponds, and slightly brackish locales like lagoons. As well as a varied habitat, it has a varied omnivorous diet: algae, seeds, leaves, insects, and fish fry appear to be the most common.

<i>Astyanax angustifrons</i> Species of fish

Astyanax angustifrons, sometimes referred to as the Campeche tetra, is a small freshwater fish from the rivers of Central and South America. It has a healthy distribution across southern Mexico and northern Guatemala, and is relatively common within its native range. Details regarding its diet and behavior are sparse, but it lives in areas with plentiful riparian vegetation, and most other members of the genus are omnivorous. Its habitat includes places affected by pollution and human activity; nonetheless, it is not endangered.

<i>Astyanax aramburui</i> Species of fish

Astyanax aramburui is a small freshwater fish from the rivers of South America, restricted to a relatively small region within the Paraná and Uruguay river basins of Argentina. It was named after the scientist who established a professional presence for ichthyology in the country, Raúl Arámburu. Considered a near-threatened species by the IUCN, its range includes creeks in a sub-basin affected by various forms of pollution.

<i>Astyanax atratoensis</i> Species of fish

Astyanax atratoensis is a small freshwater fish that occupies the Atrato river basin in Colombia. Originally described from a tributary therein, the Truandó River, it gets its specific epithet from the region. Though it faces no imminent threats, A. atratoensis inhabits waterways with a history of severe environmental pressure in the form of anthropogenic pollution. Several restoration efforts have been undertaken in the relevant regions.

<i>Astyanax bagual</i> Species of fish

Astyanax bagual is a small species of freshwater fish known only from the Taquari-Antas river basin in southern Brazil. It is unusual in the genus Astyanax because mature male specimens display bony hooks on the rays of all fins; in opposition, most others have them on the anal, pelvic, or pectoral fins - sometimes on more than one of these, but very rarely on all fins. It can further be told apart from various congeners by way of dentition and some aspects of coloration, including the presence of two humeral spots instead of one.

<i>Astyanax baileyi</i> Species of fish

Astyanax baileyi is a small freshwater fish native to northern Guatemala. Based on several visual aspects, it was once considered a member of the genus Bramocharax, which is now obsolete, and has since been synonymized with Astyanax. As such, former members of Bramocharax are now a part of Astyanax, like Astyanax bransfordii and Astyanax caballeroi.

<i>Astyanax belizianus</i> Species of fish

Astyanax belizianus is a small freshwater fish native to various regions of Central America. Little is known of its diet or specific environmental preferences, but it was first recorded in Belize. Modern ichthyology has expanded its range into Guatemala and Honduras, where it inhabits various rivers and lake tributaries. It is a silvery fish that may have a slight yellowish tint to its scales. The body is deep, especially in comparison to similar species from the same genus.

<i>Astyanax biotae</i> Species of fish

Astyanax biotae is a small species of freshwater fish native to various localities in Brazil. It primarily eats invertebrates, like copepods and aquatic fly larvae, and its diet also includes seeds, fruits, and filamentous algae. Its scales are largely silver, with a touch of yellow-brown on the back and a hint of blue on the sides. Like many species of Astyanax, it has a humeral spot, which is a blotch of pigmentation in the area above or around the pectoral fin.

<i>Astyanax boliviensis</i> Species of fish

Astyanax boliviensis is a small species of fish native to a handful of rivers in northern Bolivia. Its scientific name is an allusion to its range, which includes the Candelaria, Madidi, and Mamoré rivers. Though it lacks a conservation status from the IUCN, a significant portion of its habitat is contained within the Madidi National Park, one of the largest protected regions in the world.

<i>Astyanax brachypterygium</i> Species of fish

Astyanax brachypterygium is a small species of freshwater fish endemic to a collection of high-elevation streams in Brazil. It was named in 2001 alongside congener Astyanax cremnobates, to which it bears a strong resemblance; physical details help to differentiate between the two. Its scales are a greenish-brown on the back and silver on the belly, with reddish fins and a dark humeral spot. One of its defining features is a notably short anal-fin base, which has 13 to 15 rays.

Astyanax bransfordii, sometimes called the longjaw tetra, is a small carnivorous species of fish endemic to a handful of lakes and slow-moving canals in Central America. Its range includes Lake Nicaragua and Lake Managua, which are two of the largest freshwater bodies in Central America; because it occurs only in the relevant areas of Costa Rica and Nicaragua, the area it actually inhabits is somewhat restricted. Its diet largely consists of various invertebrates and smaller fish. This is in contrast to various other species of Astyanax, which are more often omnivorous.

<i>Astyanax brevimanus</i> Species of fish

Astyanax brevimanus, sometimes referred to as the Quiché tetra, is a small species of freshwater fish native to various locales in Guatemala. Its native range is somewhat restricted, but it is a populous and adaptable species, so there is no risk of it going extinct anytime soon. It is unknown what A. brevimanus eats, or what specific habitats it prefers; current information is largely in the form of physical descriptions, general areas of occurrence, and hypotheses regarding relationships to congeners. Its silvery scales, indistinct humeral (shoulder) spot, and dark caudal-peduncle spot are features not unusual in species of Astyanax.

<i>Astyanax brevirhinus</i> Species of fish

Astyanax brevirhinus is a small species of freshwater fish known only from a river basin in northeastern Brazil. It is somewhat understudied and lacks a conservation status, but it is present in a region that is the subject of an ecological restoration project - the Jequitinhonha River. Specifics of diet and behavior are unknown, though shoaling activity has been observed in laboratory conditions.

<i>Astyanax caballeroi</i> Species of fish

Astyanax caballeroi is a small species of freshwater fish endemic to a single lake system in Mexico. It has a longer snout and more slender body than most other species in the genus Astyanax, thought to be the result of predatory behavior; while A. caballeroi eats invertebrates and smaller fish, other Astyanax species are more broadly omnivorous, and have deeper bodies with shorter snouts. This difference in body shape once placed A. caballeroi, along with several other species of Astyanax, into the former genus Bramocharax.

Astyanax apiaka is a small freshwater fish endemic to the Apiacá river in Mato Grosso, Brazil. Its discovery is recent, as of 2023, which results in little published research of its natural behaviors or preferred biotopes. However, descriptions of its appearance and general environment have been solidified, as well as some baseline information regarding its diet. It lacks a conservation status from the IUCN.

<i>Astyanax chaparae</i> Species of fish

Astyanax chaparae, sometimes called the Chapare tetra, is a small species of freshwater fish only found in Bolivia. It is endemic to its type locality, the Río Chapare, which is a tributary of the Mamoré located in the Cochabamba department. Little else is known of its diet, behavior, and ecology. Its conservation status is similarly unclear, as the IUCN ranks it a data deficient species.

<i>Astyanax clavitaeniatus</i> Species of fish

Astyanax clavitaeniatus is a small species of freshwater fish native to various rivers in the Amazon basin. It is characterized by a club-shaped lateral stripe, which is where it gets its scientific name; "clava" means "club", and "taenia" means "stripe". It is a deep-bodied fish with a silvery base color, which is not uncommon for members of Astyanax. Its markings - including a humeral spot and two vertical brown bars - indicate that it is a part of a species complex centered around congener Astyanax bimaculatus.

References

  1. 1 2 3 4 5 Schmitter-Soto, J. (2019). "Astyanax argentatus". IUCN Red List of Threatened Species . 2019: e.T132562408A132564213. doi: 10.2305/IUCN.UK.2019-2.RLTS.T132562408A132564213.en . Retrieved 18 April 2023.
  2. 1 2 3 4 Baird, S. F.; Girard, Charles (March 1854). "Descriptions of new species of Fishes collected in Texas, New Mexico and Sonora, by Mr. John H. Clark, on the U. S. and Mexican Boundary Survey, and in Texas by Capt. Stewart Van Vliet, U. S. A." Proceedings of the Academy of Natural Sciences of Philadelphia. 7: 26–27. Retrieved 21 April 2023.
  3. ↑ Godman, Frederick Du Cane; Horman-Fisher, Maud; Knight, H.; Salvin, Osbert; Saunders, G. S.; Schlereth, M. v.; Sharp, M. A.; Wilson, Edwin; Wulp, F. M. van der (1879). Biologia Centrali-Americana :zoology, botany and archaeology. [London: Published for the editors by R. H. Porter]. pp. 171–172. doi:10.5962/bhl.title.730 . Retrieved 20 April 2023.
  4. ↑ Eigenmann, Carl H.; Myers, George S. (July 1921). "The American Characidae". Memoirs of the Museum of Comparative Zoölogy at Harvard College. 43 (3): 227–232. doi: 10.5962/bhl.title.49183 . Retrieved 21 April 2023.
  5. ↑ Rossini, Bruno César; Oliveira, Carlos Alexandre Miranda; Melo, Filipe Augusto Gonçalves de; Bertaco, Vinicius de Araújo; Astarloa, Juan M. Díaz de; Rosso, Juan J.; Foresti, Fausto; Oliveira, Claudio (19 December 2016). "Highlighting Astyanax Species Diversity through DNA Barcoding". PLOS ONE. 11 (12): e0167203. Bibcode:2016PLoSO..1167203R. doi: 10.1371/journal.pone.0167203 . PMC   5167228 . PMID   27992537.
  6. 1 2 3 4 Schmitter-Soto, Juan J. (26 June 2017). "A revision of Astyanax (Characiformes: Characidae) in Central and North America, with the description of nine new species". Journal of Natural History. 51 (23–24): 1331–1424. Bibcode:2017JNatH..51.1331S. doi:10.1080/00222933.2017.1324050. S2CID   90642754.
  7. ↑ Terán, Guillermo E; Benitez, Mauricio F; Mirande, J Marcos (11 April 2020). "Opening the Trojan horse: phylogeny of Astyanax, two new genera and resurrection of Psalidodon (Teleostei: Characidae)". Zoological Journal of the Linnean Society. 190 (4): 1217–1234. doi:10.1093/zoolinnean/zlaa019.
  8. ↑ Mirande, Juan Marcos (June 2019). "Morphology, molecules and the phylogeny of Characidae (Teleostei, Characiformes)". Cladistics. 35 (3): 282–300. doi: 10.1111/cla.12345 . hdl: 11336/86318 . PMID   34622981.
  9. ↑ Bailly, Nicolas (2020). "Astyanax argentatus Baird & Girard, 1854". WoRMS. World Register of Marine Species . Retrieved 21 April 2023.
  10. ↑ "Astyanax argentatus Baird & Girard, 1854". Ocean Biodiversity Information System. UNESCO. Retrieved 21 April 2023.
  11. 1 2 3 4 Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax argentatus" in FishBase . April 2023 version.
  12. ↑ "Astyanax argentatus Baird & Girard, 1854". MCZBase. Harvard Museum of Comparative Zoology. Retrieved 21 April 2023.
  13. ↑ Cohen, Adam E. (9 February 2023). "Fishes of Texas Project Documentation - Scientific Names". qual.wikis.its.utexas.edu. University of Texas at Austin. Retrieved 21 April 2023.
  14. ↑ Scharpf, Christopher; Lazara, Kenneth J. (28 December 2023). "Family CHARACIDAE: Subfamily STETHAPRIONINAE Eigenmann 1907 (American Tetras)". The ETYFish Project. Retrieved 27 January 2023.
  15. 1 2 3 "Astyanax argentatus Baird and Girard 1854". treatment.plazi.org. Plazi. Retrieved 21 April 2023.
  16. ↑ "Astyanax mexicanus (de Filippi 1853)". treatment.plazi.org. Plazi. Retrieved 21 April 2023.
  17. ↑ "River Basins - Nueces River Basin". www.twdb.texas.gov. Texas Water Development Board. Retrieved 21 April 2023.
  18. 1 2 "Nueces River". txrivers.org. Texas Rivers Protection Association. 3 January 2022. Retrieved 21 April 2023.
  19. ↑ Vilella, Fábio Silveira; Becker, Fernando Gertum; Hartz, Sandra Maria (June 2002). "Diet of Astyanax species (Teleostei, Characidae) in an Atlantic Forest River in Southern Brazil". Brazilian Archives of Biology and Technology. 45 (2): 223–232. doi:10.1590/S1516-89132002000200015. hdl: 10183/78925 .
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