''Chalceus epakros'' is a species of freshwater fish in the family Chalceidae, found in 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 ...

. It is a fairly recent addition to its genus, alongside the species '' C. guaporensis'' and '' C. spilogyros''.

Description

''Chalceus epakros'' bears visual similarities to other members of the genus ''

Chalceus ''Chalceus'' is a genus of fish that inhabits freshwater habitats in South America. Members can be found in the Amazon and Orinoco basins, as well as in the Guianas and various tributaries of the former. It is the sole representative of the famil ...

'', like metallic scales and a vivid red or pink caudal fin, though several differences help separate it from its congeners. It has a thin stripe laterally that reaches the caudal peduncle, as well as a longer and more pointed snout. It may occasionally bear humeral spots (a spot above each pectoral fin), but they are rather indistinct, especially compared to the humeral spots of '' C. spilogyros''. Its fins are a mixture of

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 ...

and reddish-pink, as opposed to the bright-yellow pelvic fins of '' C. erythrurus''. ''Chalceus erythrurus'' and ''C. macrolepidotus'' may occasionally bear a similar lateral stripe to ''C. epakros'', but theirs are broader and more indistinct. It is hypothesized to be related to mating habits, and may be more prominent around mating season. ''C. epakros''' stripe is composed of chromatophores closer to the surface than that of ''C. erythrurus'' and others. ''Chalceus epakros'' is incredibly visually similar to '' C. guaporensis'', including a thin lateral stripe, a pointed snout, and the occasional indistinct humeral patch.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). ''C. epakros'' and ''C. guaporensis'' are also alike in that they lack 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) on the head, while the other three species have one between the frontal and parietal bone. However, ''C. guaporensis'' is slightly larger, and it has 7 pelvic fin rays as opposed to eight on ''C. epakros''. C. epakros is the smallest ''Chalceus'' species, reaching 17.4 cm TL (with the caudal fin included); ''C. guaporensis'' reaches that same length in SL (without the caudal fin).

Etymology

The specific name ''epakros'' is from Greek, and means "pointed at the end", in reference to the longer and more pointed snout; compare ''Cryptocentrus epakros'', the pointedfin shrimpgoby, The genus name ''Chalceus'' comes from "chalkos", which is the Greek word for copper. French biologist

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 named the first member of ''Chalceus'' (''C. macrolepidotus''), named it this because the preserved specimen's scales were copper-colored ("sometimes golden") when preserved in alcohol, though its scales are silvery in life.

Taxonomy

In the year 2004, Brazilian biologists Mônica Toledo-Piza and

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 ...

performed a re-examination of the genus ''Chalceus'', resulting in the nomination of not only ''C. epakros'' but its congeners ''C. guaporensis'' and ''C. spilogyros''. Upon study in 2005, ''C. epakros'' and ''C. guaporensis'' were determined to form a clade, accounting for their visual similarities, while ''C. spilogyros'', ''C. erythrurus'', and ''C. macrolepidotus'' share another. Previously, specimens of ''C. epakros'' had been misidentified as specimens of ''C. macrolepidotus'' and ''C. erythrurus''; ''C. macrolepidotus'' (

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 nat ...

) and ''C. erythrurus'' (

Cope The cope (known in Latin as ''pluviale'' 'rain coat' or ''cappa'' 'cape') is a liturgical vestment, more precisely a long mantle or cloak, open in front and fastened at the breast with a band or clasp. It may be of any liturgical colours, litu ...

) are long-established members of the genus, having been named in 1818 and 1870, respectively.

Habitat

Like the rest of its genus, ''C. epakros'' is a freshwater fish from northern South America. ''C. epakros'' has the widest distribution of all ''Chalceus'' species, inhabiting the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...

, the

Orinoco river The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wo ...

, and the

Essequibo river The Essequibo River (Spanish: ''Río Esequibo'' originally called by Alonso de Ojeda ''Río Dulce'') is the largest river in Guyana, and the largest river between the Orinoco and Amazon. Rising in the Acarai Mountains near the Brazil–Guyana b ...

. Despite sharing a clade, ''C. epakros'' and ''C. guaporensis'' are not found in the same areas; this could either be due to competition between the species, or due to slight differences in environmental needs. ''Chalceus epakros'' and ''C. macrolepidotus'' are the only two ''Chalceus'' species known to occur in Guyana.

Diet and behavior

''Chalceus epakros'' seems to largely be an

insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...

, targeting

ants Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Creta ...

and

wasps A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...

. In one study (Torrente-Vilara et al.), very few examined specimens had food material in their stomachs, making diet-mapping difficult. This lines up with other, more thoroughly-studied ''Chalceus'' species, which target similar invertebrate spreads. Behaviorally, ''C. epakros'' is lacking in data. Other members of the genus are active, fast-moving, and somewhat skittish.

References

{{Taxonbar, from=Q5536361 Freshwater fish of South America Chalceidae Fish described in 2004