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.
| Astyanax bacalarensis | |
|---|---|
| |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Characiformes |
| Family: | Characidae |
| Genus: | Astyanax |
| Species: | A. bacalarensis
|
| Binomial name | |
| Astyanax bacalarensis Schmitter-Soto, 2017
| |
Before its nomination, A. bacalarensis was considered synonymous with Astyanax aeneus. The silver scales and humeral spot that A. bacalarensis sports are not uncommon features in its genus, but it can be differentiated from congeners by several means. Its fins have some unique markings, like a patch of bright red on the anal fin, and its humeral spot is rectangular or ovoid, instead of triangular or p-shaped in some other Astyanax.
Taxonomy
editAstyanax bacalarensis was first described by Mexican ichthyologist Juan Jacob Schmitter-Soto during a revision of the genus in 2017. Before being identified as a different species altogether, specimens of A. bacalarensis were often classified as specimens of congener Astyanax aeneus (the banded tetra).[2] There are various subgenera in Astyanax - Poecilurichthys, Zygogaster, and Astyanax itself[3] - and A. bacalarensis belongs to Astyanax, based on a complete predorsal series of scales.[4]
Etymology
editThe genus Astyanax is named after a figure in Homer's Iliad. Astyanax was a warrior from Troy, son of prince Hector. The specific name "bacalarensis" is in reference to the type locality of the species, Lake Bacalar, with the suffix "-ensis" denoting a location.[5]
Astyanax bacalarensis is sometimes called the Bacalar tetra.[1][6]
Description
edit
Astyanax bacalarensis reaches 9.5 cm (3.7 in) standard length (SL), and the head makes up roughly a quarter of this (28% or less SL).[7] The origin of the dorsal fin is in the center of the body, and the fin itself has 9–11 rays. The anal fin has 21–27 rays, most often 25, and the pectoral fins have 10–11 rays.[4] Sexual dimorphism is unknown.
Astyanax bacalarensis is mostly silver, and has a single dark humeral spot that is rectangular or ovoid. The anal fin has a light margin, but is otherwise a uniform yellow, with a touch of bright red on the first few rays.[4] There is a black spot on the caudal peduncle that continues onto the middle rays of the caudal fin. The dorsal fin is lemon-yellow, the caudal fin is orange, and the pectoral and pelvic fins are largely clear or yellowish with red margins.[8]
Distribution and habitat
edit
Astyanax bacalarensis was originally described from Lake Bacalar in the Mexican state of Quintana Roo. It has been further cited from Sittee River in the Toledo district of Belize, as well as from the Mopán River in Guatemala.[4] Though it is largely a freshwater fish, it has been described from delta areas in the Chetumal Bay (in the Caribbean Sea) with middling levels of salinity for the region (9 psu, practical salinity units; for comparison, the ocean averages 34.7 psu).[9] It can also be found in cenotes on the Yucatán peninsula, as well as in caves and in seasonal wetlands.[1]
Diet and ecology
editAs a juvenile, A. bacalarensis is planktivorous, but graduates to omnivory as an adult. In turn, it is preyed upon by wading birds and various fish species, including Belonesox belizanus, Petenia splendida, and Rhamdia guatemalensis, depending on the specific location.[1]
Astyanax bacalarensis appears to be a species that readily adapts to its environment. For instance, in a 2019 study, A. bacalarensis was captured from areas where it had not been seen in previous years, which suggests an expanding range.[9] Another example is its introduction to the Mexican locale Laguna Chichancanab, a lake in which it is not normally found; A. bacalarensis can out-compete various native Cyprinodon species therein.[10]
Conservation status
editThe IUCN considers A. bacalarensis a species of least concern. Its wide native range, adaptable nature, high numbers, and tolerance to variable environmental conditions makes it unlikely to be at risk of extinction.[1] Its relative abundance in several locations serves as part of a biotic index of integrity for streams in the Hondo river basin.[11]
While A. bacalarensis is found spread throughout southern Central America and northern South America, it nonetheless inhabits locations currently facing ecological pressure. Lake Bacalar, for instance, is a tourism hotspot known for its clear waters and unique wildlife, but this tourism can damage natural structures within the lake and introduce pollution.[12] Proposals to label the lake a Ramsar site - a protected wetland habitat - have been unsuccessful in the past; the hotel and tourism sectors were concerned about potential profit impact.[13]
References
edit- ^ a b c d e Schmitter-Soto, J. (2019). "Astyanax bacalarensis". IUCN Red List of Threatened Species. 2019: e.T132569524A132572607. doi:10.2305/IUCN.UK.2019-2.RLTS.T132569524A132572607.en. Retrieved 8 May 2023.
- ^ Valdez-Moreno, Martha; Ivanova, Natalia V.; Elías-Gutiérrez, Manuel; Pedersen, Stephanie L.; Bessonov, Kyrylo; Hebert, Paul D. N. (22 April 2019). "Using eDNA to biomonitor the fish community in a tropical oligotrophic lake". PLOS ONE. 14 (4): e0215505. Bibcode:2019PLoSO..1415505V. doi:10.1371/journal.pone.0215505. PMC 6476559. PMID 31009491.
- ^ 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 (19 December 2016). "Highlighting Astyanax Species Diversity through DNA Barcoding". PLOS ONE. 11 (12): e0167203. Bibcode:2016PLoSO..1167203R. doi:10.1371/journal.pone.0167203. PMC 5167228. PMID 27992537.
- ^ a b c d 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. Bibcode:2017JNatH..51.1331S. doi:10.1080/00222933.2017.1324050. S2CID 90642754.
- ^ Scharpf, Christopher; Lazara, Kenneth J. (29 December 2022). "Order CHARACIFORMES: Family CHARACIDAE: Subfamily STETHAPRIONINAE (a-g)". The ETYFish Project. Retrieved 3 May 2023.
- ^ "Astyanax bacalarensis Schmitter-Soto 2017". Encyclopedia of Life. National Museum of Natural History. Retrieved 6 May 2023.
- ^ Froese, Rainer; Pauly, Daniel (eds.). "Astyanax bacalarensis". FishBase. May 2023 version.
- ^ "Astyanax bacalarensis, Schmitter-Soto, 2017". treatment.plazi.org. Plazi. Retrieved 8 May 2023.
- ^ a b Schmitter-Soto, Juan J.; Herrera-Pavón, Roberto L. (6 December 2019). "Changes in the Fish Community of a Western Caribbean Estuary after the Expansion of an Artificial Channel to the Sea". Water. 11 (12): 2582. doi:10.3390/w11122582.
- ^ Lyons, Timothy; Máiz-Tomé, Laura; Tognelli, Marcelo F.; Daniels, Adam; Meredith, Clayton; Bullock, Robert; Harrison, I. J. (2020). "The status and distribution of freshwater fishes in Mexico". IUCN Grey Literature. 1. IUCN. Retrieved 8 May 2023.
- ^ Schmitter-Soto, Juan J. (March 2020). "La ictiofauna cenotícola (peces de cenote) más relevante de la península de Yucatán" (PDF). Bioagrociencias (in Spanish). 13 (1): 9–22. doi:10.56369/BAC.3219. ISSN 2007-431X. S2CID 258575097. Retrieved 8 May 2023.
- ^ Keeley, Allison (12 July 2021). "How a Mexican Lagoon Lost Its Colors". newyorker.com. Retrieved 7 May 2023.
- ^ Ruiz, Ricardo Hernández (15 June 2022). "Bacalar Microbialites Struggle to Survive the Degradation of their Habitat". earthjournalism.net. Retrieved 7 May 2023.