Iguanodectes Variatus

''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). 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,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. though the light-brown mottling is unique to ''I. variatus'' within ''Iguanodectes'' regardless. 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.

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

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'' and '' I. purusii'', 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''."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

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''. These three species are the most recent additions to the genus, out of eight species total. ''I. variatus'' has retained its original name, and has no known synonyms.

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

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".

Distribution and habitat

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

Diet and ecology

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

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. 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.

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''. However, ''I. variatus'' is at least of minor note in aquaria, seen in reports from hobbyists in European locations such as Poland.

Conservation status

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

References

{{Taxonbar, from=Q2876061
Fish described in 1993
Taxa named by Jacques Géry
Characiformes
Fish of South America
Fish of Brazil