Biology:Astyanax argyrimarginatus

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Short description: Species of fish

Astyanax argyrimarginatus
Astyanax argyrimarginatus.png
Scientific classification edit
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. argyrimarginatus
Binomial name
Astyanax argyrimarginatus
Garutti, 1999

Astyanax argyrimarginatus is a small species of freshwater fish native to various river basins in Brazil . Originally thought to be restricted to the Tocantins-Araguaia river system, a study in 2012 expanded its range to include the Rio Xingu, as well. Specific biotope preferences are unknown, but it is mostly collected from clearwater streams in fairly good health. Its relative abundance and presence in some protected locales means that it is not endangered.

This species is a part of a complex centered around congener Astyanax bimaculatus. Visually, it bears similarities to other species also within the complex, including reddish fins and a dark humeral spot, but its most distinguishing feature is a black lateral stripe with bright-silver edges. This stripe is the origin of its scientific name, which means "silver border".[1]

Taxonomy

Astyanax argyrimarginatus was originally described in 1999 by Brazilian ichthyologist Valdener Garutti. Given morphological similarities to various other members of the genus, Garutti assigned the species to the Astyanax bimaculatus species complex, which is where it remains today, alongside various other species.[2] It has no known synonyms.[3]

In genetic research, A. argyrimarginatus has been found to have karyotypic (chromosomal) similarities with congeners A. bimaculatus and A. altiparanae. This is not unusual, considering that A. altiparanae is in the A. bimaculatus species complex with the other two.[4] It is unlikely, however, that A. argyrimarginatus is synonymous with any known species; it can be identified strongly and without confusion through genetic information, using a technique known as DNA barcoding.[5]

Etymology

The specific epithet originates in Greek. The word "argyros" means "silver", and "marginatus" means "bordered"; this is in reference to the silver lining around the black lateral stripe. The genus name, Astyanax, is an allusion to the Iliad, in which a Trojan warrior named Astyanax appeared. The reason for this allusion was not made clear in the nominal text, but it may originate in the scales of type species Astyanax argentatus, which are large and silver, like armor or a shield.[1]

In terms of a common name, A. argyrimarginatus is one of many species of small fish sometimes referred to as "lambari" in South America.[6]

Description

A preserved specimen of Astyanax argyrimarginatus. Note the silver outline on the lateral stripe, which is still visible upon preservation.

Astyanax argyrimarginatus reaches a maximum of 4.5 cm (1.8 in) standard length (SL).[7] There are 42–46 scales in the lateral line, 27–31 rays in the anal fin, and a single tooth in the maxillary bone; the premaxilla sports multiple multicuspid teeth.[2] The head averages a length of 26.8% of the body, and the eye is large, taking up 34–38% of the head's length.[8]

The scales are silver. The fins are largely red, with more intense coloration on the caudal fin and on the front rays of the anal fin.[8] There is a dark humeral spot in the shape of a horizontal oval, and two dark-brown vertical bars in the same region of the body. A dark blotch of color on the caudal peduncle extends to the tips of the middle caudal-fin rays. Perhaps the most distinctive feature is the dark lateral stripe, which has a bright silver border.[2]

Sexual Dimorphism

On the anal fins of males larger than 7.5 cm (3.0 in), bony hooks are present. This is a feature not uncommon in the entire family Characidae.[8] Otherwise, few morphometric or coloration differences can be discerned upon examination. Some congeners demonstrate more dramatic instances of sexual dimorphism, such as A. aramburui; mature males therein bear the same bony hooks, but they also grow small fleshy protrusions on the head and scales.[9]

Distribution and ecology

A preserved specimen of Astyanax argyrimarginatus, captured from the rio Araguaia basin.

Astyanax argyrimarginatus was originally described from the Araguaia River basin of Brazil.[2] Its range also includes the Tocantins and Xingu river basins, in the Brazilian states of Goiás and Mato Grosso. The Xingu is a more recent addition, from a study of the species' geographical range in 2012.[8] Generally, it can be found in river headwaters and in various small streams.[6]

The Araguaia and Tocantins rivers are a part of a single river system, despite differing ecotypes. The Tocantins is relatively clear, with rapids and waterfalls;[10] the Araguaia is muddy and winding, part of the local floodplains.[11] The Xingu is another clearwater river, and it runs through the stony areas of the Brazilian geoscape.[12]

Little is known regarding the physiology and feeding habits of A. argyrimarginatus. Other members of the genus are generally adaptable omnivores, and are not shy of allochthonous material;[13][14] this may remain the case for A. argyrimarginatus, but specifics are sparse.

Conservation status

Astyanax argyrimarginatus is considered a species of least concern by the IUCN. Though its habitat includes some locations affected by human development and pollution, no threats are of direct importance to the population as a whole.[6]

A specific example of threatened habitat for A. argyrimarginatus is the Xingu river, which is the subject of various infrastructure projects. One project with notable impact on the Xingu as a whole is the Belo Monte dam, which radically altered the flow of the river upon construction.[15] Agriculture and the corresponding deforestation also pose a threat to the health of the riparian zone, not just the waters.[16] On the other hand, a great deal of the Xingu is contained within the protected Xingu National Park and Indigenous Peoples Preserve, which was put in place as a protective measure for various indigenous cultures and the biodiversity of the region.[17]

References

  1. ↑ 1.0 1.1 Scharpf, Christopher; Lazara, Kenneth J. (28 December 2023). "Family CHARACIDAE: Subfamily STETHAPRIONINAE Eigenmann 1907 (American Tetras)". https://etyfish.org/stethaprioninae/. 
  2. ↑ 2.0 2.1 2.2 2.3 Garutti, V. (November 1999). "Descrição de Astyanax argyrimarginatus sp. n. (Characiformes, Characidae) procedente da bacia do Rio Araguaia, Brasil". Revista Brasileira de Biologia 59 (4): 585–591. doi:10.1590/S0034-71081999000400008. PMID 23505647. 
  3. ↑ Bailly, Nicolas. "Astyanax argyrimarginatus Garutti, 1999". WoRMS. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=1010297. 
  4. ↑ Tenório, Renata Cristina Claudino de Oliveira; Vitorino, Carla de Andrade; Souza, Issakar Lima; Oliveira, Claudio; Venere, Paulo Cesar (September 2013). "Comparative cytogenetics in Astyanax (Characiformes: Characidae) with focus on the cytotaxonomy of the group". Neotropical Ichthyology 11 (3): 553–564. doi:10.1590/S1679-62252013000300008. 
  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. doi:10.1371/journal.pone.0167203. PMID 27992537. 
  6. ↑ 6.0 6.1 6.2 Cite error: Invalid <ref> tag; no text was provided for refs named IUCN
  7. ↑ Froese, Rainer and Pauly, Daniel, eds. (2023). "Astyanax argyrimarginatus" in FishBase. April 2023 version.
  8. ↑ 8.0 8.1 8.2 8.3 Andrade, Marcelo; Bastos, Douglas; Giarrizzo, Tommaso (1 August 2012). "Astyanax argyrimarginatus Garutti, 1999 (Characiformes: Characidae): first Xingu basin distribution record and geographic distribution map". Check List 8 (4): 802. doi:10.15560/8.4.802. 
  9. ↑ Protogino, Lucila C.; Miquelarena, Amalia M.; López, Hugo L. (17 August 2006). "A new species of Astyanax (Teleostei, Characiformes, Characidae), with breeding tubercles, from the Paraná and Uruguay river basins". Zootaxa 1297: 1. doi:10.11646/zootaxa.1297.1.1. 
  10. ↑ "Tocantins-Araguaia River System (Brazil)". Latin America and Caribbean Geographic. 10 June 2022. https://lacgeo.com/tocantins-araguaia-river-system-brazil. 
  11. ↑ "Araguaia & Tocantins Rivers" (in en). International Rivers Archive. https://archive.internationalrivers.org/campaigns/araguaia-tocantins-rivers. 
  12. ↑ Sidagis-Galli, C.; Abe, Ds.; Rodrigues-Filho, Jl.; Blanco, Fp.; Medeiros, Gr.; Faria, Crl.; Tundisi, Jg. (August 2015). "Ionic characterization of the Xingu River water's in the region of the future UHE Belo Monte (PA)". Brazilian Journal of Biology 75 (3 suppl 1): 30–33. doi:10.1590/1519-6984.03314BM. PMID 26691073. 
  13. ↑ 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. 
  14. ↑ Souza, Rosangela Guarisso de; Lima-Junior, Sidnei Eduardo (6 May 2013). "Influence of environmental quality on the diet of Astyanax in a microbasin of central western Brazil". Acta Scientiarum Biological Sciences 35 (2): 179–184. doi:10.4025/actascibiolsci.v35i2.15570. 
  15. ↑ Hansen, Kathryn (6 October 2017). "Reshaping the Xingu River" (in en). NASA Earth Observatory Archive. https://earthobservatory.nasa.gov/images/91083/reshaping-the-xingu-river. 
  16. ↑ Durigan, Giselda; Guerin, Natalia; da Costa, José Nicola Martorano Neves (5 June 2013). "Ecological restoration of Xingu Basin headwaters: motivations, engagement, challenges and perspectives". Philosophical Transactions of the Royal Society B: Biological Sciences 368 (1619): 20120165. doi:10.1098/rstb.2012.0165. PMID 23610171. 
  17. ↑ "Xingu National Park" (in en). NASA Earth Observatory Archive. 11 August 2003. https://earthobservatory.nasa.gov/images/3693/xingu-national-park. 

Wikidata ☰ Q2885159 entry



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