Chalceus Epakros
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''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 considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. 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 River, Amazon and Orinoco basins, as well as in the The Guianas, Guianas and various tributaries of the former. It is the sole ...
'', 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 spot Humeral spot (from Latin ''humerus'', pertaining to the shoulder) is a mark or pattern found on several species of fish, typically above the pectoral fin. In insects, the humeral spot may be found on the Glossary_of_entomology_terms#Costa, cost ...
s (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 , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...
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 human body, anatomical feature of the infant human skull comprising soft Membrane, membranous gaps (suture (joint), sutures) between the cranial bones that make up the calvaria (skull), ...
(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 natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...
, 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 {{Short pages monitor