Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae) from the rio Preto, São Francisco basin, northeastern Brazil

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Keywords
Caatinga domain, Hypsolebias, Cynolebias parnaibensis,
introduced species.
Abstract
A new species of Cynolebias is described from temporary
pools from the Rio Preto drainage, São Francisco basin,
Bahia, Brazil, within the Caatinga domain. The type-local-
ity is an altered aquatic environment, with the presence of
exotic fish species and in contact with a permanent water-
course. Cynolebias akroa sp. n., along with Hypsolebias
faouri, that inhabits the same annual pool, are in great dan-
ger of extinction. Cynolebias akroa sp. n.,appears to be
more closely related to Cynolebias parnaibensis, with which
it shares several features, than to the remaining species of
Cynolebias from the middle Rio São Francisco basin.
Cynolebias akroa sp. n. differs from other species of
Cynolebias by the male color pattern, relative position of
dorsal fin to the anal fin, pelvic-fin rays counts, shape of
the urogenital papilla, and cephalic neuro mast pattern.
Zusammenfassung
Beschrieben wird eine neue Cynolebias-Art aus temporä-
ren Tümpeln im Einzugsgebiet des Rio Preto, São-Francis-
co-Becken, Bahia, Brasilien, im Bereich der Caatinga. Die
Typus-Lokalität ist eine veränderte aquatische Umwelt, wo
exotische Fischarten vorkommen und Kontakt zu einem
dauerhaften Wasserlauf besteht. Cynolebias akroa sp. n.,
ebenso Hypsolebias faouri, der denselben zeitweiligen Tüm-
pel bewohnt, sind stark von Ausrottung bedroht. Cynole-
bias akroa sp. n. ist offenbar näher mit Cynolebias parnai-
bensis verwandt – mehrere Merkmale stimmen überein –
als mit den anderen Cynolebias-Arten vom mittleren Rio-
São-Francisco-Becken. Cynolebias akroa sp. n. unterschei-
det sich von den anderen Arten der Gattung durch das
Farbmuster der Männchen, die Stellung der Rückenflosse
relativ zu der Afterflosse, die Zahl der Bauchflossenstrah-
len, die Form der Urogenitalpapille und das Muster der
Neuromasten im Kopfbereich.
Resumo
Uma nova espécie de Cynolebias é descrita a de uma poça
temporária da drenagem do Rio Preto, bacia do São Fran-
cisco, Bahia Brasil, no bioma da Caatinga, em um ambien-
te aquático alterado, com introdução de espécies exóticas e
em contato com um curso de água permanente. Cynolebias
akroa sp. n., juntamente com Hypsolebias faouri, que habita
a mesma poça anual, estão em grande perigo de extinção.
Cynolebias akroa sp. n., parece estar mais relacionada com
Cynolebias parnaibensis, por uma série de características co-
muns, do que com as demais espécies de Cynolebias do mé-
dio rio São Francisco. Cynolebias akroa sp. n. difere de ou-
tras espécies do gênero Cynolebias pelo padrão de colorido
dos machos, posição relativa da nadadeira dorsal em rela-
ção a nadadeira anal, número de raios na nadadeira pélvica,
forma da papila urogenital e padrão dos neuromastos cefá-
licos.
Résumé
Une nouvelle espèce de Cynolebias est décrit à partir de
mares temporaires du Rio Preto, drainage du bassin du São
Francisco, Bahia, Brésil, dans le domaine de caatinga. La
localité type est une altération de l'environnement aquati-
que, avec la présence d'espèces de poissons exotiques et en
aqua vol. 23 no. 4 - 15 March 2018
113
aqua, International Journal of Ichthyology
Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae)
from the rio Preto, São Francisco basin, northeastern Brazil
Dalton Tavares Bressane Nielsen1, Mayler Martins2, Luciano Medeiros de Araujo3, Fabio Origuela de Lira4and
Amer Faour5
1) Laboratório de Zoologia, departamento de Biologia, Universidade de Taubaté,
Av. Tiradentes180, CEP: 12030-180, Taubaté, SP, Brazil. E-mail: dnielsen@uol.com.br
2)Instituto Federal Minas Gerais- Campus Bambuí- Fazenda Varginha-Estrada Bambuí-Medeiros Km 5,
CEP: 38900-000, MG, Brazil. E-mail: mayler.martins@ifmg.edu.br
3) Fundação Zoobotânica de Belo Horizonte – Aquário da Bacia do São Francisco Avenida Otacílio Negrão
de Lima, 8000; Belo Horizonte, MG Brasil. E-mail: luciano.araujo@pbh.gov.br
4) Meandros Consultoria Ambiental Ltda., Rua Maria Cândida Cerqueira, 75, Santa Amélia,
Belo Horizonte/MG, Brasil. Email: fabio.origuela@meandrosambiental.com.br
5) C/ Las Fuentes 4 bajo C - 37439 - San Cristóbal de la Cuesta - Salamanca. E-mail: amerfaour@gmail.com
Received: 20 October 2017 – Accepted: 25 November 2017

contact avec un cours d'eau permanent. Cynolebias akroa
n. sp., avec Hypsolebias faouri, qui habite le même taux an-
nuel d'extérieure, sont en grand danger d'extinction. Cyno-
lebias akroa n. sp., semble être plus étroitement liée à Cy-
nolebias parnaibensis, avec laquelle elle partage plusieurs ca-
ractéristiques, que pour les autres espèces de Cynolebias du
milieu du bassin du Rio São Francisco. Cynolebias akroa n.
sp. diffère des autres espèces de Cynolebias par l'homme,
position relative de nageoire dorsale à la nageoire anale,
rayons pelviens-chefs, la forme de la papille urogénitale,
neuro-mast céphalique et motif.
Sommario
Una nuova specie di Cynolebias è descritta da pozze tem-
poranee del sotto bacino del Rio Preto, bacino idrografico
del Rio São Francisco, Bahia, Brasile, all'interno del domi-
nio Caatinga. La località tipo è un ambiente acquatico al-
terato, con la presenza di specie ittiche esotiche e in con-
tatto con un corso d'acqua permanente. Cynolebias akroa
sp. n., insieme a Hypsolebias faouri, che abita nella stessa
pozza annuale, sono in grande pericolo di estinzione. Cy-
nolebias akroa sp. n., sembra essere più strettamente impa-
rentato con Cynolebias parnaibensis, con cui condivide di-
verse caratteristiche, rispetto alle restanti specie di Cynole-
bias dal bacino centrale del Rio São Francisco. Cynolebias
akroa sp. n. differisce dalle altre specie di Cynolebias per la
colorazione del maschio, per la posizione della pinna dor-
sale rispetto alla pinna anale, per il numero dei raggi della
pinna pelvica, per la forma della papilla urogenitale e per il
pattern neurommastico cefalico.
INTRODUCTION
The first annual fish species described from in
South America was Cynolebias porosus Steindachner,
1876. The stated type-locality was “Pernambuco”
(now Recife, the capital city of the state of Pernam-
buco in northeastern Brazil), but as discussed by
Costa (2001), it is difficult to ascertain the precise
origin of this species, which was never collected
again in nature.
For a long time, the genus Cynolebias was a catch-
all taxon, harboring species which are currently as-
signed to several other genera of Rivulidae. In fact, a
great proportion of the South American annual fish
species that were described before the 1980 s were
then assigned to the genus Cynolebias. With the in-
crease of studies on the family, along with fieldwork
and discovery of new species, new genera were cre-
ated for species previously assigned to Cynolebias,
such as Austrolebias, Nematolebias, Simpsonichthys,
Hypsolebias, Ophthalmolebias, Xenurolebias, Plesi-
olebias, Cynopoecilus, Leptolebias, Terranatos, and
Maratecoara.
The majority (15 out of 21) of the species of
Cynolebias were described during the last 15 years.
Fifteen Cynolebias species occurs at the middle São
Francisco basin, while Cynolebias microphthalmus
Costa & Brasil (2001) occurs in the Rio Jaguaribe
basin, Cynolebias parnaibensis Costa et al. (2010)
occurs in the Rio Parnaíba basin, Cynolebias itapi-
curuensis Costa (2001) occurs in the Rio Itapicuru
basin, Cynolebias paraguassuensis Costa et al.
(2007), occurs in the Rio Paraguaçu basin,
Cynolebias vazabarriensis Costa (2001) occurs in
the Rio Vaza-Barris basin, and Cynolebias griseus
Costa et al. (1990) occurs in the Rio Tocantins
basin.
All species of Cynolebias genus have an annual re-
production cycle, with an elaborated reproductive
behavior (Belote & Costa 2003), including the
production of sounds by males (Costa 2010). In
contrast to most other Rivulidae, the genus
Cynolebias contains medium to large sized species,
which can surpass 80 mm SL; the largest known
species, C. altus, presents 133.3 mm SL (Costa
2001). Despite their size, they are not used for hu-
man comsuption because they are said to have a
very bad taste. In some areas species of the genus
are called “peixe-sabão” (“soap fish”), but more of-
ten they are popularly known as “peixe-das-nu-
vens” (“cloud s fish”).
In most of the known localities of species of
Cynolebias, they are sympatric with species of the
annual fish genus Hypsolebias. It has been suggested
that species of Cynolebias prey on species of the
genus Hypsolebias (Wildekamp 1995).
The new species described herein was found in a
tributary of the left bank of the rio São Francisco,
situated farther away from its main channel than
any other species of the genus. The aim of the pre-
sent contribution is to describe formally this unde-
scribed species.
MATERIALS AND METHODS
Measurements were taken point-to-point under a
stereomicroscope with a digital caliper to the near-
est 0.01 mm, on the left side of the specimens,
whenever possible, following Costa (1995, 2007).
Measurements are expressed as percentages of stan-
dard length (SL), except subunits of the head,
which are recorded as percentages of head length
(HL).
In the description, counts of vertebrae and pleural
ribs were taken from one male and one female
cleared and stained (c&s) paratypes, which were
prepared according to Taylor & Van Dyke (1985).
Terminology for frontal squamation follows
aqua vol. 23 no. 4 - 15 marzo 2018 114
Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae) from the rio Preto, São Francisco basin, northeastern Brazil

Hoedeman (1958) and Costa (2006). For vertebral
counts, the caudal compound centrum was count-
ed as a single element. Osteological features includ-
ed in the description are those considered phyloge-
netically informative by recent studies on
Cynolebias (Costa 2001, 2014, 2017; Costa et al.
2010). Institutional abbreviations follow Sabaj
(2016), with addition of UNITAU (Universidade
de Taubaté).
Cynolebias akroa, n. sp.
(Figs 1-2; Table I)
Holotype: ZUEC 14768, male, 75.0 mm SL: Bra-
zil, Bahia, Prazeres, temporary pool at road BA-
225, rio Preto basin (Rio São Francisco basin),
11°23’24.8”S 44°54’11.2”W, altitude 522 m, 25
January 2014; Mayler Martins, Fabio Origuela de
Lira & Luciano Medeiros de Araujo.
Paratypes: ZUEC 14769, 5 males 35.1-62.5 mm
aqua vol. 23 no. 4 - 15 March 2018
115
Dalton Tavares Bressane Nielsen, Mayler Martins, Luciano Medeiros de Araujo, Fabio Origuela and Amer Faour
Fig.1. Cynolebias akroa, ZUEC 14768, male, holotype, 75.0 mm SL: Brazil, Bahia, Santa Rita de Cássia. Photo by
D. Nielsen.
Fig. 2. Cynolebias akroa, ZUEC 14769, female, paratype, 59.2 mm SL: Brazil, Bahia, Santa Rita de Cássia. Photo by
D. Nielsen.

SL, 6 females 44.5-61.3 mm SL, 2 c&s, 54.7-77.9
mm SL, same date as holotype.
Diagnosis: Cynolebias akroa differs from the re-
maining species of Cynolebias by presenting overall
color pattern metallic golden-green, with 11-13
large, light black bars (vs. 16-18 narrow, dark
brown bars in C. obscurus, 17-19 yellow brown
bars separated by narrow dark golden interspace in
C. oticus, faint gray vertical bars (sometimes ab-
sent) in C. microphthalmus, C. vazabarriensis, C.
itapicuruensis, C. perforatus, C. porosus, C. altus, C.
leptocephalus, C. attenuatus, C. gibbus, narrow pale
golden bar in C. parnaibensis), color pattern of cau-
dal fin hyaline, without dots (vs. light gray in C.
gorutuba, dark brown in C. paraguassuensis, dark
grey with white dots in C. microphthalmus, C. poro-
sus, and C. vazabarriensis, grey with bluish white
dots in C. itapicuruensis, C. rectiventer, C. gilbertoi,
C. obscurus, and C. parietalis, yellowish gray with
white dots in C. perforatus, C. altus, C. lepto-
cephalus, C. attenuatus, C. gibbus, and C. par-
naibensis, dark ochre-yellow with bluish white dots
in C. roseus, greenish yellow in C. oticus), seven
pelvic fin rays (vs. 5 in C. griseus and 6 in the re-
maining species), dorsal-fin origin through base of
8th or 9th anal-fin ray (vs. 3rd-6th in C. altus, C. at-
tenuatus, C. gibbus, C. itapicuruensis, C. lepto-
cephalus, C. microphthalmus, C. oticus, C. parietalis,
C. parnaibensis, C. paraguassuensis, C. rectiventer,
C. vazabarriensis, C. gorutuba, and 5th-7th in C. ob-
scurus, and C. roseus), number of anterior rostral
cephalic neuromasts 6 (vs. 2-3 in C. obscurus, C.
ochraceus, C. oticus, C. paraguassuensis, C. parietalis,
C. parnaibensis, C. elegans, and C. gorutuba, and 3-
4 in C. rectiventer), and urogenital papilla in males
cylindrical and elongated (vs. cylindrical and
short).
Females of Cynolebias akroa differs from females
of the remaining species of Cynolebias by overall
color pattern light gray, with 10-12 pale, large
brown bars, and black spot in the center of body
sometimes absent (vs. overall color pattern light
gray without bars and black spot always present in
C. microphthalmus, C. porosus, C. vazabarriensis, C.
perforatus, C. altus, C. leptocephalus, C. attenuatus,
C. gibbus, and C. rectiventer, light gray body with
faint gray vertical bars, and one or two dark gray to
black spots in C. itapicuruensis, C. paraguassuensis,
and C. parnaibensis, pale brownish grey, lacking
spot on anteriormedial portion of flank, and 1-3
dark brown blotches on humeral region in C. ob-
scurus, light gray body with faint gray vertical bars,
one or two dark gray to black blotches in C. roseus),
lower caudal fin length 20.0-28.2 % SL (vs. 34.1-
38.0 % SL in C. ochraceus or 28.7-32.4 % SL in C.
parietalis).
Additionally, Cynolebias akro can be distinguished
from the remaining species of the Cynolebias, ex-
cept C. gorutuba, by a higher number of post-otic
cephalic neuromasts (11, vs. 5-8 in C. obscurus, C.
ochra ceus, C. oticus, C. paraguassuensis, C. parietalis,
C. parnaibensis, and C. rectiventer).
Description: Morphometric data are presented in
Table I. Largest male specimen examined 75.0 mm
SL, largest female 77.9 mm SL. Dorsal and ventral
profiles convex between snout and anterior part of
caudal peduncle, nearly straight on caudal peduncle.
Body moderately deep, slightly compressed, greatest
body depth at level of vertical just anterior to pelvic-
fin base. Snout very short, blunt. Dorsal and anal
fins slightly pointed in males, without filaments,
rounded in females. Pectoral-fin long, rounded,
reaching vertical between base of 2nd and 3rd anal-
fin rays in males, and between pelvic-fin base and
anus in females. Tip of pelvic fin reaching between
base of 1st and 3rd anal-fin rays in males, 1st anal-fin
rays in females. Pelvic-fin bases medially separated
by interspace.
Dorsal-fin origin through base of 8th or 9th anal-
aqua vol. 23 no. 4 - 15 marzo 2018 116
Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae) from the rio Preto, São Francisco basin, northeastern Brazil
Table I. Morphometric and meristic data for the holotype
(H) and paratypes of Cynolebias akroa.
H Paratypes
Male Males n=5 Females n=6
Standard length (mm) 75.0 35.1-62.5 44.5-61.3
Percents of standard length
Body depth 28.8 26.4-29.8 29.0-30.9
Caudal peduncle depth 15.1 11.1-14.4 13.6-15.6
Pre-dorsal length 62.5 61.3-68.4 64.0-70.0
Pre-pelvic length 52.0 47.5-52.9 50.3-56.6
Length of dorsal-fin base 24.0 22.1-25.6 19.7-23.8
Length of anal-fin base 27.2 27.4-30.6 17.4-28.2
Caudal-fin length 26.5 27.3-30.7 20.0-28.2
Pectoral-fin length 25.0 21.4-27.0 19.3-23.6
Pelvic-fin length 7.5 4.2-7.3 5.7-7.4
Head length 35.5 32.5-33.8 31.9-34.6
Percents of head length
Head depth 82.6 76.8-80.5 70.0-82.4
Head width 64.5 60.3-63.4 27.5-33.6
Snout length 13,9 13.8-14.4 11.1-11.6
Lower jaw length 25.2 24.2-27.3 22.1-24.9
Eye diameter 24.8 24.1-28.3 20.1-23.3

fin ray in males, and above base of 4th or 5th anal-
fin ray in females; dorsal-fin origin between neural
spines of vertebrae 15-17 in both sexes. Anal-fin ori-
gin between pleural ribs of vertebrae 13 in males,
and pleural ribs of vertebrae 12 in females. Dorsal-
fin rays 17 in males, 15-16 in females; anal-fin rays
19 in males, 18-20 in females; caudal-fin rays 28-30;
pectoral-fin rays 13-14; pelvic-fin rays 7.
Frontal scales irregularly arranged; 28 small
supraorbital scales. Longitudinal series of scales 37-
39; transverse series of scales 16-18; scale rows
around caudal peduncle 22. No contact organ on
flank. Minute papillate contact organs on inner
surface pectoral fin-rays in males. No contact or-
gans on pelvic and unpaired fins.
Cephalic neuromasts: supraorbital 29-39, parietal
4, anterior rostral 6, posterior rostral 5, infraorbital
4+29-30, preorbital 3, otic 9, post-otic 11,
supratemporal 5, median opercular 3, ventral oper-
cular 3-5, preopercular + mandibular 47-57, lateral
mandibular 8-9, paramandibular 1.
One neuromast on each scale of lateral line. Two
neuromasts on caudal-fin base.
Second pharyngobranchial teeth absent. Gill-rak-
ers on first branchial arch 10, 8 in the second arch.
Vomerine teeth absent. Urogenital papilla cylindri-
cal, large and elongated. Total vertebrae 32-33.
Coloration: Males. Side of body metallic
golden-green, with 11-13 large light black bars,
fading ventrally before reaching the belly and the
anal-fin base. Opercular region metallic golden-
green. Venter whitish. Head metallic golden, with
black lines along laterosensory series of neuromasts
around orbit and on postorbital region. Iris white
with black vertical bar through eye. Dorsal-fin hya-
line with gray pigmentation on interradial mem-
branes of fin basis, and thin brown lines on inter-
radial membranes at distal portion of fin. Caudal-
fin hyaline. Anal-fin hyaline with brown pigmenta-
tion in the last rays. Dorsal and pelvis fins hyaline.
Females. Sides of body light gray, with 10-12
pale, large brown bars; single rounded black spot in
the center of body, sometimes absent. Venter
whitish. Head sides yellowish gray, pale golden on
opercular region; small dark reddish brown spots
along laterosensory series of neuromasts around or-
aqua vol. 23 no. 4 - 15 March 2018
117
Dalton Tavares Bressane Nielsen, Mayler Martins, Luciano Medeiros de Araujo, Fabio Origuela and Amer Faour
Fig. 3. Map from northeastern Brazil (inset) showing known localities for Cynolebias from the rio São Francisco basin.

bit and on postorbital region. Iris orangish yellow
with dark reddish brown vertical bar through cen-
ter of eye. Dorsal and anal fins hyaline, with small
blue metallic spots between last rays. Caudal-fin
hyaline with small metallic blue spots. Paired fins
hyaline.
Distribution (Fig. 3): Known only from the type
locality, a temporary pool beside the highway BA-
225, at Santa Rita de Cássia, rio Preto, rio São
Francisco basin, Bahia state, Brazil.
Habitat (Fig. 4): The type-locality is a typical an-
nual pool of the Caatinga, located about 96 km
north of Barreiras. The substrate is composed of clay
and sand, with a slightly dark water. There is a dense
cover of aquatic vegetation, mostly composed by
Echinodorus sp. and Nymphaea sp.The average
depth of the pool is 100 cm, with deepest portions
about 130 cm, pH 6.5 and a low electric conductiv-
ity (146µs). Other physico-chemical parameters
were: total hardness (GH) 2°dGH, carbonate hard-
ness (KH) 4°dKH, dissolved iron (Fe) 1.0 mg/l, dis-
solved calcium (Ca) 60 mg/l, dissolved copper (Cu)
0 mg/l. The temperature on the water surface was
approximately 28°C and, in the deepest portion and
at the margins, approximately 25°C. The region’s
annual average temperature is 28°C, with maxi-
mum of 34°C and minimum of 20°C. The rainy
season ranges from December to March. The period
of collection coincided with a “Veranico” (Indian
Summer), a phenomenon which consists of a dry
period with high temperatures within the rainy sea-
sons (Nielsen 2008). Together with Cynolebias akroa
were also found Hypsolebias faouri, Astronotus ocella-
tus and Oreochromis niloticus (Figs 5-6).
The pool is close to a road near a small village. A
family living in this village introduced Oreochromis
niloticus and Astronotus ocellatus on the pool, as a
means of having an alternative source of protein.
At one end the pool was dug so the water would re-
main throughout the year, so part of the pool does
not dry, which explains the survival of the intro-
duced species.
aqua vol. 23 no. 4 - 15 marzo 2018 118
Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae) from the rio Preto, São Francisco basin, northeastern Brazil
Fig. 4. Type locality of Cynolebias akroa, Brazil, Bahia, temporary pool at road BA-225. Photo by M. Martins.

Etymology: In honor Akroá ethnic, an ethnic
group belonging to Macro-Jê linguistic trunk, that
lived in the region until the century XIX, when
they were decimated.
DISCUSSION
Cynolebias akroa is easily distinguished from its
congeners by the presence of light dark vertical bars
in the flank. This color pattern is unique within
the genus Cynolebias, other species of the genus
may present vertical bars, but never as wide and
conspicuous as the ones present in the new species.
The area of occurrence of the new species is locat-
ed approximately 175 km in a straight line from
the Rio São Francisco, but the real distance from
its main channel, considering the actual rivers
courses is approximately 570 km. The middle Rio
São Francisco basin lies within the Caatinga do-
main, an area with a relatively high rate of biodi-
versity, with high level of speciation for rivulids,
but with a consequently limited distribution of
each species. The accelerated pace of environmen-
tal degradation, due to the disorderly occupation
of the area by human activities, poses a great risk of
extinction for rivulid species occurring at the
Caatinga domain (Costa 2017).
Cynolebias species are commonly found in annual
pools sintopically with two other annual fish species
of the genus Hypsolebias, typically one species be-
longing to the Hypsolebias magnificus species group
and other species belonging to the Hypsolebias flav-
icaudatus species group. Rarely, Cynolebias species
are found alone in an annual pool. Cynolebias akroa
was found syntopically with Hypsolebias faouri.
Hypsolebias faouri is closely related to H. igneus
(Britzke et al. 2016), a species that occurs in annual
pools at the banks of the Rio São Francisco, near
the Rio Preto mouth with the Rio São Francisco.
Cynolebias akroa could be putatively closely related
to Cynolebias roseus, considering the geographic
proximity between the two species and a similar dis-
tribution of H. faouri and H. igneus. However,
Cynolebias akroa appears to be more closely related
to C. parnaibensis, since both species share the fol-
lowing characteristics: color pattern with vertical
bars, absence of contact organs in the body sides of
males vomerine teeth absent, second pharyngob-
ranchial teeth absent, a similar count of dorsal-fin
rays (17 in males vs. 16-18 in other species), a com-
mon count of dorsal-fin rays in females (15-16), a
common count of anal-fin rays (19 in males and
18-20 in females), a common count of caudal-fin
rays (28-30), a common count of pectoral-fin rays
(13-14), frontal scales irregularly arranged, dorsal
fin origin vertebrae 15-17, and the presence of
minute papillate contact organs on inner surface
pectoral fin-rays in males. Interestingly, the clade
formed by H. faouri and H. igneus is closely related
to the clade formed by H. coamazonicus and H.
martinsi (Britzke et al. 2016), which is similar to the
putative biogeographic relation between C. akroa
from the middle Rio São Francisco basin with C.
parnaibensis from the Rio Parnaíba basin.
In spite of the modification of its habitat, with
aqua vol. 23 no. 4 - 15 March 2018
119
Dalton Tavares Bressane Nielsen, Mayler Martins, Luciano Medeiros de Araujo, Fabio Origuela and Amer Faour
Fig. 5. Astronotus ocellatus, a specimen of an exotic invasive
species, collected at the type-locality of Cynolebia akroa.
Photo by M. Martins.
Fig. 6. Oreochromis niloticus, a specimen of an exotic inva-
sive species, collected at the type-locality of Cynolebia
akroa. Photo by M. Martins.

the establishment of a connection to a permanent
water body and with the invasion of exotic fish that
potentially can act as predators as Astronotus ocella-
tus and Oreochromis niloticus, Cynolebias akroa still
survives in its habitat. Cynolebias akroa is not the
most abundant species of annual fish at its habitat,
being outnumbered by Hypsolebias faouri, with a
population ratio of 5: 1 in relation to H. faouri,
which may indicate that C. akroa preys on H.
faouri, as reported for other syntopic associations
among annual rivulids (e.g., Wildekamp 1995).
The morphological characteristics of the teeth, typ-
ical of piscivorous fishes, common to all Cynolebias
species and shared with other annual fishes from
both South America and Africa, as Austrolebias
elongatus and Nothobranchius ocellatus, which are
reported to prey on smaller sympatric congeners
(Costa 2006, 2009, 2011, 2017), also points to
this possible relation of predator-prey between
Cynolebias akroa and Hypsolebias faouri.
ACKNOWLEDGEMENTS
Thanks are due to Itamar Alves Martins from
Universidade de Taubaté (UNITAU) for laboratory
support and Flávio C. T. Lima (ZUEC), who read
the manuscript and offered useful suggestions.
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Cynolebias akroa, a new species of annual fish (Cyprinodontiformes: Rivulidae) from the rio Preto, São Francisco basin, northeastern Brazil