Iguanodectes variatus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Iguanodectidae
Genus: Iguanodectes
Species:
I. variatus
Binomial name
Iguanodectes variatus
Géry, 1993

Iguanodectes variatus is a small freshwater fish, described from the rivers of South America in 1993. It has a minor presence in the aquarium trade, but lacks the popularity that would make excessive wild capture a legitimate threat. That being said, the threats facing South American aquatic environments are of ongoing concern for the associated biodiversity. Still, I. variatus has been recorded from various rivers and has shown general adaptability to its environment, which speaks to a high survivability.

Description

Iguanodectes variatus reaches a maximum of 10.3 cm (4.1 in) standard length (SL).[1] As with the rest of its genus, its base scale color ranges from silver to silvery-yellow (more often the former), but it has characteristic mottling on its sides in light-brown. The top of the snout is also colored brownish, which can help distinguish it from similar-looking congeners,[2] though the light-brown mottling is unique to I. variatus within Iguanodectes regardless.[3] It has a lateral line in reflective green, somewhat reminiscent of congener I. spilurus, and it has a dark stripe on its caudal fin that strictly occupies the middle portion therein.[2]

Species of Iguanodectes are generally narrow-bodied and slender, drawing comparisons to smelt or minnows.[4][5] They usually bear some resemblance to sister genus Piabucus, but members of Piabucus have deeper chests and longer pectoral fins.[6]

Sexual dimorphism

The sexual dimorphism, or lack thereof, within I. variatus specifically is unknown. However, male specimens of several congeners demonstrate small hooks or spines on the first few rays of the anal fin during mating season, such as I. geisleri[7] and I. purusii,[2] which suggests the possibility of similar features in I. variatus. This particular dimorphism is not uncommon within the family Iguanodectidae as a whole, and is slightly more prevalent in familial genus Bryconops.[8]

Taxonomy

Named in 1993, I. variatus is one of three species described by French ichthyologist Jacques Géry in its nominal paper; the other two are congeners Iguanodectes polylepis and Iguanodectes gracilis.[2] These three species are the most recent additions to the genus, out of eight species total.[9] I. variatus has retained its original name, and has no known synonyms.[10]

DNA barcoding has revealed some genetic similarity to related species Bryconops melanurus, though not enough for it to be of taxonomic note.[11]

Etymology

The specific name "variatus" means "spotting", as in "variation of color", which is in reference to the mottling on the sides of adults. The generic name "Iguanodectes", while without a specified origin in its nominal text, is likely from "iguana", the lizard, and "dectes", meaning "bite" or "tooth".[3]

Distribution and habitat

Iguanodectes variatus is found throughout the basins of the Branco, Guaporé, Trombetas, and Urubu rivers, as well as the Madeira.[12] This restricts its range to Brazil. It was originally described from a stream called the Igarapé Jatuarana, in the Guaporé watershed.[6] Furthermore, it has most often been sighted in the upper portions of the water column, inhabiting areas of somewhat stronger current.[13]

Diet and ecology

Though information regarding the diet of I. variatus is somewhat sparse, aquarists report omnivorous tendencies.[14] The general tooth structure suggests food intake similar to the rest of the genus, including filamentous algae and aquatic invertebrates.[2] Other reports of Iguanodectes as a whole describe a more herbivorous disposition.[8]

It is reportedly a social fish that prefers to live in schools, which is in keeping with habits seen in the rest of the genus.[15] The specific extent of sympatry with other species is unknown, but it is known to be widespread and adaptable in nature, and is thus unlikely to be particularly territorial.[16]

Presence and behavior in aquaria

The genus Iguanodectes as a whole is not often exported for trade from within its native range. Several species are more popular than I. variatus, including I. geisleri, I. adujai, and I. spilurus.[7] However, I. variatus is at least of minor note in aquaria, seen in reports from hobbyists in European locations such as Poland.[14][15]

Conservation status

Iguanodectes variatus has not been evaluated by the IUCN.[1] It is known to live in areas affected by the pesticide Chlorpyrifos, though knowledge of its response to contamination has not been published. [17] Otherwise, it is wide-ranging and adaptable, which means a stable population and a low likelihood of endangerment.[16]

References

  1. 1 2 Froese, Rainer; Pauly, Daniel (eds.) (2022). "Iguanodectes variatus" in FishBase. December 2022 version.
  2. 1 2 3 4 5 Géry, J. 1993. "Description de trois espèces nouvelles du genre Iguanodectes (Pisces, Characiformes, Characidae), avec quelques données récentes sur les autres espèces." Revue française d'Aquariologie Herpétologie 19(4): 97-106.
  3. 1 2 Scharpf, Christopher; Lazara, Kenneth J. (15 September 2020). "Order CHARACIFORMES: Families IGUANODECTIDAE, TRIPORTHEIDAE, BRYCONIDAE, CHALCEIDAE and GASTEROPELECIDAE". The ETYFish Project. Retrieved 29 December 2022.
  4. ↑ Eigenmann, Carl H.; Meyers, George S. (1917–1929). The American Characidae. Cambridge. pp. 493–499. Retrieved 31 December 2022.
  5. ↑ Böhlke, James E. (1954-02-01). "XV.—Studies on fishes of the family Characidae.—No. 6. A synopsis of the Iguanodectinae". Annals and Magazine of Natural History. 7 (74): 97–104. doi:10.1080/00222935408651699. ISSN 0374-5481.
  6. 1 2 Check list of the freshwater fishes of South and Central America. Roberto E. Reis, Sven O. Kullander, Carl J. Ferraris, Pontifícia Universidade Católica do Rio Grande do Sul. Museu de Ciências e Tecnologia. Porto Alegre, Brasil: EDIPUCRS. 2003. pp. 172–173. ISBN 85-7430-361-5. OCLC 54496178.{{cite book}}: CS1 maint: others (link)
  7. 1 2 Schäfer, Frank (6 May 2013). "Iguanodectes geisleri". aquariumglaser.de. Aquarium Glaser GmbH. Retrieved 2 December 2022.
  8. 1 2 "THE FISH FAMILIES". Field Guide to the Fishes of the Amazon, Orinoco, and Guianas, edited by Peter van der Sleen and James S. Albert, Princeton: Princeton University Press, 2017, pp. 95-96. https://doi.org/10.1515/9781400888801-009
  9. ↑ Bailly, Nicolas. "Iguanodectes Cope, 1872". www.marinespecies.org. World Register of Marine Species. Retrieved 29 December 2022.
  10. ↑ "Iguanodectes variatus (Géry, 1993)". Global Biodiversity Information Facility. Retrieved 28 December 2022.
  11. ↑ Guimarães, Karen Larissa Auzier; de Sousa, Marcos Paulo Alho; Ribeiro, Frank Raynner Vasconcelos; Porto, Jorge Ivan Rebelo; Rodrigues, Luís Reginaldo Ribeiro (21 December 2018). "DNA barcoding of fish fauna from low order streams of Tapajós River basin". PLOS ONE. 13 (12): e0209430. Bibcode:2018PLoSO..1309430G. doi:10.1371/journal.pone.0209430. PMC 6303048. PMID 30576366.
  12. ↑ "Iguanodectes variatus (Géry, 1993)". seriouslyfish.com. SeriouslyFish. Retrieved 1 January 2023.
  13. ↑ Fróis, Raul de Paula da Silva; Ribeiro, Bruno Oliveira; Zuanon, Jansen; Mortati, Amanda Frederico (2021). "Fish fauna of small-order streams of savannah and forest fragments landscape in the lower Tapajós River basin, Amazonia". Biota Neotropica. 21 (4). doi:10.1590/1676-0611-BN-2020-1179. S2CID 239721769. Retrieved 1 January 2023.
  14. 1 2 "Iguanodectes variatus". akwa-mania.mud.pl. AKWA-MANIA. Retrieved 31 December 2022.
  15. 1 2 "Iguanodectes variatus". akwarium.info.pl (in Polish). Retrieved 30 December 2022.
  16. 1 2 Carvalho, Rodrigo Assis; Tejerina-Garro, Francisco Leonardo (June 2015). "The influence of environmental variables on the functional structure of headwater stream fish assemblages: a study of two tropical basins in Central Brazil". Neotropical Ichthyology. 13 (2): 349–360. doi:10.1590/1982-0224-20130148.
  17. ↑ dos Santos, Soraia B. (6 August 2019). "Evaluation of the Toxicity of the Pesticide Chlorpyrifos and its effect on the behavior of fish of the species Iguanodectes variatus (Géry, 1993)". Unpublished master defense. PPGBIO Graduate Program in Biosciences. Retrieved 1 January 2023.
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