Astyanax abramis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. abramis
Binomial name
Astyanax abramis
(Jenyns, 1842)

Astyanax abramis is a small freshwater fish from the inland rivers of South America. It is plentiful in almost the entire continent, with a habitat including the La Plata, upper Amazon, and Meta River basins. The body shape is subrhomboidal (somewhat rhomboidal) and laterally compressed, and the scales are largely silver, with a blue or green tint on the dorsal side.

As a cryptic species, A. abramis could possibly constitute multiple species that are currently undescribed. A. abramis is also a part of a species complex that includes itself and various congeners, including Astyanax bimaculatus, the namesake of the complex, and Astyanax lacustris, which is very closely related to A. abramis and looks very similar. Astyanax is a particularly speciose genus wherein cryptics and complexes are not uncommon.

Description

Abramis astyanax is a small fish that has a maximum recorded length of 14.0 cm (5.5 in) in standard length (SL) and a maximum recorded weight of 29.70 g.[1]  The body is compressed laterally and is subrhomboidal. It is a silvery fish with a green or blue tint on the back, and there is a dark spot, starting on the caudal peduncle, that reaches the posterior margin of the caudal fin.[2] Its fins, while largely transparent, can also have a slight red, orange, or yellow tint.[3]

There is a dark humeral spot on each side behind the top of the head ("humeral" means "around or related to the shoulder", as in "humerus"). This spot manifests as a horizontal oval, and the humeral region also sports two vertical brown bars. There is a black lateral stripe, just above the lateral line, that starts at the humeral spot or just behind it.[4]

Morphometric characteristics include 1 dorsal-fin spine, 10 dorsal-fin rays, and 30 to 34 anal-fin rays. A. abramis also has 42 to 48 lateral-line scales; this can be used to differentiate it from closely related congener A. lacustris, which has 36 to 39.[2] The scales are generally small, with concentric grooves near the posterior margin.[3] A. abramis lacks maxillary teeth, which can be used to tell it apart from various other similar congeners;[5] however, the premaxilla still sports teeth, and A. abramis is believed to demonstrate unilateral replacement of missing teeth.[6]

Sexual dimorphism

While there are few morphometric differences between the sexes, male A. abramis can be distinguished from female by the presence of small hooks or barbs on the anal-fin rays of male specimens.[3] Females also tend to be more common than males.[7]

Taxonomy

When first described, A. abramis was given the basionym Tetragonopterus abramis.[8] English naturalist Leonard Jenyns prescribed this name in 1842, building from the work of well-known English natural historian Charles Darwin, who collected the type specimens in the 19th century.[3][9] At one point, it was described as a separate species under the name Bertoniolus paraguayensis, but this name has been synonymized with A. abramis.[10] In 2016, its classification as a species was confirmed as valid, and it received a redescription.[11]

Within Astyanax, there are three subgenera - Astyanax stricto sensu, Poecilurichthys, and Zygogaster.[12] A. abramis belongs to Poecilurichthys.

Multiple species in the genus Astyanax are considered cryptic - that is, two or more possible species that are currently considered synonymous because of remarkable similarity, but that cannot reproduce with each other. A. abramis is no exception to this and is considered a cryptic species.[2] It is also a part of the Astyanax bimaculatus species complex, alongside Astyanax lacustris.[13]

At the time of description, Jupiaba species J. abramoides was believed to be closely related to A. abramis. This is the origin of its specific epithet - "oides" means "having the shape of".[14] The basionym of J. abramoides is, in fact, Astyanax abramoides.[15]

Etymology and nomenclature

The specific name "abramis" is an allusion to European species Abramis brama, a leuciscid that has a similar body shape (described as "subrhomboidal"). The genus name "Astyanax" comes from a figure in Homer's Iliad, Astyanax, who was the son of Hector, a famed Trojan warrior. Why the genus has this name was not made clear in the original text, but could possibly refer to the large, armor-like scales of species A. argentatus.[16]

In terms of a common name, A. abramis is one of various species of Astyanax referred to as "lambari".[2]

Distribution and habitat

Astyanax abramis can be found in the La Plata basin, as well as the upper Amazon and Meta River basins. It is most often found in lentic (still water) environments.[1] Lentic environments, without the oxygenation provided by flowing water, are generally lower in dissolved oxygen, which has resulted in A. abramis developing adaptations to such conditions, including morphological plasticity (albeit limited).[17]

The relevant habitat stretches through multiple countries, including Brazil, Argentina, Bolivia, Uruguay, and Paraguay.[3] Specific rivers, regions, and tributaries include the Juramento,[18] Yabotí,[19] and Parana.[4]

Ecology and biology

In environments of strong hypoxia, A. abramis can develop reversible dermal extensions, possibly as a way to increase the efficacy of aquatic surface respiration (ASR). Previous research on similar traits had revealed a demonstrable link between morphological plasticity and ASR, and this is likely to remain the case in A. abramis.[17] ASR is a trait in many species of fish that need to cope with hypoxic environments.[20]

Astyanax abramis lives in syntopy with sister species A. lacustris.[13] It is also known to live in sympatry with other congeners, including A. puka, A. asuncionensis, A. eigenmanniorum, and A. lineatus, specifically in the Juramento River.[18] Because it is an unspecialized feeder that also eats other fish, sympatry with smaller species is unlikely.[7]

Astyanax abramis is also subject to parasite infestation. The parasitic nematode worm Procamallanus (Spirocamallanus) hilarii has been recorded from a wide variety of neotropical fish species, including A. abramis.[21]

Reproduction

Astyanax abramis has a split spawning season, with higher reproduction activity in April and October. These months correspond with periods of higher water temperature and greater rainfall. In female fish, the length of the body is positively correlated with the size of the ovaries, so a period of greater reproductive activity is likely to have more large female specimens.[7]

Diet

Astyanax abramis is a highly-adaptable omnivore that lives in regions strongly influenced by flood cycles. The intestines can become larger in periods of food scarcity, which allows it to eat items that are more difficult for it to digest, like plant material. Juveniles, being smaller, are not afforded as much flexibility, and as such are sometimes more carnivorous than the omnivorous adults.[7]

Other studies report that the juveniles are more herbivorous than the adults, but this is likely explained by environmental differences;[21] there is also evidence that general food abundance influences diet (such as increased allochthonous plant consumption in areas with plentiful riparian vegetation), which means that the role of A. abramis in the trophic system changes depending on the region.[22] Disregarding age, however, smaller adults also tend to be more carnivorous than larger adults, further diversifying observed feeding habits.[23]

Conservation status

Astyanax abramis has not been evaluated by the IUCN.[1] Given its wide distribution and the fact that it can easily be collected in various locations, it is most likely to be a species of least concern.[3] For instance, in an evaluation of the fish fauna of the Yabotí stream, Hirt et al. ranked A. abramis as the ninth most abundant species, and the Yabotí stream is largely within the protected Yabotí Biosphere Reserve.[19]

References

  1. 1 2 3 Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax Abramis" in FishBase. February 2023 version.
  2. 1 2 3 4 Paiz, Leonardo; Baumgätner, Lucas; Júnio da Graça, Weferson; Margarido, Vladimir (2015-02-09). "Basic cytogenetics and physical mapping of ribosomal genes in four Astyanax species (Characiformes, Characidae) collected in Middle Paraná River, Iguassu National Park: considerations on taxonomy and systematics of the genus". Comparative Cytogenetics. 9 (1): 54–65. doi:10.3897/CompCytogen.v9i1.9002. ISSN 1993-078X. PMC 4387380. PMID 25893074.
  3. 1 2 3 4 5 6 Terán, Guillermo E.; Mirande, J. Marcos (30 March 2019). "Astyanax abramis (Mojarrón)" (PDF). Universo Tucumano (26). ISSN 2618-3161. Retrieved 17 February 2023.
  4. 1 2 "Astyanax abramis". Global Biodiversity Information Facility. Retrieved 17 February 2023.
  5. ↑ Azpelicueta, M. de las Mercedes; Mirande, J. Marcos; Almirón, Adriana E.; Casciotta, Jorge R. (11 September 2003). "A new species of Astyanax (Characiformes, Characidae) from Paraná river basin in Argentina" (PDF). Revista del Museo de la Plata, Zoología. 15 (166): 1–12. Archived from the original (PDF) on 9 July 2020.
  6. ↑ Stuart, Courtney E.; Green, Stephanie J.; Vernygora, Oksana; LeBlanc, Aaron R. H.; Bertschi, Mary H.; Brown, Maria (April 2021). "New insights into patterns and rates of tooth replacement in serrasalmid and characid fishes, with implications for the subsistence fishery of P eru's remote ribereños villages". Journal of Fish Biology. 98 (4): 1196–1201. doi:10.1111/jfb.14634. ISSN 0022-1112. PMID 33249600. S2CID 227236074.
  7. 1 2 3 4 Leite, Erica Ferreira; Godoi, Divina Sueide de; Jacyntho, Luiz Antonio; Maceno, Jhonathan Ferreira Santos; Duarte, Cristiane Regina do Amaral (2021). "FEEDING HABITS AND REPRODUCTIVE BIOLOGY OF ASTYANAX ABRAMIS/HÁBITO ALIMENTAR E BIOLOGIA REPRODUTIVA DE ASTYANAX ABRAMIS". Brazilian Journal of Development. 7 (1): 2582–2597. doi:10.34117/bjdv7n1-176. S2CID 234215105.
  8. ↑ "Astyanax abramis". National Center for Biotechnology Information (NCBI). Retrieved 17 February 2023.
  9. ↑ Pauly, Daniel (17 August 2007). Darwin's Fishes. Cambridge University Press. p. 33. ISBN 9781139451819. Retrieved 17 February 2023.
  10. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Bertoniolus paraguayensis". Catalog of Fishes. California Academy of Sciences. Retrieved 17 February 2023.
  11. ↑ Lucena, Carlos Alberto S. De; Soares, Helena Gouvea (2016-01-28). "Review of species of the Astyanax bimaculatus "caudal peduncle spot" subgroup sensu Garutti & Langeani (Characiformes, Characidae) from the rio La Plata and rio São Francisco drainages and coastal systems of southern Brazil and Uruguay". Zootaxa. 4072 (1): 101–125. doi:10.11646/zootaxa.4072.1.5. ISSN 1175-5334. PMID 27395912.
  12. ↑ 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 (2016-12-19). Rétaux, Sylvie (ed.). "Highlighting Astyanax Species Diversity through DNA Barcoding". PLOS ONE. 11 (12): e0167203. Bibcode:2016PLoSO..1167203R. doi:10.1371/journal.pone.0167203. ISSN 1932-6203. PMC 5167228. PMID 27992537.
  13. 1 2 Teixeira, Thais K. S. S.; Venere, Paulo C.; Ferreira, Daniela C.; Mariotto, Sandra; Castro, Jonathan P.; Artoni, Roberto F.; Centofante, Liano (2018-03-26). "Comparative cytogenetics of Astyanax (Teleostei: Characidae) from the upper Paraguay basin". Neotropical Ichthyology. 16 (1). doi:10.1590/1982-0224-20170092. ISSN 1982-0224.
  14. ↑ Scharpf, Christopher; Lazara, Kenneth J. (15 September 2020). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (h-t)". The ETYFish Project. Retrieved 17 February 2023.
  15. ↑ "Astyanax abramoides". Global Biodiversity Information Facility. Retrieved 17 February 2023.
  16. ↑ Scharpf, Christopher; Lazara, Kenneth J. (29 December 2022). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (a-g)". The ETYFish Project. Retrieved 17 February 2023.
  17. 1 2 Scarabotti, Pablo A.; López, Javier A.; Ghirardi, Romina; Parma, María Julieta (November 2011). "Morphological plasticity associated with environmental hypoxia in characiform fishes from neotropical floodplain lakes". Environmental Biology of Fishes. 92 (3): 391–402. doi:10.1007/s10641-011-9850-y. hdl:11336/100779. ISSN 0378-1909. S2CID 26086109.
  18. 1 2 Terán, Guillermo; Aguilera, Gastón; Mirande, Juan (14 October 2014). "First record of Astyanax puka Mirande, Aguilera & Azpelicueta, 2007 (Teleostei: Characidae) in Juramento River basin, Salta, Argentina". Check List. 10 (5): 1231–1233. doi:10.15560/10.5.1231. hdl:11336/13025.
  19. 1 2 Ojeda, Alejandra Paola; Zapata, Pedro Darío; Hirt, Lourdes M. (June 2012). "Amplificación interespecífica de microsatélites de Astyanax abramis, utilizando cebadores para la especie emparentada Astyanax fasciatus" [Interspecific amplification of Astyanax abramis microsatellites using primers for the related astyanax fasciatus]. Revista de Ciencia y Tecnología (in Spanish) (17). Retrieved 17 February 2023.
  20. ↑ Abdallah, Sara J.; Thomas, Benjamin S.; Jonz, Michael G. (June 2015). "Aquatic surface respiration and swimming behaviour in adult and developing zebrafish exposed to hypoxia". The Journal of Experimental Biology. 218 (Pt 11): 1777–1786. doi:10.1242/jeb.116343. ISSN 1477-9145. PMID 25944921. S2CID 207171848.
  21. 1 2 Gallas, Moisés; Calegaro-Marques, Cláudia; Bencke-Amato, Suzana (September 2015). "Supplemental observations on the morphology of Procamallanus (Spirocamallanus) hilarii (Nematoda: Camallanidae) parasitizing two species of Astyanax (Characiformes: Characidae) and ecological analyses". Revista Mexicana de Biodiversidad. 86 (3): 590–596. doi:10.1016/j.rmb.2015.07.005.
  22. ↑ Thierry, Rejas, D.A. (ed.) Aguirre, L.F. (ed.) Zepita,C. Ibanez,C. Bigorne, Rémy Zubieta,J. Oberdorff (2008). Plasticidad alimenticia de Astyanax abramis (Characidae) en rios de alta y baja conductividad en la subcuenca del Chapare (Cochabamba - Bolivia). UMSS. OCLC 959938976.{{cite book}}: CS1 maint: multiple names: authors list (link)
  23. ↑ Eugenia, Barros, Silvina (2004). Alimentación de Astyanax abramis (Characiformes: Characidae) en el Embalse Cabra Corral, Salta, Noroeste de Argentina. Universidad de Zaragoza: Facultad de Veterinaria. OCLC 803587389.{{cite book}}: CS1 maint: multiple names: authors list (link)
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