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Astyanax cordovae

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Astyanax cordovae
  1917 illustration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Acestrorhamphidae
Genus: Astyanax
Species:
A. cordovae
Binomial name
Astyanax cordovae
Günther, 1880

Astyanax cordovae is a small species of freshwater fish only found in Argentina. Its range is restricted to the Primero and Segundo rivers at low elevations, and it is an infrequent sighting therein. This makes it unique, as the only fish species endemic to the region. Most of its time is spent near the riverbed. It is an omnivore with a preference for land-dwelling insects that get washed into the river from shore.

While A. cordovae has a limited collection of species-specific research, conservationists are certain that it is a threatened species. This is not only due to its limited range but also because that range is decreasing. A variety of factors are at play, such as exploitation of biological resources and the destruction of riparian zones. Further, there are no protections in place for it.

Taxonomy

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Astyanax cordovae was originally described as Tetragonopterus cordovae by prolific zoologist Albert Günther in 1880.[2][3] It was placed into the genus Astyanax by ichthyologists Barton Warren Evermann and William Converse Kendall in 1906, and has retained that designation since.[4] It received a minor redescription from German-American ichthyologist Carl H. Eigenmann in 1921, in which Eigenmann respecified the fin-ray and scale counts.[5]

Specimens of congener Astyanax rutilus may have mistakenly been catalogued as A. cordovae in the past.[5]

Etymology

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The specific epithet cordovae originates in the Argentine province from which the species was described, Córdoba. The generic name Astyanax has origins in the Iliad, a Greek epic poem in which Astyanax was a great warrior, but the source text did not provide a reason for this choice of name; one possibility is the large silver scales of type species A. argentatus, and their resemblance to polished armor.[6][7]

While it lacks a species-specific common name widely accepted by the scientific community, A. cordovae is one of multiple species referred to as a "mojarra" in Spanish.[8] "Cordoba tetra" or "Cordoba astyanax" have been suggested based upon the type locality and range.

Description

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Astyanax cordovae is a fish commonly 3–5 in (7.6–12.7 cm) long, sometimes described as the largest of the genus.[9][10] It has a body roughly 1–1.7 in (2.5–4.3 cm) deep.[3] The caudal peduncle – the joint where the tail fin attaches – is 1/3rd as deep as the body.[5] There are 43-45 scales in the lateral line, which is a high number for the genus but not uncommon; other congeners with 43 or more scales in the lateral line include A. microlepis, A. maximus, and A. multidens.[11][12]

The general body color in life is silvery-gray with an unclear lateral stripe. There is a diffuse humeral spot that Günther noted was not always present in the original description;[3] in the years since, having a humeral spot has become part of the identifying criteria.[9] Upon preservation in alcohol, the body color becomes a reflective yellow and the lateral stripe becomes further diffuse. The humeral spot, while unclear, remains visible.[13]

Astyanax cordovae demonstrates sexual dimorphism. Mature males have small bony hooks on the fin-rays of the anal and pelvic fins, which is a common feature of the genus.[9]

Distribution and habitat

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Astyanax cordovae has a restricted range, native only to the Primero River and Segundo River of Argentina.[14] It considered the only fish endemic to the region.[15] It can most frequently be found in the elevation range from sea level up to 600 meters.[16] It is generally benthopelagic, which means that it spends most of its time close to the riverbed.[6]

The Primero River is a large river with a long history of flooding.[17] The Segundo river runs through rocky terrain formed by volcanic activity,[18] with a sediment load consisting of clays, silts, and fine sands. The Primero and Segundo rivers both flow into Mar Chiquita, the largest lake in Argentina.[19] The riparian zone is largely woodland, with notable agricultural use.[20]

Diet and ecology

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Astyanax cordovae is an omnivore with a strong preference for invertebrates of various kinds. In the Primero river specifically, A. cordovae subsists largely on a diet of algae and arthropods, with seasonal variation in the origins of its prey (aquatic vs flying vs terrestrial); terrestrial arthropods make up most of its diet in the spring, taken over by aquatic larvae in the summer.[10]

Astyanax cordovae's range overlaps with several congeners, including A. eigenmannorum and A. asuncionensis.[10][21] Its range also overlaps with Paslidodon hermosus, which was originally a member of Astyanax but was redesignated.[21][22]

Conservation status

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When assessed by the IUCN in 2007, A. cordovae was designated a vulnerable species due to habitat loss and competition from introduced and invasive species. Water pollution from pesticides and from the city of Cordoba also plays a part in its decreasing habitat quality.[1] An earlier report from 2001 placed emphasis on A. cordovae's restricted range, and considered it a vulnerable species of highest priority.[23] A more recent report in 2021, published by the National University of Cordoba and released by the province's government, classified it as critically endangered.[24]

References

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  1. ^ a b Reis, R.; Lima, F. (2009). "Astyanax cordovae". IUCN Red List of Threatened Species. 2009: e.T167776A6380672. doi:10.2305/IUCN.UK.2009-2.RLTS.T167776A6380672.en. Retrieved 14 June 2025.
  2. ^ Bailly, Nicolas (16 November 2020). "Astyanax cordovae (Günther, 1880)". WoRMS. World Register of Marine Species. Retrieved 13 June 2025.
  3. ^ a b c Günther, Albert (1880). "A contribution to the knowledge of the fish fauna of the Rio de la Plata". The Annals and magazine of natural history; zoology, botany, and geology. 6 (5): 12–13. Retrieved 14 June 2025.
  4. ^ Evermann, Barton Warren; Kendall, William Converse (1906). "Notes on a collection of fishes from Argentina, South America, with descriptions of three new species". Proceedings of the United States National Museum. 31 (1482): 82. doi:10.5479/si.00963801.31-1482.67. Retrieved 14 June 2025.
  5. ^ a b c Eigenmann, Carl H.; Meyers, George S. (1921). "The American Characidae". Memoirs of the Museum of Comparative Zoology. 43 (3): 275–276. doi:10.5962/bhl.title.49183. Retrieved 13 June 2025.
  6. ^ a b Froese, Rainer; Pauly, Daniel (eds.). "Astyanax cordovae". FishBase. June 2025 version.
  7. ^ Scharpf, Christopher; Lazara, Kenneth J. (21 April 2025). "Family ACESTRORHAMPHIDAE Eigenmann 1907 (American Tetras)". The ETYFish Project. Retrieved 13 June 2025.
  8. ^ "Astyanax cordovae (Günther, 1880)". Encyclopedia of Life. National Museum of Natural History. Retrieved 13 June 2025.
  9. ^ a b c Miquelarena, A. M.; Menni, R. C. (2005). "Astyanax tumbayaensis, a new species from northwestern Argentina highlands (Characiformes: Characidae) with a key to the Argentinean species of the genus and comments on their distribution" (PDF). Revue suisse de zoologie. 112. doi:10.5962/bhl.part.80319. Retrieved 14 June 2025.
  10. ^ a b c Vales, Daniel Gustavo; Haro, José Gustavo (21 April 2005). "Hábitos Alimentarios de Astyanax Cordovae (Günther, 1880) (Pisces, Characidae) en el Río Primero (Suquía) (Córdoba, Argentina)". Natura Neotropicalis (in Spanish). 2 (29): 89–96. doi:10.14409/natura.v2i29.3726.
  11. ^ Terán, Guillermo E.; Butí, Cristina I.; Mirande, J. Marcos (2017). "A new species of Astyanax (Ostariophysi: Characidae) from the headwaters of the arheic Río Sucuma, Catamarca, Northwestern Argentina". Neotropical Ichthyology. 15 (2). doi:10.1590/1982-0224-20160165.
  12. ^ 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". Journal of Fish Biology. 91 (4): 5. doi:10.1111/JFB.13405.
  13. ^ "Astyanax cordovae". Global Biodiversity Information Facility.
  14. ^ López, Hugo L.; Menni, Roberto C.; Donato, Mariano; Miquelarena, Amalia M. (September 2008). "Biogeographical revision of Argentina (Andean and Neotropical Regions): an analysis using freshwater fishes" (PDF). Journal of Biogeography. 35 (9). doi:10.1111/j.1365-2699.2008.01904.x. Retrieved 14 June 2025.
  15. ^ Bucher, Enrique H. (2019). "Fish". The Mar Chiquita Salt Lake (Córdoba, Argentina): Ecology and Conservation of the Largest Salt Lake in South America. Cham: Springer. ISBN 978-3-030-15812-5. Retrieved 14 June 2025.
  16. ^ Bistoni, M. A.; Hued, A. C. (November 2002). "Patterns of fish species richness in rivers of the central region of Argentina". Brazilian Journal of Biology. 62. doi:10.1590/S1519-69842002000500004.
  17. ^ Chaij, Ana Carolina; Quinteros, Ivana (8 April 2024). "The great flood of the Primero river in 1903". Iberarchivos - Programa ADAI. Retrieved 14 June 2025.
  18. ^ Lagorio, Silvia Leonor; Geuna, Silvana Evangelina; Vizán, Haroldo (2016). Early Cretaceous Volcanism in Central and Eastern Argentina During Gondwana Break-Up (1st 2016 ed.). Cham: Springer International Publishing : Imprint: Springer. ISBN 978-3-319-29593-0.
  19. ^ Kröhling, Daniela M.; Iriondo, Martı́n (June 1999). "Upper Quaternary Palaeoclimates of the Mar Chiquita area, North Pampa, Argentina". Quaternary International. 57–58: 149–163. doi:10.1016/S1040-6182(98)00056-1.
  20. ^ Pilati, Alberto; Castellino, Marcela; Bucher, Enrique H. (2016). "Nutrient, chlorophyll and zooplankton seasonal variations on the southern coast of a subtropical saline lake (Mar Chiquita, Córdoba, Argentina)". Annales de Limnologie - International Journal of Limnology. 52: 263–271. doi:10.1051/limn/2016014.
  21. ^ a b Miquelarena, Amalia M; Protogino, L C; López, H L (2005). "Astyanax hermosus, a new species from the Primero River basin, Córdoba, Argentina (Characiformes, Characidae)" (PDF). Revue suisse de zoologie. 112: 13–20. doi:10.5962/bhl.part.80284. Retrieved 14 June 2025.
  22. ^ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Astyanax hermosus". Catalog of Fishes. California Academy of Sciences. Retrieved 13 June 2025.
  23. ^ Zayas, Marcelo A.; Cordiviola, Elly (2007). "Estado de Conservacion de peces Characidae (Pisces: Characiformes) en un area de la cuenca del plata, Argentina" [The conservation state of Characidae fish (Pisces: Characiformes) in an area of the Plata Basin, Argentina]. Gayana (Concepción) (in Spanish). 71 (2). doi:10.4067/S0717-65382007000200006. Retrieved 14 June 2025.
  24. ^ "Anexo I: listado de la categorización de peces de la provincia de Córdoba (Argentina) según su estado de conservación" [Annex I: List of fish categorizations in the province of Córdoba (Argentina) according to their conservation status] (PDF). Ministry of Environment and Circular Economy (in Spanish). Editorial de la UNC. Retrieved 14 June 2025.
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