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Astyanax bourgeti

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Astyanax bourgeti
1917 illustration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. bourgeti
Binomial name
Astyanax bourgeti
Eigenmann, 1908

Astyanax bourgeti is a small species of freshwater fish native to the upper Amazon river in Brazil. Originally described in 1908, it is not a particularly well-studied member of the genus Astyanax, but there is enough information available to establish a native range, an appearance, and potential relationships to congeners; for example, A. bourgeti is a known member of the subgenus Poecilurichthys, and has been considered such for most of its existence. Biotope preferences, sympatry, diet, and behavior are all unknown.

Its gray scales, dark humeral spot, and silver lateral stripe are not uncommon features within the genus, but A. bourgeti can be told apart from congeners by means including the number scales in the lateral line and the number of anal-fin rays. It also has a smaller, silver spot slightly above and behind the normal humeral spot, which isn't as common as its other markings. Besides this, it also has darkened anal, pelvic, and ventral fins, which are somewhat unusual for a species of Astyanax.

Taxonomy

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Astyanax bourgeti was originally described by German-American ichthyologist Carl H. Eigenmann in 1908, as one of various nomenclatural acts performed based upon the Thayer Expedition to Brazil, which was an 1865 trip directed by Swiss-American biologist Louis Agassiz.[2][3] Since then, its scientific name has not changed, and it has no known synonyms, with the exception of an occasional reference as A. boulengeri instead.[4][5]

There are three subgenera in Astyanax (Astyanax, Poecilurichthys, and Zygogaster);[6] of these, A. bourgeti belongs to Poecilurichthys.[7]

Etymology

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The specific name "bourgeti" is to honor the collaborator responsible for collecting the type specimens, a French naturalist living in Rio de Janeiro simply credited as "Monsieur Bourget" in the original description and as "D. Bourget" in the accounts of the original voyage to Brazil.[3][8] Further research unearths naturalist Jean-Baptiste Dieudonné Bourget as the likely identity of this namesake.[9][10]

Astyanax bourgeti lacks a common name, but is one of various small fishes referred to as "sardinita" in Spanish and "piaba" in Portuguese.[11][12]

Description

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Astyanax bourgeti reaches 9.2 cm (3.6 in) total length.[13] The snout is pointed, and the jaw is roughly the same length as the eye. There are 11 rays on the dorsal fin, 34 rays on the anal fin, and roughly 53 scales in the lateral line.[14] The high number of lateral-line scales is a feature shared with congeners Astyanax cordovae and Astyanax microlepis,[15] as well as Astyanax elachylepis; the lattermost of these can be readily differentiated from A. bourgeti due to the lower number of anal-fin rays on A. elachylepis.[16] Sexual dimorphism is unknown.

Astyanax bourgeti is a base silver color, and has a distinct dark humeral spot in a flattened oval shape, with a smaller silvery spot above the upper-back edge of the first. It has a narrow lateral stripe in rather faint silver. Its anal fin is a uniform dark color, and its pectoral and ventral fins also sport conspicuous pigmentation, though not as uniform.[3] There is no spot on the caudal peduncle directly, which can help differentiate A. bourgeti from some congeners, but the middle rays of the caudal fin remain darkened.[17] There may be an "echo" of the humeral spot behind the first, not often well-defined; this marking is shared with several species known to be in the Astyanax bimaculatus species complex, such as Astyanax abramis and Astyanax orthodus, which both demonstrate a well-defined humeral spot and faint vertical bars in the humeral region.[18]

Distribution and ecology

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Astyanax bourgeti is a species endemic to the Amazon basin, found only within the main channel of the Amazon river.[19] Specifically, it is found in the upper Amazon, in the portions sometimes referred to as the Solimões.[20] The type specimen was originally collected from the Solimões at Tabatinga, Brazil, in 1865.[13] Little is known of specific biotope preferences, or of diet and sympatry.

The Solimões river is an alluvial river with heavy sediment carry. (Alluvial rivers are rivers without a single set form, due to flowing through loose substrate that is easily affected by floods in the region.) Its channels have not demonstrated high amounts of movement, as they are held in by the cliffs of the Alter do Chão Formation.[21] The sediments carried in the Solimões are often rich in nutrients, which contributes to the biodiversity of the Amazon.[22]

Conservation status

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Astyanax bourgeti has been evaluated by the IUCN Red List as "Least Concern".[1] The Brazilian ecological organization Chico Mendes Institute for Biodiversity Conservation gave it a data deficient listing in 2014 due to its generally understudied nature.[12] There is already security for the species, however, in the form of the Central Amazon Conservation Complex, which has its approximate center at the confluence of the Solimões and Negro rivers.[23] Because of the region's protected status, the area - and therefore A. bourgeti - is not at particular risk, as far as conservation goes.[24]

References

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  1. ^ a b Lima, F. (2023). "Astyanax bourgeti". IUCN Red List of Threatened Species. 2023: e.T49830034A159049252. doi:10.2305/IUCN.UK.2023-1.RLTS.T49830034A159049252.en. Retrieved 7 May 2024.
  2. ^ "Astyanax bourgeti Eigenmann, 1908". www.zoobank.org. International Commission on Zoological Nomenclature. Retrieved 6 June 2023.
  3. ^ a b c Eigenmann, Carl H. (1908). "Preliminary descriptions of new genera and species of tetragonopterid characins. (Zoölogical Results of the Thayer Brazilian expedition.)". Bulletin of the Museum of Comparative Zoology at Harvard College. 52 (6): 95–96. Retrieved 6 June 2023.
  4. ^ Bailly, Nicolas (2017). "Astyanax bourgeti Eigenmann, 1908". WoRMS. World Register of Marine Species. Retrieved 6 June 2023.
  5. ^ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Astyanax bourgeti". Catalog of Fishes. California Academy of Sciences. Retrieved 6 June 2023.
  6. ^ 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. PMC 5167228. PMID 27992537.
  7. ^ Riuz-C, Raquel I.; Román-Valencia, César; Taphorn, Donald C.; Buckup, Paulo A.; Ortega, Hernán (8 February 2018). "Revision of the Astyanax orthodus species-group (Teleostei: Characidae) with descriptions of three new species". European Journal of Taxonomy (402). doi:10.5852/ejt.2018.402.
  8. ^ Scharpf, Christopher; Lazara, Kenneth J. (29 December 2022). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (a-g)". The ETYFish Project. Retrieved 30 May 2023.
  9. ^ Antunes, Anderson Pereira (2015). A rede dos invisíveis: uma análise dos auxiliares na expedição de Louis Agassiz ao Brasil (1865-1866) (PDF) (Master's). Oswaldo Cruz Foundation. Retrieved 6 June 2023.
  10. ^ Antunes, Anderson Pereira; Massarani, Luisa Medeiros; Moreira, Ildeu de Castro (19 June 2016). "Uma análise da rede de auxiliares na expedição de Louis Agassiz ao Brasil (1865-1866)". Revista Brasileira de História da Ciência. 9 (1): 111–125. doi:10.53727/rbhc.v9i1.149.
  11. ^ "Astyanax bourgeti Eigenmann 1908". Encyclopedia of Life. National Museum of Natural History.
  12. ^ a b "Astyanax bourgeti Eigenmann, 1908". ala-bie.sibbr.gov.br. Brazilian Biodiversity Information System. Retrieved 6 June 2023.
  13. ^ a b Black, Nina. "MCZ Ichthyology 89557". mczbase.mcz.harvard.edu. Harvard Museum of Comparative Zoology. Retrieved 6 June 2023.
  14. ^ Eigenmann, Carl H.; Myers, George S. (1917). "The American Characidae / by Carl H. Eigenmann". Memoirs of the Museum of Comparative Zoology at Harvard College. 43 (3): 244–245. doi:10.5962/bhl.title.49183. Retrieved 6 June 2023.
  15. ^ da Graça, W. J.; Oliveira, C. A. M.; Lima, F. C. T.; da Silva, H. P.; Fernandes, I. M. (October 2017). "A new species of Astyanax (Characiformes: Characidae) from Dolina Água Milagrosa, Rio Paraguai basin, Mato Grosso, Brazil: a new astyanax from rio paraguai basin". Journal of Fish Biology. 91 (4): 1123–1138. doi:10.1111/jfb.13405. PMID 28868674.
  16. ^ Bertaco, Vinicius A.; Lucinda, Paulo H. F. (September 2005). "Astyanax elachylepis, a new characid fish from the rio Tocantins drainage, Brazil (Teleostei: Characidae)". Neotropical Ichthyology. 3 (3): 389–394. doi:10.1590/S1679-62252005000300006.
  17. ^ Garutti, Valdener (1998). "Descrição de Uma Espécie Nova de Astyanax (Teleostei, Characidae) da Bacia do Tocantins, Brasil" [Description Of A New Species Of Astyanax (Teleostei, Characidae) From Tocantins Basin]. Iheringia (in Portuguese). 85. Pôrto Alegre: Museu Rio-Grandense de Ciências Naturais: 121. Retrieved 6 June 2023.
  18. ^ Costa, Wilson J.E.M. (1995). "Description of a new species of the genus Astyanax (Characiformes: Characidae) from the rio Araguaia basin, Brazil". Revue suisse de zoologie. 102: 257–262. doi:10.5962/bhl.part.80464. Retrieved 6 June 2023.
  19. ^ Dagosta, Fernando C.P.; Pinna, Mário De (13 June 2019). "The Fishes of the Amazon: Distribution and Biogeographical Patterns, with a Comprehensive List of Species". Bulletin of the American Museum of Natural History. 2019 (431): 72. doi:10.1206/0003-0090.431.1.1. S2CID 196645665. Retrieved 6 June 2023.
  20. ^ Froese, Rainer; Pauly, Daniel (eds.). "Astyanax bourgeti". FishBase. June 2023 version.
  21. ^ Ianniruberto, Marco; Trevethan, Mark; Pinheiro, Arthur; Andrade, Joao Fernando; Dantas, Elton; Filizola, Naziano; Santos, André; Gualtieri, Carlo (January 2018). "A field study of the confluence between Negro and Solimões Rivers. Part 2: Bed morphology and stratigraphy". Comptes Rendus Geoscience. 350 (1–2): 43–54. doi:10.1016/j.crte.2017.10.005.
  22. ^ Administrator, NASA Content (7 August 2017). "Solimões and Negro Rivers". www.nasa.gov. National Aeronautics and Space Administration. Retrieved 6 June 2023.
  23. ^ Centre, UNESCO World Heritage. "Central Amazon Conservation Complex". whc.unesco.org. UNESCO World Heritage Centre. Retrieved 6 June 2023.
  24. ^ "Central Amazon Conservation Complex | World Heritage Outlook". worldheritageoutlook.iucn.org. IUCN World Heritage Outlook. Retrieved 6 June 2023.
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