Phycocharax rasbora, a new genus and species of Brazilian tetra (Characiformes: Characidae) from Serra do Cachimbo, rio Tapajós basin

Abstract

A new genus and species of characid fish is described from rio Braço Norte, a tributary of rio Teles Pires, Tapajós basin, Mato Groso, Brazil. The new taxa can be diagnosed from the remaining characids by a unique combination of characters that includes the presence of a single row of relatively compressed premaxillary teeth, large teeth with four to nine cusps on premaxillary and dentary, absence of pseudotympanum, incomplete lateral line with 7–13 pored scales, sexually-dimorphic males with distal margin of anal fin approximately straight, and presence of a nearly triangular and horizontally elongated blotch from the posterior half of the body to caudal peduncle. The most parsimonious phylogenetic hypothesis, using morphological data, recovered the new genus and species in a clade including Paracheirodon axelrodi and Hyphessobrycon elachys.

Full text

RESEARCH ARTICLE
Phycocharax rasbora, a new genus and species
of Brazilian tetra (Characiformes: Characidae)
from Serra do Cachimbo, rio Tapajo
´s basin
Willian Massaharu Ohara
1
*, Juan Marcos Mirande
2
, Fla
´vio Cesar Thadeo de Lima
3
1Museu de Zoologia da Universidade de São Paulo, CEP, São Paulo, São Paulo, Brazil, 2CONICET-
Fundacio
´n Miguel Lillo, Miguel Lillo, San Miguel de Tucuma
´n, Argentina, 3Museu de Zoologia da
Universidade Estadual de Campinas “Adão Jose
´Cardoso”, Campinas, São Paulo, Brazil
*willianmohara@gmail.com
Abstract
A new genus and species of characid fish is described from rio Brac¸o Norte, a tributary of rio
Teles Pires, Tapajo
´s basin, Mato Groso, Brazil. The new taxa can be diagnosed from the
remaining characids by a unique combination of characters that includes the presence of a
single row of relatively compressed premaxillary teeth, large teeth with four to nine cusps on
premaxillary and dentary, absence of pseudotympanum, incomplete lateral line with 7–13
pored scales, sexually-dimorphic males with distal margin of anal fin approximately straight,
and presence of a nearly triangular and horizontally elongated blotch from the posterior half
of the body to caudal peduncle. The most parsimonious phylogenetic hypothesis, using mor-
phological data, recovered the new genus and species in a clade including Paracheirodon
axelrodi and Hyphessobrycon elachys.
Introduction
The Characidae is one of the richest families among bony fishes, and depending of the alterna-
tive proposals followed [1,2], the family comprise between 1,100 to over than 1,200 species [3].
Although much advance to understand the relationships within Characidae family has been
accomplished, it still constitutes in an unsettled issue. A stable classification of the Characidae
is still far to be established, given the great diversity and complexity of the family and the lack
of comprehensive analysis combining morphological and molecular data [4]. Many members
of the Characidae have low variation either in molecular data [2] as in morphological [5,6],
and most deep relationships within the family are incongruent between different analysis or
have low support.
During recent ichthyological field surveys in the northern of the Brazilian State Mato
Grosso, was discovered from the rio Brac¸o Norte, a tributary of the rio Teles Pires (Serra do
Cachimbo, rio Tapajo
´s basin), an attractively-colored characid tetra that proved to be not
assignable to any previously known genus. The new taxon is described herein due to its
unusual combination of single row of compressed premaxillary teeth, pseudotympanum
absent, and sexual dimorphism with males exhibiting a straight distal margin of the anal fin,
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 1 / 15
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OPEN ACCESS
Citation: Ohara WM, Mirande JM, de Lima FCT
(2017) Phycocharax rasbora, a new genus and
species of Brazilian tetra (Characiformes:
Characidae) from Serra do Cachimbo, rio Tapajo
´s
basin. PLoS ONE 12(2): e0170648. doi:10.1371/
journal.pone.0170648
Editor: Michael Schubert, Laboratoire de Biologie
du De
´veloppement de Villefranche-sur-Mer,
FRANCE
Received: July 26, 2016
Accepted: January 6, 2017
Published: February 15, 2017
Copyright: ©2017 Ohara et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within othe paper and its Supporting Information
files.
Funding: Part of the type series was collected
during an expedition funded by the South American
Characiformes Inventory (FAPESP 2011/502827,
http://www.projeto-saci.com). The authors are
supported by FAPESP (WMO: grant # 2013/
22473–8; FCTL: grants # 2011/51532–7 and 2013/
20936–0), CONICET (JMM: PIP–0301), and

while females present the more generalized condition among characids (i.e., an anal fin with a
distinct anterior lobe). In addition, the new taxon shows a remarkable color pattern with a
large and elongated triangular blotch extending along middle flanks from vertical through the
base terminus of dorsal fin to the caudal peduncle end. Such blotch is similar in shape and
position to the one present in the Neotropical characid Hemigrammus pulcher Ladiges and the
Asian cyprinids of the genus Trigonostigma Kottelat & Witte. The aim of the present study is
to describe this new taxon, assigned herein to a new genus, due to both phylogenetic position
and unique combination of characters.
Materials and methods
Fishes were prior anesthetized with eugenol solution (1 ml/L), then fixed in 10% formalin, and
finally preserved in 70% ethanol. The field studies did not involve endangered species. Collec-
tion permit was granted by Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais
Renova
´veis (IBAMA 2621–1). Counts and measurements follow Fink & Weitzman [7] and
Menezes & Weitzman [8], except for counts of the horizontal scale rows below the lateral line,
which were counted between lateral line and pelvic-fin insertion. Horizontal scale rows
between the dorsal-fin origin and lateral line does not include the scale of median predorsal
series situated just anterior to the first dorsal-fin ray. The distance from the pelvic-fin origin to
the anal-fin origin was added to the set of measures. Counts and measurements were taken on
the left side of specimens, whenever possible. Measurements are presented as proportions of
standard length (SL), except for subunits of the head, which are given as proportions of head
length (HL). The frequency of each count is provided in parentheses after the respective count,
asterisks indicate holotype values. Counts of vertebrae, supraneurals, procurrent caudal-fin
rays and gill rakers of the first arch were taken from 108 cleared and stained specimens (c&s)
prepared according to Taylor & Van Dyke [9]. Vertebrae of the Weberian apparatus were
counted as four elements, and the fused PU1+U1 of the caudal region as a single element. Sex-
ual dimorphism related with the color in life was confirmed by the examination of gonads via
incision of 22 selected specimens. Animal research involving fish at the Museu de Zoologia da
Universidade de São Paulo is associated with the project number 226/2015, approved by the
Ethics Committee on Animal Use (CEUA) of Instituto de Biologia da Universidade de São
Paulo (IB-USP). The list of material examined is provided as S1 Appendix. Institutional abbre-
viations follow Mirande [1,10] with inclusion of INPA (Instituto Nacional de Pesquisas da
Amazo
ˆnia, Manaus), MUSM (Museo de Historia Natural de la Universidad Nacional Mayor
de San Marcos, Lima), UFRGS (Universidade Federal do Rio Grande do Sul, Porto Alegre),
MPEG (Museu Paraense Emı
´lio Goeldi, Bele
´m), MNRJ (Museu Nacional do Rio de Janeiro,
Rio de Janeiro), and ZUEC (Museu de Zoologia da Universidade Estadual de Campinas “Adão
Jose
´Cardoso”, Campinas).
Phylogenetic relationships of the new taxon among characids were assessed by parsimony
using TNT software [11] following the characters of Mirande [1,10] and Mirande et al. [12,13].
Thirty-five additional species were included to the dataset to evaluate possible close relatives to
the new taxon or to check its possible inclusion in some genus already known, as well as to
have a most comprehensive framework within the Characidae phylogeny. The coding of the
new taxon plus 212 species analyzed herein are included in S1 Table and the dataset is available
online at MorphoBank [14,15]. The complete list of 387 characters analyzed herein, with com-
ments on those added (two new) or modified (15) from Mirande et al. [12], is provided as
S2 Appendix.
As in the mentioned papers (i.e. [1,10,12,13]), analysis were performed under extended
implied weighting [16,17] in a broad range of values of K (concavity constant). Differing from
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 2 / 15
FONCyT (JMM: PICT 2011–0992). A travel by the
second author to ZUEC was funded by FAPESP
[grant # 2011/51532–7, "Systematics of tetras
(genera Hemigrammus, Hyphessobrycon,
Thayeria, Parapristella and Bryconella), with
emphasis on the species from northern cis-andean
South America"]. The funders had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.

previous contributions, the phylogenetic analysis in a broad range of values of K was herein
performed only to evaluate the possible relationships and generic assignments of the new
taxon, rather than to reach to some general phylogenetic hypothesis for the family. Support
was calculated with Symmetric Resampling and results are expressed as GC values according
to Goloboff et al. [18].
Nomenclatural acts
The electronic edition of this article conforms to the requirements of the amended Interna-
tional Code of Zoological Nomenclature, and hence the new names contained herein are avail-
able under that Code from the electronic edition of this article. This published work and the
nomenclatural acts it contains have been registered in ZooBank, the online registration system
for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated
information viewed through any standard web browser by appending the LSID to the prefix
“http://zoobank.org/”. The LSID for this publication is: urn:lsid:zoobank.org:pub:D0FD20E4-
D2EB-4E52-9094-DDFE45EE0BE0. The electronic edition of this work was published in a
journal with an ISSN, and has been archived and is available from the following digital reposi-
tories: PubMed Central, LOCKSS.
Results
Family characidae agassiz
Phycocharax, new genus. urn:lsid:zoobank.org:act:27E0CD39-AD63-4D08-BE0F-
60670B17406F
(Figs 1–3)
Type species: Phycocharax rasbora, new species, by monotypy and original description.
Diagnosis: Phycocharax can be diagnosed from the remaining characid genera by the com-
bination of the following character-states, none of them unique: 1) presence of single row of
relatively compressed premaxillary teeth (Fig 2); 2) large teeth on premaxillary, and dentary
with four to nine cusps (Fig 2); 3) pseudotympanum absent; 4) incomplete lateral line with
7–13 pored scales; 5) anal fin dimorphic, males with distal margin approximately straight, and
decreasing gently posteriorly (Figs 1a and 3a), while females present slightly concave margin of
anal fin with anteriormost branched rays distinctly longer than remaining rays (Figs 1b and
3b); 6) presence of horizontally-elongated somewhat triangular blotch extending from vertical
through dorsal-fin terminus to caudal peduncle end (Figs 1and 3).
Etymology: From the Greek phykos, meaning “algae”, in allusion to the feeding habit of the
new taxon owing to the dominance of this resource in its stomach contents, plus charax,
meaning “pointed stake” or “palisade of pointed sticks”, the first generic name in Characidae.
Gender masculine.
Phycocharax rasbora, new species. urn:lsid:zoobank.org:act:B26FDDEB-E6C0-4BB4-
9DE3-2AD71673352C
(Figs 1–3)
Holotype: MZUSP 119843, 29.1 mm SL, Brazil, Mato Grosso, Guarantãdo Norte, Igarape
´
do Arnaldo, small stream of the rio Brac¸o Norte, a tributary of rio Peixoto de Azevedo, rio
Teles Pires drainage, rio Tapajo
´s basin, 9˚37’13”S 54˚57’38”W, 9 Feb 2014, W. M. Ohara & J.
Bilce.
Paratypes: All from Brazil, Mato Grosso, Guarantãdo Norte at rio Brac¸o Norte as data of
holotype. INPA 52858, 25, 17.1–30.1 mm SL; MCP 49957, 20, 15.8–29.7 mm SL; MNRJ 45956,
18, 20.2–30.5 mm SL; MZUSP 115341, 115 (8 c&s), 15.0–32.1 mm SL, collected with holotype.
CI-FML 7164, 4 (2 c&s), 25.8–29.0 mm SL; MZUSP 115344, 42, 17.1–30.5 mm SL; ZUEC
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 3 / 15

10440, 10 (2 c&s), 17.5–28.6 mm SL, PCH Brac¸o Norte IV reservoir, 9˚37’51”S 54˚58’38”W, 28
April 2012, J. Bilce & R. Rosa. MZUSP 115313, 3, 26.4–32.1 mm SL, immediately downstream
of the PCH Brac¸o Norte IV, 9˚41’22”S 54˚57’56”W, 9 Feb 2014, W. M. Ohara & J. Bilce.
MZUSP 115343, 20, 27.9–33.2 mm SL; ZUEC 12775, 3, 32.3–34.1 mm SL, rio Brac¸o Norte,
Brac¸o Norte IV reservoir, 9˚37’48”S 54˚58’15”W, 28 April 2012, J. Bilce et al. ANSP 200243,
10, 20.3–29.2 mm SL; CAS 241425, 10, 18.5–31.0 mm SL; CI-FML 7165, 10, 21.5–29.2 mm SL;
MPEG 33928, 10, 23.4–29.0 mm SL; ZUEC 12776, 20, 14.3–30.8 mm SL; MZUSP 119405, 309,
11.6–32.1 mm SL, same locality as holotype; O. T. Oyakawa, W. M. Ohara & M. Pastana, 4
Aug 2015.
Diagnosis: Same as for the genus.
Description: Morphometric data presented in Table 1. Small sized characid, largest exam-
ined specimen with 34.1 mm SL. Body compressed, moderately short and deep (Fig 1a) to hor-
izontally elongated (Fig 3a). Greatest body depth situated slightly anterior to vertical through
dorsal-fin origin. Dorsal profile of head convex from upper lip anterior tip to vertical through
anterior nostril; slightly concave or straight from that point to tip of supraoccipital spine.
Fig 1. Phycocharax rasbora, holotype, MZUSP 119843, 29.1 mm SL, male; MZUSP 115341, 25.3 mm SL, paratype, female.
doi:10.1371/journal.pone.0170648.g001
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 4 / 15

Dorsal profile of body convex from supraoccipital spine tip to base of last dorsal-fin ray,
approximately straight or convex from that point to adipose-fin insertion and slightly concave
between adipose-fin insertion and origin of anteriormost dorsal procurrent caudal-fin ray.
Ventral profile of head and body convex from anterior dentary tip to anal-fin origin. Ventral
profile of caudal peduncle slightly concave. Pseudotympanum absent.
Jaws of equal size, mouth terminal. Posterior terminus of maxilla reaching vertical through
anterior margin of pupil. Maxilla approximately at 45˚ angle relative to longitudinal axis of
body. Anterior and posterior nostrils separated only by skin fold, posterior opening crescent-
shaped. Frontals meeting each other only through the epiphyseal bar. Rhinosphenoid present
with developed dorsal process. Relatively long sphenotic spine, reaching dorsal margin of hyo-
mandibula. Frontal fontanel triangular and parietal fontanel large. Infraorbital series with five
or six elements. Anterior region of third infraorbital not reaching preopercle.
Single row of premaxillary teeth, 4(9) or 5(37) slightly compressed teeth with four to nine
cusps. Symphyseal tooth narrower distally than subsequent two teeth and slightly asymmetric.
Maxilla with 0(2), 1(8), 2(33) or 3(1) compressed teeth on anterodorsal margin of bone, with
Fig 2. Phycocharax rasbora, medial view of left side; premaxilla, 29.8 mm SL; dentary and maxilla,
29.1 mm SL, paratypes, both MZUSP 115341. Scale bar: 100 μm.
doi:10.1371/journal.pone.0170648.g002
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 5 / 15

three to seven cusps (Fig 2); anteriormost tooth usually largest. Maxilla suddenly expanded
ventrally to maxillary teeth. Dentary with 4(2) or 5(6) slightly compressed teeth with four to
nine cusps, followed by 3(2), 4(2), 5(2) or 8(2) relatively smaller conical or tricuspid teeth. Cen-
tral cusp of all teeth more developed than remaining lateral cusps. Premaxillary teeth with
cusp edges slightly curved outward, and dentary teeth cusp edges curved inward.
Scales cycloid, moderately large, circuli restricted to anterior field and five to twelve slightly
divergent radii extending to posterior margin of scales. Incomplete lateral line slightly
deflected downward with 7(6), 8(11), 9(9), 10(4) 11(3), 12(1) or 13(2) perforated scales. Lat-
eral series with 30(1), 31(8), 32(15), 33(9) or 34(1) scales including pored scales. Horizontal
scale rows between dorsal-fin origin and lateral line 5(38). Horizontal scale rows between lat-
eral line and pelvic-fin origin 3(7) or 4(30). Scales in median series between tip of supraocci-
pital spine and dorsal-fin origin 6(1), 9(10) or 10(20). Circumpeduncular scale rows 12(1), 13
(4) or 14(31). Anteriormost anal-fin rays base with single row of 2(9), 3(18) or 4(6) scales.
Caudal fin with scales only basally.
Dorsal-fin rays ii, 8(1) or 9(42), not including small ossification anterior to first dorsal fin
unbranched ray present in all examined specimens. Dorsal-fin origin slightly ahead of mid-
body. First dorsal-fin pterygiophore located behind neural spine of 10th(3) or 11th(5) verte-
brae. Adipose fin present. Anal-fin rays iv(7) or v(1), 16(24), 17(20) or 18(2), anteriormost
rays slightly longer, subsequent rays decreasing posteriorly in size; distal margin of anal fin
slightly concave in females or straight in males (see “Sexual Dimorphism”, below).
Fig 3. Phycocharax rasbora, MZUSP 119843, paratype, 29.1 male (a) and MZUSP 115313, paratype,
26.4 mm SL, female (b), immediately after collection.
doi:10.1371/journal.pone.0170648.g003
New characid from Brazil
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Anteriormost anal-fin pterygiophore inserted posterior to haemal spine of 16th(2), 17th(5) or
18th(1) vertebrae. Pectoral-fin rays i, 9(1), 10(24), 11(16) or 12(4). Pectoral-fin tip typically
not reaching pelvic-fin insertion. Pelvic-fin rays i, 7(46). Pelvic-fin tip almost reaching anal-
fin insertion. Caudal fin with i, 9(39) rays on the upper and 8, i (39) rays on lower lobe. Cau-
dal fin forked with lobes similar in size, and rounded tips. Ten (5) or 11 (3) dorsal procurrent
caudal-fin rays, and 7(1), 8(3) or 9(3) ventral procurrent caudal-fin rays.
Total vertebrae 32(4), 33(3) or 34(1). Precaudal vertebrae 16(6) or 17(2); caudal vertebrae
16(4) or 17(4). Supraneurals 4(1) or 5(7) with narrow bony lamellae on upper portion. Bran-
chiostegal rays 4(8). First gill arch with 1(1), 2(6) or 3(1) gill rakers on hypobranchial, 8(4) or 9
(4) on ceratobranchial, 1(8) on cartilage between ceratobranchial and epibranchial, and 6(7) or
7(1) on epibranchial. One row of gill rakers on first ceratobranchial; two rows on remaining
ones.
Color in alcohol: Overall body color beige to light brown, darker dorsally (Fig 1). Snout,
top of head, anterior portion of maxilla, and dentary tip dark; numerous small dark chromato-
phores scattered on infraorbital series, opercle, and gular area, mainly in males (females lack
dark chromatophores on gular area and infraorbitals). Scales on upper portion of body pre-
senting conspicuous reticulated pattern formed by dark pigmentation concentrated along
scale borders, gradually fading to lower flanks, typically more intense in males (Fig 1a) than in
females (Fig 1b). Two vertically elongated and narrow humeral blotches, the first lying at level
of third and fourth pored lateral-line scales, extending vertically over two or three vertical
scales rows above lateral line and over one or two below it. Second blotch lying at level of sixth
Table 1. Morphometric data for holotype and 38 paratypes of Phycocharax rasbora.Values for the
holotype included in range, range and mean ±SD (standard deviation).
Characters Holotype Range Median±SD
Standard length (mm) 29.1 23.7–32.1 27.9±1.9
Percentage of standard length
Body depth at dorsal-fin origin 39.7 33.2–40.8 36.7±2.0
Snout tip to dorsal-fin origin 53.5 49.8–56.4 53.2±1.5
Snout tip to pectoral-fin origin 28.4 27.1–32.4 28.7±1.2
Snout tip to pelvic-fin origin 51.0 47.3–56.0 51.8±1.9
Snout tip to anal-fin origin 65.2 63.7–71.1 68.7±1.8
Caudal-peduncle depth 11.3 10.5–12.9 11.5±0.5
Caudal-peduncle length 14.3 12.4–16.3 14.1±0.9
Pectoral-fin length 19.8 16.9–21.8 19.3±1.2
Pelvic-fin length 19.2 15.7–19.5 17.1±1.0
Pelvic-fin origin to anal-fin origin 17.9 15.9–20.2 18.1±1.0
Dorsal-fin base length 13.8 12.9–18.5 15.0±1.2
Dorsal-fin length 30.0 23.5–31.7 27.6±1.9
Dorsal-fin origin to caudal-fin origin 53.1 49.3–54.5 51.8±1.3
Anal-fin base length 27.2 20.5–27.4 24.8±1.8
Anal-fin length 17.9 16.7–21.8 19.0±1.1
Posterior margin of eye to dorsal-fin origin 39.9 37.4–42.1 40.0±1.1
Head length 25.7 24.2–28.6 25.6±1.0
Percentage of head length
Horizontal length eye 41.0 36.7–42.7 40.0±1.4
Snout length 26.8 21.7–27.4 24.6±1.5
Least interorbital width 33.2 30.7–36.7 33.2±1.6
Upper jaw length 44.0 38.1–44.3 40.5±1.7
doi:10.1371/journal.pone.0170648.t001
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 7 / 15

and seventh pored lateral line, extending vertically over two scales rows above lateral line.
Humeral blotches usually conspicuous, excepting in specimens smaller than 20.8 mm SL.
Posterior region of flanks with conspicuous horizontally-elongated blotch, approximately
triangular, of variable size, and extending posteriorly from vertical through dorsal-fin terminus
to caudal peduncle end; its intensity ranging from blurred to sharply defined. One series of
9–20 longitudinal, anteriorly directed V-shaped marks of variable intensity along horizontal
septum, more discernible in alcohol-preserved specimens. Dorsal and anal fins with numerous
large dark chromatophores concentrated along interradial membranes, giving overall dark col-
oration to these fins, more intense in males (Fig 1a) than in females (Fig 1b). Pelvic, caudal,
and adipose fins also with dark chromatophores, but in little amount in females. Pectoral fin
hyaline in both sexes.
Color in life: Males noticeably more colored than females (Fig 3). Dorsal portion of body
light beige. Humeral blotches and large dark triangular blotch located on posterior portion of
the body conspicuous. Upper portion of eye red to shiny red in males (Fig 3a) and pale red in
females (Fig 3b). Dorsal, adipose, caudal, and anal fins pale yellow with interradial membranes
more intensely pigmented by dark chromatophores in males than females. Pectoral and pelvic
fins hyaline. Head and anterior portion of body of males exhibiting red pigmentation irregu-
larly scattered (Fig 3a). Red pigmentation in males situated anterior to vertical through anal-
fin origin and more concentrated in anteroventral portion of body and head. Head and body
of females predominantly silver yellowish.
Sexual dimorphism: Males notably more brightly colored than females (Fig 3: see “Color
in life”) with conspicuous concentration of dark chromatophores on body and fins (Fig 1: see
“Color in alcohol”). In addition, males show anal-fin base slightly convex and distal margin
approximately straight with rays decreasing posteriorly in size, whereas females present anal-
fin base straight and distal margin clearly concave, with anteriormost rays distinctly longer
than remaining rays, forming a discrete anterior lobe (Fig 3). Profile along anal-fin base
approximately straight (in females) or slightly convex (in males). Males apparently reach larger
size than females (largest specimens examined, male 34.1 mm SL vs. female 31.4 mm SL). Sec-
ondary sexual characters related to bony-fin hooks on fins were not found and are certainly
absent given the sexual maturity of many examined specimens (see “Ecological notes”). Gill fil-
aments lack fusion.
Ecological notes: Phycocharax rasbora was collected primarily in dammed portions of the
rio Brac¸o Norte. Contrasting from other tributaries of the rio Tapajo
´s basin, which are primar-
ily clearwaters rivers, the rio Brac¸o Norte is a blackwater tributary of the rio Teles Pires. In the
site of occurrence of P.rasbora was build a small hydroelectric dam (PCH Brac¸o Norte IV),
and apparently the reservoir condition promoted the proliferation of algae. As consequence of
the damming, the species thrived and can be considered as highly abundant at the dammed
portion of the rio Brac¸o Norte. In addition, P.rasbora seems to be uncommon in the lotic
stretch of rio Brac¸o Norte downstream of the dam, where only three specimens were collected.
The type locality of the P.rasbora, the igarape
´do Arnaldo, is a small tributary which was
flooded during the damming of river, presenting muddy substrate with a great amount of
decomposed organic matter with undergrowth marginal vegetation formed by grasses (Fig 4).
In this area, Phycocharax rasbora was the most abundant species with 77% of all specimens col-
lected. The section of the rio Brac¸o Norte downstream the dam present sandy bottom with
pebbles and rocks. Phycocharax rasbora occurs syntopically at Brac¸o Norte reservoir with
other Characiformes species, such as Cyphocharax cf. spilurus (Curimatidae), Leporinus frider-
ici (Anostomidae), Serrapinus aff. micropterus,Astyanax aff. bimaculatus (Characidae), Hopler-
ythrinus unitaeniatus (Erythrinidae), Gymnotiformes, as Gymnotus diamantinensis
(Gymnotidae), and Cichliformes, i.e., Aequidens sp. and Apistogramma sp. (Cichlidae).
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 8 / 15

Although little abundant downstream the dam, P.rasbora was found co-occurring with the fol-
lowing Characiformes: Leporinus desmotes (Anostomidae), Hemiodus quadrimaculatus (Hemi-
odontidae), Astyanax aff. bimaculatus,Bryconops sp., Jupiaba polylepis,Jupiaba paranatinga,
Moenkhausia hasemani,Serrapinnus aff. micropterus (Characidae), and with a single species of
Siluriformes, Hypostomus sp. (Loricariidae).
Phycocharax rasbora was collected during the rainy seasons (April 2012; February 2014)
and a dry season (August 2015). Males and females presented gonads well developed in both
seasons. Oocytes with different sizes are present in the gonads, suggesting that females present
multiple spawning, as well as several other small characids (e.g. [19,20]). Stomach contents of
ten examined specimens contained mainly algae and vegetal matter.
Distribution: Phycocharax rasbora is so far known only from its type locality at upper rio
Brac¸o Norte, a right-bank tributary of the rio Peixoto de Azevedo, part of rio Teles Pires drain-
age, rio Tapajo
´s basin (Fig 5). The rio Brac¸o Norte drains the Serra do Cachimbo at northern
Mato Grosso State, Brazilian Amazon.
Etymology: From the Bengali word “rasbora”, the common name of the fish Rasbora ras-
bora (Hamilton). Rasbora is a generic name encompassed a great radiation of small cyprinids
from southeastern Asia, including the species currently allocated in the genus Trigonostigma
[21], which possess a dark triangular blotch on body sides very reminiscent in shape and posi-
tion similarly as found in the new species. Gender masculine. A noun in apposition.
Phylogenetic analysis: The analysis gave relatively divergent hypotheses, especially by
instabilities of some taxa whose relationships are not in the scope of this paper. However, in a
broad range of values of K between 5.9 and 23.5, most parsimonious trees ranging from 2750
to 2869 steps (CI = 0.138–0.144, RI = 0.652–0.669), results are stable concerning the new
taxon. In that range of parameters, Phycocharax rasbora is recovered as the sister species of
[Paracheirodon axelrodi (Schultz) + Hyphessobrycon elachys Weitzman] (Fig 6). Although far
from conclusive, the clade recovered by P.rasbora disclosed positive GC value, suggesting a
Fig 4. Igarape
´do Arnaldo, a tributary of rio Brac¸o Norte, near Brac¸o Norte hydroelectric dam,
Guarantãdo Norte, Mato Grosso, Brazil, type-locality of Phycocharax rasbora.
doi:10.1371/journal.pone.0170648.g004
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 9 / 15

well-supported relationship. In most analysis the clade composed of Phycocharax rasbora,
Paracheirodon axelrodi and Hyphessobrycon elachys is sister group of clade formed by Hyphes-
sobrycon loweae +H.vanzolinii. It is worth noting that this latter clade is relatively little sup-
ported compared with its sister clade (i.e. P.rasbora,P.axelrodi and H.elachys). The single
synapomorphy found for the Phycocharax clade is the abrupt expansion of the maxilla ven-
trally to the maxillary teeth (character 107, state 1). The section of the phylogenetic tree where
Phycocharax is included, with clade supports and obtained synapomorphies provided (Fig 6).
The complete phylogenetic hypothesis including clade supports is available in S1 Fig.
Discussion
The characters combination of the new taxon presented by phylogenetic analysis is not shared
by any known genus. According to the traditional classification of Characidae [22,23,24], Phy-
cocharax could be included into the subfamily Cheirodontinae, given that it possesses a single
row of aligned, expanded, and compressed premaxillary teeth. However, the new taxon proved
Fig 5. Map of Tapajo
´s and Xingu Rivers and adjoining areas, indicating distribution and type-locality
(square) of Phycocharax rasbora.
doi:10.1371/journal.pone.0170648.g005
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 10 / 15

not share the synapomorphies of Cheirodontinae according to the current phylogenetic analy-
sis [1,25]. Cheirodontinae have as synapomorphies the absence of humeral blotch, the pres-
ence of single row of aligned, pedunculate, and similarly-shaped premaxillary teeth, and the
presence of pseudotympanum between the anteriormost unmodified pleural ribs [25].
Although the new taxon shares the single premaxillary row of distally expanded teeth, they are
different from cheirodontine teeth since they have irregularly sizes with the medial teeth more
cuspidate and broader than the lateral ones (vs. number of cusps and shape with similar in
Cheirodontinae’s teeth). Furthermore, Phycocharax lacks pseudotympanum and possess two
humeral blotches (vs. presence of pseudotypanum and humeral blotch absent in Cheirodonti-
nae). Cheirodontinae have as unreversed synapomorphies the presence of an anguloarticular
lateral ridge and an abrupt dorsoventral expansion of the interopercular posterior region,
according to Mirande[1]. Both characters are absent in Phycocharax.
Fig 6. Phylogenetic relationships of Phycocharax rasbora under implied weighting (K = 7.5–11.4). Numbers above branches denote
GC values; negative values are not shown. Synapomorphies. A: 243(0); B: 68(1), 180(1), 253(0), 307(0); C: 285(0); D: 158(1), 224(0), 246
(0); E: 29(1), 65(0), 138(1); F: 107(1); G: 294(0), 365(1); H: 331(1); I: 141(0), 163(1); J: 246(0), 325(0); K: 93(1), 347(1); L: 20(1), 29(1), 45
(0); M: 91(0), 235(1); N: 293(0), 314(1); O: 333(1); P: 180(1); Q: 126(1), 182(0); R: 164(1); S: 29(1), 148(0), 307(0), 347(0); T: 247(0), 370
(2); U: 96(1), 141(1), 163(0). Autapomorphy of P.rasbora: 350(1).
doi:10.1371/journal.pone.0170648.g006
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 11 / 15

Most non-cheirodontine and non-iguanodectine genera of Characidae have usually two or
three premaxillary teeth rows. Among those taxa, only the monotypic genera Carlana Strand,
Erythrocharax,Myxiops Zanata & Akama, and also the species Paracheirodon axelrodi have
distally expanded premaxillary teeth with five or more cusps, similarly as is presented by
Phycocharax.
Carlana shares with the remaining Rhoadsiinae the elongation of the maxilla, along with
the acquisition of strong conical teeth during growth [7], missing feature in Phycocharax of
any size observed. Erythrocharax has been diagnosed from remaining Characidae genera by
having several features not shared by Phycocharax, such as the medial articulation of contralat-
eral pelvic bones (not observed in one c&s specimen of Erythrocharax altipinnis examined in
this study—MZUSP 119081), humeral blotch absent, presence of pseudotympanum, and
absence of fifth and sixth infraorbitals bones [4]. In addition, the nasal openings of the Erythro-
charax are separate by a narrow skin without fold, while in Phycocharax this character is con-
tiguous to each other and limited by a skin fold, which is the generalized condition in
Characidae. Erythrocharax was recovered as sister group of Rhoadsiinae and included in a
clade with the Aphyoditeinae and Cheirodontinae (S1 Fig). Myxiops in turn is distinguishable
from Phycocharax by having complete lateral line, and maxillary teeth edges aligned with pre-
maxillary teeth edges, forming a continuous line between both bones [26]. In contrast, Phyco-
charax possess incomplete lateral line, and does not have the maxillary teeth forming a
continuous line with premaxillary teeth. In the present analysis, Myxiops aphos was obtained
as the sister group of a large clade including, among others, the Aphyocharacinae, Aphyoditei-
nae, Cheirodontinae, Gymnocharacinae, Rhoadsiinae, and Stevardiinae. The evaluation of the
phylogenetic relationships of Myxiops could be more accurately assessed with a better taxon
sampling, especially in Deuterodon. However, according to the analysis presented herein, Deu-
terodon is not a taxon closely related to Phycocharax.
The anal-fin dimorphism observed in Phycocharax rasbora, with males possessing a straight
distal margin or almost so, is similar to the found in some species of Hyphessobrycon Durbin,
primarily H.bifasciatus Ellis, H.heliacus Moreira, Landim & Costa, H.igneus Miquelarena,
Menni, Lo
´pez & Casciotta, H.kayabi Teixeira, Lima & Zuanon, H.loweae Costa & Ge
´ry, H.
peugeoti Ingenito, Lima & Buckup, and H.procyon Pastana & Ohara [27,28]. Between the two
Hyphessobrycon species examined herein, H.bifasciatus and H.loweae, just this latter was
herein recovered as close related to Phycocharax rasbora. However, the referred clade includes
both species that exhibit sexual dimorphism as those that not.
The black triangular blotch on posterior flank portion of the Phycocharax is unique among
the characids, but a similar-shaped blotch is present in Hemigrammus pulcher. In contrast, H.
pulcher is easily distinguished from Phycocharax rasbora by having, as well as the remaining
Hemigrammus species, two rows of premaxillary teeth (vs. single row). In addition, the pre-
maxillary teeth of the new taxon are relatively compressed and distally expanded, while those
of H.pulcher are relatively cylindrical with parallel lateral margins. Furthermore, H.pulcher
was obtained by phylogenetic analysis in a clade along with H.haraldi Ge
´ry and H.aguaruna
Lima, Correa & Ota (Fig 6), corroborating the hypothesis that H.pulcher belongs to the Hemi-
grammus ocellifer (Steindachner) species group [29,30] and, therefore, different from P.
rasbora.
Phylogenetic relationships of the new taxon were supported only by a few characters in
many analysis performed here. In most analysis, Phycocharax rasbora was recovered as the sis-
ter group of Paracheirodon axelrodi plus Hyphessobrycon elachys, in a clade that also includes
Hyphessobrycon loweae and Hyphessobrycon vanzolinii. The uncertainty about the phylogenetic
relationships of the new taxon, in addition to its unique combination of characters, lead us to
erect a new monotypic genus in the Characidae. The erection of a new generic name when
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 12 / 15

there is a stable and well-supported sister-group relationship with some available genera is
undesirable in most cases, mainly when the candidates are morphologically similar. However,
in this particular case, neither the phylogenetic relationships are stable or even well supported,
nor the candidate genera are similar enough to include this new taxon under a common
diagnosis.
Supporting information
S1 Table. Characters states of all Characidae species analyzed herein plus Phycocharax ras-
bora, new genus. Analyzed characters are listed in S2 Appendix. Polymorphisms of states 0
and 1 are denoted with a “z”.
(DOCX)
S1 Fig. Phylogenetic relationships among the Characidae based in morphological data,
under implied weighting with K values between 11.9 and 13.1. Numbers on nodes are GC
values after a Symmetric Resampling. Clades with negative values (shown between brackets)
are weakly supported.
(TIF)
S1 Appendix. List of material examined. Only c&s and alcohol specimens are listed.
(DOCX)
S2 Appendix. List of characters used in the phylogenetic analysis.
(DOCX)
Acknowledgments
This paper benefited from comment and criticism of Marcelo Andrade (UFPA). The authors
are grateful to Rosalvo Rosa, James Bilce (MapsMut); Osvaldo T. Oyakawa and Murilo Pastana
(MZUSP) for help and assistance during the field work. We are also grateful to Michel Gianeti,
Ale
´ssio Datovo, and again to Osvaldo T. Oyakawa (MZUSP) for curatorial assistance and loan
of material used in this study, and to Tu
´lio F. Teixeira (MZUSP) for help with the sex determi-
nation of dissected specimens. SEM images were taken by Lara Guimarães (MZUSP). TNT
software is available free from the Willi Hennig Society. Most of the analysis and some figures
have been done in a Linux platform; we thank Manjaro, Gimp, and InkScape communities.
Part of the type series was collected during an expedition funded by the South American Char-
aciformes Inventory (FAPESP 2011/502827, http://www.projeto-saci.com). Authors are sup-
ported by FAPESP (WMO: grant # 2013/22473–8; FCTL: grants # 2011/51532–7 and 2013/
20936–0), CONICET (JMM: PIP–0301), and FONCyT (JMM: PICT 2011–0992). A travel by
the second author to ZUEC was funded by FAPESP [grant # 2011/51532–7, "Systematics of tet-
ras (genera Hemigrammus,Hyphessobrycon,Thayeria,Parapristella and Bryconella), with
emphasis on the species from northern cis-andean South America"].
Author contributions
Conceptualization: WMO FCTL.
Data curation: JMM WMO FCTL.
Formal analysis: JMM WMO.
Funding acquisition: WMO FCTL.
New characid from Brazil
PLOS ONE | DOI:10.1371/journal.pone.0170648 February 15, 2017 13 / 15

Investigation: WMO FCTL JMM.
Methodology: JMM WMO FCTL.
Project administration: WMO FCTL JMM.
Resources: WMO FCTL JMM.
Software: JMM WMO.
Supervision: WMO FCTL JMM.
Validation: WMO FCTL JMM.
Visualization: WMO FCTL JMM.
Writing – original draft: WMO FCTL JMM.
Writing – review & editing: WMO FCTL JMM.
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