Astyanax belizianus

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Astyanax belizianus
A preserved specimen from the London Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. belizianus
Binomial name
Astyanax belizianus
Bocourt, 1868
Synonyms

Tetragonopterus belizianus (Bocourt, 1868)

Astyanax belizianus is a small freshwater fish native to various regions of Central America. Little is known of its diet or specific environmental preferences, but it was first recorded in Belize. Modern ichthyology has expanded its range into Guatemala and Honduras, where it inhabits various rivers and lake tributaries. It is a silvery fish that may have a slight yellowish tint to its scales. The body is deep, especially in comparison to similar species from the same genus.

Its original description nominated it as a member of genus Tetragonopterus, which is not uncommon for members of Astyanax named in the late 1800s. A. belizianus was considered synonymous with congener Astyanax aeneus for a great deal of its existence, but recent research into the phylogeny of the genus (2017) has resurrected it from synonymy and re-granted it species status.

Taxonomy[edit]

When originally described by French ichthyologist Marie Firmin Bocourt in 1868, A. belizianus was named Tetragonopterus belizianus.[1] By 1899, German-American ichthyologist Carl H. Eigenmann had synonymized it under congener Astyanax aeneus;[2] at the time, A. aeneus was considered a subspecies of Astyanax fasciatus, a species that has since been renamed Psalidodon fasciatus.[3]

For a period in 1908, Astyanax aeneus was moved to genus Tetragonopterus as T. aeneus, and A. belizianus (Listed as T. belizianus) was still considered a synonym.[4] In 1997, A. belizianus had not been recognized, but A. aeneus had been moved back into Astyanax; Mexican ichthyologist Juan J. Schmitter-Soto performed a thorough examination of the genus in 2017 and revived the specific epithet belizianus, placing it in the genus Astyanax for the first time, which is where the species currently stands.[5]

The original description was sparse, but noted upon a similarity to congener Astyanax panamensis, also a member of Tetragonopterus at the time.[6]

Etymology[edit]

The specific name belizianus means "belonging to Belize", in reference to the type locality. The genus name Astyanax is an allusion to the Iliad, wherein Astyanax was a Trojan warrior and the son of prince Hector. The specific reasons for this allusion were not made clear in the nominal paper, but a potential origin is in the scales of the type species, Astyanax argentatus, which are large and silvery in a way that could be compared to armor or a shield.[7]

Due to its scientific name and type locality, A. belizianus is sometimes referred to as the Belizean tetra.[8]

Description[edit]

Astyanax belizianus is roughly 9.7 cm (3.8 in) total length, TL (with the tail fin included, as opposed to standard length, SL, without the tail fin).[9] Some larger specimens can reach 10.9 cm (4.3 in) SL.[10] The body is deep, which reportedly becomes more noticeable upon comparison to congeners.[11] There are 10 dorsal-fin rays (occasionally 9), 22–29 anal-fin rays (with a mean of 26), and 11–12 pectoral-fin rays. There are 32–39 lateral-line scales, most often 36.[5]

Its back is a slate-gray, its sides are tinged yellow, and the underside is gray.[12] There is a dark blotch of pigment on the caudal peduncle and caudal fin.[13] There is a single humeral spot, which can be p-shaped or indistinct.[5] There is a lateral stripe of bright, reflective scales in greenish or yellowish on both flanks.[14] When preserved in alcohol, the scales turn uniformly brassy, with a broad stripe down the side that is slightly paler.[9]

Astyanax belizianus is morphologically similar to various other species of Astyanax, such as A. aeneus and A. panamensis. Until 2021, at least one specimen of A. belizianus was mistakenly included in the type series for A. aeneus,[15] and several syntypes of A. panamensis have since been determined to be A. belizianus instead.[13]

Sexual dimorphism[edit]

Mature males display tiny protrusions, called nuptial tubercles, on the head and scales. These are always simple, which means that they are in one piece, as opposed to bifid, split down the middle.[10] Otherwise, little is known of differentiating coloration or morphometric aspects between the sexes.

Distribution and ecology[edit]

The specific type locality is unknown; Bocourt's 1868 description simply stated "Environs de Belize".[6] Since then, the range of A. belizianus has been elaborated upon. Starting in the Mullins River of central Belize, it extends south to tributaries of Lake Izabal, in Guatemala and northern Honduras.[1] Specific biotope preferences are unknown, as are diet and sympatry, though there is the possibility that records have been made while A. belizianus was grouped under A. aeneus.

Conservation status[edit]

Astyanax belizianus has not been evaluated by the IUCN.[8] Members of Astyanax as a whole are generally hardy and adaptive, but A. belizianus inhabits localities that face both natural and anthropogenic environmental pressures.

The Mullins River area is subject to hurricanes, which has a recorded impact on the geoscape, including surface sediments;[16] this, in turn, can impact water quality. Lake Izabal generally resists sediment disturbance thanks to the nearby wetlands, but has been subject to human pollution in modern times, largely due to mining activity.[17] One element to consider is that, due to the presence of both an inlet river and an outlet river, the water of the lake is totally replaced, or "cycled", every 6.6 months;[18] it is unknown what impact this has on its tributaries, if any.

References[edit]

  1. ^ a b Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Astyanax belizianus". Catalog of Fishes. California Academy of Sciences. Retrieved 29 May 2023.
  2. ^ Hatcher, J. B.; Morgan, J. Pierpont; Scott, William Earl Dodge; Scott, William Berryman; Sharpe, Richard Bowdler; Stone, Witmer.; Allen, J. A.; Stejneger, Leonhard; Eigenmann, Carl H. (1901). Reports of the Princeton University Expeditions to Patagonia, 1896-1899. J. B. Hatcher in charge. Princeton: The University. p. 433. Retrieved 29 May 2023.
  3. ^ Bailly, Nicolas (2021). "Psalidodon fasciatus (Cuvier, 1819)". WoRMS. World Register of Marine Species. Retrieved 30 May 2023.
  4. ^ "Biologia Centrali Americana Zoology, Botany, and Archæology". Nature. 96 (2408): 170. 1915. doi:10.1038/096448a0. ISSN 0028-0836. Retrieved 29 May 2023.
  5. ^ a b c Schmitter-Soto, Juan J. (2017-06-26). "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. ISSN 0022-2933.
  6. ^ a b Bocourt, M. F. (1868). "Note sur les poissons du genre Tétragonoptère provenant du Mexique et du Guatemala". Annales des sciences naturelles Zoologie. 5 (9): 61. Retrieved 29 May 2023 – via BHL.
  7. ^ Scharpf, Christopher; Lazara, Kenneth J. (28 December 2023). "Family CHARACIDAE: Subfamily STETHAPRIONINAE Eigenmann 1907 (American Tetras)". The ETYFish Project. Retrieved 27 January 2023.
  8. ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax belizianus" in FishBase. May 2023 version.
  9. ^ a b "1907.4.10.3". data.nhm.ac.uk. 1 February 2021. Retrieved 29 May 2023.
  10. ^ a b "Astyanax belizianus - Plazi TreatmentBank". treatment.plazi.org. Retrieved 2023-05-30.
  11. ^ Pamphlets on forestry. Fish and game. 1900. p. 336. doi:10.5962/bhl.title.30796.
  12. ^ Pellegrin, Jacques (1903). "Poissons récoltés dans l'Ouellé, par la mission du Bourg de Bozas". Bulletin du Musée D'histoire Naturelle. 9 (7): 326. Retrieved 29 May 2023 – via BHL.
  13. ^ a b "Astyanax panamensis - Plazi TreatmentBank". treatment.plazi.org. Retrieved 2023-05-30.
  14. ^ Schmitter-Soto, Juan J. (2017-07-03). "Figure 25 in A revision of Astyanax (Characiformes: Characidae) in Central and North America, with the description of nine new species". doi:10.5281/zenodo.5181939. Retrieved 2023-05-30.
  15. ^ Schmitter-Soto, Juan J. (2021-05-03). "New lectotype designation for Astyanax aeneus (Teleostei: Characidae)". Journal of Natural History. 55 (17–18): 1071–1073. doi:10.1080/00222933.2021.1933231. ISSN 0022-2933.
  16. ^ McCloskey, T.A.; Keller, G. (February 2009). "5000 year sedimentary record of hurricane strikes on the central coast of Belize". Quaternary International. 195 (1–2): 53–68. doi:10.1016/j.quaint.2008.03.003.
  17. ^ Hernández, Elisandra; Obrist-Farner, Jonathan; Brenner, Mark; Kenney, William F.; Curtis, Jason H.; Duarte, Edward (November 2020). "Natural and anthropogenic sources of lead, zinc, and nickel in sediments of Lake Izabal, Guatemala". Journal of Environmental Sciences. 96: 117–126. doi:10.1016/j.jes.2020.04.020.
  18. ^ RobledoI, José; Chacón, Eddi; García Álvarez, Nancy (2014). "La calidad del agua del lago de Izabal, Guatemala. Relaciones temporales y espaciales de variables físico-químicas y biológicas". Revista Ciencias Técnicas Agropecuarias. 23 (4): 28–32. Retrieved 29 May 2023.
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