Copeia 2009, No. 3, 446–452
Two New Species of Acestridium Haseman, 1911 (Loricariidae:
Hypoptopomatinae) from the Rio Madeira Basin, Brazil
Roberto E. Reis1 and Pablo Lehmann A.1
Acestridium gymnogaster and A. scutatum are described as new from small tributaries to the middle Rio Madeira,
Amazonas, Brazil. Acestridium gymnogaster is most similar to A. discus from which it differs in the number of medial
unpaired predorsal plates, the arrangement of chromatophores in predorsal area, and the absence of contact
midventrally between the lateral abdominal plates. Acestridium scutatum is most similar to A. triplax from which it differs
in having a longer snout and by the shape of the preanal plate. A key to the species of Acestridium is provided.
Acestridium gymnogaster e Acestridium scutatum, espécies novas, são descritas de pequenos rios tributários do médio Rio
Madeira, Estado do Amazonas, Brasil. Acestridium gymnogaster é mais semelhante à A. discus, de quem difere pelo número
de placas ı́mpares médias pré-dorsais, arranjo dos cromatóforos na área pré-dorsal, e a ausência de contato entre as
placas laterais abdominais na linha media. Acestridium scutatum é mais semelhante à A. triplax, de quem difere por ter o
focinho mais longo e pela forma da placa pré-anal. Uma chave para as espécies de Acestridium é apresentada.
A
CESTRIDIUM has been known since the description
of A. discus by Haseman (1911) almost a century ago
based on specimens that originated in the Igarapé da
Cachoeira Grande near Manaus. However, it was only in the
last decade that we began to develop an understanding of
the species-level diversity within this highly distinctive
hypoptopomatine genus. Since 1999, four additional species
were described: A. dichromum, A. martini, and A. colombiensis
from the Rı́o Orinoco basin in Venezuela and Colombia, and
A. triplax from the lower Rio Amazonas.
Sampling small tributaries to the Rio Madeira along the
Trans-Amazonica road, east of Humaitá, Amazonas, Brazil,
we discovered two additional species of Acestridium that we
describe herein. We also provide a key to the species of
Acestridium.
MATERIALS AND METHODS
The morphometric variables were measured with digital
calipers (0.1 mm precision) and follow Rodriguez and Reis
(2007). Proportional ranges presented in couplet 4 of key are
from Retzer (2005). Names and counts of lateral, abdominal,
and rostral plates follow Schaefer (1997). Prenuchal plate
definition follows Rodriguez and Reis (2007). Specimens
were cleared and stained (CS) for bone and cartilage
according to the procedures of Taylor and Van Dyke
(1985). In the lists of material examined, museum abbreviations and catalog numbers are presented first, followed by
the number of specimens examined, number of cleared-andstained specimens, size range of specimens, and locality
information. Accounts of new species also include number
and size range of specimens measured for the morphometric
comparisons, and date of collection and collectors. Institutional abbreviations follow Leviton et al. (1985).
Acestridium gymnogaster, new species
Figure 1, Table 1
Holotype.—MCP 43199, 59.1 mm SL, female, Brazil, Amazonas, Municı́pio de Humaitá, Rio Traira, approximately
35 km E of Rio Madeira on Trans-Amazonica road,
1
7u359330S, 62u449450W, 27 July 2004, R. E. Reis, F. Langeani,
E. H. L. Pereira, and A. R. Cardoso.
Paratypes.—Brazil, Amazonas, Humaitá: MCP 37784, 12+2
CS, 25.2–61.8 mm SL, 3, 40.2–61.8 mm SL, same data as
holotype. MCP 37783, 10, 27.9–60.1 mm SL, 6, 38.0–
60.1 mm SL, MNRJ 32558, 2, 41.6–42.4 mm SL, creek ca
68 km E of Rio Madeira on Trans-Amazonica road,
7u439580S, 62u299400W, 27 July 2004, R. E. Reis, F. Langeani,
E. H. L. Pereira, and A. R. Cardoso. MCP 37786, 1, 43.9 mm
SL, ANSP 189026, 2, 39.9–44.4 mm SL, Rio Maici-mirim, ca
45 km E of Rio Madeira on Trans-Amazonica road,
7u379560S, 62u399440W, 27 July 2004, R. E. Reis, F. Langeani,
E. H. L. Pereira, and A. R. Cardoso.
Diagnosis.—Acestridium gymnogaster differs from all remaining
Acestridium species except for A. discus in having three or four
medial unpaired predorsal plates (one nuchal and two or three
prenuchal plates), versus two median unpaired predorsal
plates (one nuchal and one prenuchal plate). Acestridium
gymnogaster is distinguished from A. discus by having two or
three (usually three) prenuchal plates anterior to the nuchal
plate (versus two or three, but usually two), in having
chromatophores arranged in lines between the aligned
odontodes of predorsal area (versus chromatophores concentrated in skin around the predorsal plates, giving a reticulated
appearance to the predorsal area), by having the lateral
abdominal plates extending to midventral line only posteriorly and always leaving a naked midventral area anteriorly
(versus lateral abdominal plates extending to midventral line
from the pectoral bridge to the preanal plate), and in
possessing a nasal plate short, not reaching the anterior
margin of the lateral ethmoid (versus nasal plate long and
reaching the anterior margin of the lateral ethmoid). Acestridium gymnogaster is further distinguished from A. colombiensis
and A. martini by having 12 branched caudal-fin rays (versus
10), the first bilateral postrostral plates not contacting each
other midventrally (versus plates contacting each other
midventrally), possessing one or two paired predorsal plates
anterior to the prenuchal plates (versus four or five), and
possessing a connecting bone present (versus absent). Acestri-
Laboratório de Sistemática de Vertebrados, Pontifı́cia Universidade Católica do Rio Grande do Sul, P.O. Box 1429, 90619-900 Porto Alegre,
RS, Brazil; E-mail: (RER) reis@pucrs.br; and (PLA) lehmanncatfish@gmail.com. Send reprint requests to RER.
Submitted: 26 August 2008. Accepted: 30 January 2009. Associate Editor: C. J. Ferraris.
DOI: 10.1643/CI-08-150
F 2009 by the American Society of Ichthyologists and Herpetologists
Reis and Lehmann—Two new species of Acestridium
447
Fig. 1. Acestridium gymnogaster, MCP 43199, holotype, 59.1 mm SL, female, Rio Traira, ca 35 km E of Rio Madeira on Trans-Amazonica road,
7u359330S, 62u449450W, Humaitá, Amazonas, Brazil.
dium gymnogaster is further distinguished from A. dichromum
by having 12 branched caudal-fin rays (versus 11) and by
lacking serrations on the inner margin of the pectoral-fin spine
(versus conspicuous serrations present). Finally, A. gymnogaster
is distinguished from A. scutatum and A. triplax by lacking a
midventral series of plates between the lateral abdominal
plates (versus abdomen with a middle series of plates).
Description.—Morphometric data given in Table 1. Head,
trunk, and caudal peduncle depressed, elongate, and
narrow. Body width 6.0–6.6% of standard length. Dorsal
profile of head and body straight or slightly concave from
snout tip to eye, straight or slightly convex from eye to
origin of dorsal fin, straight from last dorsal-fin ray to
penultimate plate of caudal peduncle.
Body covered with bony plates except for ventral part of
head, midventral portion of abdomen between lateral
abdominal plates, and very narrow area surrounding pelvicfin base and anus. Body plates uniformly covered by small
odontodes arranged in longitudinal rows. Predorsal area with
two paired plates followed by three median prenuchal plates
(but one specimen with two and other with four prenuchal
plates) and one nuchal plate anterior to dorsal fin. Connecting bone present, linking distal portion of first rib to anteriormost prenuchal plate. Postdorsal plates 15 (one specimen with
14, n 5 12). Postanal plates 14 or 15 (mean 5 14.5, n 5 12).
Four lateral series of plates, mid-dorsal series absent. Parietosupraoccipital bone and predorsal plates with keels formed by
ridges of aligned odontodes.
Profile of head acutely triangular from dorsal view, with
ovate spatulate projection on tip of snout. Spatulate projection
formed by anterior portion of rostral plates and bearing large
odontodes. Tip of spatulate projection of snout with small
naked area. Rostral plate short, spatulate projection approximately one-half length of rostral plate. Two postrostral plates
on each side follow rostral plate. Anterior portions of first
postrostral plates not contacting each other along ventral
midline. Postrostral plates and cheek plate bent ventrally and
visible in ventral view. Cheek plate with canal continuous
with canal in fifth infraorbital. Eye placed laterally, not visible
from ventral view. Iris operculum present. Mouth rounded,
with globular papillae on both upper and lower lips. Maxillary
barbel shorter than eye diameter. Premaxilla with ten to 18
(mean 5 13.5, n 5 12) bilobed teeth in functional series.
Dentary with nine to 14 (mean 5 11.4, n 5 12) bilobed teeth in
functional series. All teeth with uneven cusps, with reddishbrown tip. Mesial cusp longer and wider than lateral one.
Abdomen with naked area anteriorly between lateral
abdominal plates. Naked area also present between pectoral
girdle and first pair of lateral abdominal plates. Three to five
(mean 5 3.5, n 5 12) lateral abdominal plates on each side.
Preanal plate roughly triangular, more acute anteriorly and
wider posteriorly.
Dorsal-fin rays i,7. Distal margin of dorsal fin straight or
slightly convex, with first or second branched ray longest. Tip
of depressed dorsal fin reaching third plate posterior to fin
base. Dorsal-fin spinelet absent. Pectoral-fin rays I,6. Pectoral
spine without serrae on inner margin. Ossified portion of
spine reaching beyond middle of first branched ray. Distal
margin of pectoral fin convex, with longest rays (first or
second branched ray) falling short of pelvic-fin origin. Pelvicfin rays i,5. Unbranched ray very thick with enlarged
odontodes turned mesially. Distal margin of pelvic fin convex.
Second, third, or fourth branched pelvic-fin ray longest,
reaching approximately one-half distance to anal-fin origin.
Anal-fin rays i,5. Unbranched anal-fin ray reaching about
four-fifths of length of first branched ray. Posterior margin of
anal fin rounded, with first, second, or third branched ray
longest. Tip of depressed anal fin reaching third plate
posterior to fin base. Two or three plates along anal-fin base.
Posterior margin of caudal fin truncate or slightly concave.
Principal caudal-fin rays i,12,i. Adipose fin absent.
Color in alcohol.—Dorsum light brown with thin stripes of
dark pigmentation running between longitudinal rows of
odontodes. Dark brown stripe running from snout along
448
Copeia 2009, No. 3
Table 1. Morphometrics of Holotype and Paratypes of Acestridium gymnogaster (n 5 12) and Acestridium scutatum (n 5 10). Values are given as
percents of standard length or head length. SD 5 standard deviation, Holo 5 holotype.
Acestridium gymnogaster
Acestridium scutatum
Holo
Min
Max
Mean
SD
Holo
Min
Max
Mean
SD
Standard length (mm)
Percent of standard length
59.1
38.0
61.8
47.0
—
62.7
36.4
62.7
40.9
—
Predorsal length
51.1
47.8
51.1
48.9
0.90
46.3
46.3
49.6
47.5
0.97
Postdorsal length
44.0
44.0
47.7
45.9
0.91
45.2
44.8
48.1
46.7
1.09
Postanal length
42.6
42.6
46.9
44.4
1.23
46.1
44.2
47.4
45.6
1.01
Body width at dorsal-fin origin
6.4
6.0
6.6
6.3
0.17
6.5
5.9
7.1
6.5
0.35
Body depth at dorsal-fin origin
5.4
4.5
5.8
5.2
0.38
4.5
4.5
5.5
4.9
0.28
Body width at anal-fin origin
6.1
5.4
6.2
5.8
0.26
6.1
5.7
6.6
6.0
0.27
Body depth at anal-fin origin
4.6
4.2
5.3
4.7
0.28
3.8
3.8
4.9
4.5
0.31
Preventral length
40.1
35.8
40.1
38.9
1.22
38.6
38.6
41.2
39.9
0.86
Supraoccipital-dorsal fin distance
18.1
13.9
18.1
16.1
1.28
15.1
12.1
15.2
13.2
0.96
Minimum depth of caudal peduncle
1.0
0.8
1.3
1.1
0.15
0.8
0.8
1.1
1.0
0.08
10.5
10.0
13.9
11.7
1.21
9.6
9.6
11.6
10.8
0.71
Length of pectoral-fin spine
8.5
8.2
10.2
9.0
0.68
8.1
7.7
9.7
8.6
0.75
Length of first pelvic-fin ray
5.7
5.5
7.2
6.4
0.52
5.1
5.1
5.9
5.6
0.28
Length of dorsal-fin spine
Length of first anal-fin ray
9.0
8.2
12.6
10.3
1.45
7.3
7.3
10.7
8.8
0.96
Snout tip to eye distance
22.2
19.6
22.9
21.6
0.89
21.7
21.5
23.5
22.4
0.69
Distance from pectoral-fin origin to pelvic-fin origin
10.6
9.2
10.8
10.3
0.58
10.7
9.5
11.1
10.5
0.53
Eye to dorsal-fin origin length
26.4
23.4
26.4
25.0
0.82
22.6
21.6
23.6
22.6
0.64
Oral disk width
6.4
5.5
8.2
7.0
1.01
5.3
5.3
7.0
6.3
0.46
Head length
Percent of head length
33.2
30.9
34.1
33.0
1.14
30.8
30.8
35.3
34.1
1.33
Head depth
17.8
16.8
19.7
18.4
0.89
16.6
14.6
17.3
16.1
0.93
Head width
26.0
24.7
29.9
26.8
1.75
25.4
24.1
26.3
25.1
0.56
Interorbital width
17.8
15.3
19.4
17.9
1.10
15.5
14.8
17.3
16.0
0.83
Length of lower armored snout
18.9
11.4
25.7
18.2
3.68
30.0
19.5
30.1
22.1
3.05
6.6
6.3
8.5
7.5
0.82
6.7
6.7
8.9
8.0
0.67
24.5
18.3
27.0
25.2
2.28
23.8
23.3
26.9
25.3
1.27
Maximum eye diameter
Length of postorbital head
side of head through eye and onto body. Stripe becoming
less distinct on body and indistinct after vertical through
dorsal fin. Cheek light yellow ventral of longitudinal stripe.
Ventral surface of body yellowish, with sparse dark pigmentation ventrally between anal and caudal fins. Snout
brownish ventrally. All spines and unbranched rays except
on caudal fin yellowish tan with round black spots
distributed regularly and interradial membranes hyaline.
Caudal-fin rays brown, with numerous darker spots sometimes forming one or two dark bands.
Color in life.—Mostly grass green dorsally, with brown lateral
stripe from snout to middle of body; light brown or
yellowish tan ventrally (based on field observations).
Distribution and habitat.—Only known from the typelocality and two other creeks near Humaitá, in the Rio
Madeira drainage (Fig. 2). The three localities are shallow
streams (0.5–1.5 m deep, 5–20 m wide), with a sandy
bottom, clear or slightly black water, moderate water
current, and dense aquatic and marginal vegetation.
Etymology.—The species epithet, gymnogaster, from the
Greek gymnos, bare, naked, and gaster, belly, referring to
the naked area of skin between the anterior lateral
abdominal plates. A noun in apposition.
Acestridium scutatum, new species
Figure 3, Table 1
Holotype.—MCP 43198, 62.7 mm SL, female, Brazil, Amazonas,
Municı́pio de Humaitá, Rio Traira, ca 35 km E of Rio Madeira on
Trans-Amazon Road, 7u359330S, 62u449450W, 27 July 2004, R. E.
Reis, F. Langeani, E. H. L. Pereira, and A. R. Cardoso.
Paratypes.—Brazil, Amazonas, Humaitá: MCP 37785, 9+2 CS,
28.6–39.7 mm SL, 9, 37.1–39.7 mm SL, MNRJ 32557, 2,
Reis and Lehmann—Two new species of Acestridium
449
predorsal plates (one nuchal and one prenuchal plate),
versus three or four medial unpaired predorsal plates (one
nuchal and two or three prenuchal plates). Acestridium
scutatum is further distinguished from A. colombiensis and
A. martini by having 12 branched caudal-fin rays (versus
10), in having the first bilateral postrostral plates not
contacting each other midventrally (versus plates articulating to each other midventrally), in possessing one or
two paired predorsal plates anterior to the prenuchal
plates (versus four or five paired predorsal plates), and in
having the connecting bone present (versus absent).
Acestridium scutatum is further distinguished from A.
dichromum by having 12 branched caudal-fin rays (versus
11) and by lacking or having very delicate serrations on
inner margin of the pectoral-fin spine (versus conspicuous serrations present).
Fig. 2. Distribution of Acestridium gymnogaster (dot) and A. scutatum
(triangle). Symbols represent more than one locality.
33.9–39.1 mm SL, ANSP 189025, 2, 34.2–39.0 mm SL, same
data as holotype.
Diagnosis.—Acestridium scutatum differs from all remaining
Acestridium species except for A. triplax in having a
middle series of abdominal plates between the lateral
abdominal plates (versus abdomen without a middle
series of plates). Acestridium scutatum is distinguished
from A. triplax by having a long snout (distance from the
snout tip to the posteroventral margin of the rostral plate
24.7–33.6% of head length), versus snout short (22.0–
24.5% of head length), and in having a preanal plate with
well developed anterior and posterior lateral expansions
(Fig. 4A), versus preanal plate with slightly developed
anterior and posterior lateral expansions (Fig. 4B). Acestridium scutatum is further distinguished from A. gymnogaster and A. discus by having two median unpaired
Description.—Morphometric data given in Table 1. Head,
trunk, and caudal peduncle depressed, elongate, and
narrow. Body width 5.9–7.1% of standard length. Dorsal
profile of head and body slightly concave from snout tip to
eye, straight to supraoccipital tip and slightly convex from
that point to origin of dorsal fin, straight from last dorsal-fin
ray to penultimate plate of caudal peduncle.
Body covered with bony plates except for ventral portion
of head and narrow area surrounding pelvic-fin base and
anus. Body plates uniformly covered by small odontodes
arranged in longitudinal rows. Predorsal area with two
paired plates followed by one median prenuchal plate and
one nuchal plate located anterior to origin of dorsal fin.
Connecting bone present, linking distal portion of first rib
to prenuchal plate. Postdorsal plates 16 (one specimen with
15, n 5 10). Postanal plates 15 or 16 (mean 5 15.6, n 5 10).
Four lateral series of plates, mid-dorsal series absent. Parietosupraoccipital bone and predorsal plates with keels formed
by ridges of aligned odontodes.
Fig. 3. Acestridium scutatum, MCP 43198, holotype, 62.7 mm SL, female, Rio Traira, ca 35 km E of Rio Madeira on Trans-Amazonica road,
7u359330S, 62u449450W, Humaitá, Amazonas, Brazil.
450
Copeia 2009, No. 3
Fig. 4. Preanal plate of species of Acestridium: (A) A. scutatum, MCP
43198; and (B) A. triplax, MPEG 12467. Scale bar: 1 mm.
Profile of head acutely triangular from dorsal view, with
ovate spatulate projection on tip of snout. Spatulate
projection formed by anterior portion of rostral plates
and bearing large odontodes. Tip of spatulate projection
of snout with small naked area. Rostral plate long,
spatulate projection approximately one-third length of
rostral plate length. Two postrostral plates on each side
follow rostral plate. Anterior portion of first postrostral
plates not contacting each other along ventral midline.
Postrostral plates and cheek plate bent ventrally and
visible from ventral view, cheek plate with canal from
fifth infraorbital. Eye placed laterally, not visible from
ventral view. Iris operculum present. Mouth rounded,
with globular papillae on both upper and lower lips.
Maxillary barbel shorter than eye diameter. Premaxilla
with 14 to 19 (mean 5 16.1, n 5 10) bilobed teeth in
functional series. Dentary with 11 to 16 (mean 5 12.9, n
5 10) bilobed teeth in functional series. All teeth with
uneven cusps, with reddish-brown tip. Mesial cusp longer
and wider than lateral one.
Abdomen fully plated except for region of pectoral girdle.
One series of middle abdominal plates present between
lateral abdominal plates. Four to six (mean 5 4.5, n 5 10)
lateral abdominal plates on each side. Preanal plate wide and
distinctly expanded laterally both anteriorly and posteriorly.
Dorsal-fin rays i,7. Distal margin of dorsal fin straight or
slightly convex, with first or second branched ray longest.
Tip of depressed dorsal fin reaching third plate posterior to
fin base. Dorsal-fin spinelet absent. Pectoral-fin rays I,6.
Pectoral spine with delicate serrae on inner margin. Ossified
portion of spine reaching beyond middle of first branched
ray. Distal margin of pectoral fin convex, with first or second
branched ray longest (but not reaching to pelvic-fin origin).
Pelvic-fin rays i,5. Unbranched ray very thick with enlarged
odontodes turned mesially. Posterior margin of pelvic fin
convex. Second, third, or fourth branched pelvic-fin ray
longest, reaching less than one-half distance to anal-fin
origin. Anal-fin rays i,5. Unbranched anal-fin ray reaching
about four-fifths length of first branched ray. Posterior
margin of anal fin convex, with first, second, or third
branched ray longest. Tip of depressed anal fin reaching
third or fourth plate posterior to fin base. Two or three plates
along anal-fin base. Posterior margin of caudal fin truncate
or slightly concave. Principal caudal-fin rays i,12,i. Adipose
fin absent.
Fig. 5. Predorsal region of species of Acestridium: (A) A. martini,
MZUSP 74275; (B) A. scutatum, MCP 37785; and (C) A. gymnogaster,
MCP 37784. CP 5 compound pterotic, NP 5 nuchal plate, PNP 5
prenuchal plates, PPP 5 paired predorsal plates, SOC 5 supraoccipital.
Scale bar: 5 mm.
Color in alcohol.—Dorsum light brown with thin stripes of
dark pigmentation running between longitudinal rows of
odontodes. Inconspicuous brown stripe running from snout
along side of head through eye, becoming less distinct as it
reaches body and becoming indistinct at vertical through
dorsal fin. Cheek light yellow ventral of longitudinal stripe.
Ventral surface of body yellowish. Body with sparse dark
pigmentation ventrally between anal and caudal fins. Snout
brownish ventrally. All spines and unbranched rays except
for caudal fin yellowish tan with round dark spots
distributed regularly; interradial membranes hyaline. Caudal-fin rays brown, with numerous darker spots sometimes
forming one or two dark bands.
Color in life.—Mostly grass green dorsally, with brown lateral
stripe from snout to middle of body; light brown or
yellowish tan ventrally (based on field observations).
Distribution and habitat.—Only known from the Rio Traira, a
small river near Humaitá, in the Rio Madeira drainage
(Fig. 2). The type-locality is a shallow stream (0.5–1.5 m
deep, 5–20 m wide), with a sandy bottom, slightly black
water, moderate water current, and dense aquatic and
marginal vegetation.
Etymology.—The species epithet, scutatum, from the Latim
scutum, shield, plate, referring to the three series of
abdominal plates present in the new species. An adjective.
KEY TO THE SPECIES OF ACESTRIDIUM
1a.
Two median unpaired predorsal plates (one nuchal
3
and one prenuchal plate; Fig. 5A, B)
Three or four median predorsal plates (one nuchal
and two or three prenuchal plates; Fig. 5C)
2
Lateral abdominal plates extending to midventral
line from pectoral bridge to preanal plate (Fig. 6A);
two or three (usually two) prenuchal plates anterior
to the nuchal plate; chromatophores concentrated
in skin around predorsal plates, giving reticulated
_____________________________
1b.
_______________
2a.
Reis and Lehmann—Two new species of Acestridium
451
Fig. 6. Abdominal plates of species of Acestridium: (A) A. discus, MZUSP
85322; (B) A. gymnogaster, MCP 37784; and (C) A. scutatum, MCP
43198. CL 5 cleithrum, CO 5 coracoid, LAP 5 lateral abdominal plate,
MAP 5 middle abdominal plate, PAP 5 preanal plate. Scale bar: 5 mm.
aspect to predorsal area; nasal plate long, reaching
anterior margin of lateral ethmoid
A. discus
Lateral abdominal plates extending to midventral
line only posteriorly, always leaving naked area
anteriorly (Fig. 6B); two or three (usually three)
prenuchal plates anterior to nuchal plate (Fig. 5C);
chromatophores not concentrated in skin around
predorsal plates, but arranged in lines between
aligned odontodes of predorsal area; nasal plate
short, not reaching anterior margin of lateral
ethmoid
A. gymnogaster, new species
Caudal fin with 11–12 branched rays; first bilateral
postrostral plates not contacting each other midventrally (Fig. 7A, B); one or two paired predorsal
plates anterior to prenuchal plates (Fig. 5B, C);
connecting bone present
5
Caudal fin with 10 branched rays; first bilateral
postrostral plates articulating to each other midventrally (Fig. 7C); four or five paired predorsal
plates anterior to prenuchal plates (Fig. 5A); connecting bone absent
4
Interorbital distance wide (25.0–29.0% of distance
between eye and origin of dorsal fin and 10.6–
13.0% in postdorsal distance)
A. colombiensis
Interorbital distance narrow (17.0–24.0% of distance between eye and origin of dorsal fin and 7.0–
10.5% in postdorsal distance)
A. martini
Abdomen without series of plates between lateral
abdominal plates (Fig. 6A, B); caudal fin with 11
branched rays; pectoral-fin spine with conspicuous
serrations on inner margin
A. dichromum
Abdomen with a middle series of plates between
the lateral abdominal plates (Fig. 6C); caudal fin
with 12 branched rays; pectoral-fin spine without
serrations or with very delicate serrations on inner
margin
6
Snout long (distance from snout tip to posteroventral margin of rostral plate 24.7–33.6% of
head length); preanal plate with well developed
anterior and posterior lateral expansions
(Fig. 4A)
A. scutatum, new species
Snout short (distance from snout tip to posteroventral margin of rostral plate 22.0–24.5% of head
length); preanal plate with slightly developed
anterior
and
posterior
lateral
expansions
(Fig. 4B)
A. triplax
________________
2b.
____________________________
3a.
_____________________________________________________
3b.
______________________________________________________________
4a.
____________
4b.
_______________________
5a.
_____________________
5b.
_________________________________________________________________________________________
6a.
________________________________
6b.
_____________________________________________________________________
Fig. 7. Spatulate projection of snout of species of Acestridium: (A) A.
triplax, MCP 41746; (B) A. discus, MZUSP 85322; and (C) A. martini,
MZUSP 74275. RP 5 rostral plates, PRP 5 postrostral plate. Scale bar:
1 mm.
MATERIAL EXAMINED
Acestridium colombiensis: Venezuela, Amazonas: ANSP
165830, 1, 44.0 mm SL, Rı́o Matiyure, at Achaguas,
7u459N, 68u119W.
Acestridium dichromum: Venezuela, Amazonas: ANSP 187061,
2+1 CS, Rı́o Sipapo, approximately 6 km upstream of
Pendaré, 4u519N, 67u439W. ANSP 160692, 1, 40.8 mm SL,
Rı́o Sipapo, 500 m upstream of Pendaré, 4u549N, 67u439W.
ANSP 161494, 6+2 CS, 34.6–50.7 mm SL, outflow stream
from series of morichales ca 5.0 km from mouth of Rı́o
Pamoni, 2u489N, 65u539W. ANSP 187061, 2+1 CS, 32.2–
38.8 mm SL, Rı́o Sipapo, ca 6 km upstream of Pendare,
4u519N, 67u439W. MCP 35016, 3, 37.4–56.1 mm SL, Caño
Cucurito, ca 1 km upstream mouth of Rı́o Autana, 4u449N,
67u419W. FMNH 103326, 6 paratypes, 27.2–57.4 mm SL,
Caño Cucurito, ca 1 km above mouth in Rı́o Autana,
4u439480N, 67u379120W.
Acestridium discus: Brazil, Amazonas: FMNH 54339, holotype, 69.1 mm SL, FMNH 54340, 1 paratype, 52.1 mm SL,
Igarapé de Cachoeira Grande, near Manaus. MHNG 2575.61,
2, 31.2–39.7 mm SL, Rio Cuiuni, Rio Negro basin. MZUSP
85320, 7+2 CS, 26.8–56.6 mm SL, Igarapé Barroso, tributary
to Rio Preto da Eva on Francisco Mendes road, 2u449N,
59u389W. MZUSP 85321, 12+2 CS, 22.4–62.4 mm SL,
bathing spot at Igarapé do Manu, Rio Preto da Eva basin,
2u409N, 59u429W. MZUSP 85322, 9+1 CS, 16.3–64.5 mm SL,
Igarapé near Sitio Bom Jesus, km 13 of Francisca Mendes
road Rio Preto da Eva basin, 2u459N, 59u379W. MZUSP
85323, 6+1 CS, 18.8–55.3 mm SL, Rio Preta da Eva, 15 km N
of town of Rio Preto da Eva, 2u359N, 59u459W. MZUSP
88878, 6, 30.4–64.3 mm SL, bathing spot ca 2 km downstream of Rio Preto da Eva, 2u429420S, 59u419360W. MZUSP
88944, 7, 32.8–65.1 mm SL, MZUSP 88966, 4, 35.4–66.9 mm
SL, creek tributary to Rio Preto da Eva, below bathing spot
Encanto da Mata, 2u379100S, 59u449300W. MZUSP 88962, 15,
19.9–62.1 mm SL, Rio Preto da Eva, ca 4 km upstream of
town, 2u409490S, 59u439150W. MZUSP 88986, 10, 17.0–
63.4 mm SL, creek on road from Rio Preto da Eva to Pousada
do Paraı́so, 2u459340S, 59u399490W.
452
Acestridium martini: Venezuela, Amazonas: ANSP 160701,
7+1 CS, 31.9–42.9 mm SL, Rı́o Sipapo, approximately 6 km
upstream of Pendaré, 4u519N, 67u439W. ANSP 160644, 1,
40.8 mm SL, Rı́o Sipapo, backwater channel behind sandbar
6–7 km above Pendaré, 4u519N, 67u439W. ANSP 165831, 6,
43.3–62.8 mm SL, Caño Horeda, at border of Bolı́varAmazonas Territories, ca 68 km NE of Puerto Ayacucho,
6u089N, 67u229W. MCP 35015, 4+1 CS, 46.5–69.7 mm SL,
Rı́o Sipapo, above Pendaré, 2u319N, 66u309W. Brazil, Amazonas: MHNG 2577.55, 4, 33.7–44.6 mm SL, Rio Araçá, Rio
Negro basin. MZUSP 26820, 3+1 CS, 46.6–48.2 mm SL, Rio
Cuieiras, Rio Negro basin, 2u509S, 60u309W. MZUSP 61945,
4, 38.6–54.6 mm SL, Rio Aiuanã, near Santa Isabel do Rio
Negro (5Tapurucuava). MZUSP 74275, 6+1 CS, 41.6–
60.5 mm SL, Igarapé Jaradá, tributary to Rio Cuieiras, ca
40 km upstream mouth. MZUSP 77945, 2, 54.4–54.9 mm SL,
Rio Aiuanã, tributary to Rio Negro.
Acestridium triplax: Brazil, Pará: MPEG 13355, holotype,
55.5 mm SL, MCP 41745, 9+1 CS, 41.8–52.8 mm SL, MPEG
12461, 9, 28.9–50.4 mm SL, Juruti, Igarapé Mutum, tributary to Rio Aruã, lower Rio Tapajós basin, 2u369450S,
56u119370W. MPEG 12614, 8+2 CS, 41.0–53.5 mm SL, MCP
41746, 8+2 CS, 30.6–52,0 mm SL, same locality as holotype.
MPEG 12468, 10, 34.1–53.3 mm SL, MPEG 12475, 7, 34.1–
52.3 mm SL, creek at 2u279540S, 56u009250W.
ACKNOWLEDGMENTS
Special thanks to the All Catfish Species Inventory (NSF-DEB
#0315963), which financed the Transcontinental Catfish
Expedition, during which all type material of the two new
Copeia 2009, No. 3
species were collected. PLA was financed by a doctoral
fellowship from CNPq (process #190033/02-9). RER is
partially financed by CNPq (process #303362/2007-3).
LITERATURE CITED
Haseman, J. D. 1911. Descriptions of some new species of
fishes and miscellaneous notes on others obtained
during the expedition of the Carnegie Museum to central
South America. Annals of the Carnegie Museum
7:315–328.
Leviton, A. E., R. H. Gibbs, Jr., E. Heal, and C. E. Dawson.
1985. Standards in herpetology and ichthyology: part I.
Standard symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia
1985:802–832.
Retzer, M. E. 2005. Description of a new species of
Acestridium (Siluriformes: Loricariidae) from Colombia.
Zootaxa 972:1–6.
Rodriguez, M. S., and R. E. Reis. 2007. A new species of
Acestridium Haseman, 1911 (Loricariidae: Hypoptopomatinae) from the eastern Amazon basin, Brazil. Neotropical
Ichthyology 5:429–434.
Schaefer, S. A. 1997. The Neotropical cascudinhos: systematics and biogeography of the Otocinclus catfishes (Siluriformes: Loricariidae). Proceedings of the Academy of
Natural Sciences of Philadelphia 148:1–120.
Taylor, W. R., and G. C. Van Dyke. 1985. Revised
procedures for staining and clearing small fishes and
other vertebrates for bone and cartilage study. Cybium
9:107–119.