Bryconops cyrtogaster explained

Bryconops cyrtogaster is a midsize species of freshwater fish found in the Oyapock river in French Guiana and Brazil. It is overall silver, with an indistinct dark patch at the base of the tail fin that spreads onto the fin rays slightly. Originally described in 1926 under a different baisonym, it was the subject of a redescription in June 2020.

Description

Bryconops cyrtogaster is about 12 cm (4.7 in) in total length, which makes it slightly longer than the average member of its genus. Its scales are generally silver, with a faint lateral line towards its back half.[1] One of its identifying features is a diffuse dark patch on the caudal peduncle that bleeds into the upper lobe of the caudal fin.[2] It also has a single humeral spot above each pectoral fin.[3]

The snout is short and the eye wide in comparison, the latter larger than the former. The mouth itself is terminal, equipped with multicuspid teeth (a feature seen in all members of Bryconops, as well as sister clade Iguanodectinae).[4] The origin of the dorsal fin is slightly closer to the caudal fin than to the tip of the snout.

Bryconops cyrtogaster bears several morphological similarities to other members of the genus. It shares the presence of a single humeral patch with congeners Bryconops humeralis, Bryconops vibex, and Bryconops marabaixo, but can be differentiated from the former two by a deeper body and a humeral spot located slightly farther back on the body. B. marabaixo has fewer predorsal scales and a shorter maxillary than B. cyrtogaster. Overall, B. cyrtogaster bears the greatest similarity to B. marabaixo, Bryconops inpai, and Bryconops munduruku.

Until 2020, Bryconops cyrtogaster was generally poorly studied, but received a redescription by Silva-Oliveira et al. in June of that year. The same study that cemented its characteristics also named similar congener B. marabaixo.

Taxonomy

When first described by English ichthyologist John Roxborough Norman in 1926, Bryconops cyrtogaster was listed under the original name Creatochanes cyrtogaster, and has undergone several classification changes since.[5] Knöppel et al. identified Bryconops cyrtogaster as a subspecies of Bryconops melanurus in 1968, dubbing it Bryconops (Creatochanes) melanurus cyrtogaster.[6] Chernoff et al. further simplified this designation, considering B. cyrtogaster a synonym of B. melanurus.[7] Finally, Silva-Oliveira et al. considered Bryconops cyrtogaster an independent species in 2018.[8]

Though its taxonomy has since been studied more closely and subsequently changed, Norman's original placement for Bryconops cyrtogaster retains an element of validity. B. cyrtogaster is considered a part of the subgenus Creatochanes, making its full scientific name Bryconops (Creatochanes) cyrtogaster. The specific epithet ""cyrtogaster" means "curved belly",[9] but B. cyrtogaster lacks an accepted common name.[10]

The genus Bryconops as a whole was once considered a member of the family Characidae, but has since been reclassified as a member of the family Iguanodectidae.[11] Some sources, such as Animal Diversity Web and ITIS, still list it under Characidae,[12] [13] but the current accepted standing of Bryconops cyrtogaster is as an Iguanodectid fish.[14] [15]

Habitat and ecology

Bryconops cyrtogaster is only known from the Oyapock river (between French Guiana and Brazil), and this has been the case ever since its discovery. It demonstrates a preference for rocky or sandy substrate, as well as fast-flowing and well-oxygenated water, such as where waterfalls intersect with the current.

Conservation status

Bryconops cyrtogaster has not been evaluated by the IUCN. The Oyapock river is not the subject of extensive development, but has a history of gold mining, which raises the amount of pollutants - specifically mercury - in the water.[16] However, regions of a high flow or with a sandy substrate have a lower mercury content, meaning that B. cyrtogaster's preferred environment shields it from potential mercury toxicity. The Oyapock river's spread of 28000 km2 offers B. cyrtogaster a relatively wide native range, meaning that it is unlikely to be at risk for extinction.[17]

Bryconops cyrtogaster is likely taken from the wild for use in the aquarium industry, but details are sparse.[18]

Notes and References

  1. Book: Eigenmann . Carl H. . The American Characidae . Meyers . George S. . 1917–1929 . Cambridge . 493–499 . 3 May 2022.
  2. Norman . J. R. . 1 July 1926 . XI.—Descriptions of nine new freshwater fishes from French Guiana and Brazil . Annals and Magazine of Natural History . 18 . 103 . 91–97 . 10.1080/00222932608633482 . 3 May 2022.
  3. Silva‐Oliveira . Cárlison . Moreira . Cristiano R. . Lima . Flávio C. T. . Py‐Daniel . Lúcia Rapp . September 2020 . The true identity of Bryconops cyrtogaster (Norman), and description of a new species of Bryconops Kner (Characiformes: Iguanodectidae) from the Rio Jari, lower Amazon basin . Journal of Fish Biology . 97 . 3 . 860–868 . 10.1111/jfb.14445 . 32584438 . 220060299 . 3 May 2022.
  4. Vari . Richard P. . 26 January 1977 . Notes on the characoid subfamily Iguanodectinae, with a description of a new species. . American Museum Novitates . 2612 . 2246/2012 . AMNH Digital Repository.
  5. Bryconops cyrtogaster (Norman, 1926) in GBIF Secretariat (2021). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2022-05-03.
  6. Knöppel . Hans-Armin . Junk . Wolfgang . Géry . Jacques . January 1968 . Bryconops (Creatochanes) inpai, a new characoid fish from the Central Amazon Region, with a review of the genus Bryconops . Amazoniana . 1 . 3 . 231–246 . 202183505 .
  7. Chernoff . Barry . Machado-Allison . Antonio . Buckup . Paulo . Royero . Ramiro . February 1994 . Systematic Status and Neotype Designation for Autanichthys giacopinii (Fernández-Yépez) with Comments on the Morphology of Bryconops melanurus (Bloch) . Copeia . 1994 . 1 . 238–242 . 10.2307/1446694 . 1446694 . 3 May 2022.
  8. Silva-Oliveira . Cárlison . Lima . Flávio C. T. . Bogotá-Gregory . J. D. . 8 November 2018 . A new species of Bryconops Kner (Characiformes: Iguanodectidae) from the Rio Maicuru, lower Amazon basin, Brazil . Zootaxa . 4514 . 3 . 372–382 . 10.11646/zootaxa.4514.3.4 . 30486203 . 54164187 . 3 May 2022.
  9. Web site: Scharpf . Christopher . Lazara . Kenneth J. . 15 September 2020 . Order CHARACIFORMES: Families IGUANODECTIDAE, TRIPORTHEIDAE, BRYCONIDAE, CHALCEIDAE and GASTEROPELECIDAE . 3 May 2022 . The ETYFish Project.
  10. Web site: Bryconops cyrtogaster (Norman 1926) Names . 3 May 2022 . Encyclopedia of Life.
  11. Oliveira, C., Avelino, G.S., Abe, K.T. et al. 26 September 2011). Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling. BMC Evol Biol. 11(275). https://doi.org/10.1186/1471-2148-11-275. Retrieved 3 May 2022.
  12. Web site: Myers . P. . Espinosa . R. . Parr . C. S. . Jones . T. . Hammond . G. S. . Dewey . T. A. . Bryconops cyrtogaster Classification . 3 May 2022 . Animal Diversity Web . University of Michigan Museum of Zoology.
  13. Web site: Bryconops cyrtogaster (Norman, 1926) . 3 May 2022 . Integrated Taxonomic Information System.
  14. Web site: Rees . Tony . 31 December 2011 . IRMNG - Bryconops cyrtogaster (Norman, 1926) . 3 May 2022 . International Register of Marine and Nonmarine Genera.
  15. Web site: Bryconops cyrtogaster (Norman, 1926) . 3 May 2022 . World Register of Marine Species.
  16. Laperche . Valérie . Hellal . Jennifer . Maury-Brachet . Régine . Joseph . Bernard . Laporte . Pierre . Breeze . Dominique . Blanchard . François . 26 June 2014 . Regional distribution of mercury in sediments of the main rivers of French Guiana (Amazonian basin) . SpringerPlus . 3 . 1 . 322 . 10.1186/2193-1801-3-322 . 25045610 . 4099412 . free .
  17. Gallay . Marjorie . Martinez . Jean-Michel . Laraque . Alain . Sarrazin . Max . Doudou . Jean-Claude . Antoine . Gardel . Vantrepotte . Vincent . Chow-Toun . Franck . April 2016 . Effect of gold mining activities on water turbidity and river sediment discharge: comparison of two nearby river basin in French Guiana, using remote sensing and field measurements data . EGU General Assembly Conference Abstracts . 18 . 2016EGUGA..1810699M . 4 May 2022.
  18. Prang, Gregory. (2007). An industry analysis of the freshwater ornamental fishery with particular reference to the supply of Brazilian freshwater ornamentals to the UK market. Uakari. 3. 10.31420/uakari.v3i1.18.

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