Bryconops giacopinii explained

Bryconops giacopinii is a mid-sized species of freshwater fish in the family Iguanodectidae. It is the largest member of the genus Bryconops, and is therefore difficult to confuse with any of its congeners. With a diet that consists largely of land-dwelling insects, it serves as an important link between the terrestrial and aquatic aspects of its native range.

Description

Bryconops giacopinii reaches 18 cm (7 in) long in total length (with the tail fin included), which makes it the longest member of its genus. A close contender is the type species of Bryconops, B. alburnoides, which reaches 15 cm (6 in) in standard length (tail fin left out). B. giacopinii is a deep-bodied and robust fish, with silvery scales and a well-defined caudal ocellus (eyespot on the tail) in yellow or orange.[1]

Bryconops giacopinii bears a notable resemblance to Bryconops caudomaculatus, which was remarked upon in its original description.[2] The original also notes that B. giacopinii, under its basionym Autanichthys giacopinni, may have had some alliance with the fish genus Deuterodon, based on morphological properties.[3]

Bryconops giacopinii has 43 to 46 pored lateral line scales.[4] The lateral line itself is rather obscure, which is a feature that can be used to differentiate it from other species of Bryconops. It can also be told apart from several of its congeners by the fact that it lacks a humeral spot, which is a distinct mark that occurs above or near the pectoral fin in many fish species, including more than one species of Bryconops.[5]

The head makes up about a quarter of the total length, with the eye taking up a little less than half the length of the head. The maxillary teeth are in a set of five, all multicuspid, and the premaxillary teeth are in a set of four, all tricuspid. The original description notes that the posterior portion of the dentary (the lower jaw bone that bears dentition) lacks a set of minute, conical teeth seen in related genera, but modern reexamination counters this with the confirmed presence of teeth; the inside of the mouth is simply very fleshy, and the minute teeth often need to be manually exposed.

Taxonomy

When first described by Venezuelan ichthyologist Agustín Fernández-Yépez in 1950, Bryconops giacopinii was named Autanichthys giacopinni.[6] The specific epithet, giacopinii, honors Fernández-Yépez's friend Jose A. Giacopini. In 1994, Chernoff et al. determined by way of morphology that A. giacopinni's true position was in the genus Bryconops, redesignating it as Bryconops giacopinii. Autanichthys, with no other members, was thus synonymized with Bryconops.[7] (Several of Fernández-Yépez's discoveries have since received the same treatment, with others under review.)

When Fernández-Yépez's initial description was reviewed and the type specimens were sought out, it was determined that they had apparently been lost. Originally part of Fernández-Yépez's private ichthyological collection, Fernández-Yépez himself wrote that he intended to send several specimens to various museums, but consulting said museums yielded no results. Therefore, a neotype was designated upon redescription in 1994.[8]

There are two subgenera in the genus Bryconops: Bryconops and Creatochanes. Bryconops giacopinii belongs to the subgenus Creatochanes along with ten others, making its full scientific name Bryconops (Creatochanes) giacopinii.[9] Others in Creatochanes include B. colanegra, B. colaroja, B. affinis, and B. melanurus;[10] Members of the subgenus Bryconops include B. collettei, B. durbinae, B. caudomaculatus, and B. disruptus.

Upon its original description and for some time after, Bryconops giacopinii was considered a member of the family Tetragonopteridae (which has since been synonymized with the subfamily Tetragonopterinae).[11] However, research in 2011 by Oliveira et al. determined that the genus Bryconops, alongside the genera Iguanodectes and Piabucus, should all be moved to the family Iguanodectidae, revived from the earlier work of German-American ichthyologist Carl H. Eigenmann.[12] Thus, B. giacopinii is currently considered an iguanodectid.[13]

Distribution and habitat

Bryconops giacopinii is known largely from the Autana river, in the upper drainage of the Orinoco river. The genus given in its baisonym, Autanichthys, is in reference to this, as it is where the holotype was collected. Its larger range is the Autana-Sipapo river system as a whole, to which it is mostly restricted.[14] However, it has also been collected from the Kakada river, a tributary of the Caura river that, in turn, flows into the Orinoco.[15] Another tributary of the Orinoco, the Vichada river, extends B. giacopinii's range into Colombia.[16]

The Autana river itself is considered an acidic blackwater environment.[17] Blackwater environments have their distinctive color due to the decay of organic matter, such as leaf litter, that leaches tannins into the water.[18] The microbes responsible for this decay consume a large amount of the available dissolved oxygen,[19] which means that B. giacopinii is not a fish with high-oxygen needs; elsewise, it would not be suited to a blackwater habitat.

Conservation status

Though the conservation status of Bryconops giacopinii has not been evaluated by the IUCN, it has been found in the protected Caura National Park, which preserves at least a small portion of its range. However, nearby rivers, such as unprotected segments of the Caura, have been subject to a rise in illegal mining activity in recent years, which threatens to disrupt the environment.[20]

Diet and ecology

Terrestrial insects usually make up a large portion of B. giacopinii's diet, but its eating habits are still considered rather generalist.[21] This flexibility is advantageous, as it occasionally needs to change its food sources if living in the same area as another species with similar prey demands.[22] Nonetheless, its reliance on the forest rather than its aquatic habitat reinforces the link between the two different environments, and the importance of maintaining one to sustain the other. B. giacopinii shares its fondness for terrestrial insects with congener Bryconops alburnoides.[23]

In turn, B. giacopinii is not only preyed upon by larger fishes, but is also subject to parasitic infestations. One such parasite is Ergasilus curticrus, a species of copepod described in 2015 after being found in the gills of B. giacopinii.[24] E. curticrus is currently only known to be hosted by B. giacopinii.[25]

Notes and References

  1. Chernoff . Barry . Buckup . Paulo Andreas . Machado-Allison . Antonio . Royero . Ramiro . 1 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 . 18 May 2022.
  2. Fernandez-Yepez . Agustín . 1950 . Algunos peces del Rio Autana . Novedades Cientificas Museo de Historia Natural . 2 . 1–18 . 18 May 2022.
  3. Wingert . Juliana Mariani . Malabarba . Luiz Roberto . 4 April 2011 . Descrição de duas novas espécies de Bryconops (Teleostei: Characidae) da Bacia do Rio Amazonas . 10183/28524 . 18 May 2022.
  4. Guedes . Tharles L. O. . Oliveira . Everton F. . Lucinda . Paulo H. F. . 14 March 2016 . A new species of Bryconops (Ostariophysi: Characiformes: Characidae) from the upper rio Tocantins drainage, Brazil . Neotropical Ichthyology . 14 . 2 . 10.1590/1982-0224-20150176 . free .
  5. Chernoff . Barry . Machado-Allison . Antonio . 13 December 2005 . Bryconops magoi and Bryconops collettei (Characiformes: Characidae), two new freshwater fish species from Venezuela, with comments on B. caudomaculatus (Günther) . Zootaxa . 1094 . 1 . 1 . 10.11646/zootaxa.1094.1.1 . 18 May 2022.
  6. Machado-Allison . Antonio . 27 February 2018 . Contributions to the knowledge of Venezuelan Continental Ichthyology . Venezuelan Biological Act . 26 . 1 . 10872/17890 . 18 May 2022.
  7. Web site: Autanichthys Fernández-Yépez, 1950 . 18 May 2022 . World Register of Marine Species.
  8. Book: Reis . Roberto E. . Check List of the Freshwater Fishes of South and Central America . Kullander . Sven O. . Ferraris, Jr. . Carl J. . 2003 . Edipucrs . 85-7430-361-5 . Porto Alegre . 120 . 18 May 2022.
  9. Silva-Oliveira . Cárlison . Canto . André Luiz C. . Ribeiro . Frank Raynner V. . 30 July 2015 . Bryconops munduruku (Characiformes: Characidae), a new species of fish from the lower Tapajós River basin, Brazil . Zootaxa . 3994 . 1 . 133–141 . 10.11646/zootaxa.3994.1.7 . 26250264 . Biotaxa.
  10. Chernoff . Barry . Machado-Allison . Antonio . 23 February 2018 . Bryconops colaroja and B. colanegra, two new species from the Cuyuni and Caroni drainages of South America (Teleostei: Characidae) . Ichthyological Exploration of Freshwaters . 10 . 4 . 355–370 . 10872/17856 . 18 May 2022.
  11. Mirande . Juan Marcos . 2010 . Phylogeny of the family Characidae (Teleostei: Characiformes): from characters to taxonomy . Neotropical Ichthyology . 8 . 3 . 385–568 . 10.1590/S1679-62252010000300001 . free . 11336/77449 . free .
  12. Oliveira . Claudio . Avelino . Gleisy S. . Abe . Kelly T. . Mariguela . Tatiane C. . Benine . Ricardo C. . Ortí . Guillermo . Vari . Richard P. . Corrêa e Castro . Ricardo M. . December 2011 . Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling . BMC Evolutionary Biology . 11 . 1 . 275 . 10.1186/1471-2148-11-275 . 21943181 . 3190395 . free .
  13. Web site: Bryconops giacopinii (Fernández-Yépez, 1950) . 18 May 2022 . World Register of Marine Species.
  14. Chernoff . Barry . Buckup . Paulo Andreas . Machado-Allison . Antonio . Royero . Ramiro . March 1993 . Las especies del genero Bryconops Kner, 1858 en Venezuela (Teleostei, Characiformes) . Venezuelan Biological Act . 14 . 3 . 1–20 . 18 May 2022.
  15. Echevarría . Gabriela . González . Nirson . November 2018 . Fish taxonomic and functional diversity in mesohabitats of the River Kakada, Caura National Park, Venezuela . Nature Conservation Research . 3 . Suppl. 2 . 10.24189/ncr.2018.048 . 18 May 2022. free .
  16. Muriel-Hoyos . Felipe . Santana-Piñeros . Ana María . Cruz-Quintana . Yanis . Suárez-Morales . Eduardo . November 2015 . A new species of Ergasilus Nordmann, 1832 (Copepoda: Cyclopoida: Ergasilidae) from Bryconops giacopinii Fernández-Yépez (Characidae) in the Vichada River Basin, Colombia . Systematic Parasitology . 92 . 3 . 241–249 . 10.1007/s11230-015-9599-3 . 26446546 . 18729069 . 18 May 2022.
  17. Greaves . Eduardo D. . Liendo . Jacinto . 2007 . Radon Concentration in the Cataniapo-Autana River Basin, Amazonas State, Venezuela . Latin American Symposium on Nuclear Physics and Applications . 7 . 469–470 . 10.1063/1.2813855 . 2007AIPC..947..469S . 18 May 2022.
  18. Web site: 2016 . Hypoxic blackwater events and water quality . 18 May 2022 . Department of Agriculture, Water and the Environment . Australian Government.
  19. Mehring . Andrew S. . Kuehn . Kevin A. . Tant . Cynthia J. . Pringle . Catherine M. . Lowrance . R. Richard . Vellidis . George . 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 . 10.1086/675507 . 85315129 . free .
  20. González . Nirson . Echevarría . Gabriela . Daza . Felix . Mass . Francis . 2012 . Illustrated list of additions to the ichthyofauna of the Caura River, Venezuela . Check List . 8 . 1 . 043 . 10.15560/8.1.043 . 18 May 2022. free .
  21. Luque . Francisco J. . Patarroyo-Baez . Jhon J. . González-Trujillo . Juan David . 1 May 2019 . Aspectos auto-ecológicos de Bryconops giacopinii (Iguanodectidae) de la Serranía de la Lindosa, San José de Guaviare, Colombia . Acta Biológica Colombiana . 24 . 2 . 255–263 . 10.15446/abc.v24n2.70450 . 150298110 . free .
  22. Barros . G. . Zuanon . J. . Deus . C. . January 2017 . Effects of species co-occurrence on the trophic-niche breadth of characids in Amazon forest streams: trophic niches of characids . Journal of Fish Biology . 90 . 1 . 326–340 . 10.1111/jfb.13183 . 27778359 . 18 May 2022.
  23. Silva . Cylene C. da . Ferreira . Efrem J. G. . Deus . Cláudia P. de . 2008 . Diet of Bryconops alburnoides and B. caudomaculatus (Osteichthyes: Characiformes) in the region affected by Balbina Hydroelectric Dam (Amazon drainage, Brazil) . Neotropical Ichthyology . 6 . 2 . 237–242 . 10.1590/S1679-62252008000200011 . free .
  24. Muriel-Hoyos . Felipe . Santana-Piñeros . Ana María . Cruz-Quintana . Yanis . Suárez-Morales . Eduardo . November 2015 . A new species of Ergasilus Nordmann, 1832 (Copepoda: Cyclopoida: Ergasilidae) from Bryconops giacopinii Fernández-Yépez (Characidae) in the Vichada River Basin, Colombia . Systematic Parasitology . 92 . 3 . 241–249 . 10.1007/s11230-015-9599-3 . 26446546 . 18729069 . 18 May 2022.
  25. Gaviria . Santiago . Aranguren-Riaño . Nelson . 15 June 2019 . Continental copepods (Crustacea: Hexanauplia) of Colombia: revision and additions to the inventory . Biota Colombiana . 20 . 1 . 50–74 . 10.21068/c2019.v20n01a04 . 18 May 2022. free .

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