Astyanax bransfordii

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Astyanax bransfordii
Astyanax bransfordii live specimen.png
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Characidae
Genus: Astyanax
Species:
A. bransfordii
Binomial name
Astyanax bransfordii
Gill, 1877, in Schmitter-Soto, 2017
Synonyms [2]

Bramocharax bransfordiiGill, 1877
Bramocharax bransfordii bransfordiiGill, 1877
Bramocharax elongatusMeek, 1907

Contents

Astyanax bransfordii, sometimes called the longjaw tetra, is a small carnivorous species of fish endemic to a handful of lakes and slow-moving canals in Central America. Its range includes Lake Nicaragua and Lake Managua, which are two of the largest freshwater bodies in Central America; because it occurs only in the relevant areas of Costa Rica and Nicaragua, the area it actually inhabits is somewhat restricted. Its diet largely consists of various invertebrates and smaller fish. This is in contrast to various other species of Astyanax , which are more often omnivorous.

Its elongated body and jaws - which garnered the common name "longjaw tetra" - once earned it the distinction of a separate genus altogether, Bramocharax, along with several other members of Astyanax. However, Bramocharax is now considered invalid, and these morphological differences are considered adaptations instead of synapomorphies - that is, changes in shape caused over time by feeding habits, rather than inherited from a relationship to each other through a common ancestor.

Taxonomy

1907 illustration. Astyanax bransfordii illustration (1907).jpg
1907 illustration.

When first described by ichthyologist Theodore Gill in 1877, A. bransfordii was called Bramocharax bransfordii, classified in the new genus Bramocharax; [3] by way of monotypy, it became the type species therein. [4] A. bransfordii remained in the genus Bramocharax for the majority of its existence as a species. Species Bramocharax elongatus, described by Seth Eugene Meek in 1907, was synonymized with then-Bramocharax bransfordii by ichthyologist Donn Eric Rosen in 1970. [5] Other species that once belonged to Bramocharax include Astyanax baileyi , Astyanax caballeroi , and Astyanax dorioni . [6]

Based on genetic factors, the genus Bramocharax is largely considered obsolete in favor of Astyanax . [7] A comprehensive 2008 study pointed to several Bramocharax species that formed clades with species of Astyanax, as opposed to with each other; A. bransfordii was found to form a clade with Astyanax nicaraguensis . [8] A large-scale examination of Astyanax in Central and North America by Mexican ichthyologist Juan J. Schmitter-Soto corrected the classification of A. bransfordii, giving it its first official designation as a member of Astyanax. There are three subgenera in Astyanax - Astyanax, Poecilurichthys, and Zygogaster - and Schmitter-Soto placed A. bransfordii in the first. [9]

The morphological differences previously used to separate genera are now thought to be an adaptation that has arisen independently in a handful of species that face similar environmental pressures; [8] as such, there is still use in the labels, but as a matter of morphology, not one of phylogeny. When describing a specific set of features including jaw length, body shape, and dentition, species with the Bramocharax morph are long-snouted, slender, and have unicuspid teeth, while species with the Astyanax morph are short-snouted, deep-bodied, and multicuspid. [10]

Etymology

The specific epithet "bransfordii" was chosen by Theodore Gill to honor John F. Bransford, an assistant surgeon in the U.S. Navy responsible for collecting the type specimens. Bransford also co-authored the paper that introduced the original description of A. bransfordii. [11] The genus name "Astyanax" is a reference to the Iliad, where Astyanax was a Trojan warrior and son of prince Hector. [12]

Astyanax bransfordii, given the shape of its body and mouth, is sometimes referred to as the longjaw tetra. [1] [13]

Description

Astyanax bransfordii reaches a maximum of 15.0 cm (5.9 in) standard length (SL). [12] The body is long and of moderate depth, with a snout equal to or larger than the eye diameter. The jaws are also elongated, and are of equal length, equipped with large unicuspid teeth in the premaxilla. [14] There are 9–11 dorsal-fin rays, 25 anal-fin rays (though occasionally up to 28), and 16 pectoral-fin rays. There are 10 or more procurrent rays (rays inserted farther apart as they move away from the fin's origin) in the caudal fin. There are 37–38 scales in the lateral line, and 12 scales in the predorsal series. [9] The lateral line is complete. [3] Sexual dimorphism is unknown.

The base scale color is a silver-white, with a darker back in an olive-gray and a gray lateral stripe. The fins are largely transparent, but some specimens demonstrate a light red blotch on the anal fin and/or an orange or red caudal fin. [14] The only part of the fins to not be transparent is the median handful of caudal-fin rays, which are always dark due to a rhomboidal blotch of dark pigment, which continues onto the rays. There is an oval-shaped or indistinct humeral spot. [15] The scales themselves are middling in size, with distinct margins and radiating lines. [3] These radii, while distinct, are weakly-developed, especially in comparison to the dense circuli (rings). Biologist Theodore Cockerell made a comparison to the scales of fish in the family Clupeidae. [16]

Distribution and habitat

The type specimens of A. bransfordii were collected from Lake Nicaragua. [17] Further specimens have been collected from Lake Managua and Cano Palma. [12] [18] It has also appeared in various areas of the Sarapiquí River. [14] It appears to prefer waterways of little current, though it can be found in some areas with moderate velocity. It has been collected from elevations of 5 to 530 meters. [12]

Due to its presence in blackwater habitats, A. bransfordii demonstrates that it does not have high-oxygen needs. Cano Palma, for example, is a blackwater canal with muddy substrate and low visibility. [18] Blackwater conditions are caused when microbial decay acts upon leaf litter and other plant materials, leaching dark-colored tannins into the water; the microbes responsible consume much of the available dissolved oxygen. [19] [20]

Diet and ecology

Closeup of jaw and face. Astyanax bransfordii jaw detail.png
Closeup of jaw and face.

Astyanax bransfordii is a carnivorous species, with a diet composed almost evenly of invertebrates (both aquatic and terrestrial) and smaller fish; [10] these smaller fish include tetras, poeciliids, and cichlids. [12] The differences in snout length between species of the Astyanax morph and the Bramocharax morph are thought to be attributable to predatory behavior on the part of former Bramocharax species. [10]

It feeds upon smaller fish, but A. bransfordii can coexist peacefully with various species of similar size to itself. For instance, other characiform fishes collected in the relevant locales include Roeboides bouchelli , Hyphessobrycon tortuguerae , Brycon costaricensis , and congener Astyanax nicaraguensis . [18]

Conservation status

Astyanax bransfordii is currently considered a near threatened species by the IUCN. This is because it has a somewhat restricted native range that has been subject to several harmful factors, including mining pollution and invasive species, but there is no evidence of immediate and severe population decline. Nonetheless, it is uncommon at sites where it is sampled, and this does not indicate a healthy enough population for a rating of least concern. [1]

Lake Nicaragua, from which the first specimens of A. bransfordii were collected, is the focal point of a watershed containing various protected areas, and the lake itself is under serious consideration for an ecotourism program to help keep the water from becoming polluted; this may help protect not only A. bransfordii but dozens of other species, including those in rare and endemic taxa. [21]

Lake Managua, also called Lake Xolotlan, is in poorer ecological shape. It is one of the largest lakes in Central America, and is subject to severe pollution due to companies and tourists dumping refuse, sewage, and - from 1967 to 1992 - mercury. This not only has negative repercussions on the wildlife, but also on the surrounding human populations, the vast majority of whom are living in poverty and need to rely on the lake for income. [22]

Caño Palma (Spanish for "palm canal") is located inside of the Barra del Colorado Wildlife Refuge, which is an area of protection for A. bransfordii under ongoing study by researchers and volunteers. [23]

Related Research Articles

<i>Astyanax</i> (fish) Genus of fishes

Astyanax is a genus of freshwater fish in the family Characidae of the order Characiformes. Some of these fish, like many of their relatives, are kept as aquarium pets and known collectively as tetras. With around 150 described species and new ones being described yearly, this genus is among the largest of the entire order; Hyphessobrycon also has more than 145 species and which one is larger at any one time depends on whether more species have been recently described in one or the other. The blind and colorless cave tetra of Mexico is a famous member of the genus, but its taxonomic position is disputed: Some recognize it as part of the Mexican tetra and this is supported by phylogenetic evidence, but others recognize the cave form as a separate species, A. jordani.

<i>Ectrepopterus</i> Species of fish

Ectrepopterus uruguayensis is a small species of characin originally recorded only from streams in Uruguay, with occasional sightings in Brazil and Argentina. It is the only known member of the genus Ectrepopterus, which was formerly a subgenus of Megalamphodus. Given its restricted range, it is considered a rare fish, and is of note for conservation researchers interested in preserving the biodiversity of the region.

<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 acatlanensis</i> Species of fish

Astyanax acatlanensis, sometimes called the Acatlán tetra, is a small species of fish from the rivers of Mexico. It is a relatively hardy species that is able to tolerate a variety of water conditions, but is only found in freshwater, never brackish or marine. It is known only from the Río Acatlán, which is its type locality, and the Río Jía, which is a small, unknown river in the Oaxaca region.

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

Astyanax aeneus, the banded tetra, is a small species of fish native to southern Central America and northern South America. It can be found in a variety of environments, including lakes, rivers, ponds, and slightly brackish locales like lagoons. As well as a varied habitat, it has a varied omnivorous diet: algae, seeds, leaves, insects, and fish fry appear to be the most common.

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

Astyanax altior, the Yucatán tetra, is a small species of freshwater fish endemic to the Yucatán Peninsula of Mexico. It largely inhabits the cenotes of the region, and can tolerate water of limited salinity, though it largely prefers freshwater. Its diet includes plant matter and invertebrates, and there may be an element of cannibalism involved.

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

Astyanax altiparanae, sometimes called the yellow-tail tetra or yellow-tail lambari, is a species of schooling freshwater fish widely distributed across the southern half of South America. It is an ecologically flexible species, able to adapt to various resource and space conditions, and its diet follows this pattern; it is considered opportunistic and omnivorous. Its widespread nature and unspecified ecology contribute to its status as a species of least concern on the IUCN Red List. It was originally described from the upper Paraná river basin, which is the origin of its specific epithet; "alto" means "higher" in Brazilian Portuguese, hence "alto Paraná".

<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 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 bacalarensis</i> Species of fish

Astyanax bacalarensis, sometimes referred to as the Bacalar tetra, is a small species of freshwater fish found in Central and South America. Its scientific and common names both refer to its type locality, Lake Bacalar in Mexico, and it further inhabits freshwater environments like cenotes, streams, and wetlands. Its widespread nature, paired with an omnivorous diet, make it a hardy species.

<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 baileyi</i> Species of fish

Astyanax baileyi is a small freshwater fish native to northern Guatemala. Based on several visual aspects, it was once considered a member of the genus Bramocharax, which is now obsolete, and has since been synonymized with Astyanax. As such, former members of Bramocharax are now a part of Astyanax, like Astyanax bransfordii and Astyanax caballeroi.

<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 bimaculatus</i> Species of fish

The twospot astyanax, also called the two-spot tetra, is a small species of freshwater fish native to South America. It is a middlingly common tetra in the aquarium industry, with hobbyist reports of its sale and presence, and it is also a well-studied member of the genus Astyanax in wild settings. Amateur aquarists report peaceful schooling behavior in captivity, though fish in wild schools may turn on one another if presented with the threat of a predatory species.

<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 brevimanus</i> Species of fish

Astyanax brevimanus, sometimes referred to as the Quiché tetra, is a small species of freshwater fish native to various locales in Guatemala. Its native range is somewhat restricted, but it is a populous and adaptable species, so there is no risk of it going extinct anytime soon. It is unknown what A. brevimanus eats, or what specific habitats it prefers; current information is largely in the form of physical descriptions, general areas of occurrence, and hypotheses regarding relationships to congeners. Its silvery scales, indistinct humeral (shoulder) spot, and dark caudal-peduncle spot are features not unusual in species of Astyanax.

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

Astyanax caballeroi is a small species of freshwater fish endemic to a single lake system in Mexico. It has a longer snout and more slender body than most other species in the genus Astyanax, thought to be the result of predatory behavior; while A. caballeroi eats invertebrates and smaller fish, other Astyanax species are more broadly omnivorous, and have deeper bodies with shorter snouts. This difference in body shape once placed A. caballeroi, along with several other species of Astyanax, into the former genus Bramocharax.

<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.

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

Astyanax chaparae, sometimes called the Chapare tetra, is a small species of freshwater fish only found in Bolivia. It is endemic to its type locality, the Río Chapare, which is a tributary of the Mamoré located in the Cochabamba department. Little else is known of its diet, behavior, and ecology. Its conservation status is similarly unclear, as the IUCN ranks it a data deficient species.

<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.

References

  1. 1 2 3 Lyons, T.J.; Angulo, A. (2020). "Astyanax bransfordii". IUCN Red List of Threatened Species . 2020: e.T149113333A149122006. doi: 10.2305/IUCN.UK.2020-2.RLTS.T149113333A149122006.en . Retrieved 13 June 2023.
  2. ↑ Bailly, Nicolas (2020). "Astyanax bransfordii (Gill, 1877)". WoRMS. World Register of Marine Species . Retrieved 13 June 2023.
  3. 1 2 3 Gill, Theodore (1877). "Synopsis of the Fishes of Lake Nicaragua". Proceedings of the Academy of Natural Sciences of Philadelphia. 29 (1): 189–190. Retrieved 13 June 2023.
  4. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species related to Astyanax bransfordii". Catalog of Fishes . California Academy of Sciences . Retrieved 13 June 2023.
  5. ↑ Villa, Jaime (1976). "Ichthyology of the Lakes of Nicaragua: Historical Perspective". Investigations of the Ichthyofauna of Nicaraguan Lakes. 8: 110. Retrieved 13 June 2023.
  6. ↑ Bailly, Nicolas (2014). "Bramocharax Gill, 1877". WoRMS. World Register of Marine Species . Retrieved 13 June 2023.
  7. ↑ Schmitter-Soto, Juan J. (6 May 2016). "A phylogeny of Astyanax (Characiformes: Characidae) in Central and North America". Zootaxa. 4109 (2): 101–130. doi:10.11646/zootaxa.4109.2.1. PMID   27394856.
  8. 1 2 Ornelas-García, Claudia; Domínguez-Domínguez, Omar; Doadrio, Ignacio (2008). "Evolutionary history of the fish genus Astyanax Baird & Girard (1854) (Actinopterygii, Characidae) in Mesoamerica reveals multiple morphological homoplasies". BMC Evolutionary Biology. 8 (1): 340. doi: 10.1186/1471-2148-8-340 . PMC   2657800 . PMID   19102731.
  9. 1 2 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. S2CID   90642754.
  10. 1 2 3 Powers, Amanda K.; Garita-Alvarado, Carlos A.; Rodiles-Hernández, Rocío; Berning, Daniel J.; Gross, Joshua B.; Ornelas-García, C. Patricia (March 2020). "A geographical cline in craniofacial morphology across populations of Mesoamerican lake-dwelling fishes". Journal of Experimental Zoology Part A: Ecological and Integrative Physiology. 333 (3): 171–180. doi:10.1002/jez.2339. PMC   7372644 . PMID   31904195.
  11. ↑ Scharpf, Christopher; Lazara, Kenneth J. (29 December 2022). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (a-g)". The ETYFish Project. Retrieved 13 June 2023.
  12. 1 2 3 4 5 Froese, Rainer; Pauly, Daniel (eds.) (2023). "Astyanax bransfordii" in FishBase . June 2023 version.
  13. ↑ Angulo, Arturo (23 December 2021). "New records and range extensions to the Costa Rican freshwater fish fauna, with an updated checklist". Zootaxa. 5083 (1): 1–72. doi:10.11646/ZOOTAXA.5083.1.1. PMID   35390941. S2CID   248024481.
  14. 1 2 3 Angulo, Arturo; Naranjo-Elizondo, Beatriz; Rojas, Emmanuel; Ley-López, Juan Manuel (27 October 2017). "Fishes from the Tirimbina Biological Reserve, La Virgen de Sarapiquí, Heredia, Costa Rica". Check List. 13 (5): 683–702. doi: 10.15560/13.5.683 .
  15. ↑ "Astyanax bransfordii Schmitter-Soto 2017, comb. nov. - Plazi TreatmentBank". treatment.plazi.org. Plazi TreatmentBank. Retrieved 13 June 2023.
  16. ↑ Cockerell, Theodore (21 September 1915). "Scales of Panama Fishes" (PDF). Proceedings of the Biological Society of Washington. 28: 156. Retrieved 13 June 2023.
  17. ↑ Eigenmann, Carl H.; Ogle, Fletcher (10 September 1907). "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): 32. doi:10.5479/si.00963801.33-1556.1 . Retrieved 13 June 2023.
  18. 1 2 3 Perez, Taegan Jessica Maya (2021). Integrative Taxonomy as a Tool for Conservation: Exploring Freshwater Fish Diversity of the Barra del Colorado Wildlife Refuge, Costa Rica (PDF) (Master of Science). University of Toronto. Retrieved 13 June 2023.
  19. ↑ "Hypoxic blackwater events and water quality". Department of Agriculture, Water and the Environment. Australian Government. 2016. Retrieved 13 June 2023.
  20. ↑ Mehring, Andrew S.; Kuehn, Kevin A.; Tant, Cynthia J.; Pringle, Catherine M.; Lowrance, R. Richard; Vellidis, George (June 2014). "Contribution of surface leaf-litter breakdown and forest composition to benthic oxygen demand and ecosystem respiration in a South Georgia blackwater river". Freshwater Science. 33 (2): 377–389. doi: 10.1086/675507 .
  21. ↑ Klytchnikova, Irina I.; Cestti, Rita E.; Escurra, NA (4 April 2013). "Policy and investment priorities to reduce environmental degradation of the Lake Nicaragua watershed (Cocibolca) : addressing key environmental challenges". Latin America and Caribbean Region Environment and Water Resources Occasional Paper Series. Retrieved 13 June 2023.
  22. ↑ Morel, Blanca (5 October 2017). "Polluted lake is poor Nicaraguans' lifeline". phys.org. Science X Network. Retrieved 13 June 2023.
  23. ↑ "Caño Palma Overview". www.coterc.org. Caño Palma Biological Station. Retrieved 13 June 2023.
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