Gymnotus ucamara: a new species of Neotropical electric fish from the Peruvian Amazon (Ostariophysi: Gymnotidae), with notes on ecology and electric organ …

Abstract

A new species of Neotropical electric fish, Gymnotus ucamara, is described from floodplain habi-tats in the Rio Ucayali Basin, Peru. The new species is distinguishable from all congeners by the following combination of characters: a clear patch at the caudal end of the anal fin; two laterosen-sory canal pores (from the preopercular-mandibular series) in the dorso-posterior portion of the pre-opercle; a coloration pattern with 18–24 dark brown bands separated by narrow pale interbands which are less than one-third the width of the dark bands; a long head (12.2–13.4 % total length); many (10–11) scales rows over the anal fin pterygiophores; few (38-43) pored lateral-line scales to the first lateral-line ramus; and a low (75–91) total number of pored lateral-line scales.

Full text

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Accepted: 15 August 2003; published: 29 August 2003
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ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2003 Magnolia Press
Zootaxa 277: 1-18 (2003)
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Gymnotus ucamara: a new species of Neotropical electric fish from
the Peruvian Amazon (Ostariophysi: Gymnotidae), with notes on
ecology and electric organ discharges
WILLIAM G.R. CRAMPTON
1
, NATHAN R. LOVEJOY
2
& JAMES S. ALBERT
1,3
1
Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611-7800, USA; E-mail:
willc@flmnh.ufl.edu
2
Department of Zoology, University of Manitoba, Winnipeg, MB, R3T 2NZ Canada; E-mail:
nate_lovejoy@umanitoba.ca
3
E-mail: albert@flmnh.ufl.edu
Abstract
A new species of Neotropical electric fish, Gymnotus ucamara, is described from floodplain habi-
tats in the Rio Ucayali Basin, Peru. The new species is distinguishable from all congeners by the
following combination of characters: a clear patch at the caudal end of the anal fin; two laterosen-
sory canal pores (from the preopercular-mandibular series) in the dorso-posterior portion of the pre-
opercle; a coloration pattern with 18–24 dark brown bands separated by narrow pale interbands
which are less than one-third the width of the dark bands; a long head (12.2–13.4 % total length);
many (10–11) scales rows over the anal fin pterygiophores; few (38-43) pored lateral-line scales to
the first lateral-line ramus; and a low (75–91) total number of pored lateral-line scales.
Key Words: biodiversity, electrogenesis, Gymnotiformes, várzea
Introduction
The weakly electric Neotropical fish genus Gymnotus has been the subject of several taxo-
nomic studies in recent years (Mago-Leccia 1994; Albert & Miller 1995; Campos da Paz
1996; Campos da Paz & Costa 1996; Albert et al. 1999; Campos da Paz 2000; Albert
2001; Albert & Crampton 2001; Campos da Paz 2002). Until recently Gymnotus was rec-
ognized as the only genus in the family Gymnotidae. The monotypic genus Electrophorus
Gill, comprising the single strongly electric species Electrophorus electricus (L.) was
recently included in the Gymnotidae (Albert 2001).

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TABLE 1. Nineteen valid species of Gymnotus with affiliation to species groups (see text) and geo-
graphical range. MA, Atlantic and Pacific slopes of Middle America; OR, Orinoco basin including
Trinidad; GU, Guyanas and upper Rio Negro; AM, Amazon basin; NE, coastal drainages of north-
east Brazil; SE, coastal drainages of southeast Brazil and Uruguay; PA, Paraguay-Paraná basin.
Sources: Albert (2001), Albert & Crampton (2001), unpublished observations.
Albert (2001) and Albert and Crampton (2001) summarized the diagnostic characters
of Gymnotus. Albert and Miller (1995) and Albert (2001) recognized three species groups
within the genus based on color pattern, body proportions and counts. These are the G.
cylindricus, G. pantherinus,andG. c a ra p o species-groups. The species composition and
geographical range of these groups are summarized in Table 1. The G. cylindricus species-
group is endemic to both Atlantic and Pacific drainages of Middle America and comprises
just two species. The G. c ar a po species-group is endemic to South America and is repre-
sented by seven species distributed from the Pacific slope of Colombia to the Pampas of
Argentina. The G. pantherinus species-group is represented by nine species with distribu-
Group Species Geographical range
cylindricus Gymnotus cylindricus La Monte, 1935 MA
Gymnotus maculosus Albert & Miller, 1995 MA
carapo Gymnotus arapaima Albert & Crampton, 2001 AM
Gymnotus bahianus Campos da Paz & Costa, 1996 NE
Gymnotus carapo Linnaeus, 1758 GU, OR, AM
Gymnotus diamantinensis Campos da Paz, 2002 AM
Gymnotus inaequilabiatus (Valenciennes, 1847) SE, PA
Gymnotus mamiraua Albert & Crampton, 2001 AM
Gymnotus sylvius Albert & Fernandes-Matioli, 1999 SE, PA
Gymnotus ucamara n. sp. AM
pantherinus Gymnotus anguillaris Hoedeman, 1962 GU, OR, AM, PA
Gymnotus cataniapo Mago-Leccia, 1994 GU, OR, AM
Gymnotus coatesi La Monte, 1935 AM
Gymnotus jonasi Albert & Crampton, 2001 AM
Gymnotus melanopleura Albert & Crampton, 2001 AM
Gymnotus onca Albert & Crampton, 2001 AM
Gymnotus pantherinus (Steindachner, 1908) SE
Gymnotus pedanopterus Mago-Leccia, 1994 GU, OR, AM
Gymnotus stenoleucus Mago-Leccia, 1994 GU, OR, AM

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tions from Panama to Paraguay. Species in the G. carapo species-group, including the new
species described here, can be distinguished from species in the G. pantherinus and G.
cylindricus species-groups by the possession of a clear or pale patch near the caudal end of
the anal fin, and two (vs. one) laterosensory canal pores in the preopercular-mandibular
series of the dorso-posterior portion of the preopercle. We use the above classification of
Gymnotus as a basis for the differential diagnosis of the newspeciesdescribed in this report.
There are currently 18 valid species of Gymnotus, of which thirteen are found in the Ama-
zon basin. Several new species of Gymnotus have recently been discovered in the Brazil-
ian portion of the Amazon basin (Albert & Crampton 2001; Campos da Paz 2002),
including seven new species from whitewater floodplains or ‘várzeas’ along the Amazon
River’s main stem (Albert & Crampton 2001). Here we describe a new species from
várzea floodplains of the Rio Ucayali Basin in the Peruvian Amazon.
Materials and methods
Specimens and their electric organ discharges (EODs) were captured from a site in the Rio
Ucayali floodplain, Peru (Figs. 1, 2). Additional material was acquired from museum col-
lections. Museum acronyms follow Leviton et al. (1985), with the addition of IIAP (Insti-
tuto de Investigaciones de la Amazonía Peruana, Iquitos), INPA (Instituto Nacional de
Pesquisas da Amazônia, Manaus), MUSM (Museo de Historia Nacional de la Universidad
Nacional Mayor de San Marcos, Lima), NRM (Swedish Museum of Natural History,
Stockholm), and UUZM (Uppsala University Zoological Museum, Uppsala).
Measurements and counts (Tables 2, 3) follow Albert and Crampton (2001) except for:
APS, anal fin pterygiophore scales as the number of scale rows over the pterygiophores
counted from an origin vertically below the base of the first lateral-line ramus; CEP, caudal
electroplate rows counted (with backlighting and with overlying scales removed) as the
number of horizontally aligned rows of electroplates in the electric organ at a distance of
one head length from the tip of the caudal appendage; MW, mouth width at rictus; PLR,
number of pored lateral-line scales in posterior lateral-line posterior to neurocranium and
counted to first ramus of the lateral-line; PLS, total number of pored lateral-line scales in
posterior lateral-line posterior to neurocranium. All measurements were taken with digital
calipers to the nearest 0.1 mm on the left side of specimens. Measurements reported as a
percentage of total length (TL) (i.e. head length, anal-fin length, body depth and body
width) and anal-fin ray counts were not included for specimens with damage to the caudal
appendage amounting to more than an estimated 5% of un-damaged TL. Counts of anal-
fin rays and precaudal vertebrae were taken from radiographs. Osteological data were
taken from specimens cleared and stained following the technique described by Dingerkus
and Uhler (1977).

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FIGURE 1. Map of part of the Pacaya-Samiria National Reserve in Loreto, Peru, illustrating the
lower Rio Pacaya and the type-series locality of Gymnotus ucamara n. sp. (1). Floodplain areas
(stippled) experience an annual flood regime of up to 7 m amplitude. Base map traced from 1998
1:300,000 Landsat TM5 images.

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FIGURE 2. Type-series locality of Gymnotus ucamara n. sp. A small drainage channel between
Rio Pacaya and Cocha Zapote, Pacaya-Samiria National Reserve, Loreto, Peru. Floating aquatic
vegetation in the foreground is dominated by Pistia stratiotes, Azolla sp., and Eichhornia crassipes.
Rooted grasses in the background include Cyperus sp. and Paspalum sp. These grasses form float-
ing rafts during the high water season. The high-water mark from the preceding flood season is vis-
ible on the trunk of a cecropia tree in the back-left of the photograph.
EOD recording techniques follow Crampton (1998). Specimens were recorded in
water from the capture locality at temperatures between 27 and 29 ºC soon after capture.
Field numbers for EOD-recorded fish follow a standard format: e.g. WGRC 09.200902
(ninth gymnotiform specimen collected and recorded on September 20 2002). Recordings
of pulse repetition rate during the day and night were taken from specimens isolated in
large (50 l) buckets of water provided with submerged vegetation, placed in a disturbance
and vibration-free place, and exposed to a subdued natural light regime. Nighttime record-
ings were taken between 1900 and 2100 (hours of peak swimming activity) on the day of
capture. Daytime recordings were taken between 1000 and 1200 on the following day.
Gymnotus ucamara n. sp.
(Fig. 3)
Holotype. — UF 126182 (156.0 mm TL, WGRC 09.200902), Peru, Loreto, Rio Ucayali,
Rio Pacaya, Cocha Zapote, in Pacaya-Samiria National Reserve, 05°20.03'S, 74°29.08'W,
collected by J. Albert, W. Crampton, N. Lovejoy, H. Ortega and R. Reis, 9 September
2002.

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Paratypes. UF 126121 (1, 174 mm TL, WGRC 02.200902); UF 126183 (1, 172 mm
TL, EOD not recorded); UF 126184 (2, 190 mm TL, WGRC 12.200902; 146 mm TL,
WGRC 13.200902). All collected by J. Albert et al. with holotype.
Nontypes. MUSM 9274 (1, 134 mm TL), Loreto, Contamana, Aguas Calientes,
approx. 07°02'S, 74°14'W, 3 June 1996; MUSM 10184 (7, 117–156 mm TL, 2 cleared and
stained), Loreto, Contamana, Rio Ucayali, approx. 07°02'S, 74°14'W, 31 May 1996. All
collectedinPerubyH.Ortegaetal.
FIGURE 3. Photographs of body and head of the holotype of Gymnotus ucamara n. sp. (UF
126182). Scale bar = 10 mm.
Diagnosis. Gymnotus ucamara differs from other species in the Gymnotus carapo spe-
cies-group in possessing the following unique combination of characters: a coloration pat-
tern with 18-24 dark brown bands separated by narrow pale interbands which are less than
one-third the width of the dark bands (a pattern that is readily distinguishable from all
other described species of the G. carapo species-group except G. mamiraua); a long head
(12.2–13.4 % total length vs. 7.9–11.8 % in all other species except G. ca r ap o and G. ara -
paima); many (10
–11) scales over anal fin pterygiophores (vs. 4–9 in all other species
except G. arapaima); few (38
–43 [median 42]) pored lateral-line scales to first ramus (vs.
32–38 [median 37] in G. mamiraua,vs.42
–52 [median 48] in G. c ar apo, and vs. 50–64 in
all other species); a low (75-91 [median 82]) total number of pored lateral-line scales (vs.
93–108 [median 98] in G. c a r a po , and vs. 106–140 in all other species except G. mamiraua
with 75–79 [median 78]), and a relatively large eye (orbital diameter 0.09–0.10 % HL vs.
0.06–0.07 % in G. c a rapo). G. ucamara is superficially most similar to G. mamiraua from
which it can be readily distinguished on the basis of the following characters; a long head
(12.2–13.4 % total length vs. 9.7–10.7 % total length in G. mamiraua) and relatively more
pored lateral line scales to first ramus (38
–43 [median 42] vs. 32–38 [median 37] in G.
mamiraua).

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TABLE 2. Morphometric data for adults of eight species of Gymnotus in the G. c a ra p o species-
group. Abbreviations: TL, total length; HL, head length; PR, preorbital distance; PO, postorbital
distance; IO, interorbital distance; MW, mouth width; HD, head depth; HW, head width; BD, body
depth; BW, body width; PA, preanal distance; P1, pectoral-fin length; AF, anal-fin length. TL and
HL expressed in mm. Percentage measurements in HL or, if marked with an asterisk, in TL. BW/
BD expressed as a ratio. N values (in parentheses) vary because measurements were excluded from
some specimens with damage (see text) or unusual preservation artifacts. NA, data not available. †,
data from original published description. All data from specimens collected in the region of the type
localities.
TABLE 2. cont
.
Species max. TL HL %HL* Mean %PR Mean %MW Mean
G. arapaima
545 (32) 14.9-31.9
(25)
12.5-15.0
(30)
13.6 32.2-38.5
(32)
35.2 31.2-36.7
(24)
34.2
G. bahianus †
241 (13) 14.8-25.5
(13)
11.9-12.9
(13)
12.4 32.4-35.7
(13)
34.2 26.0-28.0
(13)
27.3
G. c a r a p o
317 (17) 17.7-38.9
(15)
11.8-13.7
(14)
12.3 34.6-39.1
(15)
36.6 31.1-47.6
(15)
42.0
G. diamantinensis †
125 (3) 11.5-13.5
(3)
10.8-11.5
(2)
11.2 33.0-34.4
(3)
33.6 26.9-28.1
(3)
27.6
G. inaequilabiatus
998 (15) 18.7-82.0
(13)
8.2-12.3
(13)
10.5 30.2-37.3
(11)
35.0 34.9-44.2
(10)
40.5
G. mamiraua
228 (13) 18.1-22.4
(7)
9.7-10.7
(7)
10.4 31.3-35.5
(7)
33.3 34.3-41.6
(7)
37.5
G. sylvius †
307 (6) 20.5-38.5
(6)
11.9-14.0
(6)
12.9 33.9-36.1
(6)
34.9 NA NA
G. ucamara n. sp.
190 (13) 15.2-23.1
(13)
12.2-13.4
(10)
12.7 33.3-38.2
(13)
35.9 37.2-46.8
(13)
41.5
Species
%PO Mean %IO Mean %HD Mean %HW Mean
G. arapaima
58.6-64.4
(32)
62.0 29.0-36.5
(32)
33.1 50.7-56.6
(32)
54.1 46.0-57.9
(31)
51.5
G. bahianus †
58.6-66.2
(13)
63.7 32.8-40.3
(13)
35.8 55.1-59.8
(13)
56.7 52.4-58.0
(13)
54.5
G. c a r a p o
59.2-62.9
(15)
61.1 36.0-42.3
(15)
38.5 52.1-65.4
(15)
57.5 56.6-64.1
(15)
60.8
G. diamantinensis †
63.8-65.2
(3)
64.5 41.1-42.9
(3)
42.2 65.2-69.6
(3)
67.1 NA NA
G. inaequilabiatus
59.4-67.1
(11)
62.8 37.0-45.7
(11)
42.5 61.7-73.8
(10)
66.0 64.9-72.0
(9)
67.6
G. mamiraua
61.9-64.5
(7)
63.6 32.4-43.2
(7)
37.8 60.9-70.7
(6)
67.1 55.6-68.6
(6)
60.7
G. sylvius †
58.7-60.9
(6)
59.8 36.4-38.2
(6)
37.5 57.1-60.5
(6)
58.4 59.5-61.8
(6)
61.0
G. ucamara n. sp.
58.4-62.3
(13)
60.4 32.9-43.2
(13)
36.5 56.5-65.0
(13)
59.1 53.9-65.5
(13)
58.6

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TABLE 2. cont.
TABLE 2. cont.
Description. Body shape and pigment patterns illustrated in Fig. 3. Morphological and
meristic data presented in Tables 2 and 3. Cephalic sensory canal pore configurations sum-
marized in Fig. 4. Size up to 190 mm TL. Size at maturity unknown. Sexual dimorphism
unknown. Scales cycloid, ovoid, present on entire post-cranial portion of body from nape
to tip of caudal appendage. Scales on dorsal surface relatively large at mid-body, six rows
from lateral-line to dorsal midline. Scales small over pterygiophores, 10
–11 scale rows.
Lateral-line scales (in holotype) approximately 1.3 mm high by 1.5 mm long in humeral
region, 2.3 mm high by 2.6 mm long at midbody, 1.4 mm high by 2 mm long dorsal to
Species PA% Mean %P1 Mean %AF* Mean %BD* Mean
G. arapaima
51.4-80.6
(30)
65.1 39.6-47.9
(32)
43.5 71.4-82.9
(31)
79.2 8.9-11.6
(31)
10.3
G. bahianus †
77.5-86.9
(13)
83.4 38.3-45.9
(13)
42.3 80.0-82.3
(13)
81.2 11.3-12.6
(13)
12.0
G. c a r a p o
67.8-89.6
(15)
79.6 37.4-55.0
(15)
43.2 71.1-88.9
(15)
79.7 10.1-11.7
(15)
10.8
G. diamantinensis †
79.8-83.7
(3)
81.7 36.3-41.1
(3)
39.4 81.8-82.3
(2)
82.1 10.6-10.9
(2)
10.8
G. inaequilabiatus
57.6-92.7
(9)
77.1 36.8-51.0
(10)
45.7 77.8-85.2
(9)
81.7 7.5-12.0
(12)
10.6
G. mamiraua
63.7-81.5
(7)
74.3 41.6-49.5
(7)
45.1 72.4-87.7
(7)
82.2 9.2-12.6
(7)
10.8
G. sylvius †
NA NA 41.6-46.7
(6)
45.1 74.5-79.2
(6)
77.7 10.3-13.1
(6)
11.7
G. ucamara n. sp.
64.5-75.0
(13)
70.1 46.2-55.3
(13)
49.7 75.7-87.2
(11)
80.1 10.0-12.2
(11)
11.2
Species %BW* Mean BW/BD Mean
G. arapaima
5.3-9.4
(31)
6.4 0.52-0.72
(26)
0.62
G. bahianus †
NA NA NA NA
G. c a r a p o
6.7-8.5
(15)
7.5 0.63-0.81
(15)
0.70
G. diamantinensis †
NA NA NA NA
G. inaequilabiatus
5.8-8.6
(12)
6.7 0.54-0.77
(12)
0.64
G. mamiraua
4.8-6.7
(7)
6.2 0.53-0.72 (7) 0.58
G. sylvius †
7.0-7.8
(6)
7.4 0.67-0.72
(6)
0.69
G. ucamara n. sp.
7.0-8.7
(11)
7.7 0.63-0.73
(11)
0.69

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anterior margin of clear patch on anal fin. Gape size in mature specimens large, extending
beyond posterior nares. Mouth position superior, lower jaw longer than upper, rictus
decurved. Chin fleshy and bulbous with thick pad of electroreceptor organs and support
tissues overlying tip of snout and oral jaws. Anterior narial pore included within gape in
large narial fold. Anterior nares large, subequal to diameter of eye. Branchial opening
moderate (32–40 % in HL). Circumorbital series ovoid. Ethmoid region between anterior
nares moderate, its anterior margin rounded. Eye position lateral, lower margin of eye
slightly ventral to rictus. Eye relatively large, orbital diameter 0.09–1.0 % HL. Premaxilla
and dentary with one or two rows of large, slightly recurved, conical teeth. Premaxilla with
11-12 (mode 12, n = 3) teeth disposed in single row along outer margin. Dentary with 16
(n = 2) teeth disposed in single row along outer margin.
FIGURE 4. Head of the holotype of Gymnotus ucamara n. sp. illustrating organization of cephalic
sensory canals and pores. Centerline of canals (ossified and unossified) indicated by dashed lines.
Pores indicated by small circles. Eye and anterior and posterior nares shaded gray. Abbreviations:
so, supraorbital; io, infraorbital; pl, posterior lateral-line; pm, preopercular-mandibular; st,
supratemporal; m, medial. Scale bar = 5 mm. Pore S01b is absent in some specimens.
Rib 5 approximately same width as rib 6. Body cavity of moderate length with 32–34
(mode 33) precaudal vertebrae. Hemal spines present. Gas bladder not extending beyond
first hemal spine. Displaced hemal spines absent. Multiple anal-fin ray branching posterior
to rays 10
–17. Variable number (11-19) of asymmetrically arranged lateral-line rami
extending posteroventrally at posterior end of lateral line. Dorsal lateral-line rami absent in
all specimens examined. Anal-fin pterygiophores at posterior portion of body cavity
shorter than first hemal spine. Caudal appendage short, less than half pectoral-fin length in
undamaged and unregenerated specimens. Single hypaxial electric organ, extending along
entire ventral margin of body. Three or four (mode 4) rows of electroplates at one HL dis-
tance from end of caudal appendage.

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TABLE 3. Meristic data for eight species of Gymnotus in the G. c ar a p o species-group. Abbrevia-
tions: BND, dark bands; AFR, anal-fin rays; P1R, pectoral-fin rays; SAL, scales above lateral line;
CEP, caudal electroplate rows; APS, anal-fin pterygiophores scales; PCV, precaudal vertebrae;
PLR, pored lateral-line scales to first ramus; PLS, total pored lateral-line scales; LRV, lateral-line
ventral rami (left or right); LRD, lateral-line dorsal rami (left or right). Med., median value. N val-
ues (in parentheses) vary because measurements were excluded from some specimens with damage
(see text) or unusual preservation artifacts. NA, data not available. †, data from original description.
All data from specimens collected in the region of the type localies
.
TABLE 3. cont.
TABLE 3. cont
Species BND Med. AFR Med. P1R Mode SAL Mode
G. arapaima
20-24 (20) 22 225-265 (17) 235 15-17 (20) 15 6-9 (18) 7
G. bahianus †
0 (13) 0 201-226 (NA) 203 17-18 (NA) 17 NA NA
G. c a r a p o
16-21 (8) 19 225-245 (6) 240 14-16 (10) 16 6-7 (8) 6
G. diamantinensis †
16-19 (2) NA 195-210 (3) 201 14-15 (3) 14 8-10 (3) 9
G. inaequilabiatus
19-24 (10) 22 170-260 (6) 220 13-16 (11) 15 6-9 (10) 6
G. mamiraua
17-21 (11) 20 195-265 (11) 225 15 (13) 15 5-9 (11) 5
G. sylvius †
21-24 (5) 22 220-230 (6) 224 16 (2) 16 8 (2) 8
G. ucamara n. sp.
18-24 (13) 21 220-245 (13) 235 15-16 (13) 15 6 (13) 6
Species CEP Mode APS Mode PCV Mode PLR Med.
G. arapaima
3-4 (16) 4 9-13 (31) 12 33-37 (21) 35 53-64 (27) 57
G. bahianus †
3-5 (NA) NA NA NA 33-34 (NA) NA NA NA
G. c a r a p o
3-4 (7) 4 7-9 (7) 8 33-34 (8) 33 45-52 (7) 48
G. diamantinensis †
NA NA NA NA NA NA NA NA
G. inaequilabiatus
3-5 (10) 4 NA NA 31-33 (6) 32 35-37 (4) 36
G. mamiraua
3-4 (6) 4 5-6 (6) 6 31-34 (8) 33 32-38 (8) 37
G. sylvius †
NA NA 6-8 (5) NA 32-35 (5) 33 NA NA
G. ucamara n. sp.
4 (5) 4 10-11 (13) 10 32-34 (13) 33 38-43 42
Species PLS Med. LRV Med. LRD Med.
G. arapaima
99-108 (17) 102 10-22 (11) 15 0 (11) 0
G. bahianus †
79-93 (NA) 90 NA NA NA NA
G. c a r a p o
93-103 (8) 98 8-22 (8) 12 0 (8) 0
G. diamantinensis †
NA NA NA NA NA NA
G. inaequilabiatus
82-115 (4) 90 7-16 (6) 15 0 (6) 0
G. mamiraua
75-103 (12) 78 1-14 (6) 10 0 (6) 0
G. sylvius †
85-100 (5) 93 NA NA NA NA
G. ucamara n. sp.
75-91 (13) 82 11-19 (13) 15 0 (13) 0

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Color in life.18–24 (median 21, n = 13) broad, dark, chocolate-colored bands, sepa-
rated by narrow, pale interbands (sensu Albert et al. 1999) less than one-third the width of
the dark bands. Slight countershading in specimens longer than 150 mm TL, more pro-
nounced anteriorly. Pale interbands extend from pectoral-fin base to tip of caudal append-
age and oriented obliquely (anterior-ventral to posterior-dorsal). Dark bands occur singly
(never divided into band pairs sensu Albert et al. 1999) and are occasionally divided into
Y or inverted-Y shapes but never divided into X shapes on anterior two-thirds of body.
Pale interbands sometimes interrupted. Pigment density slightly greater at the dark band
margins than in the middle at mid-body. Band-interband margins wavy and highly con-
trasted with one another. Pale interbands irregular in shape and width, narrower and more
regularly shaped anteriorly. Pale interbands usually do not extend to mid-dorsum along
anterior 2/3 of body. Incomplete pale interband present in middle of some dark bands.
Three pale interbands from either side terminate near ventral midline, often not meeting,
betweentheanusandanal-finorigin. One or two bands lie posterior to last anal-fin ray.
FIGURE 5. EOD waveform (A) and Fourier Power Spectrum (B) of holotype of G. ucamara n. sp.
The EOD is plotted with head-positivity upwards and its component phases labeled P-1 through P3.
P1 represents the dominant positive component. The Power Spectrum was computed from a 2048
point Fast-Fourier-Transform and the Peak-Power-Frequency scaled to the minimum attenuation of
0dB.
P1
P2
P0
P-1
P3
0.5 ms
A
-18
-15
-12
-9
-6
-3
0
012345678
Frequency (kHz)
Amplitude (dB
)
B

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ZOOTAXA
Head never banded, spotted or blotched, uniformly dark brown but slightly paler in
gular region. Numerous minute chromatophores speckled over branchiostegal membranes
and ventral surface of head. Pectoral-fin rays dark brown or black, interradial membranes
hyaline. Anal fin never blotched, spotted or marked. Anal fin rays and membrane dark
gray or black on anterior 80% of fin length, translucent on posterior 20%. Color variation
is not known to be correlated with size, sex or EOD waveform. Specimens fixed in 10%
formalin and preserved for 1-6 years in 70% ethanol maintain approximate colors of life,
although the darker pigments sometimes pale with time.
Electric organ discharge. G. ucamara n. sp. generates EODs as discrete pulses of 1.25
–1.73 ms duration (mean 1.51, n = 5). These comprise four or five phases (Fig. 5). The
waveform comprises a dominant tri-phasic component (P0, P1, P2) with a duration of
approximately 0.78–0.92 ms (mean 0.87, n = 5) followed by a low-voltage positive final
phase (P4). A very low-voltage initial positive phase (P-1) precedes P0 in most specimens.
The Peak Power Frequency (PPF) (Fig. 4) of the Fourier Transform of EODs of G. u c a-
mara n. sp. ranges from 1.71–1.95 kHz (mean 1.78, n = 5).
The EOD pulse repetition rate of G. u c amar a n. sp. is relatively low and less variable
during the day when this species lodges itself into the submerged root mats of floating
plants (range 44.5–45.9 Hz, mean 45.3, standard deviation [SD] 0.3, n = 4). G. ucamara n.
sp. can instantaneously increase its EOD pulse repetition rate to around 90–110 Hz in
response to a sudden stimulus such as a loud underwater noise or a light prod with a glass
rod. Following such a ‘fright response’ the EOD repetition rate returns to close to the nor-
mal resting rate within a few milliseconds and back to the normal resting rate within a few
seconds. The EOD pulse repetition rate is usually higher and more variable at night. The
highest pulse rates occur during swimming (range 62.5–76.9 Hz, mean 69.4, SD 6.2, n =
4) and the lowest rates occur when a specimen stops swimming, usually by resting its body
against a submerged structure, or wedging itself between submerged roots (range 50.0–
66.7 Hz, mean 59.7, SD 8.7, n = 4).
Distribution. Known only from the lowland Rio Ucayali basin in Peru, at sites near
Contamana and in the Rio Pacaya-Samiria National Reserve near the confluence of the
Rio Ucayali and Rio Marañon.
Habitat and Ecology. All the type specimens were captured from static, vegetation-
choked water in a shallow (maximum depth 0.5 m) channel connecting a floodplain lake
(Cocha Zapote) to the Rio Pacaya (Figs. 1,2). The habitat structure, vegetation and water
quality of the locality are typical of whitewater floodplains of the Central and Upper Ama-
zon (Ayres 1993; Junk 1997). The type specimens were captured during the low-water
month of September. Aquatic vegetation at the site consisted of plants typical of floating
meadows, an important substrate for floodplain gymnotiform fish communities throughout
the year (Crampton 1996; Albert & Crampton 2001). The dominant species were Cyperus
sp., Eichhornia crassipes Solms., Pistia stratiotes (L.), Ludwigia sp., Salvinia spp., and
Utricularia sp. Water quality at the locality was recorded as: dissolved oxygen, 2.4 mg/l;

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electrical conductivity, 240 Scm
-1
at 25ºC; transparency with Sechhi disc 0.6 m, surface
temperature 31.2 ºC. Other gymnotiform electric fish collected from the same locality and
habitat were Gymnotus carapo (L.), Eigenmannia sp., and three undescribed species of
Brachyhypopomus. One of the two non-type lots from Contamana (MUSM 10184) was
collected in rafts of floating vegetation along the edge of the Rio Ucayali. These rafts may
have been swept out of nearby floodplain lakes (H. Ortega pers. comm.). The other non-
type lot (MUSM 9274) was collected from floating vegetation along the edge of a sedi-
ment-laden ‘whitewater’ stream near its confluence with the Rio Ucayali. Water tempera-
ture was reported as 28ºC. This stream flows out of hot springs from nearby mountains,
but gymnotiforms were only found well downstream of the influence of unusually warm
waters (H. Ortega pers. comm.). G. ucamara n. sp. feeds on aquatic invertebrates. Stomach
content analyses of the paratype and non-type series are summarized in Table 4.
TABLE 4. Proportional composition of food items in stomachs of Gymnotus ucamara n. sp.
Autochthonous food items are aquatic invertebrates living in submerged roots and in the benthos.
Allochthonous food items have fallen into the water from the foliage of overhanging or floating
vegetation.
Etymology. Named for the geological term “Ucamara Depression” describing the low-
lying region between the lower reaches of the Ucayali and Marañon Rivers caused by sub-
sidence in the Upper Amazon foreland basin.
Additional materials examined.
Materials examined follow Albert et al. (1999), Albert (2001), and Albert & Crampton
(2001), with the addition of:
Gymnotus arapaima (56 specimens, 48
–460 mm). — Brazil: Amazonas: Rio
Solimões, Lago Calado, Município Manaus, approx. 03°07'S, 60°01'W, INPA 6387 (2,
Paratypes MUSM 10184 Mean %
1234 123456
Estimated % fullness
75 75 100 100 100 100 100 100 50 50 85%
Autochthonous:
Conchostraca (adults)
25 10 3.5
Coleoptera (larvae)
50 100 100 100 35
Coleoptera (adults)
100 50 15
Odonata (naiads)
50 100 75 90 31.5
Unidentified invertebrates
75 7.5
Allochthonous:
Lepidoptera (larvae)
50 5
Orthoptera (adult)
25 2.5

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255–395); Cidade de Manaus, Igarapé do Quarenta, Município Manaus, approx. 03°06'S,
60°01'W, INPA 10376 (1, 255); Rio Solimões-Japurá confluence, Mamirauá Sustainable
Development Reserve (MSDR), Cano do Lago Mamirauá, 03°05.22'S, 64°48.03'W, INPA
11514 (5, 145
–457), INPA 18389 (1, 55); Rio Tefé, Lago Tefé, Igarapé Curupira,
03º26.02'S, 64º43.78'W, INPA 18390 (1, 55); Rio Tefé, Lago Tefé, Estrada Agrovila,
swamp in forest nr. Igarapé Curupira, 03º26.02'S, 64º43.78'W, INPA 18391 (2, 48-51); Rio
Negro, Lower Rio Demini, c. 30 km upstream mouth Rio Aracá, Município Barcelos,
approx. 00°23'N, 62°51'W, MCP uncat (1, 272); Rio Tefé, nr. Cabeçeira do Lago Tefé,
03°41.39'S, 64°59.13'W, MZUSP 75165 (1, 190); Rio Solimões-Japurá confluence,
MSDR, Jarauá lake system, Ressaca do Caetono, 02°50.22'S, 64°55.79'W, MZUSP 75166
(1, 133); Rio Tefé, same locality as INPA 18390, MZUSP 75169 (1, 102); Rio Tefé, same
locality as MZUSP 75165, MZUSP 75170 (1, 147), MZUSP 75171 (1, 128), MZUSP
75172 (1, 158), MZUSP 75173 (1, 160), MZUSP 75174 (1, 128), MZUSP 75175 (1, 129),
MZUSP 75176 (1, 141); Rio Tefé, same locality as INPA 18390, MZUSP 75177 (1, 129);
Rio Tefé, Lago Tefé, Igarapé Repartimento, 03º24.46’S, 64º44.17'W, MZUSP 75178 (1,
123); Rio Solimões-Japurá confluence, MSDR, Ressaca do Pau, 03º02.30'S, 64º51.96'W,
MZUSP 75179 (1, 107). All localities from Rio Tefé and MSDR in the municipalities of
Tefé and Alvarães respectively. Mato Grosso: Rio Aripuanã, Igarapé do Castanhal,
Município Aripuanã, INPA 6390 (part) (11, 128
–460). Rondônia: Rio Madeira, Rio
Jamari, nr. UHE Samuel, Município Porto Velho, approx. 08°26'S, 63°30'W, INPA uncat.
(POLO 463) (2, 115
–195), INPA uncat. (POLO 482) (2, 435-460); Rio Machado, Nazaré,
Município Jí-Paraná, 10°4'59"S, 62°17'59"W, INPA uncat. (POLO 626) (1, 147); Rio
Madeira, same locality as INPA uncat. (POLO 463), INPA uncat. (POLO 872) (11, 160
–
252), INPA uncat. (POLO 895) (1, 185), INPA uncat. (POLO 951), (2, 183-187).
Gymnotus bahianus (25 specimens, 55
–275 mm). — Brazil: Bahia: Uruçuca, Fazenda
Almada, Município Ilheus, approx. 14°34'59"S, 39°15'59"W, MNRJ 4188 (2, 200
–207),
MNRJ 4346 (10, paratypes, 133
–240), MNRJ 4381 (3, 84–168); Pirataquice, Município
Ilheus, approx. 14°34'59"S, 39°15'59"W, MNRJ 4382 (10, 55
–275).
Gymnotus carapo (185 specimens, 32–367 mm, referring only to populations from
region of type locality [Surinam] and from the Upper Amazon).
— Brazil: Amazonas: Rio
Tefé, Ilha do Martelo, 03°46.82'S, 64°59.48'W, MZUSP 75168 (1, 119); Rio Tefé,
Cabeçeira do Lago Tefé, 03°34.59'S, 64°59.32'W, MZUSP 76061 (1, 260); Rio Tefé, Lago
Tefé, Ressaca do Socorro, 03°19.18'S, 64°41.76'W, MZUSP 76062 (1, 94); Rio Solimões-
Japurá confluence, Mamirauá Sustainable Development Reserve (MSDR), Ressaca da
Vila Alencar, 03º07.70'S, 64°48.03'W, MZUSP 76063 (1, 298); MSDR, Cano do Lago
Mamirauá, 03º04.43'S, 64º48.65'W, MZUSP 76064 (1, 253); MSDR, Lago Secretaria,
03º06.74'S, 64°48.02'W, MZUSP 76066 (2, 97
–136); Rio Solimões, Rio Cayari, Municí-
pio Benjamin Constante, approx. 04°22'S, 70°02'N, UMMZ 230734 (2, 190–210). All
localities from Rio Tefé and MSDR in the municipalities of Tefé and Alvarães respec-
tively.
— Ecuador: Napo: Rio Napo, Rio Tiputini, approx. 00°49'S, 75°31'W, FMNH

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GYMNOTUS UCAMARA SP. N.
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103329 (10, 33–320); Rio Napo, Rio Aguarico, Laguna Zancudococha, approx. 00°17'S,
75°52'W, FMNH 103334 (2, 48
–64). – Peru: Loreto: Rio Amazonas, Maynas, nr. Iquitos
(no locality data): IAAP (uncat.) (1, 367); Rio Ucayali, Contamana, Aguas Calientes,
approx. 07°02'S, 74°14'W, MUSM 9274 (1, 136); Rio Napo, Rio Aguarico, Maynas, PV
Castaña, 00°48.22'S, 75°14.40'W, MUSM 14482 (7, 118
–198); Rio Samiria, Maynas, right
bank stream tributary to R. Samiria between Caño Pastos and Hamburgo, 05°12'S,
75°08'W, NRM 27650 (1, 305); Rio Maniti, Maynas, 50 km NE of Iquitos, 03°29'S,
72°44'W, NRM 40772 (1, 91); Rio Amazonas, Maynas, reportedly Rio Nanay (procured
from ornamental fish exporting company in Iquitos), UF 116573 (2, 189
–279), UF 122820
(1, 275), UF 122822 (1, 330), UF 122825 (1, 158), UF 122847 (1, 188), UF 122848 (1,
112), UF 122849 (1, 132), UF 122850 (1, 188), UF 122851 (1, 107), UF 122852 (1, 92);
Rio Nanay, Maynas, 3 km upstream Mishana, Reserva Allpahuayo-Mishana, 03°52.08'S,
73°29.05'W, UF 116665 (1, 298); Rio Pacaya, Cocha Zapote, 05°20.03'S, 74°29.08'W, UF
126181 (2, 245
–272); Rio Nanay, Rio Momon, Amazon camp near Iquitos, approx.
03°42'S, 73°16'W, UMMZ 228998 (4, 38
–172); Rio Tahuayo, 04°10'S, 73°12'W, UMMZ
228999 (1, 162); Rio Javari, Buen Suceso, Quebrada Carana, approx. 04º08'S, 70º26'W,
UMMZ 230733 (1, 251). Ucayali: Rio Ucayali, Pucallpa, Estación del IVITA, Quebrada
Piscigranja, approx. 08°23'S, 74°32'W, MUSM 529 (7, 83-109), MUSM 532 (1, 181),
MUSM 537 (2, 222-260); Rio Ucayali, Rio Huacamayo km 155, 12°46'S, 69°52'W,
MUSM 1547 (1, 122); Rio Ucayali, Pucallpa, Utuguinia, approx. 08°23'S, 74°32'W,
MUSM 1757 (3, 154
–267); same locality as MUSM 529, MUSM 2691 (5, 132–222),
MUSM 2971 (1, 187). – Surinam: unknown localities: NRM 8224 (1,331 Linnean syn-
type), UUZM 56 (1,331 Linnean syntype). Brokopondo District: Suriname River, Tapeo-
eripa creek nr. Brokopondo village, 05°04'N, 54°58'W, UMMZ 190414 (6, 71
–260).
Nickerie District: Lucie River, creek, upstream of Amotopo-Camp Geologie Rd., 03º36'N,
57º37'W, USNM 225274 (8, 81
–318); Corantijn River, E bank creek, 350 m downstream
from Wilhelm II Falls, 03º34'N, 57º15'W, USNM 225275 (11, 81
–270); Corantijn River,
Dalbana Creek, ca. 3 km upstream from Amotopo-Camp Geologie Rd., 04º20'N, 57º37'W,
USNM 225276 (16, 75
–148); Corantijn River, Lana Creek, ca. 4 km from intersection with
W. Corantijn River, 05º28'N, 57º15'W, USNM 225284 (10, 54
–143); Corantijn River,
creek south of Matapi, approx. 2 km downstream of Cow Falls, 04º59'N, 57º38'W, USNM
225285 (12, 85
–257); Corantijn River, Koekwie creek, 05º31'N, 57º10'W, USNM 225286
(15, 80-319); Corantijn River, Dalibane Creek, Camp Dacclemmen, 05º34'N, 57º11'W,
USNM 225290 (19, 14
–157); Corantijn River, stream on S. side Lucie River, 03º35'N,
57º39'W, USNM 225297 (14, 53
–137).
Gymnotus mamiraua (122 specimens, 33
–244 mm). — Bolivia: Beni: Rio Madeira,
Rio Beni, Tributary to Lago Tumi, 26 km SSW Riberalta, 10°59'S, 66°05'W, AUM 23644
(1, 154).
— Brazil: Amazonas: Rio Japurá, Ilha da Arauacá, Município Maraã, approx.
02°04'S, 65°10'W, INPA (uncat.) (1, 121); Rio Solimões, Ilha da Marchantaria, Município
Manaus, approx. 03°06'S, 60°01'W, INPA 13609 (1, 46); Rio Purus, Sacado da Santa

CRAMPTON ET AL.
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Luzia, 04°42.3'S, 62°22.4'W, INPA 17177 (1, 146); Rio Solimões-Japurá confluence,
Mamirauá Sustainable Development Reserve (MSDR), Lago Periquito Redondo,
03º05.00'S, 64°46.57'W, INPA 18392 (1, 210); INPA 18393 (1, 181), INPA 18401 (2, 178
–
205); MSDR, Cano do Lago Arauaé, 03º03.82'S, 64º50.08'W, INPA 18394 (1, 234);
MSDR, Lago Araçazinho, 02º59.27'S, 64º51.46'W, INPA 18395 (1, 165), INPA 18408 (3,
210
–243); MSDR, Cano do Lago Sapucaia, 03º04.11'S, 64°48.53'W, INPA 18396 (25, 33–
210), INPA 18397 (1, 192); MSDR, Cano do Lago Rato, 03º02.97'S, 64º51.52'W, INPA
18398 (3, 207
–225); MSDR, Ressaca da Vila Alencar, 03º07.70'S, 64°48.03'W, INPA
18399 (1, 57), INPA 18418 (1, 160); MSDR, Jarauá lake system, Ressaca Caetono,
02º50.22'S, 64º55.79'W, INPA 18400 (2, 75-86); MSDR, Lago Promessa, 03º04.38S,
64°46.97'W, INPA 18403 (1, 160); MSDR, Lago Geraldo, 03º06.95'S, 64°49.16'W, INPA
18404 (2, 194
–194); MSDR, Lago Curuça Comprido, 03º05.50'S, 64°48.98'W, INPA
18405 (1, 227); MSDR, Lago Miratinin, 03º04.61'S, 64°50.28'W, INPA 18406 (1, 121);
MSDR, Lago Promessinha, 03º04.83S, 64°47.13'W, INPA 18407 (4, 132
–183); MSDR,
Lago Tracajá, 03º05.67'S, 64°46.57'W, INPA 18409 (1, 100); MSDR, Lago Matá-Matá,
03º06.68'S, 64°47.36'W, INPA 18410 (6, 182
–222), INPA 18415 (1, 203); MSDR, Paraná
do Apara, 03º02.52'S, 64º51.01'W, INPA 18411 (2, 212
–215); MSDR, Lago Secretaria,
03º06.74'S, 64°48.02'W, INPA 18412 (1, 204), INPA 18413 (2, 163
–215), INPA 18414 (1,
217); INPA 18416 (5, 95
–244), INPA 18419 (1, 205), INPA 18421 (1, 215); MSDR, Cano
do Lago Mamirauá, 03º06.62'S, 64°47.81'W, INPA 18417 (3, 50
–217); MSDR, Lago
Apolônia, 03º07.35'S, 64°49.82'W, INPA 18420 (1, 177); MSDR, Cano do Lago Sapucaia,
03º04.11'S, 64°48.53'W, MCP 1131 (2, 180
–187), MCP 29805 (35, 39–50); Rio Amazonas
at Manaus, Município Manaus, approx. 03°07'S, 60°01'W, MCZ 78146 (1, 198). All local-
ities from MSDR in the municipalities Alvarães.
— Pará: Lago Uruirá, Município, approx.
01°45'S, 55°52'W, MUSM 0536 (1, 146).
— Peru: Madre de Dios: Rio Madre de Dios,
Tambopata, L. Copamanu, approx. 12°44'S, 69°11'W, MUSM 16711 (1, 180); Rio Madre
de Dios, Rio de Los Amigos, approx. 12°35'S, 70°04'W, MUSM 19993 (2, 133
–148).
Gymnotus inaequilabiatus (51 specimens, 77
–998 mm). — Argentina: Rio Bermejo,
26°52'0"S, 58°22'59"W, UF 125973 (6, 191
–241). — Brazil: Rio Grande do Sul: Rio Uru-
guai, Santana Velha, Uruguaina, 29°45'0"S, 57°4'59"W, MCP 6956 (1 [2], 602); Rio
Maquine, Uruguaina, 29°44'0"S, 50°7'59"W, MCP 7155 (1, 245).
— São Paulo: Rio
Paraná, Porto Primavera, 22°30'0"S, 53°0'59"W, MZUSP 46001 (1, 998); Rio Capivara,
trib. of Rio Paranapanema, 22°47'59"S, 50°58'0"W, MZUSP 51268 (1, 270). Paraibo do
Sul, Jacarei, 23°19'0"S, 45°58'0"W, MZUSP 51667 (1).
— Paraguay: Alto Paraná: Puerto
Max, 22°40'59"S, 57°44'0"W, BMNH 1910.5.26.50 (1); Rio Paraguay, Alto Paraguay,
Bahia Negra, 58°0'0"W, 20°0'0"S, NRM 22850 (1, 80); Concepcion, Estancia Laguna
Negra, 23°4'0"S, 57°7'0"W, NRM 23121 (1, 275); Rio Paraguay, Alto Paraguay, Riacho
Mosquito, 22°12'0"S, 57°57'0"W, NRM 43303 (1, 83), NRM 43790 (1, 165); Rio Parana,
Rio Guyraugua, Caaguazu, 25°27'0"S, 56°0'59"W, NRM 45257 (1, 118); Alto Paraná,
Pedro Juan Caballero, 22°34'0"S, 55°37'0"W, UMMZ 206703 (4, 113
–280); Alto Paraná,

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GYMNOTUS UCAMARA SP. N.
277
ZOOTAXA
near Pto. Stroessner, Arroyo Venecia, 25°34'0"S, 54°49'59"W, UMMZ 206939 (1, 154);
Rio Paraná, Rio Confuso, Presidente Hayes, Estancia la Golondrina, approx. 25°8'59"S,
57°33'59"W, UMMZ 206971 (2, 255
–261), UMMZ 207096 (3, 132–210), UMMZ 215183
(1, 170), UMMZ 216576 (1, 322); Rio Paraná, Rio Confuso, Presidente Hayes, 34 km NW
Pt. Remaro bridge, approx. 25°8'59"S, 57°33'59"W, UMMZ 207025 (17, 215
–235); Rio
Paraná, Rio Confuso, Presidente Hayes, Rio Pilcomayo near Puerto Falcon, 25°15'0"S,
57°43'00"W, UMMZ 207564 (2, 220
–242); Rio Paraná, Rio Confuso, Presidente Hayes,
Riachuelo Pilco, 26°6'0"S, 56°14'0"W, UMMZ 207619 (1, 144); Alto Paraná, Arroyo
Peguajho, Ypan, 25°27'0"S, 57°31'59"W, UMMZ 207760 (2, 77
–78).
Acknowledgements
We acknowledge the following for access to specimens and information; J. Armbruster
(AUM); O. Crimmen, D. Siebert (BMNH); R. Robins (UF); B. Chernoff, M. Rogers
(FMNH); L. Rapp Py-Daniel, J. Zuanon (INPA); R. Reis (MCP); K. Hartel (MCZ); H.
Ortega (MUSM); M. de Pinna, J. Lima De Figueiredo, O. Oyakawa, (MZUSP); E. Ahl-
ander, S. Kullander (NRM); W. Fink, D. Nelson (UMMZ); M. Hagedorn, S. Jewett, L.
Parenti, R. Vari (USNM). We acknowledge the Neodat project (NSF/AID DEB grant 90-
24797) for collection information. Thanks to H. Ortega and L. Verdi for field assistance,
and to K. Aviles, R. Co, J. Hill, N. Kook and D. Thorsen for laboratory assistance. This
research was conducted in collaboration with Universidade Nacional de la Amazonia
Peruana (UNAP) and funded by National Science Foundation (NSF-DEB 0084704,
0102593, 0138633), University of Florida Research Opportunity Fund, and Florida
Museum of Natural History.
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