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A New Species of the Armored Catfish Parotocinclus (Loricariidae: Hypoptopomatinae) from the Upper Xingu River Basin, Brazil

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Parotocinclus kwarup, new species, is described as a new hypoptopomatine cascudinho from tributaries of the upper Xingu River in the Amazon basin of Brazil. The new species is distinguished from its congeners in northeastern and southeastern Brazil by having the cheek canal plate elongated posteriorly on the ventral surface of the head and in contact with the cleithrum. Parotocinclus kwarup, new species, is diagnosed from other species of Parotocinclus in the Amazon, Orinoco, and Guianas watersheds by the number of oral teeth, the snout length, having odontodes on the ventral surface of the first pelvic-fin ray bent and pointing mesially, lacking a Y-shaped light marking dorsally on the head (from the posterodorsal margin of orbit to posterior parieto-supraoccipital tip), lacking premaxillary and dentary accessory teeth, and having an adipose fin. The extinction risk of the new species is preliminarily assessed as Least Concern based on its wide distribution area and its inferred presence in the large Xingu Indigenous Park.
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A New Species of the Armored Catfish Parotocinclus (Loricariidae:
Hypoptopomatinae) from the Upper Xingu River Basin, Brazil
Pablo Lehmann A.
1
and Roberto E. Reis
2
Parotocinclus kwarup, new species, is described as a new hypoptopomatine cascudinho from tributaries of the upper
Xingu River in the Amazon basin of Brazil. The new species is distinguished from its congeners in northeastern and
southeastern Brazil by having the cheek canal plate elongated posteriorly on the ventral surface of the head and in
contact with the cleithrum. Parotocinclus kwarup, new species, is diagnosed from other species of Parotocinclus in the
Amazon, Orinoco, and Guianas watersheds by the number of oral teeth, the snout length, having odontodes on the
ventral surface of the first pelvic-fin ray bent and pointing mesially, lacking a Y-shaped light marking dorsally on the
head (from the posterodorsal margin of orbit to posterior parieto-supraoccipital tip), lacking premaxillary and dentary
accessory teeth, and having an adipose fin. The extinction risk of the new species is preliminarily assessed as Least
Concern based on its wide distribution area and its inferred presence in the large Xingu Indigenous Park.
PAROTOCINCLUS is the most diverse genus in subfam-
ily Hypoptopomatinae, with 37 species currently
recognized as valid (Fricke et al., 2021), and these
species are widely distributed across cis-Andean South Amer-
ica. Although the genus has been shown to be non-
monophyletic by both morphology-based (Gauger and Buck-
up, 2005; Lehmann et al., 2013) and molecular studies
(Cramer et al., 2011; Roxo et al., 2014), species of Parotocinclus
from the Amazon, Orinoco, and the coastal drainages of the
Guianas do form a clade. This clade is diagnosed by the canal
cheek plate on the ventral surface of the head being
posteriorly elongated and contacting the anterior margin of
the cleithrum (Lehmann and Reis, 2012; Lehmann et al.,
2014, 2015, 2018). This clade includes species that have more
elongated and generally pointed snouts, like P. collinsae
(Essequibo River, Guyana), P. eppleyi (R´
ıo Orinoco, Venezuela),
P. halbothi (Trombetas River, Brazil and Marowijne River,
Suriname), P. longirostris (middle Amazon River, Brazil), P.
polyochrus (Casiquiare, Venezuela), P. variola (upper Amazon
River, Colombia), and P. y a k a (Tiqui´
e River, upper Negro basin,
Brazil), as well as species with more rounded and not very
elongated snouts, like Parotocinclus amazonensis (lower Ama-
zon Basin), P. aripuanensis (lower Madeira Basin), and P. b r i t s k i i
(Guyana, eastern Venezuela, and Roraima State, Brazil).
In the present paper, an additional species of Parotocinclus
with a more rounded and short snout is described from the
upper Xingu River. This species was first discovered during
the 2002 expedition of the project ‘‘Knowledge, conserva-
tion, and rational use of the diversity of fish fauna in Brazil’’
within the scope of the Program of Support to Centers of
Excellence (PRONEX) financed by the Financiadora de
Estudos e Projetos (FINEP) and Conselho Nacional de
Desenvolvimento Cient´
ıfico e Tecnol ´
ogico (CNPq), and
coordinated by Naercio Menezes.
MATERIALS AND METHODS
Body measurements of the left side of individuals were taken
as point-to-point linear distances with digital calipers under a
dissecting microscope and recorded to the nearest 0.1 mm,
following the measurements described mainly by Boeseman
(1968) and Schaefer (1997). Standard length (SL) is expressed
in millimeters, and other measurements are given as percent
of SL or head length (HL). Specimens were cleared and stained
(CS) for inspection of bones and cartilages following Taylor
and Van Dyke (1985). Dermal plates and vertebral centra were
counted from CS specimens. Identification and counts of
dermal plates follow the serial homology scheme proposed by
Schaefer (1997). Vertebral counts include the five centra
modified into the Weberian apparatus and one compound
caudal centrum (PU1þU1). In the description, counts of the
holotype are presented in parentheses following the range of
all type specimens. Specimens examined belong to fish
collections using the acronyms presented in Sabaj (2020). In
the list of examined material, museum abbreviation and
catalog number come first, followed by the number and SL
range of specimens in that lot, the number and SL range of
specimens measured for the morphometric comparisons, in
parentheses, and locality. Conservation status of the new
species was assessed following the categories and criteria of the
International Union for Conservation of Nature (IUCN
Standards and Petitions Subcommittee, 2019). Comparative
material examined is listed in Lehmann and Reis (2012) and
Lehmann et al. (2014, 2015, 2018).
Parotocinclus kwarup, new species
urn:lsid:zoobank.org:act:7FCD2927-C17B-4B30-A266-
DE1EE6FCFCA8
Figure 1
Holotype.—MZUSP 125830, 21.9 mm SL, female, Couto de
Magalha
˜es River near Vila Sa
˜o Jos´
e do Couto, Campina
´polis,
MT, Brazil, 1385001700 S, 5380305300 W, F. Lima, C. Moreira, F.
Machado, A. Ribeiro, and C. Leite, 6 October 2007.
Paratypes.—All from Mato Grosso State, Brazil: LBP 15894, 6,
23.9–29.9 mm SL, creek tributary to Coluene River, Canar-
ana, 13825030.9 00 S, 52816047.000 W, C. Oliveira, M. Taylor, G.
1
Laborat´
orio de Ictiologia, Universidade do Vale do Rio dos Sinos, Av. Unisinos, 950, 93022-000 Sa
˜o Leopoldo, RS, Brazil; Email: pablole@
unisinos.br.
2
Pontif´
ıcia Universidade Cat´
olica do Rio Grande do Sul, P. O. Box 1429, 90619-900 Porto Alegre, RS, Brazil; Email: reis@pucrs.br. Send reprint
requests to this address.
Submitted: 12 April 2021. Accepted: 15 April 2021. Associate Editor: W. L. Smith.
Ó2021 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/i2021046 Published online: 31 May 2021
Ichthyology & Herpetology 109, No. 2, 2021, 449–455
Silva, and J. Martinez, 1 August 2012; MCP 32146, 3, 20.1–
25.3 mm SL, Von der Stainer River (¼Atelchu River) on road
from Santa Terezinha to Iberˆ
e, ca. 28 km W of Iberˆ
e, Nova
Ubirata
˜,12847005 00 S, 5484004900 W, R. Reis, L. Malabarba, V.
Bertaco, A. Cardoso, and E. Pereira, 29 January 2002; MCP
32296, 12, 18.1–23.5 mm SL þ3 CS 21.0–21.2 mm SL, Arraias
River on road from Vera to Feliz Natal, ca. 5 km NW of Feliz
Natal, 12821046 00 S, 5485703000 W, R. Reis, L. Malabarba, V.
Bertaco, A. Cardoso, and E. Pereira, 29 January 2002; MCP
32297, 32, 16.5–22.6 mm SL (5 measured for morphometric
comparisons 20.9–22.2 mm SL) þ3 CS 19.4–23.8 mm SL,
Azul River on road MT-140, ca. 7 km NNW of Santa Carmen,
11854042 00 S, 5581704800 W, R. Reis, L. Malabarba, V. Bertaco, A.
Cardoso, and E. Pereira, 28 January 2002; MCP 32298, 2,
20.3–23.0 mm SL, creek on road from Santa Terezinha to
Iberˆ
e, ca. 10 km W of Iberˆ
e, Nova Ubirata
˜,12845019 00 S,
54834025 00 W, R. Reis, L. Malabarba, V. Bertaco, A. Cardoso,
and E. Pereira, 29 January 2002; MCP 32299, 2, 20.5–23.0
mm SL, creek tributary to Azul River on road MT-423, ca. 51
km SW of Cla
´udia, Sinop, 11840017 00 S, 5581205400 W, R. Reis, L.
Malabarba, V. Bertaco, A. Cardoso, and E. Pereira, 28 January
2002; MCP 32300, 1, 22.3 mm SL, C ´
orrego Etn´
eia Creek on
Fig. 1. Holotype of Parotocinclus kwarup, MZUSP 125830, 21.9 mm SL, female, Rio Couto de Magalha
˜es near Vila Sa
˜o Jos´
e do Couto, Campina
´polis,
MT, Brazil.
450 Ichthyology & Herpetology 109, No. 2, 2021
road MT-423, ca. 60 km SW of Cla
´udia, Sinop, 11842021 00 S,
558170300 W, R. Reis, L. Malabarba, V. Bertaco, A. Cardoso, and
E. Pereira, 28 January 2002; MCP 32301, 1, 20.3 mm SL, creek
tributary to Saudade River on road MT-423 ca. 38 km SE of
Marcela
ˆndia, Anala
ˆndia do Norte, 11813023 00 S, 5481702400 W,
R. Reis, L. Malabarba, V. Bertaco, A. Cardoso, and E. Pereira,
27 January 2002; MCP 32302, 1, 12.7 mm SL, Ferro River on
road from Novo Mato Grosso to Nova Ubirata
˜, ca. 25 km SW
of Novo Mato Grosso, Nova Ubirata
˜,1380303200 S,
55802012 00 W, R. Reis, L. Malabarba, V. Bertaco, A. Cardoso,
and E. Pereira, 30 January 2002; MCP 39805, 1 CS 24.4 mm
SL, C´
orrego Capora
˜Creek, tributary to Ribeira
˜oTr
ˆ
es Marias
Creek, Suiazinho River, on road BR-158, Ribeira
˜o Cascalheira,
12832010 00 S, 5184604500 W, J. Pezzi da Silva, 31 October 2005;
MNRJ 24970, 64, 18.9–23.7 mm SL þ3 tissue samples,
Ribeira
˜o das Tra´
ıras Creek, tributary to Comandante Fontoura
River on road BR-158, S from Posto da Mata, Alto Boa Vista,
11849043 00 S, 5183800900 W, P. Buckup, A. Aranda, F. Silva, and
C. Figueiredo, 27 January 2002; MNRJ 25073, 1, 22.1 mm SL,
C´
orrego Trinta Creek, Alo Brasil, 1281405400 S, 51842045 00 W, P.
Buckup, A. Aranda, F. Silva, and C. Figueiredo, 27 January
2002; MNRJ 25138, 2, 21.5–22.2 mm SL, Ribeira
˜o Bonito
Creek, tributary to Suiazinho River, Ribeira
˜o Cascalheira,
12857009 00 S, 5185100700 W, P. Buckup, A. Aranda, F. Silva, and
C. Figueiredo, 27 January 2002; MZUSP 95576, 61, 16.6–22.8
mm SL (8 measured for morphometric comparisons 18.8–
22.3 mm SL), collected with holotype; MZUSP 95679, 9,
16.9–26.7 mm SL, Ribeira
˜o da Anta Creek and marginal pool
in its mouth into Culuene River, Ga´
ucha do Norte,
13830053 00 S, 5380503400 W, F. Lima, L. Moraes, A. Ribeiro, and
C. Leite, 12 October 2007; MZUSP 95709, 21, 16.1–24.3 mm
SL (6 measured for morphometric comparisons 19.2–23.7
mm SL), Coronel Vandick River, ca. 20 km of Vila do Rio
Culuene, Ga ´
ucha do Norte, 13831034 00 S, 5284305200 W, F. Lima,
C. Moreira, A. Ribeiro, L. Moraes, and C. Leite, 8 October
2007; MZUSP 97040, 89, 17.1–22.5 mm SL, Couto de
Magalha
˜es River at mouth of C ´
orrego A
´gua Clara Creek,
fazenda Meu Ranchinho, Campina
´polis, 13848002 00 S,
53803043 00 W, F. Lima, A. Ribeiro, C. Leite, and L. Moraes, 10
October 2007; MZUSP 97068, 51, 16.3–24.6 mm SL, C ´
orrego
A
´gua Fria Creek, tributary to Couto de Magalha
˜es River, ca
2.5 km S of Vila Sa
˜oJos
´
edoCouto,Campina
´polis,
13849025 00 S, 5380403000 W, F. Lima, C. Moreira, F. Machado,
A. Ribeiro, and C. Leite, 6 October 2007; MZUSP 99007, 3,
22.1–22.2 mm SL, Von den Steinen River (¼Atelchu River) at
Fazenda A.R.S., Nova Ubirata
˜,1380503500 S, 54849008 00 W, F.
Machado, C. Leite, N. Silva, N. Flausino, Jr., and G. Alencar,
21 January 2006.
Diagnosis.—Parotocinclus kwarup is distinguished from its
congeners from coastal drainages of the Brazilian Shield (P.
adamanteus,P. arandai,P. bahiensis,P. bidentatus,P. cabessa-
decuia,P. cearensis,P. cesarpintoi,P. cristatus,P. doceanus,P.
fluminense,P. haroldoi,P. jacumirim,P. jequi,P. jimi,P. jumbo,P.
maculicauda,P. minutus,P. muriaensis,P. nandae,P. planicauda,
P. prata,P. robustus,P. seridoensis,P. spilosoma, and P. spilurus)
in having the cheek canal plate elongated posteriorly on the
ventral surface of the head and contacting the cleithrum (Fig.
1; vs. canal plate rounded, not elongated posteriorly and not
contacting the pectoral girdle). Parotocinclus kwarup is
distinguished from other congeners from the Amazon,
Orinoco, and the Guianas by the following features: from P.
collinsae and P. halbothi by having the odontodes on the
ventral surface of the first pelvic-fin ray bent and pointing
mesially (vs. odontodes aligned with main ray axis); from P.
eppleyi,P. longirostris, and P. polyochrus by lacking a Y-shaped
light marking dorsally on the head, from the posterodorsal
margin of orbit to posterior parieto-supraoccipital tip (vs. Y-
shaped light markings present on dorsum of head, Fig. 2D, F,
G); from P. collinsae,P. halbothi, and P. variola by lacking
premaxillary and dentary accessory teeth (vs. accessory teeth
present); and from P. dani and P. pentakelis by having an
adipose fin (vs. adipose fin lacking); from the short-snouted
species, P. amazonensis,P. aripuanensis, and P. britskii by
having more numerous oral teeth (28–33 premaxillary and
27–31 dentary, vs. 17–27 and 18–27 in P. amazonensis and P.
aripuanensis, and 19–28 and 20–26 in P. britskii); and from
other congeners in having fewer oral teeth (vs. 38–42 and 31–
38 in P. longirostris, 38–46 and 39–46 in P. variola, and 38–43
and 37–42 in P. yaka). Although Parotocinclus kwarup is a
short-snouted species along with P. amazonensis,P. aripua-
nensis, and P. britskii (Fig. 2A, B), it has a slightly longer snout
than these latter three species. While the snout of P. kwarup is
50.0–55.8% HL (mean 53.1%), it is 45.1–53.9% HL (mean
50.7%) in P. amazonensis and P. aripuanensis and 43.9–53.1%
HL (mean 49.7%) in P. britskii. As a comparison, among the
long-snouted species (Fig. 2C–I), P. longirostris (68.7–74.6%
HL) and P. polyochrus (71.2–74.2% HL) have the longest
snouts.
Description.—Proportional measurements in Table 1. Dorsal
profile of head straight to slightly concave from snout tip to
posterior border of rostral plate, convex from that point to
parieto-supraoccipital tip and straight to slightly concave
from that point to origin of dorsal fin. Dorsal profile of body
mostly straight from dorsal-fin origin to insertion of caudal
fin, with slight elevation in front of adipose fin. Trunk
horizontally ovoid to roundly triangular, and caudal pedun-
cle rounded to ovoid in cross section, slightly flattened
ventrally at anal-fin and compressed caudally. Body progres-
sively narrowing posteriorly from cleithrum.
Head straight to slightly convex between orbits; dorsal
margin of orbit slightly elevated. Snout not very elongated,
depressed, its anterior margin rounded in dorsal view, with
small depression in front of naris. Eye comparatively small,
positioned dorsolaterally, with well-developed iris opercu-
lum. Posterior tip of parieto-supraoccipital variably with
small patch of enlarged odontodes. Slightly enlarged odont-
odes on snout border, especially on rostral and postrostral
plates and on lower surface of pectoral and pelvic spines;
enlarged odontodes curved and posteriorly oriented. Odont-
odes on head and trunk otherwise of uniform size and
distribution, sometimes somewhat aligned on trunk. Cheek
canal plate bent and elongated posteroventrally, contacting
or almost contacting anterior margin of cleithrum. Lips
rounded, covered with minute papillae; papillae decreasing
in size towards lip margin. Lower lip margin with uniformly
distributed papillae forming delicate fringe. Maxillary barbel
short; mostly adnate to lower lip but with free distal portion.
Teeth slender and delicate, bifid. Larger, medial cusp blade-
like and slightly rounded, not elongated. Smaller, lateral cusp
minute and pointed. Premaxillary teeth 28–33 (29); dentary
teeth 27–31 (27); accessory teeth lacking on both dentary
and premaxilla.
Body entirely covered by dermal plates except for ventral
surface of head around lips and area around anus. Lateral
Lehmann and Reis—New Parotocinclus from Xingu River 451
plates arranged in five longitudinal series on trunk. Dorsal
plate series complete, with 18–19 plates; mid-dorsal series
incomplete, with 6–7 plates; middle series complete, with 1–
2 ossified tubes and 23–24 plates. Lateral line either
uninterrupted or with 5–8 anterior canal-bearing plates
followed by 1–4 unperforated plate, then 12–14 posterior
canal-bearing plates, and 1–2 terminal plates without canal.
Mid-ventral series incomplete with 13–15 plates; series
terminating anterior to adipose fin. Ventral series complete
and continuous from pelvic-fin origin to caudal-fin base,
with 18–19 plates. Predorsal plates forming two transverse
rows anterior to nuchal plate. Single pre-adipose azygous
Fig. 2. Snout shape of Parotocinclus in dorsal and lateral views. (A) P. amazonensis, INPA 32983; (B) P. britskii, MCP 34709; (C) P. collinsae, AUM
62851; (D) P. eppleyi, MCP 33313; (E) P. halbothi, MCP 48029; (F) P. longirostris, MZUSP 85786; (G) P. polyochrus, AMNH 74482; (H) P. variola,
MCP 48245; (I) P. yaka, MZUSP 123655.
452 Ichthyology & Herpetology 109, No. 2, 2021
plate. Coracoid completely exposed ventrally; cleithrum
mostly exposed but covered by skin medially; arrector fossa
opened medially. Lateral abdominal plates 3–6; middle
abdominal plates arranged in four irregular series between
lateral abdominal ones. Preanal plate present, large and
triangular to pentagonal. First anal-fin pterygiophore ex-
posed in front of anal fin as small, plate-like bone supporting
odontodes. Total vertebrae 27 (in one dissected).
Dorsal-fin rays I,7; spine slightly arched. Dorsal-fin origin
posterior to vertical through pelvic-fin origin by a distance
similar to one eye diameter. Dorsal-fin spinelet present, plate-
like and roundly triangular, V-shaped with paired anterior
tips. Spinelet articulated to first dorsal-fin pterygiophore and
dorsal-fin spine locking mechanism functional. Adipose fin
small, with fully developed spine and membrane. Pectoral-
fin rays I,6. Large spine slightly arched; tip of adpressed spine
reaching between distal third or fourth pelvic-fin ray.
Pectoral-fin axillary slit present, with large slanted opening
ventral to tip of posterior process of cleithrum. Pelvic-fin rays
i,5. Fin short, with tip of adpressed fin falling short of anal-
fin origin in females, barely reaching that point in males.
Adult males with fleshy flap along proximal half to two-
thirds of posterodorsal margin of thickened first pelvic-fin
ray. Odontodes on ventral surface of thickened first pelvic-fin
ray bent and mesially oriented. Anal-fin rays i,5. Caudal-fin
rays i,14,i, with upper and lower unbranched rays equal or
lower slightly longer than upper.
Color in alcohol.—Dorsal and lateral portions of head and
trunk light brown, cream to pale yellow ventrally (Fig. 1).
Dorsal surface of snout and head with dark brown and
reddish brown spots. Middle ridge of snout with uneven
cream stripe that bifurcates to nares forming irregular Y-
shaped mark. Compound pterotic and anterior portion of
parieto-supraoccipital dark brown, with darker patch at limit
of these bones. Posterior portion of parieto-supraoccipital
and predorsal region lighter than surrounding areas, but not
forming Y-shaped mark. Trunk with four conspicuous dark
brown bars, extending transversely from dorsal midline to
ventral surface, narrowing ventrally. First bar at dorsal-fin
origin, also coloring fin membrane. Second bar immediately
posterior to dorsal-fin base and usually reaching ventrally to
anal-fin origin. Third bar wide and conspicuous at adipose
fin. Fourth bar immediately anterior to caudal fin. Ventral
surface mostly unpigmented, but scattered dark chromato-
phores sometimes on cheeks, lateral and central abdominal
plates, anus, and around anal-fin base. Dorsal surface of
anterior lip usually with sprinkled dark chromatophores,
forming mustache-like mark. Dorsal surface of lower lip
sometimes also with dark chromatophores. Dentary- and
premaxillary-tooth cusps reddish orange. Fins with trans-
verse, conspicuous brown bands formed by concentration of
chromatophores on rays; bands more numerous on leading
rays; membranes mostly hyaline. Dorsal-fin spine with 3–4
dark brown spots; branched rays with 1–2 dark bands,
anterior one triangular and very conspicuous. Pectoral-fin
spine with 4–5 dark spots, branched rays with 2–3 irregular
dark bands. Pelvic fin with 2–3 irregular dark band. Anal fin
with 1–2 dark bands. Adipose-fin lighter than dorsal plates,
usually with one dark spot. Caudal fin with conspicuous dark
oblique band at base and 2–3 irregular, oblique dark brown
bands.
Sexual dimorphism.—Males possess a conical urogenital
papilla, absent in females, and a skin fold on the proximal
half or third of the pelvic-fin unbranched ray, also absent in
females. Pelvic fin of males is slightly longer than those of
females, almost reaching or reaching to anal-fin origin;
falling short of that point in females.
Distribution and habitat.—Parotocinclus kwarup is known from
several localities in the upper Xingu River basin, in the
Brazilian state of Mato Grosso (Fig. 3). Specimens collected by
the MCP team in the 2002 expedition are from creeks and
small to medium rivers, with slow to medium water current,
usually clear water, and a bottom formed mostly by sand and
stones. Fish were mainly collected from marginal vegetation.
River banks were mostly covered by Cerrado savanna or
Amazon forest.
Etymology.—Parotocinclus kwarup in named after the Kwarup
(also known as Kuarup or Quarup), an annual ritual
celebrated by the upper Xingu indigenous people in honor
of their beloved dead, that originally aimed to bring them
back to life. A noun in apposition. This name is in honor to
the nearly 5,500 people belonging to 14 different ethnicities
that currently live in the Xingu Indigenous Park, which plays
an essential role in the conservation of this and other fish
species.
Conservation assessment.—The extinction risk of Parotocinclus
kwarup is assessed as low because of its wide geographic
distribution. The species is known from several localities in
the upper Xingu River basin, with an Extension of Occur-
Table 1. Morphometrics of holotype (H) and paratypes (n¼20) of
Parotocinclus kwarup as percent of standard length or head length.
Range includes the holotype. SD ¼standard deviation.
Measurement H Min Max Mean SD
Standard length (mm) 21.9 18.8 23.7 21.3
Percent of standard length
Body depth 14.9 13.6 17.2 15.7 0.89
Predorsal distance 44.0 4.0 48.4 46.6 1.17
Prepelvic distance 41.8 40.6 44.8 42.4 0.99
Preanal distance 64.7 62.2 67.5 65.1 1.40
Preadipose distance 77.2 72.3 80.0 76.6 1.62
Dorsal-fin spine length 23.4 20.5 27.7 24.0 1.59
Anal-fin unbranched ray length 15.8 12.1 17.1 14.8 1.11
Adipose-fin spine length 7.2 5.3 8.4 7.1 0.74
Pectoral-fin spine length 28.2 23.9 29.6 26.5 1.60
Pectoral-fin spine depth 2.0 1.2 2.0 1.6 0.21
Caudal peduncle depth 8.0 7.3 8.6 7.8 0.34
Dorsal–adipose fin distance 19.7 18.9 20.9 19.8 0.52
Dorsal-fin base length 12.0 9.5 12.7 11.2 0.92
Lower caudal-fin principal ray 23.6 21.1 28.7 25.0 1.82
Cleithral width 26.7 24.4 27.3 26.0 0.93
Head length 35.3 32.4 37.4 35.4 1.60
Percent of head length
Head depth 43.0 41.2 48.0 44.4 1.92
Interorbital distance 36.7 31.9 37.7 35.3 1.74
Orbital horizontal diameter 19.6 16.7 21.3 18.6 1.38
Snout length 54.0 50.0 55.8 53.1 1.31
Internarial distance 8.9 6.4 10.4 8.5 0.99
Tooth count
Premaxilla 29 28 33 30.4 1.81
Dentary 27 27 31 29.4 1.51
Lehmann and Reis—New Parotocinclus from Xingu River 453
rence (EOO) calculated by the minimum convex polygon of
approximately 81,750 square kilometers. The area where
most specimens were collected is heavily impacted by
deforestation and agriculture, but a very large preservation
area (the Xingu Indigenous Park, with 26,420 km
2
) is located
at the center of the species’ distribution area. As no specific
threats to the species were detected and its presence is
inferred in the Xingu Indigenous Park, P. kwarup is prelim-
inarily categorized as Least Concern (LC) according to the
International Union for Conservation of Nature (IUCN)
categories and criteria (IUCN Standards and Petitions
Subcommittee, 2019).
DISCUSSION
The taxonomic impediment (Raposo et al., 2020) has many
sources, the shortage of well-trained, qualified taxonomists
being among the most important. As happens with many
taxa discovered by taxonomists, material of Parotocinclus
kwarup was first discovered and identified as a new species
during a 2002 expedition to Central Brazil and remained on
museum shelves for almost two decades. It is now being
described in an effort to increase knowledge on the
ichthyofauna of the Xingu River, which has been deeply
affected by two of the most severe threats to aquatic habitats
in South America: land conversion in the form of deforesta-
tion for agriculture and cattle ranching and hydroelectric
damming (Reis et al., 2016).
Most of the northern part of the Mato Grosso State has
been clear-cut for extensive agriculture, destroying immense
areas of Amazon forest and Cerrado savannas in recent
decades. Further, the erosion, subsequent silting, and
increased turbidity of rivers caused by deforestation, along
with the introduction of herbicides, pesticides, and fertilizers
from agriculture, severely impact the ecology of freshwater
systems and represent a significant threat to the fish
populations in highly converted basins (Van den Brink et
al., 2006; Reis et al., 2016). One exception to the ecological
crisis in northern Mato Grosso State is the Xingu Indigenous
Territory which includes the Xingu Indigenous Park and
three contiguous indigenous lands (Pequizal do Naruvˆ
otu,
Wawi, and Batovi), forming a permanent preservation area of
over 28,000 km
2
. This territory includes well-preserved forest
which has been instrumental in conserving the fish fauna in
the upper Xingu, including P. kwarup. However, threats to the
ichthyofauna are also posed by the hydroelectric dams of the
Xingu River. The ill-famed Belo Monte hydroelectric power
plant and its associated Pimental hydrolectric dam are in the
lower Xingu River, severely affecting the ichthyofauna and
native human populations of that portion of the basin. In
the upper Xingu, however, there are already small hydro-
power plants, like the Culuene, Paranatinga I, and Para-
natinga II in the Culuene River; Corredeira do Noronha in
the Piranha River; A
´gua Suja in the Curisevo River;
Jatobazinho in the Jatoba
´River; and ARS in the Atelchu
River, as well as additional planned power plants. These
hydropower projects directly affect and threaten the tribu-
taries where P. kwarup lives.
DATA ACCESSIBILITY
Unless an alternative copyright or statement noting that a
figure is reprinted from a previous source is noted in a figure
caption, the published images and illustrations in this article
are licensed by the American Society of Ichthyologists and
Herpetologists for use if the use includes a citation to the
original source (American Society of Ichthyologists and
Herpetologists, the DOI of the Ichthyology & Herpetology
article, and any individual image credits listed in the figure
caption) in accordance with the Creative Commons Attribu-
tion CC BY License. ZooBank publication urn:lsid:zoobank.
org:pub:D44B7B01-63F2-4469-9587-43A517A8E408.
ACKNOWLEDGMENTS
We are grateful to Carlos and Margarete Lucena for the
continuous support at MCP. For loaning specimens and
providing information, we are grateful to J. Armbruster
(AUM), P. Buckup (MNRJ), A. Datovo, M. Gianeti, O.
Oyakawa, and M. de Pinna (MZUSP), C. Oliveira (LBP), L.
Rapp Py-Daniel and R. Ribeiro (INPA), and S. Schaefer and B.
Brown (AMNH). We thank B. Calegari for preparing the base
map in Figure 3. We are grateful to N. Menezes for leading the
project ‘‘Knowledge, conservation and rational use of the
diversity of fish fauna in Brazil’’ within the scope of the
Program of Support to Centers of Excellence (PRONEX),
which led to the discovery of this new species. RER was
partially funded by the Conselho Nacional de Desenvolvi-
mento Cient´
ıfico e Tecnol ´
ogico–CNPq (grants #306455/
2014-5 and #400166/2016-0).
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Lehmann and Reis—New Parotocinclus from Xingu River 455
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The genus Otocinclus Cope (1872) of the siluriform family Loricariidae is diagnosed as monophyletic on the basis of shared derived characters of the cranial and hyobranchial skeleton, dorsal gill arch musculature, and gut. Otocinclus are relatively small herbivorous catfishes restricted to small streams and quiet slow-flowing margins of larger rivers, most frequently living in close association with aquatic macrophytes and terrestrial marginal grasses extending into the water column. Otocinclus species share a novel modification of the distal esophageal wall which is developed into an accessory blind diverticulum that may function in aerial respiration and for providing additional modulatory positive buoyancy for remaining in the upper water column at stream margins. Otocinclus has no junior synonyms, however several nominal species originally described in Otocinclus are here formally re-assigned to other genera in the subfamily Hypoptopomatinae. Otocinclus cephalacanthus Ribeiro 1911, O. depressicauda Ribeiro 1918, O. francirochai Ihering 1928, O. laevior Cope 1894, O. leptochilus Cope 1894, O. maculipinnis Regan 1904, O. nigricauda Boulenger 1891, and O. paulinus Regan 1908 are all placed in the genus Microlepidogaster Eigenmann & Eigenmann 1889; O. obtusos Ribeiro 1911 was placed in Pseudotothyris Britski & Garavello 1984; the genus Nannoptopoma Schaefer 1996 was erected for O. spectabilis Eigenmann 1914 in the tribe Hypoptopomatini; O. gibbosus Ribeiro 1908 is removed from Otocinclus, yet remains of undetermined generic status. Thirteen species are recognized in Otocinclus: O. affinis Steindachner 1877 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. bororo n. sp. of the upper Río Paraguay; O. caxarari n. sp. of the middle Río Guaporé/Mamoré system; O. flexilis Cope 1894 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. hasemani Steindachner 1915 of northern Brazil; O. hoppei Ribeiro 1939 of the upper Amazon, Tocantins and Paraguay basins and coastal streams of northeastern Brazil; O. huaorani n. sp. of the upper Amazon and Orinoco basins; O. macrospilus Eigenmann & Allen 1942 of the upper Amazon basin of Colombia, Ecuador, and Peru; O. mariae Fowler 1940 of the lower Amazon, upper Madeira and Paraguay basins; O. mura n. sp. of the middle Amazon River; O. vestitus Cope 1872 of the upper Amazon and lower Paraná basins; O. vittatus Regan 1904 of the Amazon, Orinoco, Paraná/Paraguay, and Tocantins basins; and O. xakriaba n. sp. of the rio São Fransisco basin. Two species are placed in synonymy: Otocinclus arnoldi Regan 1909 and O. fimbriatus Cope 1894 are junior synonyms of O. flexilis. Keys to the species of Otocinclus and genera of the Hypoptopomatinae are provided. A descriptive treatment of the osteology and cranial myology is provided for O. vittatus. Detailed analysis of meristic and morphometric variation based on geometric morphometric procedures is provided for the phenetically similar species pairs O. mariae and O. vittatus, O. bororo and O. huaorani in an a posteriori evaluation of separate species status. The phylogenetic relationships among Otocinclus species, and the phylogenetic position of Otocinclus among genera of the Hypoptopomatinae, are determined based on analysis of 27 morphological features using cladistic parsimony. Monophyly of Otocinclus was confirmed; within Otocinclus, a clade comprised of O. affinis and O. flexilis is the sister-group to the remainder of the genus. Within that latter clade, O. hasemani and O. xakriaba are the first and second-level sister-groups to the remainder of the genus, within which relationships among species are not fully resolved with available data. The phylogenetic biogeography of Otocinclus is informative regarding the historical relationships among major river drainage basins, particularly of those river systems of the Brazilian Shield. A biogeographic hypothesis is proposed based on the area cladogram derived from the species-level phylogenetic relationships, which suggests successive vicariance and speciation in the non-Amazonian regions of endemism of southeastern and eastern South America, followed by speciation and dispersal within the Amazon, Orinoco and upper Paraguay basins. The pattern of vicariance revealed by the Otocinclus species-level phylogeny is congruent with the geologic history of the major river drainage basins of the Brazilian Shield. This result suggests that, for Otocinclus and perhaps other loricariid catfishes, much of their generic and species-level diversification occurred prior to the formation of the Amazon basin.