Astyanax atratoensis

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Astyanax atratoensis
1907 illustration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. atratoensis
Binomial name
Astyanax atratoensis
Eigenmann, 1907

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.

Populations exist at both low and high elevations, and have adapted to their respective surroundings; higher-elevation specimens have deeper bodies than lower-elevation ones. The color pattern, however, remains the same - largely silver, with a reflective silver lateral stripe and a small blotch of pigment on the caudal peduncle. It also has an ovoid humeral spot with vertical elongation, which can be used to differentiate it from similar congeners.

Taxonomy[edit]

Astyanax atratoensis was first described by prolific German-American ichthyologist Carl H. Eigenmann in 1907, with findings published in the relevant edition of the Proceedings of the United States National Museum.[2] The article was co-authored by Fletcher Ogle, a fellow ichthyologist.[3] The type specimen has since gone missing, though when this happened is unknown.[4]

In the nominal article, Eigenmann remarked that A. atratoensis is closely related to congener Astyanax caucanus, which was named by Austrian ichthyologist Franz Steindachner in 1879.[5] Further, it is related to multiple other species of Astyanax that all share the subgenus Zygogaster, to which A. atratoensis was originally designated.[6] More modern interpretations often place it in the subgenus Poecilurichthys.[7][8]

Etymology[edit]

Given that A. atratoensis is endemic to the Atrato River basin in Colombia, its specific epithet originates therein. The genus name "Astyanax" is slightly less clear, as it had no defined reasoning in the original text, but the allusion lies in Homer's Iliad; Astyanax was a warrior of Troy, and the son of prince Hector.[9] One possible reason for such a name is that the scales of type species Astyanax argentatus are large and silvery, such that they could be compared to armor or a shield.[10]

Description[edit]

Astyanax atratoensis is subrhomboidal in body shape, and commonly reaches a maximum length of roughly 10.3 cm (4.1 in) standard length (SL).[9] It is possible for the fish to reach nearly twice that length, however; specimens from a particular delta in the Arato River were as large as 21.5 cm (8.5 in) total length.[11] It is largely an iridescent silver, with a distinct humeral spot of a vertically elongated oval shape. There is a silver lateral stripe that terminates at a small dark blotch on the caudal peduncle.[5]

There are between 35 and 39 rays in the anal fin (depending on the source consulted), which can be used as an identifying characteristic when comparing A. atratoensis to similar congeners.[5][12] The dorsal fin has 10–11 rays,[5] and the predorsal series of scales is incomplete.[8] Though environment can affect morphology, resulting in a deeper body at higher elevations, separate populations of A. atratoensis do not demonstrate differences severe enough to warrant confusion with another species.[6][13]

Distribution and ecology[edit]

Astyanax atratoensis is endemic to its namesake, the Atrato River basin in Colombia. Its type locality is the Truandó River.[1] It can be found at both high and low elevations within the basin, and the environment in which a particular specimen was found can have an impact on its morphology. Specifically, populations of A. atratoensis at higher elevations have a deeper body than those at lower elevations, which are more fusiform. The reasons for this differentiation are unclear, but current hypotheses include differing riparian zones, hydrological features like current speed, and risk of exposure to predatory birds.[13]

Other members of the genus in regions with healthy riparian vegetation tend to be adaptable omnivores that consume plentiful allochthonous material.[14][15] When it comes to the dietary needs and preferences of A. atratoensis in particular, details are sparse.

Conservation status[edit]

Astyanax atratoensis is considered a species of least concern by the IUCN. Despite a somewhat restricted distribution, nothing currently serves as an imminent threat to population levels, and so A. atratoensis is not endangered.[1]

Its native range, however, may face some environmental pressure. The Atrato River basin has a history of severe pollution. Nonetheless, recent action - most notably a court ruling in 2016 - has prompted conservation and cleanup efforts, largely on the part of the Colombian government.[16] The 2016 ruling sought out a different approach to conservation in that, rather than enacting protective legislation, the Colombian Constitutional Court recognized the river as its own distinct entity deserving of protection and restoration, as a human would be; as of 2021, this had resulted in only minor project implementation, with several larger aspects still in the planning stages.[17]

References[edit]

  1. ^ a b c Villa-Navarro, F.; Sanchez-Duarte, P. (2016). "Astyanax atratoensis". IUCN Red List of Threatened Species. 2016: e.T49830326A61473903. doi:10.2305/IUCN.UK.2016-1.RLTS.T49830326A61473903.en. Retrieved 29 April 2023.
  2. ^ Bailly, Nicolas (2017). "Astyanax atratoensis Eigenmann, 1907". WoRMS. World Register of Marine Species. Retrieved 3 May 2023.
  3. ^ Jaime, Villa (1976). "Ichthyology of the Lakes of Nicaragua: Historical Perspective". Investigations of the Ichthyofauna of Nicaraguan Lakes. 8. Retrieved 3 May 2023.
  4. ^ Reis, Roberto E.; Kullander, Sven O.; Ferraris, jr, Carl J. (January 2003). "Genera incertae sedis in Characidae". Checklist of the Freshwater Fishes of South and Central America: 106–169.
  5. ^ a b c d Eigenmann, Carl H.; Ogle, Fletcher (1908). "An annotated list of characin fishes in the United States National Museum and the Museum of Indiana University, with descriptions of new species". Proceedings of the United States National Museum. 33 (1556): 1–33. doi:10.5479/si.00963801.33-1556.1. ISSN 0096-3801. OCLC 1259735. Retrieved 3 May 2023.
  6. ^ a b Ruiz-C., R. I.; Román-Valencia, C.; Herrera-M., B. E.; Peláez, O. E.; Ermakova-A., A. (2011). "Variación morfológica de las especies de Astyanax, subgénero Zygogaster (Teleostei, Characidae)". Animal Biodiversity and Conservation. 34 (1): 47–66. doi:10.32800/abc.2011.34.0047. Retrieved 3 May 2023.
  7. ^ Schmitter-Soto, Juan J. (6 May 2016). "A phylogeny of Astyanax (Characiformes: Characidae) in Central and North America". Zootaxa. 4109 (2): 101. doi:10.11646/zootaxa.4109.2.1.
  8. ^ a b "Astyanax panamensis (Günther 1864)". treatment.plazi.org. Plazi. 11 August 2021.
  9. ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax atratoensis" in FishBase. May 2023 version.
  10. ^ Scharpf, Christopher; Lazara, Kenneth J. (29 December 2022). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (a-g)". The ETYFish Project. Retrieved 3 May 2023.
  11. ^ Correa-Herrera, T.; Jiménez-Segura, L. F.; Barletta, M. (July 2016). "Fish species from a micro-tidal delta in the Caribbean Sea: species from a Colombian Caribbean Estuary". Journal of Fish Biology. 89 (1): 863–875. doi:10.1111/jfb.12860.
  12. ^ 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. doi:10.1080/00222933.2017.1324050.
  13. ^ a b Sosa, Timothy (December 2012). Evolution in Fresh Waters During the Great American Interchange (PhD Dissertation). University of Chicago. doi:10.6082/uchicago.1574. Retrieved 3 May 2023.
  14. ^ 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.
  15. ^ 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.
  16. ^ Ebus, Bram (22 May 2017). "Colombia's constitutional court grants rights to the Atrato River and orders the government to clean up its waters". news.mongabay.com. Mongabay. Retrieved 3 May 2023.
  17. ^ Wesche, Philipp (17 November 2021). "Rights of Nature in Practice: A Case Study on the Impacts of the Colombian Atrato River Decision". Journal of Environmental Law. 33 (3): 531–555. doi:10.1093/jel/eqab021.
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