Astyanax brevirhinus

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Astyanax brevirhinus
Astyanax brevirhinus illustration (1917).jpg
1917 illustration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. brevirhinus
Binomial name
Astyanax brevirhinus
Eigenmann, 1908

Astyanax brevirhinus is a small species of freshwater fish known only from a river basin in northeastern Brazil. It is somewhat understudied and lacks a conservation status, but it is present in a region that is the subject of an ecological restoration project - the Jequitinhonha River. Specifics of diet and behavior are unknown, though shoaling activity has been observed in laboratory conditions.

Contents

The species name "brevirhinus" means "short nose"; this is because A. brevirhinus can be told apart from several congeners by its abbreviated snout length. Other factors, such as a lateral stripe and horizontal humeral spot, are shared with other Astyanax species, but aspects of dentition and fin structure can be used to differentiate. Nonetheless, these and other aspects - such as the deep body and silver scales - are not uncommon features within Astyanax as a whole.

Taxonomy

Astyanax brevirhinus was first cataloged by prolific German-American ichthyologist Carl H. Eigenmann in 1908. [2] The type specimen, however, was collected much earlier; during the Thayer Expedition to Brazil, an ecological and biological endeavor undertaken by multiple scientists, took place in 1865, and resulted in various type specimens that were later recognized as new species by those that had attended. [3] [4] (Another example is a congener of A. brevirhinus, Astyanax bourgeti .) [5] The original description of A. brevirhinus was somewhat brief, but it received a more detailed update from Eigenmann in the 1921 volume of "The American Characidae", a series of articles published in the journal Memoirs of the Museum of Comparative Zoology at Harvard College and later compiled into a book. [6]

Astyanax brevirhinus has not undergone any notable taxonomic changes during its existence as a species, and lacks any known synonyms. [7]

Etymology

The species name "brevirhinus" means "short-nosed". This is in reference to the particularly short snout that helps differentiate A. brevirhinus from its congeners. The genus name "Astyanax", while slightly less clear, is linked to the Iliad; Astyanax was a Trojan warrior, and son of Prince Hector. The reason for this allusion, while not articulated in the nominal text, is thought to refer to the type species Astyanax argentatus , which has large, silvery scales, like armor or a shield. [8]

Astyanax brevirhinus lacks a common name, [9] but "shortsnout astyanax" has been suggested based upon physical traits and the specific epithet.

Description

Astyanax brevirhinus reaches a maximum of roughly 10.0 cm (3.9 in) TL (total length, with the tail fin included). [10] The holotype specimen was 6.8 cm (2.7 in) SL (standard length, excluding the tail fin). [4] The body is about 2.5 times as long as its depth, which makes for a fairly deep-bodied fish. The snout is notably short. [2] The body is deepest at the point just after the start of the dorsal fin. [11] There are 6 scale rows above, 35 scales in, and 4 scale rows below the lateral line. There are 11 rays in the dorsal fin, and 28 rays in the anal fin. [6] The premaxillary has between three and five teeth on each side, which can help differentiate A. brevirhinus from similar species with fewer teeth, such as Deuterodon burgerai (which was originally placed in Astyanax , and has only two or three teeth in the same position). [11]

The body is a base silvery color. There is one humeral blotch, which is either rounded or horizontally elongated, and a dark lateral stripe that meets a blotch of dark pigment on the caudal peduncle. This blotch extends through the median caudal-fin rays. [12] (When preserved in alcohol, the dark lateral band turns silver, and the humeral spot becomes obscured.) [2] The caudal fin is mostly a middlingly-dark opaque color, while the middle rays are darkened (especially towards the tips). [6] When in distress, such as during laboratory transport or in conditions perceived as threatening, individuals of A. brevirhinus may slightly darken in color. [13]

Sexual dimorphism

Male specimens of A. brevirhinus exhibit bony hooks on the rays of the anal and pelvic fins. This is a feature seen on most species of Astyanax, though some demonstrate bony hooks on all fins instead of just the pelvic and anal. [12] Otherwise, no morphometric or coloration differences are known between the sexes of A. brevirhinus.

Distribution and ecology

Astyanax brevirhinus is endemic to the Jequitinhonha River basin in Brazil. [10] The holotype specimen was collected along the Jequitinhonha valley during the Thayer expedition in 1865–66. [4] Its preferred water parameters appear to be within the pH range of 6.2–7.5, and the temperature range of 23 °C (73 °F); [14] tests with higher water temperatures upon captive specimens have resulted erratic swimming behavior and difficulty staying close to the surface of the water. [13]

Observation in laboratory conditions reveals shoaling behavior amongst conspecifics of A. brevirhinus, not uncommon in species of Astyanax (both captive and wild). [13] Otherwise, little has been published of the species' diet or behavior. It is known to live in the same river basin as congener Astyanax turmalinensis , but sympatric behavior has not been observed. Other congeners within a similar general region include Astyanax lacustris , Astyanax jacobinae , and Astyanax epiagos , all from rivers to the northeast of Brazil. [12]

Conservation status

Astyanax brevirhinus has been classified as data deficient by the IUCN. Without further knowledge of its distribution, biology, and general population trends, a definite conservation status cannot be ascertained. [1] Previous diamond mining activity in the Jequitinhonha River region has been met with an ongoing preservation project in hopes of restoring local flora and fauna diversity, but the prognosis is not entirely positive; the riparian zone has been deemed unlikely to return to its former health. However, efforts have not been entirely without payoff, and the riparian zone has had some recovery in the past 7 to 11 years, which means that aquatic species like A. brevirhinus are likely to retain the associated benefits if the trend continues. [15]

Related Research Articles

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<i>Deuterodon pelecus</i> Species of fish

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<i>Carlastyanax</i> Genus of fishes

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<i>Astyanax argentatus</i> Species of fish

Astyanax argentatus is a small freshwater fish native to northern Central America and southern North America. Given its native range, it is also known as the Texan tetra. Little has been published regarding the feeding habits or behavior of A. argentatus, but it is known to have the northernmost distribution of any member of the genus Astyanax.

<i>Astyanax angustifrons</i> Species of fish

Astyanax angustifrons, sometimes referred to as the Campeche tetra, is a small freshwater fish from the rivers of Central and South America. It has a healthy distribution across southern Mexico and northern Guatemala, and is relatively common within its native range. Details regarding its diet and behavior are sparse, but it lives in areas with plentiful riparian vegetation, and most other members of the genus are omnivorous. Its habitat includes places affected by pollution and human activity; nonetheless, it is not endangered.

<i>Astyanax aramburui</i> Species of fish

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<i>Astyanax argyrimarginatus</i> Species of fish

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<i>Astyanax asuncionensis</i> Species of fish

Astyanax asuncionensis is a small species of freshwater fish described in 1972 from Asunción, the capital of Paraguay in South America. Its specific epithet is in reference to this. Currently, its range is known to encompass areas of not just Paraguay but also Argentina and Brazil. It is an adaptable, omnivorous species that easily lives in sympatry with various congeners.

<i>Astyanax atratoensis</i> Species of fish

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.

<i>Astyanax bagual</i> Species of fish

Astyanax bagual is a small species of freshwater fish known only from the Taquari-Antas river basin in southern Brazil. It is unusual in the genus Astyanax because mature male specimens display bony hooks on the rays of all fins; in opposition, most others have them on the anal, pelvic, or pectoral fins - sometimes on more than one of these, but very rarely on all fins. It can further be told apart from various congeners by way of dentition and some aspects of coloration, including the presence of two humeral spots instead of one.

<i>Astyanax belizianus</i> Species of fish

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.

<i>Astyanax biotae</i> Species of fish

Astyanax biotae is a small species of freshwater fish native to various localities in Brazil. It primarily eats invertebrates, like copepods and aquatic fly larvae, and its diet also includes seeds, fruits, and filamentous algae. Its scales are largely silver, with a touch of yellow-brown on the back and a hint of blue on the sides. Like many species of Astyanax, it has a humeral spot, which is a blotch of pigmentation in the area above or around the pectoral fin.

<i>Astyanax bourgeti</i> Species of fish

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.

<i>Astyanax brachypterygium</i> Species of fish

Astyanax brachypterygium is a small species of freshwater fish endemic to a collection of high-elevation streams in Brazil. It was named in 2001 alongside congener Astyanax cremnobates, to which it bears a strong resemblance; physical details help to differentiate between the two. Its scales are a greenish-brown on the back and silver on the belly, with reddish fins and a dark humeral spot. One of its defining features is a notably short anal-fin base, which has 13 to 15 rays.

<i>Astyanax caucanus</i> Species of fish

Astyanax caucanus is a small species of freshwater fish only found in Colombia. While little research exists regarding its ecological habits, such as diet and mating practices, its environment preferences are known to include marshy lowlands, and it easily lives in sympatry with various other fish species in the Cauca and Magdalena river basins. It is not known to share a habitat with any other species of Astyanax, but has a noted phyletic relationship to a group of congeners including Astyanax filiferus, Astyanax stilbe, and Astyanax magdalenae.

Astyanax apiaka is a small freshwater fish endemic to the Apiacá river in Mato Grosso, Brazil. Its discovery is recent, as of 2023, which results in little published research of its natural behaviors or preferred biotopes. However, descriptions of its appearance and general environment have been solidified, as well as some baseline information regarding its diet. It lacks a conservation status from the IUCN.

<i>Astyanax clavitaeniatus</i> Species of fish

Astyanax clavitaeniatus is a small species of freshwater fish native to various rivers in the Amazon basin. It is characterized by a club-shaped lateral stripe, which is where it gets its scientific name; "clava" means "club", and "taenia" means "stripe". It is a deep-bodied fish with a silvery base color, which is not uncommon for members of Astyanax. Its markings - including a humeral spot and two vertical brown bars - indicate that it is a part of a species complex centered around congener Astyanax bimaculatus.

<i>Deuterodon oyakawai</i> Species of fish

Deuterodon oyakawai is a small species of characin endemic to a large river basin along the Atlantic coast in southeast Brazil. It was originally one of three members of the genus Probolodus, but Probolodus is now considered obsolete, synonymized with Deuterodon. Much like other members of Deuterodon, and like some species in related genera, D. oyakawai is a small, silvery fish with fins in some combination of red and clear. It has a defined humeral spot that can be used for identification.

<i>Deuterodon sazimai</i> Species of fish

Deuterodon sazimai is a small freshwater fish endemic to a handful of river basins in southeastern Brazil. Upon being first described, it was considered a member of genus Probolodus; Probolodus is now considered obsolete, synonymized with Deuterodon. Much like other members of Deuterodon, and like some species in related genera like Astyanax or Jupiaba, D. oyakawai is a silvery fish with fins in some combination of red and clear. It sports a wedge-shaped humeral spot, and an oval-shaped blotch on its tail joint.

Astyanax anai is a small freshwater fish native to Central America. It has a restricted range, inhabiting a handful of Atlantic drainages in Costa Rica and Panama, and is known from locales only up to 100 meters elevation. As an endangered species, A. anai is a point of interest for conservation biologists studying the region. It can be found living sympatrically with other species of Astyanax, but is less common than its relatives.

References

  1. 1 2 Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) (2021). "Astyanax brevirhinus". IUCN Red List of Threatened Species . 2021: e.T187185A1824394. doi: 10.2305/IUCN.UK.2021-1.RLTS.T187185A1824394.pt . Retrieved 19 July 2023.
  2. 1 2 3 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): 96–97. Retrieved 18 July 2023.
  3. ↑ "Astyanax brevirhinus Eigenmann, 1908". www.zoobank.org. International Commission on Zoological Nomenclature. Retrieved 19 July 2023.
  4. 1 2 3 Black, Nina. "MCZ Ichthyology 20905". mczbase.mcz.harvard.edu. Harvard Museum of Comparative Zoology. Retrieved 19 July 2023.
  5. ↑ "Astyanax bourgeti Eigenmann, 1908". www.zoobank.org. International Commission on Zoological Nomenclature. Retrieved 6 June 2023.
  6. 1 2 3 Eigenmann, Carl H.; Myers, George S. (1921). The American Characidae. Vol. 43. Cambridge: Printed for the Museum. p. 306. doi:10.5962/bhl.title.49183 . Retrieved 18 July 2023.
  7. ↑ Bailly, Nicolas (2017-07-14). "Astyanax brevirhinus Eigenmann, 1908". WoRMS. World Register of Marine Species . Retrieved 19 July 2023.
  8. ↑ Scharpf, Christopher; Lazara, Kenneth J. (19 June 2024). "Family CHARACIDAE: Subfamily STETHAPRIONINAE Eigenmann 1907 (American Tetras)". The ETYFish Project. Retrieved 10 July 2024.
  9. ↑ "Astyanax brevirhinus Eigenmann 1908". Encyclopedia of Life . National Museum of Natural History . Retrieved 19 July 2023.
  10. 1 2 Reis, Roberto E.; Kullander, Sven O.; Ferraris Jr., Carl J. (2003). Check List of the Freshwater Fishes of South and Central America. Porto Alegre: Edipucrs. p. 108. ISBN   85-7430-361-5 . Retrieved 17 July 2023.
  11. 1 2 Zanata, Angela M.; Camelier, Priscila (June 2009). "Astyanax vermilion and Astyanax burgerai: new characid fishes (Ostariophysi: Characiformes) from Northeastern Bahia, Brazil". Neotropical Ichthyology. 7 (2): 175–184. doi: 10.1590/S1679-62252009000200007 .
  12. 1 2 3 Camelier, P.; Zanata, A. M. (February 2014). "A new species of Astyanax Baird & Girard (Characiformes: Characidae) from the Rio Paraguaçu basin, Chapada Diamantina, Bahia, Brazil, with comments on bony hooks on all fins: New Astyanax with hooks on all fins of males". Journal of Fish Biology. 84 (2): 475–490. doi:10.1111/jfb.12295.
  13. 1 2 3 Pereira, Caroline Reis (2018). Aquecimento x respostas fisiológicas: mecanismos de estabilidade térmica em Astyanax brevirhinus (Teleostei, Characidae) (Master's thesis) (in Portuguese). UFVJM. Retrieved 18 July 2023.
  14. ↑ Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax brevirhinus" in FishBase . July 2023 version.
  15. ↑ Costa, Cinthia B.; Ribeiro, Sérvio P.; Castro, Paulo T. A. (September 2010). "Ants as Bioindicators of Natural Succession in Savanna and Riparian Vegetation Impacted by Dredging in the Jequitinhonha River Basin, Brazil". Restoration Ecology. 18: 148–157. doi:10.1111/j.1526-100X.2009.00643.x.
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