''Chalceus spilogyros'', sometimes misspelled as ''Chalceus spilogyrus'', is a species of freshwater fish in the family Chalceidae that inhabits northern South America. It is a relatively new member of the genus ''Chalceus'', along with '' C. epakros'' and '' C. guaporensis''.

Description

''Chalceus spilogyros'' bears many visual similarities to other ''Chalceus'' species, including metallic scales and a vividly-colored caudal fin (usually red or pink); the rest of its fins are

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

. Its scales also bear a reticulate (net-like) pattern, which is often uniform across the whole body. It has a comparatively rounded snout, and lacks the thin lateral stripe of ''C. guaporensis'' and ''C. epakros'', but it bears a small-yet-distinct humeral patch (a patch above each of the pectoral fins) to differentiate it from ''C. macrolepidotus'' and ''C. erythrurus''. Its hyaline fins further separate it from ''C. erythrurus'', whose pelvic fins are bright yellow. ''C. erythrurus'' may bear a humeral spot somewhat similar to that of ''C. spilogyros'', but it is less conspicuous, and also has a notch on the upper side. ''C. spilogyros'' may have a lateral stripe on some occasions (likely relating to the mating cycle), but it is much broader and less distinct than those of ''C. epakros'' and ''C. guaporensis''. ''C. spilogyros'' also has a

fontanel A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow f ...

(soft, membranous spot) between the frontal and parietal bones of the head to further differentiate it from ''C. epakros'' and ''C. guaporensis'', which have none.Zanata, Angela M. and Vari, Richard P
The family Alestidae (Ostariophysi, Characiformes): a phylogenetic analysis of a trans-Atlantic clade
Zoological Journal of the Linnean Society (2005). The longest documented ''C. spilogyros'' specimen was 22.3 cm SL. This makes it one of the larger species of the genus ''Chalceus'', competing with ''C. erythrurus'' (21.4 cm SL) and outsized only by ''C. macrolepidotus'' (24.5 cm SL). In specimens more than 12 cm in length, the head is more robust in comparison to the body, suggesting that 12 cm may be the point of some kind of maturation.

Etymology

The specific name ''spilogyros'' is Greek in origin. "Spilos" means "spot", and "gyros" means "circle" or "round", in reference to the distinct and un-notched humeral spot. As of 2022, it has no widely accepted common name. The genus name ''Chalceus'' comes from the Greek word "chalkos", which means "copper".

Georges Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in na ...

, who originally described the genus, named it so because he observed that the original specimen's scales were copper-colored ("sometimes golden") when preserved in alcohol. This is an observation replicated by modern researchers.

Taxonomy

''Chalceus spilogyros'' is a modern addition to the genus ''Chalceus'', named by

Angela M. Zanata Angela may refer to: Places * Angela, Montana * Angela Lake, in Volusia County, Florida * Lake Angela, in Lyon Township, Oakland County, Michigan * Lake Angela, the reservoir impounded by the source dam of the South Yuba River Fiction * An ...

and Mônica Toledo-Piza in 2004. the same redescription of ''Chalceus'' also resulted in the recognition of ''C. spilogyros''' congeners '' C. epakros'' and ''C. guaporensis''. While ''C. epakros'' and ''C. guaporensis'' form a clade of their own, ''C. spilogyros'' shares a clade with the other two recognized species in the genus - the pinktail chalceus, ''C. macrolepidotus'', and the tucan fish or yellowfin chalceus, ''C. erythrurus''. ''C. macrolepidotus'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

of the genus.

Habitat

''Chalceus spilogyros'' lives in rivers spanning northern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

, like the other Chalceus species. It largely inhabits the Trompetas,

Tapajós The Tapajós ( pt, Rio Tapajós ) is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. It is one of the largest cle ...

, and

Madeira ) , anthem = ( en, "Anthem of the Autonomous Region of Madeira") , song_type = Regional anthem , image_map=EU-Portugal_with_Madeira_circled.svg , map_alt=Location of Madeira , map_caption=Location of Madeira , subdivision_type=Sovereign st ...

rivers, occurring in the lower drainages of the latter two. This puts it as an inhabitant of inland wetland areas. ''C. guaporensis'' is also known to occur in the Madeira river. As of 2022, ''C. spilogyros'' is considered a species of

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. Th ...

by the

International Union for the Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN).

Diet and behavior

''Chalceus spilogyros''' diet and behavior have not been the subject of intensive study on their own. Other members of the genus have been observed to largely be insectivores, taking occasional plant material as well. The study of behavior is much the same; the pinktail and yellowfin chalceuses in particular have been observed to be active, fast-moving, and somewhat skittish.

References

{{Taxonbar, from=Q6420960 Chalceidae Fish of South America Freshwater animals of South America Fish described in 2004