A New Species of Characidium Reinhardt (Characiformes, Crenuchidae) with a Distinctively Dimorphic Male

Abstract

We herein describe Characidium satoi, new species, only known from its type locality at Rio Curral das Éguas, a small tributary of Rio Abaeté, in the Rio São Francisco basin, Brazil. It can be distinguished from its congeners by the following characteristics: area between the pelvic fin and the origin of anal fin moderate to strongly convex in lateral view; presence of irregular and discontinuous bars, forming dorsal blotches separated from ventral V-, W-, or diamond-shaped marks; and the first anal-fin radials inserted between the fifth and sixth caudal vertebrae. The juveniles and mature females of Characidium satoi, new species, have smooth fin rays, while mature males have hooks on pelvic and, in some specimens, pectoral and dorsal fins. Moreover, females and immature males have irregular bars on dorsum and fuzzy vertical bars on body; during the breeding season, males develop uniformly darker pigmentation on body and head, lacking any distinctive vertical bar on body. This seasonal color dimorphism i...

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A New Species of Characidium Reinhardt (Characiformes, Crenuchidae) with a
Distinctively Dimorphic Male
Author(s): Marcelo R. S. Melo and Osvaldo T. Oyakawa
Source: Copeia, 103(2):281-289.
Published By: The American Society of Ichthyologists and Herpetologists
DOI: http://dx.doi.org/10.1643/CI-14-073
URL: http://www.bioone.org/doi/full/10.1643/CI-14-073
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A New Species of Characidium Reinhardt (Characiformes, Crenuchidae)
with a Distinctively Dimorphic Male
Marcelo R. S. Melo
1
and Osvaldo T. Oyakawa
2
We herein describe Characidium satoi, new species, only known from its type locality at Rio Curral das E
´guas, a small
tributary of Rio Abaete´, in the Rio Sa˜o Francisco basin, Brazil. It can be distinguished from its congeners by the following
characteristics: area between the pelvic fin and the origin of anal fin moderate to strongly convex in lateral view;
presence of irregular and discontinuous bars, forming dorsal blotches separated from ventral V-, W-, or diamond-
shaped marks; and the first anal-fin radials inserted between the fifth and sixth caudal vertebrae. The juveniles and
mature females of Characidium satoi, new species, have smooth fin rays, while mature males have hooks on pelvic and, in
some specimens, pectoral and dorsal fins. Moreover, females and immature males have irregular bars on dorsum and
fuzzy vertical bars on body; during the breeding season, males develop uniformly darker pigmentation on body and
head, lacking any distinctive vertical bar on body. This seasonal color dimorphism is reported in the family Crenuchidae
for the first time.
THE genus Characidium Reinhardt currently includes
59 valid species of Neotropical fishes, including the
species described herein (Eschmeyer, 2015). The
genus is in urgent need of a major taxonomic revision,
and the total number of species is far underestimated, with
many species yet to be described. We herein formally
describe Characidium satoi, new species, known from a
single locality in the upper Rio Sa˜o Francisco, downstream
from the Treˆs Marias reservoir.
Two species of Characidium have previously been de-
scribed from the Rio Sa˜o Francisco basin: C. fasciatum
Reinhardt, 1867 and C. lagosantense Travassos, 1947. Both
species were described from the Rio das Velhas, a major
tributary of the upper Rio Sa˜o Francisco, in the vicinity of
Lagoa Santa, Minas Gerais. Only two additional species were
reported from the Rio Sa˜o Francisco basin: Characidium aff.
zebra Eigenmann, 1909 and Characidium aff. bimaculatum
Fowler, 1941 (Travassos, 1956; Britski et al., 1984; Buckup,
1992; Casatti and Castro, 1998; Alves and Pompeu, 2001;
Rosa et al., 2004; Barbosa and Soares, 2009).
In a field guide of the fishes from the Treˆs Marias dam
area, Britski et al. (1984) reported the occurrence of a single
species in the area, Characidium fasciatum. A re-examination
of the material obtained by Y. Sato and H. Britski for that
field guide revealed the existence of three species, none of
which were C. fasciatum:Characidium aff. zebra,Characidium
aff. bimaculatum, and an undescribed species. Noteworthy,
Britski et al. (1984) was published before Buckup’s (1992) re-
description of C. fasciatum, which elucidated the common
confusion between C. fasciatum and C. zebra.
MATERIALS AND METHODS
Morphometric and meristic data were obtained under a
binocular stereo microscope. A modified protocol for taking
the morphometric data is introduced as follows, based on
Buckup (1993a) with the addition of nine measurements
taken between homologous landmarks. Landmarks for
measurements are defined in Figure 1. 1) Pectoral-fin height:
distance from the origin of the first unbranched pectoral-fin
ray to the distal tip of the third unbranched pectoral-fin ray,
as there are usually three unbranched rays in the pectoral fin
in Characidium. 2) Dorsal-fin height: distance from the
origin of the first dorsal-fin ray to the distal tip of the second
dorsal-fin ray; the first and second rays are generally
unbranched and the third is branched in Characidium.3)
Dorsal-fin base: distance from the origin to the insertion of
the dorsal fin. 4) Pelvic-fin height: distance from the origin
to the tip of the first pelvic-fin ray; in general, this is the
only unbranched pelvic-fin ray in Characidium. 5) Anus to
anal fin distance, following Melo and Buckup (2002):
distance from the anus to the origin of the anal fin. 6)
Anal-fin height: distance from the origin of first anal-fin ray
to the distal tip of the second anal-fin ray, as there are
usually two unbranched anal-fin rays in Characidium.7)
Anal-fin base: distance from the origin to the insertion of
the anal fin. 8) Adipose-fin height: distance from the origin
to the distal tip of the adipose fin. 9) Peduncle length:
distance from the insertion of the last anal-fin ray to the
midpoint of a vertical that passes through the distal margin
of the hypurals—i.e., same as landmark used for standard
length. Following Melo and Buckup (2002), we included the
count of the total number of scale rows between the anus
and the insertion of the first anal-fin ray. In some
specimens, there were two small, side-to-side scales, poste-
rior to the anus; in these cases, they were counted as a single
scale.
With the addition of the above morphometric and
meristic data, we intend to better describe the proportions
of the fins’ height, bases, and their proportions in relation to
the standard length of the body. We did not include the
caudal-fin length, since it can be evaluated by total length of
the specimen versus the standard length, as indicated in
Buckup’s (1993a) protocol. We understand that, in certain
cases, those measurements will not necessarily fit the length
of the longest fin ray; however, our choice was based on
homologous landmarks, which are easy to identify on any
species of Characidium and allow further comparison of the
proportions between species.
All measurements were taken using a digital caliper to the
nearest 0.1 mm. Counts are listed in the text, followed by
their frequencies in parentheses, with an asterisk indicating
1
Instituto Oceanogra´fico, Universidade de Sa˜ o Paulo, Departamento de Oceanografia Biolo´ gica, Laborato´ rio de Sistema´ tica de Peixes, Prac¸a do
Oceanogra´fico 191, 05508-120 Sa˜o Paulo, SP, Brazil; E-mail: melomar@usp.br. Send reprint requests to this address.
2
Museu de Zoologia da Universidade de Sa˜o Paulo, Laborato´ rio de Ictiologia, Avenida Nazare´ 481, 04263-000 Sa˜o Paulo, SP, Brazil; E-mail:
oyakawa@usp.br.
Submitted: 9 May 2014. Accepted: 7 October 2014. Associate Editor: R. E. Reis.
F2015 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/CI-14-073 Published online: May 4, 2015
Copeia 103, No. 2, 2015, 281–289

the value for the holotype. Specimens were cleared and
stained according to the method described by Taylor and
Van Dyke (1985); supernumerary dorsal- and anal-fin
elements, skeletal counts, and ectopterygoid teeth were
counted only in cleared-and-stained (CS) specimens. The
caudal-fin rays were counted from ventral to dorsal,
following McDowall (2003). Vertebral count includes the
four anteriormost elements modified into the Weberian
Apparatus, and the urostyle was counted as a single element.
Sex of individuals was determined by observing eggs
through the skin or, if necessary, by making a small incision
on the right side of the flank.
Institutional abbreviations are as listed at http://www.
asih.org/resources. Abbreviations: CS, cleared and stained;
SL, standard length; n, number of specimens; mun., the
Brazilian word municı´pio (municipality).
Characidium satoi, new species
Figures 2, 3, 4; Table 1
Characidium fasciatum.—Britski et al., 1984:54 (non Rein-
hardt), in part.
Holotype.—MZUSP 114614, female, 50.7 mm SL, Brazil,
Minas Gerais, mun. Treˆs Marias, Co´ rrego Curral das E
´guas,
tributary of Rio Abaete´, Rio Sa˜o Francisco basin, 18u079130S,
45u249520W, M. R. S. Melo, O. T. Oyakawa, and P. Camelier,
7 December 2012.
Paratypes.—All from Brazil, Minas Gerais, Rio Sa˜o Francisco
basin: MZUSP 39676, 15 (7 mature females, 3 mature males,
5 unsexed but probably females), 15.2–38.9 mm SL, Co´ rrego
Curral das E
´guas, tributary of Rio Abaete´, 18u079S, 45u249W
(coordinates inferred), Projeto UHE Formoso, 21 March
1988; MZUSP 95289, 10 (all mature males, 1 CS), 36.3–
41.8 mm SL, Co´ rrego Curral das E
´guas, at the border
between mun. Treˆs Marias and Sa˜o Gonc¸alo do Abaete´,
18u079130S, 45u249520W, O. T. Oyakawa, M. Toledo-Piza, I.
Fichberg, and C. C. Chamon, 3 October 2007; MZUSP
95293, 10 (all mature females, 1 CS), 25.3–42.4 mm SL,
collected with MZUSP 95289; MZUSP 115059, 17 (13 mature
females, 4 juveniles), 26.2–44.3 mm SL, collected with
holotype; ROM 95300, 2 (mature females), 48.7–52.2 mm
SL, collected with holotype; ZUEC 8549, 2 (1 male, 1
female), 42.4–46.2 mm SL, collected with MZUSP 95289.
Non-type specimens.—Brazil, Minas Gerais, Rio Sa˜o Francisco
basin: MZUSP 115060, 2 (both females), 40.5–40.8 mm SL,
collected with holotype, 95%ethanol preserved specimens
for DNA extraction.
Diagnosis.—Characidium satoi can be diagnosed externally
from its congeners by having area between pelvic fin and
origin of anal fin moderate to strongly convex in lateral view
(vs. area between the pelvic fin and the anal-fin origin
straight); and by color pattern, with females, juveniles, and
non-breeding males having irregular and discontinuous bars,
forming dorsal blotches separated from ventral part, which is
V-shaped, W-shaped, or diamond-shaped, or breeding males
having less distinct patterning and an overall darker, more
uniform pigmentation. Characidium satoi has one putative
internal autapomorphy: anteriormost first anal-fin radials
inserted between the fifth and sixth caudal vertebrae (vs.
insertion of anal fin between the second and third caudal
vertebrae in C. fasciatum,C. lanei,C. lauroi,C. schubarti, and
C. interruptum, between third and fourth or fourth and fifth
vertebrae in C. japuhybense,C. pterostictum, and C. xanthop-
terum). Other useful external diagnostic characteristics are as
follows: isthmus scaled (vs. isthmus lacking scales in C.
alipioi,C. amaila,C. crandellii,C. declivirostre,C. fasciatum,C.
grajahuensis,C. gomesi,C. japuhybense,C. lauroi,C. macro-
lepidotum,C. timbuiense,C. oiticicai,C. pterostictum,C.
schubarti, and C. vidali); lateral line complete, with 34–37
perforated scales (vs. lateral line incomplete, with 15 or less
perforated scales in C. bahiense,C. interruptum,C. laterale,C.
mirim,C. nupelia,C. rachovii,C. stigmosum, and C. xavante);
origin of anal fin far posterior from anus, separated by four to
seven scales (vs. origin of anal fin close to anus, separated
from anus by two to four scales in all species of Characidium,
except in C. hasemani,C. litorale, and C. zebra); distal tip of
anal-fin rays reaching base of ventral caudal-fin ray (vs. not
reaching, except in C. bahiense,C. hasemani,C. mirim, and C.
zebra, and mature males of C. rachovii); and by the hooks
present on the pectoral- and pelvic-fin rays of males (vs.
Fig. 1. Landmarks on body (left) and head (right) of Characidium used for taking morphometric data: (1) tip of snout; (2d, v) posteriormost tip of
dorsal or ventral caudal-fin lobe, respectively; (3) middle of vertical line that passes through the posterior edge of hypurals; (4) posterior tip of opercle
bone; (5) origin of pectoral fin (5base of anterior pectoral-fin ray); (6) tip of the third unbranched pectoral-fin ray; (7) origin of dorsal fin; (79)
contralateral spot on belly to origin of dorsal fin, for the body depth at the origin of dorsal fin; (8) tip of the second dorsal-fin ray; (9) insertion of the
dorsal fin; (10) origin of pelvic fin; (11) tip of the unbranched pelvic-fin ray; (12) anus; (13) origin of anal fin; (139) contralateral spot on dorsum to
origin of anal fin, for the body depth at the anal-fin origin; (14) tip of second anal-fin ray; (15) tip of longest anal-fin ray; (16) insertion of anal fin;
(17) origin of adipose fin; (18) distal tip of adipose fin; (19 and 199) origin of dorsal and ventral anterior procurrent caudal-fin ray, respectively; (20)
anterior, soft margin of eye; (21) posterior, soft margin of eye; (22) ventral, soft margin of eye; (23) posterior tip of maxilla; (24) anterior rim of
anterior naris; (25) anterior rim of posterior naris; (26) posterior prolongation of dermal fold that overlays the maxilla when mouth is closed; (27)
lateral margin of frontal bone, at its greatest concavity. Continuous line indicates the body limits, and dotted line indicates bones only seen by
transparence of skin; abbreviations are: op, opercle bone; sop, subopercle bone.
282 Copeia 103, No. 2, 2015

hooks absent, except in C. bahiense,C. bimaculatum,C.
lagosantense,C. litorale,C. mirim,C. nupelia,C. stigmosum,C.
xanthopterum, and C. xavante).
Description.—Morphometric data summarized in Table 1.
Species of Characidium reaching 44.3 mm SL. Body elongat-
ed; dorsal profile of body moderately concave between head
and last dorsal-fin ray; gently concave between last dorsal-
fin ray and adipose fin; straight between adipose fin and
base of dorsal caudal-fin ray. Ventral profile straight or
gently convex from symphysis of dentaries to pelvic-fin
base; moderately to strongly convex between pelvic-fin base
to anal-fin origin; concave at anal-fin base, and straight in
ventral profile of caudal peduncle. Greatest depth of body
slightly anterior to dorsal-fin origin.
Snout short and blunt in lateral view. Mouth small,
subterminal; ventral margin of premaxilla at level of inferior
margin of eye. Posterior tip of maxilla reaching level of
anterior margin of eye. Orbit oval, slightly elongated
anterodorsally; margin of eye free. Nares distinctly separat-
ed; distance between nares larger than distance between
posterior naris and eye. Margin of anterior naris expanded,
forming circular rim; posterior naris crescent-shaped. Pari-
etal branch of supraorbital laterosensory canal present,
reaching parietal bone; frontal branch of supraorbital
laterosensory canal present. Fontanel wide, anteriorly
bordered by frontals, laterally by parietals and posteriorly
by supraoccipital bones.
Dentary teeth 6(2), 7(7), 8(9), 9(9), or 10(3*), in single row;
teeth decreasing gradually in size posteriorly, conical,
unicuspid or triscuspid with small medial and lateral
cuspids. Premaxillary teeth 5(7*), 6(15), or 7(8), in single
row; teeth decreasing gradually in size posteriorly, conical,
unicuspid or triscuspid with small medial and lateral
cuspids. Maxillary teeth absent. Ectopterygoid teeth 8(1) or
9(1), in single row; conical, unicuspid. Mesopterygoid teeth
Fig. 2. Characidium satoi, new species: (A) holotype, MZUSP 114614, 50.7 mm SL, female, in dorsal, lateral, and ventral views; (B) paratype, MZUSP
95289, 48.5 mm SL, dimorphic male in dorsal, lateral, and ventral views; (C) paratype, MZUSP 11464, 52.8 mm SL, female in dorsal and lateral views;
(D) paratype, MZUSP 11464, 50.0 mm SL, female, in dorsal and lateral views, and (E) same as (D), live specimen. All specimens from Co´ rrego Curral
das E
´guas, Treˆ s Marias, Minas Gerais (18u079130S45u249520W).
Melo and Oyakawa—A new species of Characidium from Rio Sa˜o Francisco 283

absent. Branchiostegal rays 5(2); 4 attached to anterior
ceratohyal (2). Gill rakers on first arch 11(2).
Scales cycloid; parallel radii present on posterior field.
Lateral series of scales 34(3), 35(18*), 36(8), or 37(1), all
perforated by lateral-line canal. Scales above lateral line
4(30*). Scales below lateral line 5(1) or 6(29*). Scales around
caudal peduncle 12(22*), 13(5), or 14(2). Pre-dorsal scale
series arranged in single, regular row; scales in pre-dorsal
series 9(1), 10(11*), 11(16), or 12(2). Scales between anus
and origin of anal fin 4(3), 5(13), 6(13*), or 7(1). Isthmus
scaled.
Pectoral-fin rays iii+7+i(8), iii+8+i(18*), iii+8+ii(2), or
iii+9+1(1). Pelvic-fin rays i+7+i(30*). Dorsal-fin rays
ii+9(30*); supranumerary element on first pterygiophore of
dorsal fin 1(2). Anal-fin rays ii+6(30*); supranumerary
element on first pterygiophore of anal fin absent. Principal
caudal-fin rays i+8+8+i(1) or i+8+9+i(29*). Adipose fin
present (30*).
Precaudal vertebrae 18(2); total vertebrae 34(2). Supra-
neurals 5(5). Upper procurrent rays 7(1) or 8(1); lower
procurrent rays 6(1) or 7(1). Epurals 2(1) or 3(1). Swim
bladderwithposteriorchamberlongerthananterior
chamber.
Color in alcohol.—Color of body and head variable. Imma-
ture specimens, females, and non-breeding males with pale
ground color in head and body (Fig. 2A, C, D). Head pale
yellow, with easily distinguishable melanophores widely
distributed on lateral sides; more concentrated around orbit
and on iris, opercle, in single stripe between tip of snout and
anterior margin of eye, and continued posteriorly between
posterior margin of eye and humeral spot. Widely spaced
melanophores often present on distal portion of maxilla,
cheek, and region posteroventral to orbit, opercle, and
subopercle. Dorsal portion of head heavily pigmented on
cranium and supraorbital region. Ventral portion of head
and gular area pale. Body ground color pale yellow.
Melanophores more abundant on posterior margin of scales.
Humeral spot at level of supracleithrum, conspicuous,
dorsoventrally elongated. Single, thin dark stripe from
humeral spot to base of caudal-fin rays, at level of horizontal
septum.
Transversal bars on body eight to ten. Dorsal portion of
bars discontinuous with ventral, forming well-marked
blotches disconnected from ventral part of bars. Bars on
dorsal midline continuous or discontinuous with contralat-
eral side (Fig. 2A, C). Ventral portion of bars along flank,
irregularly distributed, forming small oval dots, V-shaped,
W-shaped, or diamond-shaped marks along and ventral do
lateral line. Bars not reaching ventral part of belly and
caudal peduncle, except for one bar immediately anterior to
anal-fin insertion. Ventral portion of body mostly pale and
without melanophores, except longitudinal dark line on
midline, between pelvic bones and origin of anal fin,
Fig. 3. Topographic map of the Rio Sa˜ o Francisco basin; only states within the drainage are indicated. The Upper Sa˜ o Francisco is highlighted, with
indications for type locality of Characidium satoi (triangle), sites mentioned in text (circles), and major rivers. State acronyms are as follows: AL,
Alagoas; BA, Bahia; DF, Distrito Federal; GO, Goia´s; MG, Minas Gerais; SE, Sergipe; PE, Pernambuco.
Fig. 4. The caudal peduncle of a cleared-and-stained specimen of
Characidium satoi (MZUSP 95289, 44.6 mm SL), showing the relative
position of anal-fin insertion in relation to the first caudal vertebrae
(asterisk) and the anus (arrow).
284 Copeia 103, No. 2, 2015

coincident with infracardinalis medius muscles, and three
transversal bars anterior to anal fin, at level of anal-fin rays,
and on caudal peduncle. Pectoral, pelvic, dorsal, anal, and
adipose fins hyaline; few diffuse melanophores on rays i to
iii of pectoral fin; caudal fin hyaline, with two diffuse, light
bands of melanophores on base and middle of caudal-fin
rays. Spot on base of caudal-fin rays conspicuous and
rounded.
Breeding mature males with distinctively darker color
(Fig. 2B). Melanophores on head expanded, covering most
part of lateral head in lateral view, darker in areas
posteroventral to orbit and opercle. All parts of head heavily
pigmented, except for branchiostegal rays. Stripe on snout
darker than head pigmentation, but posterior stripe between
orbit and humeral spot indistinguishable. Overall body
color dark with irregular lighter areas; melanophores more
concentrated on posterior margin of scales. Humeral spot
inconspicuous, darker than background coloration. Stripe
and bars slightly darker than body, or indistinguishable.
Dorsal bars fused, forming single, uniformly dark area from
head to insertion of caudal fin. Ventral part of body
pigmented, slightly lighter than flank. Pectoral, pelvic,
dorsal, anal, and caudal fins uniformly dusky, with mela-
nophores more concentrated on fin rays than on interradial
membrane; adipose fin uniformly dusky.
Color in life.—Only documented from mature females
(Fig. 2E). Darker areas as described above. General body
and head ground color bright yellow, darker above lateral
line, and dorsal portion of premaxilla and maxilla, snout,
and head. Ventral part of head and body whitish including
cheek and belly to anus. Golden hue on dorsal and lateral
sides of head and body; silvery hue along flanks. Anal-,
caudal-, dorsal-, pectoral-, and pelvic-fin rays yellow, darker
on their bases; fin membranes hyaline; adipose fin light
yellow.
Sexual dimorphism.—Mature males can be distinguished by
the presence of hooks on the pelvic-fin rays and, in some
specimens, pectoral- and dorsal-fin rays. The hooks are
present exclusively on the branched rays. Breeding males
have a characteristic color pattern as described above, and
relatively thicker bodies.
Distribution.—Characidium satoi appears to be narrowly
endemic, being known from a single locality in the Rio
Sa˜o Francisco Basin (Fig. 3), the Co´ rrego Curral das E
´guas, a
small tributary of the right margin of Rio Abaete´ . The Rio
Abaete´ is one of the major tributaries of the upper Rio Sa˜o
Francisco basin, and the first tributary downstream from the
Treˆs Marias dam. The Rio Curral das E
´guas has fast flowing
waters with periodic shallow riffles no more than 0.4 m deep
alternating with artificial pools more than 2 m deep.
Characidium satoi was only found in the rapids. Despite
proximity between the type locality and the Treˆs Marias
Lake, about 13 km to the nearest margin and 20 km to the
Table 1. Morphometric data for Characidium satoi. Range values are for holotype and paratypes (MZUSP 114614, MZUSP 95289, MZUSP 95293,
ROM 95300, ZUEC 8549). Distances are based on landmarks indicated in Figure 1. n: total number of specimens examined; SD: standard deviation.
Distances Character Holotype nRange Mean SD
1–2v Total length (mm) 50.70 28 29.8–52.8 46.5
1–3 Standard length (mm) 42.33 30 25.3–44.3 38.8
Percentage of standard length
1–4 Head length 24.2 30 23.4–28.5 25.0 1.1
1–5 Prepectoral distance 21.8 30 21.8–28.8 24.0 1.6
5–6 Pectoral-fin height 17.8 30 16.9–23.4 19.8 1.6
1–7 Predorsal distance 46.3 30 45.8–51.8 47.8 1.4
7–8 Dorsal-fin height 14.7 29 14.1–20.9 16.2 1.4
7–9 Dorsal-fin base 13.7 30 12.2–15.0 13.5 0.6
1–10 Prepelvic distance 50.6 30 49.8–53.9 51.4 1.1
10–11 Pelvic-fin height 11.1 30 10.3–15.9 12.2 1.4
1–13 Preanal distance 77.2 30 75.1–80.4 77.4 1.2
1–15 Anal-apex distance 95.6 30 93.5–101.9 96.1 2.0
12–13 Anus to anal-fin distance 11.8 30 9.0–14.6 11.3 1.2
13–14 Anal-fin height 12.6 30 11.9–16.2 13.6 1.1
13–16 Anal-fin base 6.6 30 6.4–9.4 7.8 0.8
17–18 Adipose-fin height 6.0 30 4.9–6.7 5.6 0.5
16–3 Peduncle length 15.3 30 14.0–18.1 15.8 0.9
7–79Body depth at dorsal-fin origin 19.9 30 19.9–26.2 23.3 1.7
13–139Body depth at anal-fin origin 14.7 30 13.9–19.6 16.1 1.9
19–199Body depth at caudal peduncle 10.9 30 10.2–13.5 11.5 0.8
5 (left–right) Body width 11.5 30 9.6–13.9 12.3 0.9
Percentage of head length
1–20 Snout length 21.9 30 19.2–26.3 22.5 1.4
1–23 Snout-maxillary tip 26.0 30 23.6–28.7 26.0 1.1
24–20 Anterior naris-orbit 10.5 30 9.3–12.5 10.5 0.7
24–20 Posterior naris-orbit 4.7 30 3.1–6.2 4.7 0.8
22–26 Cheek 7.6 30 6.7–10.6 8.5 1.0
20–21 Orbital diameter 25.6 30 23.3–28.0 25.6 1.3
27 (left–right) Interorbital diameter 17.4 30 17.4–23.1 20.2 1.6
Melo and Oyakawa—A new species of Characidium from Rio Sa˜o Francisco 285

dam, it does not seem to be directly affected by the
damming of the Rio Sa˜o Francisco. There is visual evidence;
however, of silting caused from deforestation of the riparian
zone.
Ecological notes.—The breeding season of Characidium satoi
in the Sa˜o Francisco basin apparently coincides with the
rainy season—which goes from October to March (Comiteˆ
da Bacia Hidrogra´fica do Rio Sa˜o Francisco, 2004). All
mature males collected in October 2007 (MZUSP 95289,
n511) have hooks on fins and a distinctively darker
pigmentation. Whereas, the mature males collected in
March 1988 (MZUSP 39676, n53) have hooks on fins,
but a lighter color pattern, indistinguishable from the
females and juveniles. A single immature male was collected
in December 2012 (MZUSP 114614, 32.7 mm SL) lacking
hooks on fins and a distinctive color pattern. Mature females
with well-developed ovaries were collected in October 2007
(MZUSP 95293, n58), and December 2012 (MZUSP 114614,
n518), indicating the breeding season. The specimens of
both lots have expanded bellies with enlarged ovaries that
occupy more than two thirds the abdominal cavity, and
contain large, orange eggs. This contrasts with the females
of collected in March 1988 (MZUSP 39676, n57), whose
ovaries were quiescent, with no visible oocytes, or at an early
stage of oogenesis with few, transparent oocytes, or eggs in
early development with very few, transparent oocytes.
Curiously, not a single mature male was collected in
December 2012. This may be due to the apparently lower
proportion of males in the basin, since we found only 15
males among the 54 specimens (sex ratio 3.6:1).
The presence of hooks exclusively on the fins of mature
males throughout the year indicates that these structures
probably arise when they become sexually mature and are
not temporary. During the breeding season, mature males
apparently undergo a temporary color change that enhances
sexual dimorphism, becoming darker and more uniformly
colored.
Etymology.—The specific name, satoi, is a patronym that
honors Dr. Yoshimi Sato, a biologist of the Companhia de
Desenvolvivmento dos Vales do Sa˜o Francisco e do Parnaı´ba
(CODEVASF), for his contributions to the knowledge and
conservation of the ichthyofauna of the Rio Sa˜o Francisco
drainage.
DISCUSSION
Of the four species previously known to occur in the Rio Sa˜o
Francisco basin, two have their type localities in the basin.
Characidium fasciatum was described from Ribeira˜o Sumi-
douro near Lagoa Santa (Minas Gerais), a tributary to the Rio
das Velhas, but is also known from other localities in the Rio
Sa˜oFranciscoandRioParana´ basins (Buckup, 1992).
Characidium lagosantense was also described from the
vicinity of Lagoa Santa, and is widespread in the Rio Sa˜o
Francisco basin and Parana´ basins and in a few localities in
the southern part of the Rio Tocantins basin (Silveira, 2008;
Melo, unpubl. data).
Two other species were previously cited for the basin:
Characidium aff. zebra and Characidium aff. bimaculatum.
Characidium zebra was described from the Ireng River, a
tributary to the Rio Branco, in Guyana, and it is part of a
species complex widely distributed in several South Amer-
ican drainages. Characidium bimaculatum was described from
Fortaleza, Ceara´ , and it apparently forms a species complex
characterized by a short, deep body, high number vertical of
bars on body (12–18), and a large, round or elongated spot
on caudal peduncle. The other members of this species
complex are C. bahiense (Almeida, 1971), described from a
costal stream in Arembepe, Bahia; C. xavante Grac¸a et al.,
2008, from the upper Rio Xingu; C. nupelia Grac¸ a et al.,
2008, from the upper Rio Paraguay; and an undescribed
species from the upper Rio Parana´ basin (sensu Silveira,
2008).
Characidium satoi further differs from C. fasciatum,C.
zebra,C. lagosantense, and Characidium aff. bimaculatum by
having indistinct bars (vs. bars distinct), sexual color
dimorphism (vs. males and females with same color
pattern), and dorsal and caudal fins marked with melano-
phores (vs. fins hyaline). Furthermore, it differs from C.
fasciatum by having a scaled isthmus (vs. isthmus naked);
from C. lagosantense and C. bimaculatum by having larger
body, up to 43.4 mm SL (vs. maximum body size of 35.0 mm
SL); and from C. bimaculatum by having 34–37 pored lateral-
line scales (vs. less than 15) and lacking a large spot on the
caudal peduncle (vs. present).
Characidium satoi resembles C. xanthopterum in having
unicuspid teeth or small lateral and medial cusps, dentary
lacking the inner row of teeth, and males having hooks on
pelvic-fin rays. The males of C. satoi also have ontogenetic
reduction of marks on body; however, females still retain
the indistinct bars on body when mature. It further differs
from C. xanthopterum by lacking the brown-reddish pigmen-
tation on body and yellow fins, and the parietal branch of
the supraorbital laterosensory canal is absent. Silveira et al.
(2008) described the parietal branch of supraorbital as
‘‘extending through almost two thirds of parietal’’. Howev-
er, the specimens of C. xanthopterum examined by us have a
short parietal branch, not reaching the parietal bone,
indicating potential intraspecific variation in this character.
Moreover, C. xanthopterum was never recorded from the Rio
Sa˜o Francisco basin, being known from the Rio Paranaı´ba—
upper Rio Parana´ basin—and from tributaries to the Rio
Tocantinzinho and Rio Maranha˜o—Rio Tocantins basin
(Silveira et al., 2008).
Establishing the phylogenetic relationship of C. satoi to its
congeners is a difficult task. The most inclusive phylogeny
available for the genus was published by Buckup (1993b),
which was clearly more focused on the non-Characidium
characidiins and included only 16 species of Characidium.
Buckup (1993b) was only able to find synapomorphies to
diagnose three major clades: C1, C4, and C5. Clade C1
(including clades C2 and C3) contains the species with
naked isthmus, such as C. fasciatum; clade C4 includes
species with deep bodies, formerly part of the genus
Jobertina,suchasC. bimaculatum,C. bahiense, and C.
lagosantense; and clade C5 (including clades C6 and C7)
include the species with very elongated body and thin bars,
which does not have representatives in the Rio Sa
˜o Francisco
basin. Without a more thorough analysis, it is impossible to
assign C. satoi to any of the aforementioned clades.
Netto-Ferreira et al. (2013) listed the absence of the
parietal branch of the supraorbital canal, a high number of
dark bars on the sides of the body (.12), and the absence of
an inner row of dentary teeth as synapomorphies to support
clade C4. The inner row of dentary teeth is also absent in C.
xanthopterum and C. satoi, and present in C. lanei. Moreover,
the parietal branch of the supraorbital canal is absent in
286 Copeia 103, No. 2, 2015

other species of Characidium which are not closely related to
the clade C4, such as C. japuhybense Travassos, 1949, C. lauroi
Travassos, 1949, C. oiticicai Travassos, 1967, and C. schubarti
Travassos, 1955 (Melo, 2001). Since the above species have
naked isthmus and are hypothesized to be nested within
clade C1 (Melo, 2001), the absence the parietal branch of the
supraorbital canal is considered to be homoplastic within
Characidium and not unique to clade C4.
Additional remarkable characters with possible phyloge-
netic significance were also overlooked until recently, such
as sexual color dimorphism (Buckup and Hahn, 2000; Melo
and Buckup, 2002); presence of hooks on fins of mature
males (Grac¸a et al., 2008; Silveira et al., 2008); variation in
shape, size, and position of the pseudotympanum (Zanata
and Camelier, 2014); proportions of the anterior and
posterior chamber of the swim bladder (Lujan et al., 2013);
and the characteristics of anal-fin insertion discussed below.
Hooks on fins rays of mature males have been reported for
the pelvic fins of C. bahiense,C. nupelia,C. xavante,C.
lagosantense, and C. xanthopterum (Almeida, 1971; Grac¸a
et al., 2008; Silveira, 2008; Silveira et al., 2008), and on the
pectoral fin of C. nupelia,C. xavante, and C. mirim (Grac¸a
et al., 2008; Netto-Ferreira et al., 2013). We also observed
hooks on the pectoral- and pelvic-fin rays of C. bimaculatum,
C. stigmosum, and C. litorale. It is very likely that other species
of Characidium also have such structures; nevertheless, a
thorough review of the distribution of this character within
Characidium is beyond of the scope of this work.
The relative position of the anal fin and the number of
precaudal and caudal vertebrae are rarely reported in
Characidium; indeed, most species descriptions do not
distinguish between counts of precaudal and caudal verte-
brae (e.g., Buckup, 1992; Melo and Buckup, 2002; Grac¸a
et al., 2008; Netto-Ferreira et al., 2013). In species other than
C. satoi, the distal tip of the anal fin generally reaches the base
of the ventral caudal-fin rays in C. lagosantense,C. hasemani,
C. xanthopterum, and the males of C. rachovii.InC. satoi,C.
hasemani, and C. zebra, the anal fin seems to be shifted
posteriorly: the first anal-fin radial inserts between the fifth
and sixth (C. satoi, Fig. 4) or sixth and seventh (C. zebra and
C. hasemani) caudal vertebrae. As a consequence, the anus is
positioned far from the anal fin, and there are four to seven
scale rows between those structures. In most species of
Characidium, the insertion of the first anal-fin ray is between
the second and third caudal vertebrae (e.g., C. fasciatum,C.
lanei,C. lauroi,C. schubarti, and C. interruptum), or third and
fourth or fourth and fifth vertebrae (e.g., C. japuhybense,C.
pterostictum, and C. xanthopterum). In those species, there are
two to four scales between the anus and the anal-fin origin.
The insertion of the first anal-fin ray more posteriorly on
body seems to be an apomorphic state which needs to be
better evaluated in a more inclusive phylogeny.
MATERIAL EXAMINED
Characidium alipioi: All from Brazil, Rio Paraı´ba do Sul
drainage: MNRJ 5555, holotype, 51.1 mm SL, Ilha dos
Pombos, Carmo, Rio de Janeiro State; MZUSP 108124, 22.7–
63.5 mm SL, creek upstream of Paraibuna dam, Natividade
da Serra, Sa˜o Paulo State.
Characidium amaila: All from Guiana, Essequibo drainage,
Potaro-Siparuni: MZUSP 109096, 8, 32.1–84.4 mm SL,
5u209160N, 59u339570W, MZUSP 109080, 3, 33.0–71.1 mm
SL, 5u219070N, 59u329450W, Kuribrong River.
Characidium bahiense: All from Brazil, Bahia State. Coastal
drainage: MZUSP 8940, holotype, 16.4 mm SL, Arembepe.
Rio Sa˜o Francisco drainage: MZUSP 58924, 114, 12.5–
19.8 mm SL, co´ rrego Livramento, tributary of Rio Sapa˜o,
Formosa do Rio Preto; MZUSP 84049, 39, 14.8–21.1 mm SL,
Rio Preto, Formosa do Rio Preto.
Characidium bimaculatum: All from Brazil, coastal drainages:
MZUSP 77917, 1, 30.4 mm SL, Rio Pitimbu, Parnamirim, Rio
Gande do Norte State; MZUSP 110781, 1, 27.4 mm SL, Rio
Acarau´ , Nova Russas, Ceara´ State.
Characidium fasciatum: All from Brazil, Minas Gerais State:
MZUSP 111952, 1, 43.9 mm SL, creek tributary of Rio
Araguari, Patrocı´nio.
Characidium gomesi: All from Brazil: MZUSP 79777, 63, 37.4–
54.7 mm SL, Rio Mogi Guac¸u, Borda da Mata, Rio Mogi
Guac¸u drainage, Minas Gerais State; MZUSP 98815, 3, 46.0–
50.4 mm SL, co´ rrego das Pedreiras, tributary of Rio
Piracicaba, Cabreu´ va, Rio Tieteˆ drainage, Sa˜o Paulo State.
Characidium hasemani: All from Brazil, Para´State,Rio
Tapajo´ s drainage: MZUSP 97332, 70, 32.8–61.0 mm SL, Rio
Jamanxim, near Vila Mil, Novo Progresso.
Characidium interruptum: All from Brazil, Rio de Janeiro State,
coastal drainages: MZUSP 20202, 1, 33.3 mm SL, co´rrego da
Lagoa Nova, Itaguaı´; MZUSP 49151, 2, 15.3–25.4 mm SL, Rio
Seco, tributary of Lagoa de Saquarema, Sampaio Correia;
MZUSP 49157, 6, 19.7–25.7 mm SL, creek tributary of Rio
Macacu, Saquarema.
Characidium japuhybense: All from Brazil, Rio de Janeiro
State, coastal drainages: MNRJ 5194, holotype, 52.7 mm SL,
Japuhyba (now Japuı´ba), 23u009S, 44u189W, Angra dos Reis;
MNRJ 11693, 21, 27.2–30.3 mm SL, Rio Japuı´ba (ou Rio do
Meio), Japuı´ba, Angra dos Reis.
Characidium lagosantense: All from Brazil, Bahia State, Rio
Sa˜o Francisco drainage: MZUSP 83822, 6, 25.1–34.0 mm SL,
Rio Sapa˜o, Formosa do Rio Preto. Minas Gerais State: MZUSP
47458, 10, 24.1–30.4 mm SL, Rio Verde, Montes Claros.
Characidium lanei: All from Brazil, Sa˜o Paulo State, coastal
drainages: MZUSP 103991, 8 (1 CS), 32.8–57.5 mm SL, Rio
Camburi, tributary of Rio Branco, Itanhae´m. Rio Ribeira de
Iguape drainage, Sa˜o Paulo State: MZUSP 101316, 23 (1 CS),
31.8–65.2 mm SL, small creek tributary of Rio Juquia´ , Juquitiba.
Characidium laterale: All from Brazil, Mato Grosso do Sul State,
Rio Paraguai drainage: MZUSP 19981, 7, 20.4–25.3 mm, SL,
Ilha de Taima˜, Rio Paraguai, Ca´ ceres; MZUSP 96659, 4, 20.3–
22.3 mm SL, Pantanal de Paiagua´s, Rio Paraguai, Bara˜o de
Melgac¸o.
Characidium lauroi: All from Brazil, Rio Paraı´ba do Sul
drainage: MNRJ 5529, holotype, 61.2 mm SL, female, Rio
das Pedras, Fazenda Penedo, Resende, Rio de Janeiro State,
22u289080S, 44u269480W; MZUSP 109826, 14, 40.5–56.5 mm
SL, Rio do Brac¸o, Estac¸a˜o Ecolo´ gica do Bananal, Bananal, Sa˜o
Paulo State. Rio Ribeira de Iguape drainage, Sa˜o Paulo State:
MZUSP 105055, 24, 33.4–47.7 mm SL, stream tributary of
Rio Pilo˜ es, Alto Ribeira State Park, Iporanga.
Characidium litorale: All from Brazil, Rio de Janeiro State,
coastal drainages: MZUSP 80228, 3, 30.5–31.3 mm SL, Rio
Sa˜o Joa˜o, locality Gavio˜es, road Boqueira˜o-Japubı´ba mun.
Silva Jardim; MZUSP 93895, 2, 27.8–29.0 mm SL, Rio Sa˜o
Melo and Oyakawa—A new species of Characidium from Rio Sa˜o Francisco 287

Joa˜o, localidade Gavio˜ es, mun. Silva Jardim, 22u349090S,
42u339100W; MZUSP 115488, 3, 23.5–40.4 mm SL, riacho no
Povoado de Aleluia, tributary of Rio Imbe´, mun. Campos de
Goytacazes, 21u47956.10S, 41u36915.10W.
Characidium mirim: All from Brazil, Mato Grosso State, Rio
Araguaia drainage: MZUSP 111123, holotype, 20.2 mm SL,
MZUSP 101393, 2, paratypes, 18.3–18.6 mm SL, Rio das Mortes,
at bridge on road between Chapada dos Guimara˜es and Campo
Verde, 15u309200S, 55u139380W; MZUSP 97705, 4, paratypes,
16.6–23.4 mm SL (1 CS, 23.4 mm SL), small stream near Santo
Antoˆnio do Leste, 14u529300S, 54u059000W; MZUSP 97724, 4,
paratypes, 18.9–19.7 mm SL, Vereda de Buriti, at BR-070,
between Campo Verde and Primavera do Leste, 15u349090S,
54u339210W.
Characidium nupelia: All from Brazil, Mato Grosso State, Rio
Paraguai drainage: MZUSP 87742, 20, 21.6–28.7 mm SL,
Co´ rrego Lajinha, tributary to Rio Manso, Chapada dos
Guimara˜es, 14u579180S, 55u419150W; MZUSP 87743, 1,
30.2 mm SL, Co´ rrego Forquilha, tributary to Rio Manso,
Rosa´ rio Oeste, 14u449580S, 56u079390W.
Characidium oiticicai: All from Brazil, Sa˜o Paulo State Rio
Tieteˆ drainage: MNRJ 9480, holotype, 34.4 mm SL, Para-
napiacaba, Santo Andre´; MZUSP 26973, 154, 32.7–54.4 mm
SL, co´ rrego do Pastinho, Estac¸a˜o Ecolo´ gica de Borace´ ia,
Saleso´ polis; MZUSP 78087, 35, 29.0–56.7 mm SL, creek
tributary of Rio Claro, Estac¸a˜o Ecolo´gica de Borace´ia,
Saleso´ polis. Coastal drainage, Sa˜o Paulo State: MZUSP
87569, 41, 37.4–59.5 mm SL, Rio Guaratuba, Estac¸a˜o
Ecolo´ gica de Borace´ia, Saleso´ polis.
Characidium pterostictum: All from Brazil, Sa˜o Paulo State, Rio
Ribeira de Iguape drainage: MZUSP 101316, 23 (2 CS), 31.2–
61.6 mm SL, stream at Fazenda Estio, tributary of Rio Juquia´,
Juquitiba; MZUSP 101321, 14, 40.0–55.6 mm SL, Ribeira˜o
das Laranjeiras, tributary of Rio Juquia´ , Juquitiba.
Characidium rachovii: All from Brazil, Rio Grande do Sul
State, coastal drainages: MZUSP 9615, 2, 37.9–39.2 mm SL,
Pelotas; MZUSP 19952, 23, 13.4–31.5 mm SL, Arroio do
Bolacha, Rio Grande.
Characidium schubarti: All from Brazil, Parana´ State, Rio
Paranapanema drainage: MNRJ 8853, holotype, 50.3 mm SL,
stream between Joaquim Murtinhos and Jaguariaı´va. Sa˜o
Paulo State: MZUSP 64536, 14 (2 CS), 36.0–49.2 mm SL,
MZUSP 64537, 19 (2 CS), 35.8–43.6 mm SL, Ribeira˜o Brac¸o
do Taquaral, Carlos Botelho State Park, Capa˜o Bonito.
Characidium stigmosum: All from Brazil, Goia´s State, Rio
Tocantins drainage: MZUSP 40804, holotype, 33.7 mm SL,
small stream tributary of Co´ rrego Ave Maria; MZUSP 113839,
1, 40.1 mm SL, creek tributary of Ribeira˜o dos Bois; MZUSP
113939, 61, 18.7–41.1 mm SL, creek tributary of Rio das Almas.
Characidium tenue: All from Brazil, Rio Grande do Sul State,
Rio Uruguai drainage: MZUSP 63808, 14, 36.4–45.7 mm SL,
Rio Inhacunda´, Sa˜o Francisco de Assis.
Characidium vidali: All from Brazil, Rio de Janeiro State,
coastal drainages: MZUSP 93892, 1, 53.6 mm SL, Rio
Macacu, Cachoeiras de Macacu; MZUSP 93909, 40, 29.0–
63.3 mm SL, creek tributary of Rio Sa˜o Joa˜o, Cachoeiras de
Macacu.
Characidium xanthopterum: All from Brazil, Goia´s State, Rio
Tocantins drainage: MZUSP 53404, 32, 30.7–40.6 mm SL,
creek tributary of Rio Tocantinzinho, Minac¸u; MZUSP
53422, 3, 38.8–45.2 mm SL, small tributary of Rio Tocan-
tinzinho, Minac¸u, Goia´s, 14u029270S, 48u129220W.
Characidium xavante: All from Brazil, Mato Grosso State, Rio
Xingu drainage: MZUSP 91774, 2, 20.5–21.8 mm SL, creek
tributary of Rio Culuene, Paranatinga; MZUSP 91912, 9, 17.4–
24.2 mm SL, Rio Culuene, Paranatinga; MZUSP 99057, 1,
26.7 mm SL, Rio Couto de Magalha˜es, Campina´ polis.
Characidium zebra: All from Brazil, Amapa´ State, Rio Jari
drainage: MZUSP 101989, 8 (1 CS) 25.6–46.0 mm SL, Igarape´
Traı´ra, tributary of Rio Jari, Laranjal do Jari.
Characidium aff. zebra: All from Brazil, Minas Gerais State,
Rio Sa˜o Francisco drainage: MZUSP 19665, 1, 62.2 mm SL,
Rio Sa˜o Francisco at Treˆs Marias dam; MZUSP 37155, 1,
66.6 mm SL, creek tributary of Rio Paraopeba, Moeda;
MZUSP 39157, 1, 46.7 mm SL, Co´ rrego Tapera; MZUSP
39268, 2, 34.5–31.1 mm SL, Ilha Grande, Rio Sa˜o Francisco;
MZUSP 39435, 2, 36.9–37.0 mm SL, MZUSP 39362, 1,
39.1 mm SL, Rio Formoso; MZUSP 39466, 12, 32.4–
40.0 mm SL, confluence of mouth of Rio Formoso into Rio
Sa˜o Francisco; MZUSP 39635, 1, 56.7 mm SL, Rio Abate´;
MZUSP 39707, 2, 56.1–39.2 mm SL, Co´ rrego Carapia´.
Characidium sp. (sensu Silveira, 2008): All Brazil, Sa˜o Paulo
State, Rio Tieteˆ drainage: MZUSP 19384, 2, 23.9–26.9 mm
SL, Lagoa do Scatolin, Pirassununga; MZUSP 97677, 2, 27.1–
28.3 mm SL, Rio Tieteˆ, below the Promissa˜o dam, Promissa˜o.
ACKNOWLEDGMENTS
For comments and suggestions in this manuscript, we thank
F. Lima and B. Frable. MRSM is indebted to M. de Pinna
(MZUSP) for providing a work space in the past few years.
This research was benefitted by the South American
Characiforms Inventory–SACI (FAPESP 2011/50282-7). Per-
mission for collecting specimens was granted by Ministe´rio
do Meio Ambiente–MMA/Instituto Chico Mendes de Con-
servac¸a˜o da Biodiversidade–ICMBio #28054-2.
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