Key to the species of Copella (per Marinho & Menezes 2017)



hy·a·line: adjective ANATOMY•ZOOLOGY - having a glassy, translucent appearance.



1a. Procurrent caudal-fin rays hyaline; darkly pigmented area extending from posteroventral portion of dentary to ventral portion of eye; brilliant white spots usually present on body scales, in live or preserved male specimens.................................................................... Copella arnoldi (lower rio Amazonas basin, coastal drainages of Guyana, French Guiana, Surinam, and mouth of rio Orinoco).

1b. Procurrent caudal-fin rays black (except in some populations of C. nattereri from the rio Negro); no dark pigmentation in the area extending from posteroventral portion of dentary to ventral portion of eye; white spots on body scales sometimes present in preserved species, spots red in life ............................................ 2

2a. Middle caudal-fin rays dark.................................................................... Copella eigenmanni (rio Orinoco basin, upper rio Negro and upper rio Putumayo, rio Amazonas basin).

2b. Middle caudal-fin rays hyaline.................................................................... 3

3a. 15–19 predorsal scales; first longitudinal scale row with 14–18 scales; fourth longitudinal scale row with 24–28 scales; clear spots (red in life) absent on posterior portion of body scales.......................................................................... 4

3b. 12–14 predorsal scales; first longitudinal scale row with 11–14 scales; fourth longitudinal scale row with 20–24 scales; clear/white spots (red in life) present on posterior portion of body scales.............................................................................. 5

4a. Males with rows of conspicuous dark scales irregularly disposed on body, gradually lighter posteriorly; females and juveniles with brownish inconspicuous wide stripe on flank.............................................. Copella vilmae (upper rio Amazonas, surroundings of Letı´cia, Colombia).

4b. Males lacking dark scales irregularly disposed on body, bearing a faint longitudinal dark stripe on flank; females with a plain coloration, without longitudinal dark stripe on body............................................................. Copella compta (upper rio Negro upstream São Gabriel da Cachoeira, Brazil and Venezuela).

5a. Clear/white spots (red in life) on posterior portion of body scales, limited dorsally, posteriorly and ventrally by dark pigmentation which is frequently horseshoe shaped; longitudinal dark stripe, when present, formed by subjacent pigmentation. .................................... Copella nattereri (rio Amazonas from Letı´cia, Colombia, to mouth of rio Tapajo´s, rio Negro basin and upper and middle rio Orinoco basin).

5b. Clear/white spots (red in life) frequently restricted to fourth longitudinal scale row of body, not limited by dark pigmentation; longitudinal black stripe conspicuous, formed by superficial pigmentation, located below the row of clear spot........................................... Copella callolepis (rio Amazonas, rio Madeira, and coastal drainages of Para´ State at Brazil).

From:
Taxonomic review of Copella (Characiformes: Lebiasinidae) with an identification key for the species
Manoela M. F. Marinho , Naércio A. Menezes
Published: August 17, 2017 https://doi.org/10.1371/journal.pone.0183069 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0183069