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Journal of Fish Biology (2018)
doi:10.1111/jfb.13526, available online at wileyonlinelibrary.com
New species of the genus Spectracanthicus (Loricariidae,
Hypostominae, Ancistrini) from the Rio Javaés (Rio
Araguaia basin), with a description of gross brain
morphology
C. C. Chamon*†, T. N. A. Pereira*, M. B. Mendonça‡and A. Akama‡
*Laboratório de Ictiologia Sistemática, Universidade Federal do Tocantins, Campus
Universitário de Porto Nacional, Setor Jardim dos Ipês, Rua 3, Quadra 17, s/no, Caixa
Postal 136, CEP: 77500-000 Tocantins, TO, Brazil and ‡Museu Paraense Emílio
Goeldi–Campus de Pesquisa, Setor de Ictiologia, Av. Perimetral, 1901, CEP: 66077-530,
Belém, PA, Brazil
urn:lsid:zoobank.org:pub:B65A8D7C-7F56-400F-ADAA-3CAAE1C7AA9C
(Received 28 July 2017, Accepted 1 December 2017)
AnewspeciesofSpectracanthicus is described from the Rio Javaés, Rio Araguaia basin. The new
species is distinguished from its congeners (except Spectracanthicus immaculatus) by colour pattern:
body dark grey to dark brown without dots or blotches (v. body colour with yellowish small dots in
Spectracanthicus murinus, Spectracanthicus punctatissimus and Spectracanthicus tocantinensis and
large white dots in Spectracanthicus zuanoni). It can be further distinguished from S. immaculatus by
having thicker and less numerous teeth, with up to eight premaxillary and 20 dentary teeth (v.teeth
thinner and more numerous with up to 22 premaxillary and 30 dentary teeth); dorsal and caudal ns
without curved spines (v. dorsal and caudal ns with curved spines). Other osteological characters
can also diagnose the new species from its congeners. In addition, a gross brain description and brief
comments on the new species’ ecological habitat are given.
© 2018 The Fisheries Society of the British Isles
Key words: brain anatomy; sh trade; Ilha do Bananal; Neotropical; taxonomy.
INTRODUCTION
Loricariidae is the largest family among Siluriformes with more than 900
species described (Eschmeyer et al., 2017), representing about a quarter of cat-
sh diversity (Reis et al., 2003; Ferraris, 2007). Species of the family are widely
distributed in the Neotropical region, from south-eastern and south-western
Costa Rica (Pacic drainage) to north-eastern Argentina (Isbrücker, 1980) and
occur in a large variety of freshwater environments. Spectracanthicus Nijssen
& Isbrücker 1987 was established as a monotypic genus to include Spectra-
canthicus murinus Nijssen & Isbrücker 1987 from the Rio Tapajós basin. The
†Author to whom correspondence should be addressed. Tel.: +55 63 33639472; email:
chamon.carine@gmail.com
1
©2018TheFisheriesSocietyoftheBritishIsles
2C. C. CHAMON ET AL.
genus Oligancistrus Rapp Py-Daniel 1989 was proposed as a junior synonym of
Spectracanthicus by Armbruster (2004) by the absence of diagnosis between Oli-
gancistrus punctatissimus (Steindachner 1881) and S. murinus and by the argument
of an unnecessary recognition of two closely related genera without exclusive
synapomorphies.
ApreviousphylogenetichypothesisforAncistrinibasedonmorphologicaldata
has indicated that Spectracanthicus is closely related to the Acanthicus clade, which
includes the genera Acanthicus Agassiz 1829,MegalancistrusIsbrücker 1980,Lepora-
canthicus Isbrücker & Nijssen 1989 and Pseudacanthicus Bleeker 1862 (Armbruster,
2004). On the other hand, a molecular hypothesis has suggested that Spectracanthicus
is closely related to Para ncistrus Bleeker 1862 and Baryancistrus Rapp Py-Daniel
1989 (Lujan et al., 2015). Recently, Chamon & Rapp Py-Daniel (2014) provided
diagnostic characters for Spectracanthicus and a taxonomic revision of the genus,
recognizing ve valid species: S. murinus,S. puctatissimus (Rio Xingu basin), S.
immaculatus (Rio Tapajós basin), S. tocantinensis (Rio Tocantins basin) and S.
zuanoni (Rio Xingu basin).
Recent expeditions to the Rio Javaés, at the Centro de Pesquisa Canguçu (CPC-UFT),
revealed the presence of a new species of the genus that is described here. In addition,
agrossbraindescriptionandbriefcommentsonthenewspecies
′ecological habitat
are given.
MATERIALS AND METHODS
Point-to-point measurements were made to the nearest 0·1 mm with digital callipers on the left
side of the specimens, following Chamon & Rapp Py-Daniel (2014). Osteological nomencla-
ture and vertebral counts follow Schaefer (1987), Armbruster (2004) and Geerinckx & Adriaens
(2006) for compound pterotic and parieto-supraocciptal bones. Specimens were cleared and
stained (CS) according to the protocol of Taylor & Van Dyke (1985). Vertebral counts include
the rst ve vertebrae modied into the Weberian apparatus and fused pre-ural centrum counted
as a single element according to Lundberg & Baskin (1969). Terminology for the laterosensory
system of the head follows Arratia & Huaquin (1995); homologies of the pre-opercular sensory
canal follow Schaefer (1987). Material examined is described in the following order: Institution
and catalogue number, count, minimum and maximum standard length (LS), locality, geograph-
ical coordinates, date of collection and collectors. Examined specimens are deposited at the
Instituto Nacional de Pesquisas da Amazônia (INPA), Museu Paraense Emílio Goeldi (MPEG),
Museu Nacional do Rio de Janeiro (MNRJ), Museu de Zoologia da Universidade de São Paulo
(MZUSP) e Coleção de Peixes do Laboratório de Ictiologia Sistemática da Universidade Federal
do Tocantins (UNT).
BRAIN EXTRACTION
Five brains were extracted for examination. All specimens were previously stained
using the technique of Datovo & Bockmann (2010) that allows a better visualization
of neurocranial bones and its sutures in prepared specimens without any undesirable
changes caused to the brain. Procedures for brain dissection and description follow
Pereira & Castro (2016), with a few modications related to the anatomical structure
of the siluriform head as described by Abrahão & Shibatta (2015). Brain images were
captured with a camera attached to a stereomicroscope and edited through software
editors.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 3
(a)
(
(
(
(a
(
(
(
(
)
(b)
(c)
Fig. 1. Holotype of Spectracanthicus javae, MPEG 34993, 74·2 mm standard length,in (a) dorsal, (c) lateral and
(c) ventral views.
RESULTS
SPECTRACANTHICUS JAVAE SP. NOV.
urn:lsid:zoobank.org:act:EAAA3ED6-0399-491D-8761-6486CD2D506A
(Figs 1 and 2 and Table I)
Holotype
MPEG 34993, 74·2mmLS, Rio Javaés, Ilha do Bananal, Pedral da Sambaíba, Pium,
Tocantins, Brazil. 10∘00′01′′ S; 50∘01′29′′ W; 2 November 2016, C. Chamon, T.
Pereira, T. Krolow, E. Oliveira, J. Silva and C. Bezerra.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Bio logy 2018, doi:10.1111/jfb.13526
4C. C. CHAMON ET AL.
Fig. 2. Colour in life of Spectracanthicus javae.
Para t y p e s
All from Brazil, Tocantins, Pium, Ilha do Bananal, Rio Javaés. INPA 53289, 20,
20·8–73·5mmLS,collectedwiththeholotype.MPEG35271,5,1CS,19·0–54·1mm
LS,neartheconuencewiththeRioAraguaia.9
∘50′42·9′′ S; 50∘12′07·2′′ W; 20 May
2016, M. Mendonça and A. Akama. MPEG 35271, 20, 36·6–51·5mmLS,Pedralda
Sambaíba, 1 July 2016, C. Chamon, T. Krolow, E. Oliveira and J. Silva. MNRJ 50453,
20, 26·3–71·9mmLS, collected with the holotype. UNT 15073, 6, 28·5–54·4mmLS;
1CS,46·6mmLS, Pedral da Sambaíba, 18 May 2016, A. Akama, C. Chamon and M.
Mendonça. UNT 15615, 74, 17·8–57·95 mm LS;4CS,46·0–52·5mmLS,Pedralda
Sambaíba. UNT 15662, 56, 15·3–85·7mmLS,collectedwiththeholotype.MZUSP
121726, 20, 21·4–67·5mmLS,collectedwiththeholotype.
Non-type
UNT 16857, 30, 13·7–48·9mmLS,collectedwiththeholotype.
Diagnosis
Spectracanthicus javae can be diagnosed from its congeners (except S. immaculatus)
by colour pattern: dark grey body, without dots or spots (v.withsmalltomid-sized
yellowish dots in S. punctatissimus,S. murinus and S. tocantinensis; and large white
spots in S. zuanoni). It further differs from S. murinus and S. immaculatus by hav-
ing a sickle-shaped opercle (Fig. 3) (v.triangular-shapedopercleandlongitudinal
bar-shaped opercle, respectively). It also differs from S. immaculatus by having thicker
and less numerous teeth, with up to eight in the premaxilla and up to 20 in the dentary
(v. teeth ner and more numerous, up to 22 in the premaxilla and up to 30 in the den-
tary); by having dorsal and caudal-n spines straight and short (v.dorsalandcaudal-n
spines curved and elongated); by having the anterior process of the metapterygoid
elongated and conspicuous (Fig. 3) (v. anterior process of the metapterygoid short
and inconspicuous) and by the anterior process of the basipterygium not reaching the
anteromesial process (v.anteriorprocessreachingtheanteromesialprocess).
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 5
Table I. Morphometric and meristics data of Spectracanthicus javae based on 33 specimens
plus the holotype
Holotype Range Mean s.d.
Standard length (LS, mm) 74·219·0–73·3
Percentage of LS
Head length (LH)37·535·6–42·838·21·7
Head depth 22·820·0–24·927·52·0
Head width 32·029·9–36·333·21·6
Body depth 22·620·0–29·725·12·8
Body width at dorsal 29·121·5–33·030·42·6
Body width at anal 15·510·8–20·116·22·1
Predorsal length 45·741·5–49·544·91·9
Postdorsal length 28·218·2–32·426·23·5
Postanal length 25·520·6–27·424·11·6
Dorsal spine length 22·826·1–33·028·91·9
Pectoral spine length 30·027·3–33·530·81·5
Pelvic spine length 26·818·6–30·528·22·2
Dorsal base length 32·127·5–37·532·52·6
Caudal Peduncle depth 12·912·5–15·614·00·7
Percentage of LH
Snout length 61·540·1–64·057·87·4
Interorbital width 34·632·5–38·835·81·6
Orbital diameter 17·115·8–21·818·31·5
Dentary length 15·16·9–16·412·12·4
Meristics Mode
Premaxilary teeth 6 3–8 7
Dentary teeth 19 7–20 16
Dorsal plates 21 17–21 20
Mid-dorsal plates 20 19–22 21
Lateral plates 22 20– 24 21
Mid-ventral plates 21 18– 23 21
Ventral plates 15 11– 16 12
Supracaudal plates 7 5 – 7 7
LH, Head length.
Description
Morphometric and meristic data are summarized in Table I. Dorsal prole of body
slightly convex from tip of snout to a vertical through dorsal-n origin; concave nearly
straight from that point to dorsal-n origin to caudal-n origin. Ventral prole straight
from snout tip to origin of caudal n. Ventral prole straight from snout tip to origin of
pelvic n; from pelvic n to caudal n slightly convex. Ventral surface from pectoral
region to urogenital papillae lacking plates, except for few small plates at pectoral and
pelvic-n origins. Greatest body width at pectoral girdle. Head and trunk without keels
or ridges. Greatest body depth at dorsal-n origin; lowest at caudal peduncle.
Head wide, dorsally convex; snout and cheeks completely covered by numerous
small plates, except for small naked area on tip of snout. Snout rounded in dorsal pro-
le. Nasal short, bar-shaped. Frontal short, with a slight contact with nares anteriorly
and orbit posteriorly. Parieto-supraoccipital short with posterior edge narrow, lacking
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Bio logy 2018, doi:10.1111/jfb.13526
6C. C. CHAMON ET AL.
Opercle
(a)
(b)
Preopercle
Angulo-articular
Preopercle
2 mm
Dentary
Metapterigoyd
Metapterigoyd
channel
Metapterigoyd
anterior process
Dentary
Angulo-articular
Cheek plates
Hiomandibula
Quadrate
Quadrate
Hiomandibula
Fig. 3. (a) Ventral and (b) lateral views of the suspensorium of Spectracanthicus javae, UNT 15073, 46·6 mm
standard length.
crest. Sphenotic short, with narrow contact with IO6, lacking conspicuous odontodes.
Orbit moderate in size (15·8–21·8% head length; LH) placed dorsolaterally. Iris opercu-
lum present. Pterotic-supracleithum short with few fenestrae; anterior process forming
most posterior margin of orbit. Posterior area of pterotic-supracleitrhum with one plate.
Mouth moderate in size, nearly as long as wide. Lips moderate in size, covered with
papillae; size of papillae decreasing towards posterior margin of lower lip; central buc-
cal papilla absent. Upper lip folded over itself. Maxillary barbel short; base of barbel
united to lips with free tip. Lower lip not reaching anterior margin of coracoid. Medial
end of premaxillary tooth series curved inwards. Premaxillae and dentaries narrow and
elongate. Dentary strongly curved inwards. Teeth moderate in size, well developed,
with long crown and large lateral cusp, its distal edge slightly curved. Evertible cheek
plates with associated hypertrophied odontodes form unique block connected to oper-
cle, evertible to approximately 90∘from head by opercular movements.
Body covered by ve longitudinal series of plates supporting odontodes. Keels
absent. Three to four predorsal plates; some small azygous predorsal plates sometimes
present. Eight bid neural spines below dorsal n. Dorsal-n pterygiophores located
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 7
above neural spines of vertebral centra seven to 15–16. Dorsal-n base very long, its
length equivalent to nine to 10 dorsal plates, reaching pre-adipose plate and connected
to adipose n by thick membrane. Dorsal-n II,7; spinelet V-shaped with locking
mechanism functional. Pectoral and pelvic ns well developed, medial portion larger
than base; distal margins rounded. Pectoral-n rays I,6; unbranched ray covered with
conspicuous odontodes. Tip of adpressed pectoral n almost reaching vertical through
medial, unbranched, pelvic-n ray. Pelvic-n rays i,5; unbranched ray reaching
vertical through anal-n base when adpressed. Anal-n rays I,4; located posterior to
haemal spines of vertebral centra 14–17. Caudal-n rays i,14,i. Caudal n obliquely
truncated; supracaudal plates 2 (5), 6 (7) or 7 (24). Three procurrent caudal-n rays.
Caudal peduncle strongly deep in lateral view. Total vertebrae 25– 26, precaudal eight
to nine. Sixth rib strongly thickened, remaining ribs slender.
Colouration
Most individuals have background colour evenly dark grey to dark brown without
blotches or spots. Ventral surface ochre to light brown, with chromatophores more con-
centrated on the pectoral and pelvic-n insertions. Some specimens (most remarkable
in specimens up to 40·0mmLS)withthin,whitebandonedgeofdorsalandcaudal
ns. Colour pattern similar, but less intense in alcohol.
Brain gross morphology (Fig. 4)
The brain limits established herein for S. javae follow Pereira & Castro (2016) with
some modications, i.e. the anterior portions of the bulbus olfactorius anteriorly, usu-
ally ending at the semi-oval olfactory epithelium (Fig. 4); and the insertion of the
complex of the spino-occipitales nerves on the ventral surface of the medulla spinallis,
posteriorly. The encephalon is slightly robust and wide; wider in its middle portion near
the mesencephalon (tectum opticus) and diencephalon. The brain occupies the entire
cranial cavity, from the region near the mesethmoid and lateral ethmoid to the region
anterior to the third neural arch, not contacting the Weberian apparatus.
Although, the olfactory epithelium is not considered as part of the telencephalon
proper, they are semi-oval structures with a robust support rod surrounded by 34 lamel-
lae that are variable in size, the anteriormost being more developed than those posterior.
The most rostral components of the telencephalon are the bulbus olfactorius. Each
nervus tractus olfactorius is composed of a slender and relatively shortened olfactory
peduncle with a terminal expansion. The olfactory bulbs are oval and shortened, nar-
rower proximately and less enlarged distally. The nervus tractus olfactorius are inserted
directly on the ventral surface of the telencephalon.
The telencephalon is divided into two distinct parts: a conspicuous and well-
developed area dorsale on its dorsal surface and a small, narrow area ventrale on
its ventral surface, both parts widely and closely interconnected; the area ventrale is
located entirely on the ventral surface of the area dorsale and it extends posteriorly to
the basement of the tectum opticum.
The diencephalon is well developed, located between the telencephalon and mesen-
cephalon and composed of the following parts: the almost inconspicuous epithalamus,
as well as a conspicuous pineal gland; both structures are easy to remove accidentally
during dissection and are located on the dorsal surface; the pineal gland is in contact
with the telencephalon and corpus cerebelli; a reduced and inconspicous saccus
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Bio logy 2018, doi:10.1111/jfb.13526
8C. C. CHAMON ET AL.
(a)
(b)
(c)
Bol
Pob
Telen Dien
Tect Cocb EgLobX
Tv Mo
Ms
Apt
Bol
Telen
Tect
Cocb
Pob
EgLobVII
LobX
Mo
Ms
TIHytHyp
Lih
Pob Telen Ch Tl
Tect
Mo Ms
HytHypLih 2 mm
Bol
Fig. 4. Brain of Spectracanthicus javae,UNT15615,in(a)dorsal,(b)lateraland(c)ventralviews.Apt,area
postrema; Bol, bulbus olfactorius; Ch, chiasma opticum; Cocb, corpus cerebelli; Dien, diencephalon; Eg,
eminentia granularis; Hyp, hypophysis; Hyt, hypothalamus; Lih, lobus inferior hypothalami LobVII, lobus
fascialis; Lobx, lobus vagi; Mo, medulla oblongata; Ms., medulla spinallis; Pob, nervus tractus olfactorius;
Sv, saccus vasculosus; Tect, tectum opticum; Telen, Telencephalon Tl, Torus lateralis; Tv, tela ventriculi.
Scale bar =2 mm.
vasculosus; a vertically developed hypothalamus that is seen as a small prominence
on the ventral surface of the diencephalon, in ventral and lateral views; an oval lobus
inferior hypothalami, which is kidney-shaped in ventral view and almost the same size
as the hypothalamus; and a small, oval, stalked hypophysis connecting to the posterior
edge of the hypothalamus.
The thalamus dorsalis arises from grooves between the tecta optici and the telen-
cephalon, being well developed along their entire length and thicker than the olfac-
tory tracts. The chiasma opticum is located anteriorly to the posterior margin of the
telencephalon.
The mesencephalon is composed of the tecta optici, tegmentum, torus longitudinalis
and the torus lateralis. The tecta optici are well developed, divided in two symmet-
rical rounded halves that are equal to approximately one-third of the brain length;
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 9
the tegmentum is small and partially covered by the tectum opticus, in dorsal view
is inconspicuous; the torus longitudinalis is conspicuous and located between the tecta
optici, near the telencephalon complex; the torus lateralis is small and located in front
of the lobus inferior hypothalami and the anterior portion of tectum opticum, with
well-dened limits, both in lateral and ventral views.
The rhombencephalon comprises the associated cerebellar complex and medullary
areas; the crista cerebellaris region is a conspicuously clear area between the eminetia
granularis and lobus vagi (in lateral view); the eminentia granularis is located at the
posterior region of the corpus cerebelli, but totally disconnected from it externally; the
corpus cerebelli is triangular and larger than the tectum opticum, being the dorsalmost
structure of the brain; the lobus vagi is reduced and like a small prominence on the
corpus cerebelli; the lobus facialis is conspicuous, located as a small structure below
the corpus cerebelli (in dorsal and lateral views).
The medulla spinalis is slightly cylindrical throughout its length, except for
its anterior portion, near the lobus vagi and corpus cerebelli, where it is at-
tened and cone-shaped, in dorsal view; the area postrema, usually is small and
short resembling an elongated oval depression in dorsal view and is almost
as wide as long throughout its length, but precise delimitation of it is pos-
sible only in stained histological preparations; the ventriculi quarti region is
inconspicuous.
Etymology
The specic epithet (a noun in apposition) is in reference to the Javaé peo-
ple, an indigenous branch of the Karajá people in Brazil who inhabit the Ilha do
Bananal and confer the name of the river (Rio Javaés), where the new species was
reported.
Distribution and habitat
Spectracanthicus javae is only known from rocky areas near the Rio Javaés,
Araguaia system, near Praia da Sambaíba and the conuence with the Rio Araguaia,
at Ilha do Bananal (Figs 5 and 6). The Rio Javaés bypasses the eastern margin of
the Ilha do Bananal, which, with a length of 400 km, a width of up to 120 km and
an area of approximately 20 000 km2,isconsideredthelargestuvialislandofthe
world (Goulding et al., 2003). The species inhabits bedrock covered by alluvial
sediment, which is typical of the median portion of the Rio Araguaia basin. This
kind of geomorphological formation, known as laterite, originates from the weath-
ering of lateritic crusts that cover the geological units of the region (Latrubesse &
Stevaux, 2002).
The new species was collected with other loricariids such as Hypostomus spp., Lep-
oracanthicus galaxias Isbrücker & Nijssen 1989, Par a n c i s t r u s a u r a n t i a c us (Castelnau
1855), Peck o l t i a spp. and taxa of other families such as: Crenicichla sp., Ituglanis sp.,
Microglanis sp., Centromochlus spp., Ta t i a sp. and a new genus of gymnotiform (C.
D. de Santana, pers. com.). The sampling effort was made in the twilight and daytime,
precisely at mid-morning with most specimens collected during the morning. Spectra-
canthicus javae as well as other species were collected from holes and cracks inside
the rocks during daytime.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Bio logy 2018, doi:10.1111/jfb.13526
10 C. C. CHAMON ET AL.
10˚ 0’
12˚ 0’
50˚ 0’ 48˚ 0’
Ilha do Bananal
Rio
Rio Araguaia
Javaés
Fig. 5. Distribution of Spectracanthicus javae, type-locality indicated by star.
DISCUSSION
In addition to the diagnosis proposed by Chamon & Rapp Py-Daniel (2014), Arm-
bruster (2004) proposed the following characters as synapomophies for Spectracanthi-
cus:mesialwallofmetapterygoidchannelmuchtallerthanlateralwall;spoon-shaped,
straight anterior process on metapterygoid; and presence of a deep lateral ethmoid
pouch. The new species has all these characters, however the anterior process of the
metapterygoid is elongate and pointed (not spoon shaped), which also occurs in S. mur-
inus and S. punctatissimus. Others features proposed for the genus by Chamon & Rapp
Py-Daniel (2014) and that also occur in S. javae are: contact between sphenotic and
(a) (b)
Fig. 6. Rio Javaés, at (a) Pedral da Sambaíba, type locality of S. javae, with (b) close-up of the holes and cracks
that the species inhabits.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 11
IO6; the elongate anterior metapterygoid process; and the elongate lateropterygium,
surpassing the vertical through the anterolateral process of the basipterygium.
AcharacterthatusuallyisusedtodiagnoseAncistrinigeneraisthepresenceofevert-
ible cheek plates bearing developed odontodes. Usually this condition in Ancistrini is
associated with changes to the shape of the opercle. Among Ancistrini, the genera
that present these evertible plates commonly have bar-shaped or sickle-shaped oper-
cles (v. oval or triangular-shaped opercles). In Spectracanthicus most species have a
sickle-shaped opercle with the exception of S. murinus,whichhastriangular-shaped
opercle and S. immaculatus,whichhasalongitudinalbar-shapedopercle.Armbruster
(2004) proposed that the bar-shaped opercle is basal in relation to the sickle-shaped
one, whereas the triangular opercle is plesiomorphic for all Loricariidae taxa and the
presence of this condition in S. murinus is due to reversion.
Although the species of Spectracanthicus,likeotherLoricariidae,arebasicallydis-
tinguished by colour pattern, S. javae is very similar to S. immaculatus,withadarkgrey
body, lacking dots or spots. Several other anatomical characters separate the species,
however, such as number of teeth and the shape of the opercle, suggesting that the
colour pattern in this case is not a diagnostic character.
The geographic distribution of the genus is restricted to the Brazilian shield, including
the Tocantins-Araguaia, Xingu and Tapajós Rivers basins and Spectracanthicus javae
is the rst record for the genus in the Rio Araguaia basin, but this may be due to lack
of sampling since species of Spectracanthicus are small (≤129·0mmofLS), inhabit
bedrocks and are usually captured manually, being rare in most sh faunal inventories.
For instance, Ferreira et al. (2011) provided a sh inventory from the Cantão State Park
where 271 species of sh were reported, but no Spectracanticus spp. were collected.
All species of Spectracanthicus have commercial interest as ornamental shes. The
ornamental sh trade is a common practice in the Amazon Basin and species of Spec-
tracanthicus are exploited in Altamira (Rio Xingu basin), Itaituba and Santarém (Rio
Tapajós basin) and Marabá (Rio Tocant i n s b a sin). There are no reports of these pra c -
tices, however, in the Rio Araguaia basin. The region where Spectracanthcius javae
was captured is between two conservation areas, the Araguaia National Park and the
State Park of the Cantão, which comprise an ecotone between the Amazon and the
Cerrado Biomes. For this reason, the area is well preserved, but there are some defor-
ested areas nearby and nearby agricultural operations use irrigation, which could pose
problems for aquatic species during the dry season.
Most characters frequently used to diagnose and hypothesize relationships among
sh taxa are based on osteology and external morphology. Only a few studies have been
based on other anatomical systems, such as myology and neuroanatomy (Datovo &
Var i , 2 0 14 ). R ec en t st u d i es h ave p ro po se d t h a t gr os s br ai n an a t o my c ou ld b e ver y in fo r-
mative for phylogenetic hypothesis reconstruction for Otophysi taxa and to infer rela-
tionships between brain morphology and ecological and behaviour attributes (Abrahão
& Shibatta, 2015; Pereira & Castro, 2016).
Even though Pereira & Castro (2016) and Abrahão & Shibatta (2015) described the
brain gross anatomy of Brycon orbignyanus (Valenciennes 1850) (Characiformes) and
Pseudopimelodus bufonius (Valenciennes 1840) (Siluriformes), respectively, there are
fewer studies in the current literature that examined the brains of loricariid species
(Rosa et al., 2014; Rosa, 2015; Angulo & Langeani, 2017). Thus, the description pro-
posed here may contribute to further studies in this area.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Bio logy 2018, doi:10.1111/jfb.13526
12 C. C. CHAMON ET AL.
The brain of Spectracanthicus javae is similar to the brains of other siluriform species
(Abrahão & Shibatta, 2015; Rosa, 2015; Angulo & Langeani, 2017). Pereira & Castro
(2016) described six putative synapomorphies for Siluriformes, all of them are present
in the new species: the area postrema is almost as wide as long throughout its length;
the rhombencephalon is well developed when compared to the size of the midbrain; the
lobus vagi is developed; the lobus fascialis is present, although it is reduced in S. javae;
the corpus cerebelli is horizontally developed; the tectum opticum is relatively smaller
than the corpus cerebelli. These aforementioned features corroborate with ecological
observation of the new species nocturnal lifestyle.
Abrahão & Shibatta (2015) suggested that the corpus cerebelli is relatively large in
all Pseudopimelodus Bleeker 1858 species when compared with species of Characi-
formes (c.f . Pereira & Castro, 2016). In S. javae, the corpus cerebelli is very con-
spicuous and larger than in Pseudopimelodus.ConsideringthatS. javae inhabits holes
and cracks inside rocks, the relatively large corpus cerebelli suggests that the species
has rened swimming movements to hide and escape from predators, because it is
accepted that this part of the brain is responsible for sensorimotor integration, which
provides spatial orientation, proprioception and coordination (Kotrschal et al., 1998).
Furthermore, the reduced lobus fascialis is probably related to small or absent bar-
bels because the lobus fascialis is responsible for sensing the environment. In Silu-
riformes, these structures generally have an important inuence on positioning and
chemosensation.
Angulo & Langeani (2017) analysed the gross brain morphology of Rineloricaria
heteroptera sbrücker & Nijssen 1976. They found that the olfactory organ has 12–24
lamellae and suggested that the enlarged olfactory bulbs in R. heteroptera could be
linked to reproductive behaviour in mature specimens, possibly associated with detec-
tion of reproductive pheromones. In S. javae,theolfactoryorganislarger(with34
lamellae) than in R. heteroptera and could be associated with the same factors. In this
study, however, the brain of only ve specimens were analysed, therefore more anatom-
ical and physiological studies would be necessary to corroborate these assumptions,
which are beyond the scope of this study.
Despite the fact that the central nervous system has been highly conserved in teleosts
during evolution, recent studies are demonstrating that there is signicant infor-
mation for reconstruction of phylogenies and for understanding sh behaviour and
habits.
COMPARATIVE MATERIAL
Spectracanthicus murinus
MZUSP 22011, holotype 59·7mmLS.S. punctatissimus: NMW 47206, holotype
103·9mmLS.S. immaculatus: MZUSP 92797, holotype 63·8mmLS.S.tocantinensis:
MZUSP 110989, holotype 49·5mmLS.S. zuanoni: INPA 25874, holotype 122·4mm
LS.
Authors wish to thank to T. Alvim (UFT) and all outsourced employees (Marilza, Sulene and
Roberto) for the facilities and hospitality in the CPC. Further thanks to V. Abrahão (MZUSP)
for help in brain images. The manuscript was beneted from reviews and suggestions by J.
Armbruster (AUM). M.B.M. and A.A. were nancially supported by the National Biodiversity
Research Program – PPBio.
© 2018 The Fisheries Society of the British Isles, Journa l of Fish Biol ogy 2018, doi:10.1111/jfb.13526
NEW SPECTRACANTHICUS SPECIES FROM RIO JAVAÉS 13
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