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Sternarchella calhamazon n. sp., the Amazon's Most Abundant Species of Apteronotid Electric Fish, with a Note on the Taxonomic Status of Sternarchus capanemae Steindachner, 1868 (Gymnotiformes, Apteronotidae)

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  • National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health

Abstract and Figures

A new species of apteronotid electric fish is described from the Brazilian and Peruvian Amazon. Sternarchella calhamazon sp. n. conspicuously differs from its congeners in caudal peduncle shape, electric organ size and shape, hemal spine elongation above the anal fin, and arrangement of intermuscular bones adjacent to the electric organ. Sternarchella calhamazon is among the most common gymnotiform species living in the principal channels of the lowland Amazon River and its large tributaries. The nominal apteronotid Sternarchus capanemae Steindachner is an earlier published, objective synonym of Sternarchella schotti Steindachner, both names appearing in 1868. Because S. capanemae was never used as a valid name after its first use, it should be considered a nomen oblitum and Sternarchella schotti should be considered a nomen protectum and the valid name of this species.
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Sternarchella calhamazon n. sp., the Amazon's Most Abundant Species of
Apteronotid Electric Fish, with a Note on the Taxonomic Status of Sternarchus
capanemae Steindachner, 1868 (Gymnotiformes, Apteronotidae)
Author(s): John G. Lundberg Cristina Cox Fernandes Ricardo Campos-Da-Paz John P. Sullivan
Source: Proceedings of the Academy of Natural Sciences of Philadelphia, 162():157-173. 2013.
Published By: The Academy of Natural Sciences of Philadelphia
DOI: http://dx.doi.org/10.1635/053.162.0110
URL: http://www.bioone.org/doi/full/10.1635/053.162.0110
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PROCEEDINGS OF THE ACADEMY OF NAT UR A L SCIENCES OF PHILADELPHIA 162: 157-173 MARCH 2013
Sternarchella calhamazon n. sp., the Amazon’s most abundant species of apteronotid electric
ÀVK ZLWK D QRWH RQ WKH WD[RQRPLF VWDWXV RI Sternarchus capanemae Steindachner, 1868
(Gymnotiformes, Apteronotidae)
JOHN G. LUNDBERG
Department of Ichthyology, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103-1195 USA.
E-mail: lundberg@ansp.org
CRISTINA COX FERNANDES
Biology Department, Morrill Science Center, University of Massachusetts, Amherst MA, 01003, USA, and Instituto Nacional de
Pesquisas da Amazônia, Manaus, BRAZIL.
E-mail: cristina@bio.umass.edu
RICARDO CAMPOS-DA-PAZ
Laboratório de Ictiologia Neotropical, Departamento de Ecologia e Recursos Marinhos, Instituto de Biociências, Universidade Federal
do Estado do Rio de Janeiro, Av. Pasteur 458/408, Urca - Rio de Janeiro - RJ, 22290-240, BRAZIL.
E-mail: rcamposdapaz@gmail.com
JOHN P. SULLIVAN
Department of Ichthyology, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA, 19103-1195 USA.
Present address: Cornell University Museum of Vertebrates, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
E-mail: jpsullivan@cornell.edu
$%675$&7³$QHZ VSHFLHVRIDSWHURQRWLG HOHFWULFÀVKLV GHVFULEHGIURPWKH %UD]LOLDQDQG3HUXYLDQ$PD]RQSternarchella
calhamazon sp. n. conspicuously differs from its congeners in caudal peduncle shape, electric organ size and shape, hemal spine
HORQJDWLRQDERYHWKHDQDOÀQDQGDUUDQJHPHQWRILQWHUPXVFXODUERQHVDGMDFHQWWRWKHHOHFWULFRUJDQSternarchella calhamazon
LVDPRQJ WKH PRVWFRPPRQ J\PQRWLIRUPVSHFLHV OLYLQJLQWKH SULQFLSDOFKDQQHOV RIWKHORZODQG$PD]RQ 5LYHUDQG LWV ODUJH
tributaries.
The nominal apteronotid Sternarchus capanemae 6WHLQGDFKQHULVDQHDUOLHUSXEOLVKHGREMHFWLYHV\QRQ\PRISternarchella
schotti Steindachner, both names appearing in 1868. Because S. capanemae ZDVQHYHU XVHGDVD YDOLGQDPHDIWHULWVÀUVWXVHLW
should be considered a nomen oblitum and Sternarchella schotti should be considered a nomen protectumDQGWKHYDOLG QDPHRI
this species.
ISSN 0097-3157
INTRODUCTION
Eigenmann (in Eigenmann and Ward, 1905) established
the apteronotid genus Sternarchella for the nominal species
Sternarchus schotti Steindachner, 1868b and Sternarchus
balaenops Cope, 1878. Sternarchus schotti, based on a
specimen from “Barra do Rio Negro” (= mouth of the rio
Negro), near Manaus, Brazil, was designated as the type
species of the genus. Sternarchus balaenops was based on
a specimen from the Peruvian Amazon (Eigenmann and
Ward, 1905:164). Sternarchella ZDV ÀUVW VHSDUDWHG IURP
Sternarchus (= Apteronotus Lacépède) in a “Key to the
genera of Gymnotidae” in Eigenmann and Ward, (1905:160)
on the basis of its short gape and snout (vs. “gape long” and
“snout long” in other nominal Sternarchus). Later in that
same contribution (Eigenmann and Ward, 1905:163), it was
also pointed out that in Sternarchella “[t]he snout is much
shorter and the mouth is very much smaller” (i.e., when
compared to Sternarchus albifrons [= Apternotus albifrons
(Linnaeus)]. The same diagnostic features Sternarchella
were restated by Ellis (1913), who called attention to the
“gape short” and “gape not reaching the posterior nostril”
in that genus (1913:150).
Mago-Leccia (1994), Albert and Campos-da-Paz
(1998) and Albert (1995, 2001) developed a phylogenetic
diagnosis of SternarchellaWKDWLQFOXGHVÀYHXQDPELJXRXV
synapomorphies among Apteronotidae: gape of mouth very
short, less than twice the eye diameter; maxilla crescent
shaped; maxillary anterior process and anteroventral
PDUJLQ XQRVVLÀHG JLOO UDNHUV ÀUPO\ DWWDFKHG WR JLOO
158 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
DUFKHVJLOOUDNHUWLSV FRYHUHG ZLWKÀEURXV FDSV )XUWKHU
the close phylogenetic relationship between Sternarchella
and Magosternarchus has been demonstrated by Albert in
Lundberg et al. (1996), Albert and Campos-da-Paz (1998),
$OEHUWDQG,YDQ\LVNL
In addition to the type species S. schotti,we
UHFRJQL]H ÀYH VSHFLHV RI Sternarchella as valid: S.sima
6WDUNV  S.terminalis (Eigenmann and Allen 1942),
S. curvioperculata Godoy 1968 (but see Discussion
below), Sternarchella orinoco Mago-Leccia 1994 and S.
orthos Mago-Leccia 1994. Although recently treated as a
synonym of S. sima (Albert 2001, 2003), reexamination
of Sternarchella orinoco E\ ,YDQ\LVNL  LQGLFDWHV
that the two nominal species are distinct. Sternarchella
balaenops was properly transferred to Adontosternarchus
Ellis by Eigenmann and Allen (1942, see Mago-Leccia et
al., 1985).
7KH SX]]OLQJ VSHFLHV GLYHUVLW\ DQG LGHQWLÀFDWLRQ
of Sternarchella ZDV ÀUVW HQFRXQWHUHG E\ -*/ )
Mago-Leccia and E. Marsh-Matthews while examining
specimens collected during the 1978-1979 Orinoco Delta
Expeditions (Mago-Leccia, 1994). Occasional references
WR XQQDPHG VSHFLHV RU XQFHUWDLQ LGHQWLÀFDWLRQV RI
SternarchellaIXUWKHUVXJJHVWHGDQLQFRPSOHWHNQRZOHGJH
RI VSHFLHV GLYHUVLW\ LQ WKH JHQXV &R[ )HUQDQGHV 
$OEHUW  &R[ )HUQDQGHV HW DO   2XU
current interest in Sternarchella emerged from analyzing
material of four distinct species collected during the
“Calhamazon Project’s” ichthyological exploration of the
FKDQQHOVRI WKH%UD]LOLDQ$PD]RQ&R[)HUQDQGHV
/XQGEHUJHW DO7KHVH VSHFLHVDUHLGHQWLÀHG
now as S. schotti,S.sima,S.terminalis and the new species
GHVFULEHG KHUH :H DOVR ÀQG DQG LOOXVWUDWH DGGLWLRQDO
specimens of Amazonian Sternarchella that are similar to
S.terminalisH[FHSW IRUYDULDEO\FRQFDYHKHDGSURÀOHVRI
XQFHUWDLQWD[RQRPLFVLJQLÀFDQFH
)LQDOO\ZHSUHVHQWDEULHIGLVFXVVLRQRIWKHWD[RQRPLF
status of Sternarchus capanemae Steindachner, 1868.
This scarcely discussed nominal species was previously
referred to as a junior synonym of S. schotti (Albert, 2001).
MATERIAL AND METHODS
The Brazilian specimens of Sternarchella examined
in this study were collected during the “Calhamazon
3URMHFWµDQGRWKHUÀHOGRSHUDWLRQVUXQE\UHVHDUFKHUVDWWKH
Instituto Nacional de Pesquisas da Amazônia (INPA). The
Peruvian specimens were collected by M. Sabaj Pérez and
colleagues on collecting trips to the Amazon near Iquitos
and the Nanay River. Specimens from the Orinoco were
collected during the late 1970s R/V Eastward Orinoco
Delta Expeditions (López et al., 1984; Mago-Leccia et
al., 1985; Mago-Leccia, 1994). Ichthyological collection
codes follow Sabaj Pérez (2012).
Measurements were made with dial calipers and
generally follow Lundberg et al. (1996): total length (TL),
standard length (SL), length from snout tip to end of
DQDOÀQEDVH/($ GLVWDQFH IURPVQRXWWLS WR RULJLQRI
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peduncle length; caudal peduncle depth at the posterior
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length to dorsal end of gill membrane; head length to
dorsoposterior corner of opercle (HL); postorbital head
length from posterior margin of eye to insertion of leading
SHFWRUDOÀQ UD\ ERG\ GHSWK DW RULJLQ RI GRUVDO ÀODPHQW
maximum body depth; head depth at occiput; snout length;
length from eye to chin tip; eye diameter; length from eye
to anterior naris; interorbital distance.
&RXQWV ZHUH PDGH RI WRWDO ÀQ UD\V LQ WKH DQDO
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HOHPHQWVRIWKH:HEHULDQFRPSOH[WKHÀUVWFDXGDOYHUWHEUD
is articulated with the anterior displaced hemal spine
(Albert, 2001; = posteroventral abdominal bone, Hilton et
al., 2007) and posterior series of displaced hemal spines
(Albert, 2001); the last caudal vertebra counted has its
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radiographs and cleared/stained preparations, excluding
specimens found to have damaged or regenerated tails.
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images differing only in focal plane. These image sets
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receptor.
Electric organ discharges (EODs) of four specimens
of Sternarchella calhamazon and eight of S. terminalis,
three of Magosternarchus duccis and two of M. raptor
were recorded during the 1993 Calhamazon Project expe-
dition on board the R/V Almirante Guimaräes in a 10 cm x
40 cm x 12 cm aquarium with silver/silver–chloride elec-
trodes positioned at the ends and a reference electrode in
WKHFHQWHU(2'VZHUHDPSOLÀHGXVLQJD&:(&RUSRUDWLRQ
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ORZ JDLQ DQG FDSWXUHG ZLWK D 7HNWURQL[  GLJLWDO VWRU-
age oscilloscope (512 point/8-bit resolution). Recordings
were made in water from the capture locality at ambient
WHPSHUDWXUHV²& ZLWKWKH ÀVKIDFLQJ WKHSRVLWLYH
electrode such that head positivity was displayed as posi-
tive voltage on the oscilloscope.
NEW STERNARCHELLA KNIFEFISH 159
Sternarchella calhamazon n. sp. Lundberg,
&R[)HUQDQGHV&DPSRVGD3D]
)LJV$%$7DEOH
Sternarchella terminalis³/XQGEHUJ &R[ )HUQDQGHV
Albert and Garcia, 1996 (Brazil; morphology); Cox
)HUQDQGHV%UD]LO$PD]RQ5LYHU
Sternarchella VS³&R[)HUQDQGHV3RGRVDQG/XQGEHUJ
2004 (Brazil, Amazon River).
Sternarchella VS³&R[ )HUQDQGHV /XQGEHUJ DQG
Sullivan, 2009 (cytochrome b gene sequence comparisons;
voucher specimen catalog number here corrected as ANSP
189210).
Holotype.—INPA 37898, 162.8 mm TL male, Brazil,
$PD]RQDV 6WDWH ULR 0DGHLUD  NP DERYH FRQÁXHQFH
with rio Amazonas, collected with 3 m bottom trawl in
FKDQQHO PGHHS PRII OLQHDUEHDFK DQGEDQN
3°35’44.2”S, 58°57’45.8”W, 6 Aug 1996, Zanata et al.
)LHOGQR$0= &ROOHFWHG ZLWKRQHSDUDWRSRW\SH
INPA 37899, see below.
Paratypes.—Twenty-nine lots containing overall 42 paratype
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=,/3DUi6WDWH 5LR ;LQJX DUHD$163 
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ZLWK  P ERWWRP WUDZO ZLWK Á\VFUHHQ OLQHU LQ FKDQQHO 
P GHHS PRIIOLQHDUEDQNZLWKIRUHVW·µ6
·µ:1RY)LHOGQR$0==DQDWD
et al. Rio Tapajos area - MZUSP 111953, 1, 147.8 mm TL, rio
Amazonas below Tapajos, collected with 3 m bottom trawl in
FKDQQHOPGHHSPRIIOLQHDUVDQG\EDQNZLWKJUDVV
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no. AMZ-94-010, Zanata et al. MZUSP 111954, 2, 95.1-145.3
mm TL, male, rio Amazonas below Tapajos, collected with 3
m bottom trawl in channel, 28- 23 m deep, 150 m off sandy
EDQN ZLWK JUDVV DQG VKUXE ··¶6 ··¶: 
1RY)LHOGQR$0==DQDWDHWDO%5$=,/$P-
D]RQDV6WDWH5LR7URPEHWDVDUHD)01+
mm TL, female, rio Amazonas below Trombetas, collected
with 3 m bottom trawl in channel, 12.8 -5.3 m deep, 150-200
m off linear muddy beach with grass and shrub, 2°02’45.7’‘S,
··¶:2FW)LHOGQR0:::HVW-
neat et al. Rio Madeira area - LACM 57530-1, 1, 119.9 mm
TL, male, rio Amazonas above rio Madeira, collected with 3
m bottom trawl in channel 12.5-10 m deep, 500 m off concave
EDQNRIVPDOO SDUDQD ··¶6··¶:2FW
)LJ/DWHUDOYLHZRISternarchella calhamazon holotype, INPA 37898. A. whole specimen, B. head and anterior body; C. tail showing
WUDQVSDUHQWHOHFWULFRUJDQZLWKWZRURZVRILQWHUPXVFXODUERQHVP\EYYHQWUDOP\RUKDEGRLIEYYHQWUDOVHULHVRIÀODPHQWRXVERQHV
DQGFDXGDOÀQ
160 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
m off convex beach with grass and cecropia, 3°49’06.5”S,
·µ: -XO )LHOGQR$0==DQDWD
HWDO8)   PP 7/ PDOHULR6ROLP}HV EH-
low rio Purus, collected with 3 m bottom trawl in channel,
40-60 m off linear beach with grass and shrub, 3°36’01.4”S,
··¶:-XO)LHOGQR0737ROHGR
Piza et al. ANSP 193098, 1, 100 mm TL, electric organ dis-
FKDUJHYRXFKHU QR -3)ULR 3XUXV DERYH6ROLP}HV
collected with 3 m bottom trawl in channel 12-13 m deep,
250-300 m off shore, 3°43’28.3”S, 61°27’12.8”W, 25 OCT
)LHOG QR -3)-)ULHO HW DO&$6 
 PP 7/ IHPDOH ULR 3XUXV DERYH ULR 6ROLP}HV FRO-
lected with 3 m bottom trawl in channel, 30-23.9 m deep, 300
PRIIFRQFDYHEDQNZLWKIRUHVW·µ6·µ:
-XO)LHOGQR$0==DQDWDHWDO5LR-DSXUi
DUHD8610PP7/ULR6ROLP}HVEHORZULR
-DSXUiFROOHFWHGZLWKPERWWRPWUDZOLQFKDQQHOP
deep, 25 m off linear sandy beach with grass, 3°18’46.3”S,
·µ:2FW)LHOGQR6/--HZHWWHW
DO8610PP7/ULR-DSXUiDERYHULR6R-
OLP}HVFROOHFWHGZLWKP ERWWRPWUDZOLQFKDQQHO P
GHHSP RIIOLQHDUPXGG\EDQNZLWKJUDVV·µ6
·µ:  1RY  )LHOG QR 6/- -HZHWW
et al. ANSP 189210, 1, 100 mm TL, tissue voucher, rio So-
OLP}HVDERYH ULR-DSXUi FROOHFWHGZLWK PERWWRPWUDZOLQ
channel, 8.5-17 m deep, 3°14’10.0”S, 64°46’08.8”W, 31 Oct
)LHOGQR-3))ULHOHWDO5LR-XUXiDUHD,13$
   PP 7/ RQH LV IHPDOH ULR -XUXi DERYH
ULR 6ROLP}HV FROOHFWHG ZLWK  P ERWWRP WUDZO LQ FKDQQHO
11.2-6.5 m deep, 60-70 m off concave shore, 2°39’24.1”S,
·µ:  1RY  )LHOG QR -3) )ULHO HW
al. ANSP 193099, 1, 179 mm TL, electric organ discharge
DQGWLVVXHYRXFKHUQR272ULR-XUXiDERYH6ROLP}HV
collected with 3 m bottom trawl in channel 9-10 m deep,
·µ6·µ: 129 )LHOG QR 272
 2 2\DNDZD HW DO$163    PP 7/
HOHFWULFRUJDQ GLVFKDUJHYRXFKHU QR-*/ULR -XUXi
DERYH6ROLP}HVFROOHFWHGZLWKPERWWRPWUDZOLQFKDQQHO
PGHHS·µ6·µ:129)LHOG
QR-*//XQGEHUJHWDO5LR,oDDUHD&8
PP7/ULR,oDDERYHULR6ROLP}HVFROOHFWHGZLWK
3 m bottom trawl in channel, 17.8-14.6 m deep, ca 120 m off
OLQHDUEDQNZLWKIRUHVW·µ6·µ:1RY
)LHOG QR-366XOOLYDQHWDO/$&0
PP7/ ULR6ROLP}HVDERYHULR,oD &RO-
lected with 3 m bottom trawl in channel, 3.2-2.1 m deep, 10
PRIIVKRUH ·µ6·µ:1RY  )LHOG
QR-3))ULHO HW DO3(58/RUHWR 'HSDUWPHQW 5tR
Amazonas - ANSP 182576, 4, 86.78-146.3 mm TL, PERU,
'HSW/RUHWR 3URY0D\QDVUtR$PD]RQDV YLFLQLW\RI ,TXL-
WRV·µ6·µ:$XJ)LHOGQR3(58
05-07, Sabaj et al.
)LHOGQR )//DQJHDQLHW DO)01+
1, 96.19 mm TL, rio Amazonas below rio Madeira, collect-
ed with 3 m bottom trawl in channel, 200 m off shore with
forest and grass, 3°19’59.7’‘S, 58°35’43.9’‘W, 9 Aug 1996,
&&)&R[)HUQDQGHVHWDO,13$PP
TL, female, rio Madeira above rio Amazonas, collected with
the holotype by a 3 m bottom trawl in channel, 16.1-13.9 m
GHHSPRIIOLQHDUEHDFKDQGEDQNZLWKIRUHVWDQGJUDVV
··¶6··¶:$XJ )LHOGQR $0=
96-139. Zanata et al. MZUSP 111955, 1, 96.5 mm TL, rio
Madeira aboverio Amazonas, collected with 3 m bottom trawl
in channel, 15-11.7 m deep, 800 m off concave shore with
forest, grass and shrub, 3°30’13.9’‘S, 58°52’54.4’‘W, 5 Aug
 )LHOG QR &&) &R[)HUQDQGHV HW DO )01+
121336, 1, 100.5 mm TL, rio Madeira above rio Amazonas,
collected with 3 m bottom trawl in channel, 16.7-13.9 m
GHHS PRIIFRQFDYHEHDFKDQG EDQNZLWK IRUHVWJUDVV
DQGVKUXE··¶6 ··¶:$XJ)LHOG
no. MTP-96-121, Toledo-Piza et al. Rio Negro area - INPA
PP7/ULR 1HJURDERYHULR 6ROLP}HV$P-
azonas, collected with 3 m bottom trawl in channel, 30-21.5
PGHHS FDPRIIFRQFDYH EHDFKDQG EDQNZLWKIRUHVW
··¶6··¶:-XO  )LHOG QR$0=
96-005, Zanata et al. ANSP 408388, 2, 82.5-113 mm TL, rio
1HJUR DERYH ULRV 6ROLP}HV$PD]RQDV FROOHFWHG ZLWK  P
bottom trawl in channel, 27.2-24.5 m deep, 750 m off convex
VDQGDQG PXGEHDFKDQGEDQN·µ6·µ:
'HF  )LHOGQR -*/ /XQGEHUJHW DO$163
199192, 3, 113-140 mm TL, rio Negro below rio Branco, col-
lected with 3 m bottom trawl in channel, 20.0-11.5 m deep,
ca. 200 m offshore, 1°59’00.5”S, 61°14’57.2”W, 4 Dec 1993,
)LHOGQR -*//XQGEHUJHWDO$163 DOF
93-102 mm TL, 1 C/S (formerly UAZ 95-160), 112 mm TL,
ULR6ROLP}HVDERYHULR1HJURFROOHFWHGZLWKPERWWRPWUDZO
in channel 39-50 m deep, 3°13’30.2”S, 59°53’41.9”W, 24 Oct
)LHOGQR-3))ULHOHWDO$163
7/HOHFWULFRUJDQGLVFKDUJHDQGWLVVXHYRXFKHUQR-*/
ULR1HJUR DERYH6ROLP}HV$PD]RQDVFROOHFWHGZLWK
m bottom trawl in channel 24-25 m deep, 300 m off linear
EHDFK·µ6·µ:'(&)LHOGQR
-*//XQGEHUJHW DO$01+   PP
7/PDOHULR6ROLP}HVDERYHULR1HJUR FROOHFWHGZLWKP
ERWWRPWUDZOLQFKDQQHOPRIIOLQHDUEHDFKDQGEDQNZLWK
grass, shrub and aquatic plants, 3°13’22.8’‘S, 59°55’24.0’‘W,
 -XO  )LHOG QR &&) &R[)HUQDQGHV HW DO
ANSP 199193, 1, 130.2 mm TL, male, rio Amazonas be-
low rio Negro, collected with 3 m bottom trawl in channel,
FDPRII OLQHDU WRFRQFDYHEDQN ZLWK JUDVV DQG DTXDWLF
SODQWV··¶6··¶: -XO)LHOG QR
AMZ-96-048, Zanata et al. Rio Purus area - ANSP 199194,
PP7/VPDOOHULVIHPDOHULR6ROLP}HVDERYH
rio Purus, collected with 3 m bottom trawl in channel, 70
NEW STERNARCHELLA KNIFEFISH 161
)LJ  /DWHUDO YLHZ RI Sternarchella calhamazon Paratypes. A. ANSP 182576, fresh specimen collected near Iquitos, Peru, photo
courtesy of M. Sabaj Peréz. B. ANSP 193096, cleared and stained specimen (112 mm TL) showing enlarged anterior displaced hemal
VSLQH'+6HDQGRQHVPDOOGLVSODFHG KHPDOVSLQH'+6V GRUVDOÀODPHQWVHSDUDWHGIURPGRUVXPVKRUWDQG GHHSFDXGDOSHGXQFOH
ORQJKHPDOVSLQHV+6RIWKHPLGGOHFDXGDOYHUWHEUDHUHODWLYHWRDQDOÀQSUR[LPDOUDGLDOV35DQGGHHSHOHFWULFRUJDQFURVVHGE\WZR
URZVRILQWHUPXVFXODUERQHVP\EYYHQWUDOP\RUKDEGRLIEYYHQWUDOVHULHVRIÀODPHQWRXVERQHVDQGFDXGDOÀQ
)LJ0DSRIFROOHFWLRQORFDOLWLHVUHFRUGHGLQ WKLVZRUNIRUSternarchella calhamazon, some single spots include multiple proximate
samples and star indicates type locality in lower rio Madeira. Base map of drainages and elevations provided by Conservation Science
3URJUDP:RUOG:LOGOLIH)XQG86LQVHWNH\VVKDGLQJRIHOHYDWLRQVEHORZPZKHUHWKHVSHFLHVPRVWO\RFFXUV
162 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
)LJ$ERYH%LSORWVVKRZLQJYDULDWLRQLQWDLOVKDSHDPRQJVSHFLHV of Sternarchella. Upper biplot. Caudal peduncle depth at end of
DQDOÀQYV/($/RZHUELSORW&DXGDOSHGXQFOHGHSWKDWHQGRIDQDOÀQYVFDXGDOSHGXQFOHOHQJWK.
)LJ 3DJH /DWHUDO YLHZVRI$Sternarchella orthos$163 UtR 2ULQRFR%Sternarchella schotti$163UtR
Amazon, C. Sternarchella terminalis ANSP 199196, rio Amazon, D. Sternarchella sima ANSP 199200, rio Amazon, E. Sternarchella
orinoco ANSP, 149921, rio Orinoco.
NEW STERNARCHELLA KNIFEFISH 163
164 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
NEW STERNARCHELLA KNIFEFISH 165
Diagnosis.—Sternarchella calhamazon is distinguished
by its unique tail shape and associated anatomical features. 1)
&DXGDOSHGXQFOHDQGHOHFWULFRUJDQXQXVXDOO\GHHS)LJV
FDXGDOSHGXQFOHGHSWKDWHQGRIDQDOÀQFRQWDLQHG
12-18 times in LEA, 0.7-2.5 times in its length, and electric
RUJDQGHSWKDWHQGRIDQDOÀQDERXWHTXDOWRRUDOLWWOHJUHDW-
er than snout length. 2) Caudal peduncle abruptly tapering
EHIRUH FDXGDO ÀQ )LJV   1RWH 7KH DEUXSW WDLO VKDSH
LVDWÀUVW VXJJHVWLYH RIGDPDJHDQG UHJHQHUDWLRQ EXWPRVW
specimens have normal electric organs, scalation, caudal ver-
WHEUDHDQGÀQV+HPDOVSLQHVDERYHPLGGOHWKLUGRIDQDO
ÀQ HORQJDWHQHDUO\ WZLFH ORQJHU WKDQ DGMDFHQW SUR[LPDO
DQDOÀQUDGLDOV)LJV%7ZRURZVRILQWHUPXVFX-
lar bones visible along ventral and ventrolateral sides of
SRVWHULRUO\GHHSHQLQJHOHFWULFRUJDQ)LJV&%7KHVH
DUHWKHYHQWUDOPRVWÀODPHQWRXVERQHVHULHVDQGORZHUURZ
of split ventral myorhabdoi series (Hilton et al., 2007). 5)
Precaudal vertebrae 13-15 (modally 14) including four
vertebrae of the Weberian complex.
Other species of Sternarchella differ from S. calhamazon
as follows. 1) Caudal peduncle and electric organ shallow
)LJVFDXGDOSHGXQFOHGHSWKDWHQGRIDQDOÀQFRQWDLQHG
>20 times in LEA, and usually contained >2.5 times in its
length in undamaged specimens, and electric organ depth at
HQG RI DQDO ÀQ OHVV WKDQ FD  RI VQRXW OHQJWK  &DXGDO
SHGXQFOHWDSHULQJJUDGXDOO\LQXQGDPDJHGVSHFLPHQV)LJ
 +HPDO VSLQHV DERYH PLGGOH WKLUG RI DQDO ÀQ VKRUW DERXW
HTXDOWROHQJWKRIDGMDFHQWSUR[LPDODQDOÀQUDGLDOV)LJ%
4) A single or no row of intermuscular bones visible along the
posteroventral part of electric organ. 5) Precaudal vertebrae
generally more than 14: S. orthos bimodally 14,15 (n = 8); S.
orinoco modally 16 (15-16, n = 7), S. sima modally 15 (14-
16, n = 5), S. terminalis modally 15 (15-16, n = 14), S. cf.
terminalis modally 15 (15-16, n = 5), S. schotti modally 17
(16-17, n = 15).
Remarks.—Three additional features are useful for
discriminating the Amazonian and Orinocoan species of
Sternarchella. 0RXWKSRVLWLRQDQGGRUVDO SURÀOHRIWKH
KHDG)LJV  Sternarchella sima and S. orinoco
have a subterminal to inferior mouth (i.e., fully visible in
ventral view) below a broadly rounded snout and dorsal
SURÀOHSternarchella calhamazon, S. orthos,S. schotti and
S. terminalis have a supraterminal or, in cases, terminal
mouth, above a slightly projecting chin and below an
anteriorly convex snout, and scarcely convex, straight
VOLJKWO\ FRQFDYH KHDG SURÀOH +RZHYHU ZH ÀQG VHYHUDO
VSHFLPHQV ZLWK PRUH GHHSO\ FRQFDYH KHDG SURÀOHV )LJ
8B-E) that are otherwise most similar to S. terminalis
)LJ$2I WKHVH WKHVSHFLPHQ LOOXVWUDWHG LQ)LJ(
may have some distortion of head shape related to ventral
K\SHUH[WHQVLRQ RI LWV K\RLG EDU EXW WKRVH LQ )LJV %'
DUHQRWXQXVXDOO\SUHVHUYHG:HÀQGERWKPDOHDQGIHPDOH
VSHFLPHQV ZLWK D FRQFDYH KHDG SURÀOH 7KH FRQFDYH
headed S. cf. terminalis also recall Magosternarchus
duccis )LJ ) ZKLFK KDV D FRQFDYH KHDG SURÀOH
upturned mouth and snout, and extremely jutting chin,
EXW WKHVH ÀVK GLIIHU WUHQFKDQWO\ LQ GHQWLWLRQ DQG RWKHU
diagnostic characters of Magosternarchus. With available
)LJ  $ERYH /DWHUDO YLHZ ;UD\ LPDJHV RI PLGVHFWLRQ RI WDLO
DQG DQDO ÀQ VKRZLQJ KHPDO VSLQH +6 OHQJWK UHODWLYH WR DQDO
ÀQSUR[LPDOUDGLDOV35$Sternarchella calhamazon holotype,
INPA 37898, B. Sternarchella orthos, ANSP 165218.
)LJ  3DJH  /DWHUDO YLHZ ;UD\ LPDJHV RI DQWHULRU ERG\
to anterior caudal vertebrae, showing enlarged displaced hemal
spine, DHS(e) and small displaced hemal spines, DHS(s).
A, B. Sternarchella calhamazon holotype, INPA 37898, C,
D. Sternarchella orthos $163  UtR 2ULQRFR ( )
Sternarchella schotti$163UtR$PD]RQ
166 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
spine. Sternarchella schotti)LJ &KDV RUPXFK H[-
panded, unevenly curved hemal spines below the two (or
one) centra posterior to the enlarged anterior displaced pos-
terior hemal spine. A cleared and stained specimen of S.
schotti (MZUSP 6558) reveals that these additional expand-
ed hemal spines are displaced to the right, adjacent to the
information we are uncertain if the concave-headed
specimens are taxonomically distinct from S. terminalis.
 $QWHULRU KHPDO VSLQHV )LJV % Sternarchella
calhamazon, S. orthos, S. sima, S. orinoco and S. terminalis
have 1 or 2 small, thin displaced hemal spines below the
centrum posterior to the enlarged anterior displaced hemal
)LJ/DWHUDO YLHZVVKRZLQJPRXWK SRVLWLRQV DQGGRUVDO SURÀOHV RIKHDGV RI$ Sternarchella terminalisIURP $163 UtR
Amazon, B-E. S. cf. terminalis´FRQFDYHPRUSKVµDOVRIURP$163)Magosternarchus duccis$163UtR$PD]RQ
NEW STERNARCHELLA KNIFEFISH 167
Radiographs of preserved specimens of Sternarchella with
ÁXLGÀOOHGJDVEODGGHUVGRQRWUHYHDOWKHVL]HDQGVKDSHRI
that organ which requires dissection to examine.
Description³/DWHUDOYLHZVLQ)LJVDQGLOOXVWUDWH
ERG\DQGKHDGVKDSHDQGIRUPDQGSRVLWLRQRIÀQV7DEOH
1 summarizes morphometric descriptors of external form.
A small-bodied species, largest specimen in type series
185 mm TL and 169 mm LEA. Body strongly compressed,
elongate but caudal peduncle deep, steeply tapered near
end, short, its length in undamaged specimens contained
6-17 times in LEA, 3-9 times in LOD. Greatest body depth
EHKLQG RULJLQ RI DQDO ÀQ WKURXJK DEGRPHQ FRQWDLQHG 
times in TL, 6-7 times in LEA, 3.5-5 times in LOD.
enlarged posterior gas bladder chamber (RCP, pers. obs.). A
VRPHZKDWVLPLODUFRQGLWLRQ RI WKHKHPDO VSLQHV LVÀJXUHG
E\$OEHUWDQG)LQNÀJLQWKHLUGHVFULSWLRQRI
WKHPRGLÀHGSRVWHULRUJDVEODGGHUFKDPEHULQSternopygus
macrurus Bloch and Schneider (Sternopygidae).
 *DV EODGGHU )LJ  Sternarchella schotti alone
has a much enlarged posterior expansion of the gas bladder
tapering into the tail region near the anterior hemal spines
)LJ$7KHRWKHUVSHFLHVRISternarchella have a small,
digitiform gas bladder that is less than half the length of the
DEGRPLQDOFDYLW\)LJ%:HQRWHWKDWWKHH[SDQGHGJDV
bladder of S. schottiLVUHDGLO\VHHQZLWKEDFNLOOXPLQDWLRQ
through the body wall in live and fresh specimens, and
in preserved specimens less than about 150 mm TL.
Table 1. Measurement data for holotype and some paratypes of Sternarchella calhamzon in mm or thousandths of standard dimensions.
$EEUHYLDWLRQV/($²OHQJWKWRHQGRIDQDOÀQ/2'²OHQJWKWRRULJLQRIGRUVDOÀODPHQW6/²VWDQGDUGOHQJWK7/²WRWDOOHQJWK
Character Holotype Range Mean N
TL in mm 162.8 82.5 - 185.4 125.3 36
SL in mm 157 79.1 - 180 120.2 35
LEA in mm 143.1 69.1 - 169.1 109.1 36
LOD in mm 54.6 28.6 - 67 43.3 36
LOD/LEA 381 343 - 467 398 36
LengthDQDOÀQEDVH/2' 2238 1789 - 2421 2103 36
Length caudal-peduncle/LOD 307 114 - 386 263 35
Length caudal-peduncle/LEA 117 45 - 159 105 35
/HQJWKWRRULJLQRIDQDOÀQ/2' 524 340 - 631 506 36
/HQJWKWRRULJLQRIDQDOÀQ/($ 200 147 - 244 200 36
Length to anus and urogenital papilla/LOD 285 120 - 408 291 36
Head length to gill membrane/LOD 532 370 - 568 478 36
Head length to gill membrane/LEA 203 162 - 209 189 36
Head length to bony opercle end/LOD 439 355 - 524 432 36
Head length to bony opercle end/LEA 167 155 - 186 171 36
(\HWRSHFWRUDOÀQRULJLQ/2' 374 246 - 441 330 36
'HSWKDWRULJLQRIGRUVDOÀODPHQW/2' 441 299 - 515 396 36
Maximum body depth/LOD 452 311 - 531 414 36
Head depth at occiput/LOD 401 276 - 453 371 36
Snout length/Head length to bony opercle end 285 276 - 366 302 36
Length from eye to chin tip/Head length to bony opercle end 305 287 - 390 332 36
Eye diameter/Snout length 56 48 - 97 69 36
Eye to anterior naris/Snout length 218 180 - 254 216 36
Interorbital distance/Snout length 98 142 - 236 194 36
168 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
'RUVDO SURÀOH ULVLQJ LQ D GHFUHDVLQJO\ FRQYH[ DUF
from snout tip to occiput, then nearly straight or slightly
FRQYH[WR EDVHRIFDXGDOÀQ9HQWUDOSURÀOHFRPPHQFLQJ
from slightly projecting chin, gently convex, descending
at about 45o to below opercle, more shallowly sloping
to abdomen, then straight or slightly convex across tail.
2ULJLQ RI GRUVDO ÀODPHQW EHIRUH D YHUWLFDO WKRXJK ÀUVW
WKLUG RI DQDOÀQ EDVH DQG RYHU th or 7th caudal vertebra,
GRUVDOÀODPHQWORQJUHDFKLQJRQWRFDXGDOSHGXQFOH/2'
contained 2-3 times in TL, 2-3 times in LEA. Origin of
DQDOÀQEHORZEDVHRISHFWRUDOÀQOHQJWKWRRULJLQRIDQDO
ÀQFRQWDLQHGWLPHVLQ7/WLPHVLQ/($WLPHV
LQ /2' /($FRQWDLQHG  WLPHV LQ 7/ &DXGDO ÀQ
bluntly pointed, small, its length less than snout length,
FDXGDOÀQ UD\V  PRGDOO\  1  3UHFDXGDO
vertebrae 13-15 (N = 14), caudal vertebrae to end of anal
ÀQ1  WRWDOYHUWHEUDHWRHQGRI DQDOÀQ
(N =8). Posteriormost one or two precaudal vertebrae just
DQWHULRUWRWKH ÀUVW FDXGDOYHUWHEUDLH WKDW ZLWKDODUJH
hemal spine and supporting the much enlarged, so-called
)LJ$'LVVHFWHGVSHFLPHQRISternarchella schotti, ANSP 199792, showing enlarged gas bladder (GB) extending beyond abdominal
cavity into tail. B. Cleared and stained specimen of Sternarchella orthos, ANSP 199205, showing the more general condition in
Sternarchella of a small gas bladder (GB) extending less than half the length of the abdominal cavity to level of 7th vertebra.
NEW STERNARCHELLA KNIFEFISH 169
displaced hemal spine) have much reduced or no ribs and
short, distally-broad or split parapophyses.
Lateral line canal high on sides at 5-6 scale rows below
GRUVDO ÀODPHQW FDQDO WHUPLQDWLQJ RQ FDXGDO SHGXQFOH
6FDOHVODFNLQJ RQKHDGGRUVXPDQWHULRUWR FDXGDOHQG RI
GRUVDO ÀODPHQW DQG VLGHV GRUVDO WR SHFWRUDO ÀQ &\FORLG
VFDOHVHQODUJHGRQPLGGOHRIÁDQNVLQFOXGLQJSRUHGODWHUDO
OLQHVFDOHURZ6PDOOHU VFDOHV RQEUHDVWDQG ORZHUÁDQNV
RYHUDQDOÀQPXVFXODWXUH
Head compressed, deeply ovoid in cross section,
smooth and scaleless. HL contained 5-7 times in LEA and
2-3 times in LOD. Head depth at nape contained 6-8 times
in LEA and 1-1.3 times in HL. Snout length contained
3-4 times in HL. Chin slightly projecting. Mouth a little
superior, closed lips meet at a horizontal through middle
or lower half of eye. Mouth small, gape opening anteriorly
and not deeply cleft, maxilla nearly vertical, elongate
and strongly curved, rictus in advance of a vertical at
DQWHULRU QRVWULO -DZ WHHWK VWURQJ EXW VOHQGHU FRQLFDO
with inwardly curved tips, 3-4 symphyseal-tooth rows on
premaxilla and dentary. Lips smooth; a short rictal fold
curving dorsally around end of maxilla. Anterior nostril
behind upper lip on dorsolateral surface of snout, with a
VKRUW ÁHVK\ WXEXODU ULP $QWHULRU DQG SRVWHULRU QRVWULOV
separated by a distance nearly twice that between eye and
posterior nostril. Posterior nostril teardrop shaped, without
D UDLVHG ÁHVK\ ULP (\H VPDOO VXEFXWDQHRXV FHQWHUHG
GRUVRODWHUDOO\ZHOO DERYHPLGKRUL]RQWDOOLQHDQGRQ ÀUVW
third of head length; eye diameter contained 12-22 times in
HL to gill membrane, 3-7 times in snout length, 2-4 times
in interorbital width.
Gill opening restricted as an anteroventrally oblique
VOLW EHIRUH DQG DERYH SHFWRUDOÀQ EDVH *LOO PHPEUDQHV
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*LOO UDNHUV ZLWK GHQVH ÀEHURXV FRYHULQJ  RU  RQ ÀUVW
gill arch.
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ORQJHVWUD\VLQPLGGOHRIÀQDQDOÀQEDVHOHQJWKFRQWDLQHG
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 DQWHULRU XQEUDQFKHG DQDOÀQ UD\V PRGDOO\  1
3HFWRUDOÀQRULJLQ YHQWURODWHUDO RQ VLGHVLPPHGLDWHO\
behind gill opening; leading pectoral rays longest, margin
VFDUFHO\FRQYH[SHFWRUDOÀQOHQJWKDERXWHTXDOWRSRVWRU-
ELWDOKHDG OHQJWKWRWDO SHFWRUDOÀQUD\V ELPRGDOO\
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Urogenital papilla and anus adjacent in both sexes
without visible sexual dimorphism, and positioned far in
DGYDQFHRIDQDOÀQRULJLQEHORZSRVWRUELWDOUHJLRQRIKHDG
between edges of united gill membranes.
&RORUDWLRQ *HQHUDOO\ D SDOOLG VSHFLHV ODFNLQJ EROG
SLJPHQWHG DUHDV IUHVK VSHFLPHQV SLQNLVK ZKLWH )LJ 
those in preservative cream white, yellowish to tan. In
PRVWVSHFLPHQVGRUVXPRIKHDGEDFNDQGXSSHUPRVWVLGHV
peppered with scattered, small chromatophores densest on
PLGOLQH FKURPDWRSKRUHV RQ GRUVDO ÀODPHQW RIWHQ ODUJHU
WKDQRWKHUV(\HVGDUN2YHUDOOFOHDUWREOXLVKWUDQVOXFHQFH
ZKHUHWKLQHVSHFLDOO\GRUVDOÀODPHQWHOHFWULFRUJDQDQGDOO
ÀQPHPEUDQHV(OHFWULFRUJDQYLVLEOHZLWKWUDQVPLWWHGOLJKW
as far anterior as close behind abdominal cavity, deepening
posteriorly, imparting a transparency to most of tail.
Electric organ discharges (EODs) of three S.
calhamazon specimens (ANSP 193098, 193099, 193100)
IURP WKH ZKLWHZDWHU WULEXWDULHV 3XUXV DQG -XUXi DUH
YHU\VLPLODU WRHDFKRWKHU )LJ$&7KH\FRQVLVWRI
triphasic (positive, negative, positive) pulses, each of about
PLOOLVHFRQGVVHSDUDWHGE\D ÁDWEDVHOLQHRI DERXW
)LJ(OHFWULF RUJDQGLVFKDUJH(2' ZDYHIRUP RVFLOORVFRSH
traces, each of 5 millisecond duration, for A-D. Sternarchella
calhamazon (A. ANSP 193100, B. ANSP 193099, C. ANSP
 ' $163  () Sternarchella terminalis (E.
$163  )  * Magosternarchus raptor ANSP
192745, H. Magosternarchus duccis ANSP 192638. Head
positivity upwards. See text for discussion.
170 J.G. LUNDBERG,C.COX FERNANDES,R.CAMPOS-DA-PAZ & J.P. SULLIVAN
milliseconds. The repetition rate is between 772 and 826
+])RU RQHVSHFLPHQ$163IURPWKH ORZHUULR
Negro near the Anavilhanas Archipelago, the EOD has a
similar repetition rate (966 Hz), but the EOD is biphasic,
with “shoulders” on the rising and falling phases.
Distribution and habitat.—Sternarchella calhamazon
is wideranging and common in the large river channels (from
aPGHHSRIWKH$PD]RQ6ROLP}HVPDLQVWHPDQGPDMRU
tributaries from the Pará and Tocantins to Iquitos, and upstream
LQULR1HJURWRDWOHDVWWKHFRQÁXHQFHRIULR%UDQFRDQGLQWKH
ULR0DGHLUDWR DWOHDVWWKH FRQÁXHQFHZLWKUtR %HQL)LJ
This species is expected to occur throughout the lowland rivers
RIWKH$PD]RQ EDVLQ)URP RXUWUDZO FROOHFWLRQVLQ WKHPDLQ
channel of the Amazon river and tributaries, S. calhamazon was
the most abundant gymnotiform species present in 12 of the
13 tributaries sampled, with the Coari being the exception. Its
highest numbers (100s to just >1000) were in the mainstream
RI WKH $PD]RQ VXFK DV EHORZ ULRV -DSXUi DQG 3XUXV DQG
also in tributaries of white Andean waters, such as rios Purus,
0DQDFDSXUXDQG0DGHLUD&R[)HUQDQGHV:LWK
a total catch of just over 5,000 individuals, Sternarchella
calhamazon was about four times more abundant than S.
terminalis, which was also abundant and present in almost
all of our sampling sites. The other three species, S. schotti,
S. sima and S. concave, exhibited 1/50th of the abundance of
S. calhamazon. We are not aware of specimens collected from
YDU]HDODNHVRUVPDOOPDUJLQDOVWUHDPV
Etymology.—The name calhamazon (phonetic
pronounciation CAL-YAH-MAZON) is from the
Portuguese calha for channel plus Amazon, and is the
name given to the 1992-1997 Brazilian-US collaborative
ichthyological inventory of the deep river channels of the
Brazilian Amazon.
DISCUSSION
Albert (2001: 77) proposed two monophyletic
sister-groups within Sternarchella. The “Sternarchella
schotti species-group” (S. orthos,S. schotti,S. terminalis)
recognized on the basis of a “terminal or slightly superior
PRXWK DV DGXOWVµ )LJV $& $OEHUW·V ´Sternarchella
sima species-group” (S. sima>)LJV'@S. curvioperculata
(but see below), “Sternarchella sp. S”, and S. orinoco
IROORZLQJ,YDQ\LVNL>@LVFKDUDFWHUL]HGE\D´YHQWUDO
mouth, a strongly rounded forehead, and large scales, 5-8
above lateral line” (Albert, 2001:77).
%DVHGRQLWVVXSHULRUPRXWK)LJVS. calhamazon
falls into the S. schottiVSHFLHVJURXS7KHIRUHKHDGSURÀOH
of S. calhmazon OLNH WKH RWKHU VSHFLHV LQ WKH S. schotti
VSHFLHVJURXSLVGRUVDOO\FRQYH[ )LJV  $&QRW
“strongly rounded” as noted for the “Sternarchella sima
VSHFLHVJURXSµ)LJV'
Scale size and number, on the other hand, do not
provide informative taxonomic discrimination or phyloge-
netic support for either species group of Sternarchella. As
indicated, species of the S. sima species-group have 5-8
ODUJH VFDOHV DERYH ODWHUDO OLQH DQG ZH ÀQG  VLPLODUO\
large scales in S. calhamazon, 5-6 in S. orthos (see Mago-
Leccia, 1994:85), 6-9 in S. schotti, and 7-9 in S. termina-
lis1RWDEO\KRZHYHURQHRIXV5&3ÀQGVSternarchella
curvioperculata to have 13-14 small scales above lateral
line. Preliminary analysis suggests that this species does
not belong in Sternarchella as delimited herein (to be dis-
cussed elsewhere by RCP). A revision of Sternarchella by
6 ,YDQ\LVN\  LQ - $OEHUW·V ODE SURPLVHV WR VROYH
these and other questions that fall beyond the scope of the
present contribution.
7KHWULSKDVLFZDYHIRUP(2'V)LJ$&RIWKUHH
S. calhamazon specimens from the white water Purus and
-XUXiULYHUVDUHFORVHO\VLPLODUWRRQHDQRWKHUDQGUHVHPEOH
the EODs reported by Turner et al. (2007) for S. terminalis,
and species of Apteronotus and Sternarchorhynchus.
Most of our EOD records for S. terminalis and all
Magosternarchus )LJ  (+ DOVR H[KLELW VLPLODU
triphasic EODs, however the repetition rates for these
species are much faster, i.e. S. calhamazon 772-966 Hz
(mean = 836 Hz, n = 4) vs. S. terminalis 1304-1781 Hz
(mean = 1572 Hz, n = 8) Magosternarchus raptor 1765-
2111 Hz (mean = 1938 Hz, n = 2) and M. duccis 1721-2260
Hz (mean = 1971 Hz, n = 3) between 1400 and 1800 Hz
)LJ(+2XUVLQJOHS. calhamazon specimen from rio
1HJURKDVDQ(2'UHFRUGLQJ)LJ'WKDWLVGLVWLQFWO\
ELSKDVLF7KLV ÀVK LVVPDOO DW PP7/DQGSHUKDSV D
juvenile with an immature waveform. However, the still
smaller Purus specimen (100 mm TL) of S. calhamazon
produced a triphasic EOD. Larger EOD sample sizes
will be needed to search for correlations between EOD
waveforms and variations in age, sex, breeding condition,
habitat or cryptic taxonomic diversity.
Sternarchus capanemae³,Q -XO\  DW D
PHHWLQJ RI WKH $NDGHPLH GHU :LVVHQVFKDIWHQ 9LHQQD
Austria), Steindachner presented a note on the
J\PQRWLIRUP ÀVKHV LH KLV ´*\PQRWLGDHµ LQ WKH ´N
N +RI1DWXUDOLHQFDELQHWHV ]X :LHQµ 7KDW FRQWULEXWLRQ
subsequently published in the “Anzeiger der Kaiserlichen
$NDGHPLH GHU :LVVHQVFKDIWHQµ 6WHLQGDFKQHU D
introduced three previously undescribed species placed
in the nominal genus Sternarchus:S. nattereri (=
Sternarchogiton nattereri), S. capanemae (= Sternarchella
capanemae) and S. mormyrus (= Sternarchorhynchus
mormyrus). Each species’s name, in that paper, was
followed by a succinct diagnosis. Concerning Sternarchus
NEW STERNARCHELLA KNIFEFISH 171
capanemae, its brief diagnosis was based on a single
specimen from the mouth of rio Negro, near Manaus,
Brazil, and mentioned only the somewhat straight dorsal
KHDGSURÀOHZKHQFRPSDUHGWRS. nattereri), and the short
snout and gape in contrast to Sternarchorhynchus mormyrus
(Steindachner, 1868a:176). No additional information was
provided in that paper concerning S. capanemae. In fact,
that was the only place Steindachner ever mentioned that
WD[RQRPLFQDPH$FFRUGLQJ WR% +HU]LJDQG (0LNVFKL
(Naturhistorisches Museum, Vienna; pers. communic. to
RCP), no specimen is labeled as “Sternarchus capanemae
LQWKHÀVKFROOHFWLRQVDWWKH10:6LQFHLWVRULJLQLQ
the name Sternarchus capanemae appeared only once in
the literature, being cited by Albert (2001:126) as a junior
synonym of Sternarchella schotti. No explanation of the
WD[RQRPLFVWDWXVRIWKHQDPHZDVSURYLGHGLQWKDWZRUN
/DWHU6WHLQGDFKQHU ESXEOLVKHGDQRWKHU ZRUN
RQ J\PQRWLIRUP ÀVKHV &XULRXVO\ S. nattereri and S.
mormyrus were again objectively and explicitly indicated as
“new species” within Sternarchus. Their names, however,
were this time associated with more detailed descriptions.
Sternarchus capanemae, however, was not listed by
name in Steindachner’s second paper. Instead, another
new binomen appears to replace S. capanemae, namely,
Sternarchus schotti (between Sternarchus nattereri and
Sternarchus mormyrus; see Steindachner, 1868b:252). The
description of Sternarchus schotti, explicitly based on a
VLQJOHVSHFLPHQÀJXUHGLQ6WHLQGDFKQHUWDEV
conforms well with the shorter one given for S. capanemae
(Steindachner, 1868a). The holotype of Sternarchus schotti
ZDV UHSRUWHGO\ FROOHFWHG E\ - 1DWWHUHU DW ´%DUUD GR ULR
Negro” (mouth of the rio Negro, near Manaus, Brazil) is
currently housed at the NMW (NMW 65335).
According to B. Herzig (pers. comm. to RCP), it
was a common procedure among Viennese naturalists in
6WHLQGDFKQHU·V GD\V WR TXLFNO\ SXEOLVK D VKRUW DFFRXQW
for instance about new species, in the “Anzeiger der
.DLVHUOLFKHQ $NDGHPLH GHU :LVVHQVFKDIWHQµ DQG WKHQ WR
SUHVHQWD PRUHGHWDLOHG ZRUNODWHU LQDQRWKHU MRXUQDO7KDW
seems to be the case for the nominal Sternarchus capanemae
and Sternarchus schotti, meaning that they are objective
synonyms based on the same single specimen (International
Commission of Zoological Nomenclature [ICZN], Art.
61.3.4). In this case, Stiendachner created the later name to
KRQRU+:6FKRWW DERWDQLFDOFRPSDWULRWZKRXQGHUWRRN
expeditions to Brazil in the early 19th century.
$ÀQDOTXHVWLRQHPHUJHVIURPWKHIDFWWKDWSternarchus
capanemae was described earlier in 1868 than Sternarchus
schotti.Sternarchus capanemae should then be treated as
the senior synonym and S. schotti the junior synonym.
However, we note the following clear situations concerning
these names, both explicitly indicated in the current version
of the ICZN: 1) “the senior synonym . . . has not been used
as a valid name after 1899” (Art. 23.9.1.1); and 2) “the
junior synonym . . . has been used for a particular taxon, as
LWVSUHVXPHGYDOLGQDPHLQDWOHDVWZRUNVSXEOLVKHGE\
at least 10 authors in the immediately preceding 50 years
and encompassing a span of not less than 10 years” (Art.
23.9.1.2). Therefore, we recommend and we will apply to
the International Commission of Zoological Nomenclature
for conservation of the species name Sternarchella schotti
Steindacher (1868b). Effective communication about
HOHFWULFÀVKHVRIWKHJHQXVSternarchella is best served by
À[LQJWKHORQJVWDQGLQJXVHRIS. schotti and by rendering
the obsolete name Sternarchus capanemae Steindacher
(1868a) suppressed.
&203$5$7,9(0$7(5,$/(;$0,1('
Magosternarchus duccis, ANSP 173506, 1, 151 mm
7/UtR$PD]RQ
Sternarchella orthos: Venezuela. ANSP 199203, 3,
PP7/UtR2ULQRFR$163
PP7/UtR$SXUH$163 IRUPHUO\'8)
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Sternarchella orinoco9HQH]XHODUtR2ULQRFR$163
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2024) 1 C/S. ANSP 199202, (formerly UAZ 95-154) 1
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Sternarchella schotti: Brazil. ANSP 199792, 2,
173-181 mm TL, rio Amazonas, Lago do Rei. ANSP
199195, 5, 147-179 mm TL, rio Amazonas above rio
Trombetas. MZUSP 6558, 1 C/S, 155 mm TL. Colombia.
)01+  PP7/$PD]RQ5LYHU3HUX
ANSP 84267, 1, 197 mm TL, Ucayali River Basin near
Cantamana.
Sternarchella sima: Brazil. ANSP 199200, 5, 105-142
mm TL, rio Pará below rio Amazonas.
Sternarchella terminalis: Brazil. ANSP 199196, 5,
109-182 mm TL, rio Amazonas above rio Tapajos. ANSP
199197, 3, 119-192 mm TL, rio Pará above rio Tocantins.
ANSP 199198 (formerly UAZ 95-163), 1 C/S, 160 mm
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Leccia and Dr. E. Marsh-Matthews for our detailed and
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systematics of Gymnotiformes with diagnoses of
58 clades: a review of available data. Pp. 419-446.
In: Malabarba, L.R., R.E. Reis, R.P. Vari, Z.M.S. de
Lucena and C.A.S. Lucena (eds) 1998 Phylogeny and
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Alegre. 1-603.
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and phylogeny of the South American Electric
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401-417. In: Malabarba, L.R., R.E. Reis, R.P. Vari,
Z.M.S. de Lucena and C.A.S. Lucena (eds) 1998
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Edipucrs, Porto Alegre. 1-603.
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in the channels of the Amazon River System, Brazil.
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Durham, 394 pp.
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Amazonian ecology: tributaries enhance the diversity
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2009. Oedemognathus exodon and Sternarchogiton
nattereri (Apteronotidae, Gymnotiformes): the
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Proceedings of the Academy of Natural Sciences of
Philadelphia 158:193-207.
Eigenmann, C.H. and D.P. Ward. 1905. The Gymnotidae.
Proceedings of the Washington Academy of Science.
v. 7: 159-188, Pls. 7-11.
Ellis, M.M. 1913. The gymnotoid eels of Tropical America.
Memoirs of the Carnegie Museum 6(3):109-195.
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Sternarchellini (Gymnotiformes: Apteronotidae):
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rivers. Unpublished MSc Dissertation. University of
Louisiana, Lafayette. 78 pp.
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Management. 4 (3):331-334.
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Garcia. 1996. Magosternarchus, a new genus with
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Apteronotidae) from the Amazon River Basin, South
America. Copeia 1996(3):657-670.
corrections and constructive comments on the manuscript;
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generously provided a color photo of the fresh Peruvian
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the Calhamazon Project’s 1993, 1994 and 1996 expedi-
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at MZUSP for laboratory space and collection access.
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Resources, Bureau of Science and Technology, of the U.S.
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(CNPq, Brazilian National Research Council). Permission to
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CNPq. Partial support for this research came from Instituto
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Institution, allowed RCP to travel to NMNH in 2001, to
study part of the Sternarchella under the sponsorship of R.P.
Vari. The “Calhamazon Project” partly supported RCP’s
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examine gymnotiforms including Sternarchella.
The Orinoco Delta Expeditions were supported by
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LITERATURE CITED
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V\VWHPDWLFVRI$PHULFDQ NQLIHÀVKHV*\PQRWLIRUPHV
Teleostei). Miscellaneous Publications, Museum of
Zoology, University of Michigan No. 190: i-vi + 1-127.
$OEHUW -6 DQG :/ )LQN  Sternopygus xingu, a
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Gymnotoidei), with comments on the phylogenetic
position of Sternopygus”. Copeia 1996 (1):85-102.
NEW STERNARCHELLA KNIFEFISH 173
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Adontosternarchus (Gymnotiformes, Apteronotidae).
Los Angeles County Museum of Natural History,
Contributions in Science, No. 359, 19 pp.
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America: 1-206, 16 unnumbered tables.
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Alegre. 2003: i-xi + 1-729.
Sabaj Pérez, M.H. (ed.). 2012. Standard symbolic codes
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and ichthyology: an online reference. Verson 3.0 (23
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www.asih.org/, American Society of Ichthyologists
and Herpetologists, Washington, DC.
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Hof-Naturaliencabinetes zu Wien. Anzeiger der
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177.
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Naturaliencabinetes zu Wien. Sitzungsberichte der
Mathematisch-Naturwissenschaftlichen classe der
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264.
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and G.T. Smith. 2007. Phylogenetic comparative
analysis of electric communication signals in ghost
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of Experimental Biology 210, 4104-4122.
... Despite the high number of fish species described for this region, the fish assemblages that inhabit the bottom depths of the main channels of large tropical rivers are among the least known ichthyofauna due to difficulties obtaining samples from this biotope (Duarte et al. 2019a, b). Thereby, studies performed in this type of environment have often led to the discovery of new taxa and records of rare species (e.g., De Santana & Vari 2012, Lundberg et al. 2013, Walsh et al. 2015. ...
... Significance of individual LCBD values was tested for using the permutation procedure of Legendre & de Cáceres (2013). In addition, for investigating the potential importance of floodplains to benthic fish assemblage of the main channel of whitewater rivers, we categorized species with higher SCBD values into resident or migratory based on some studies of fish diversity, description and record of these species in distinct habitats such as floodplain lakes or adjacent wetlands (e.g., Cox-Fernandes 1997, De Santana & Vari 2012, Lundberg et al. 2013, Duarte et al. 2022. ...
... The family Apteronotidae represented 21 species and Doradidae represented 19 (Table S2). Sternarchella calhamazon (Lundberg, Cox Fernandes, Campos da Paz & Sullivan, 2013) was the most abundant species in the Japurá and Purus rivers, representing 45.7% and 16.3%, of the total collected, respectively. For the Madeira River, the doradidae Opsodoras boulengeri (Steindachner, 1915) was the most abundant species, with 19.2% of the total collected in this river (Table S2). ...
Article
Full-text available
Despite the high number of fish species described for the Amazon region, the ichthyofauna that inhabits the depths of the main channels of large tropical rivers is one of the least known. In order to know the diversity patterns of these fish in whitewater rivers of the Central Amazon, we used data from the main channel benthic fish assemblage of the Japurá, Purus and Madeira rivers and tested the hypothesis that there are marked spatial and seasonal differences in the composition of the fish community among them. For this, we used a multivariate dispersion test, total β diversity and its decomposition into local (LCBD) and species contribution to β diversity (SCBD). Additionally, we tested for relationships between LCBD values and richness, total abundance, and environmental variables. We categorized species with higher SCBD values into resident or migratory to investigate the potential importance of floodplains to benthic fish assemblage of the main channel of whitewater rivers. Our results corroborate the proposed hypothesis, showing that there are seasonal and inter-river differences in benthic ichthyofauna, being more evident for the Purus River. LCBD showed strong negative relationships with species richness and total abundance, particularly in the Japurá and Madeira rivers in rising season, indicating that rivers and season with high uniqueness in their composition also had low richness and abundance. LCBD was negatively correlated with conductivity and pH, which increased with declining these environmental variables, as observed mainly in Japurá River in both seasons. Approximately one third of the species had higher than average SCBD values and were considered major contributors to β diversity, as well as classified as migratory. This demonstrates the importance of conducting studies that use spatial and seasonal variables, in addition to including the background fish fauna in conservation studies, expanding the protected area and taking into account the different patterns of diversity between rivers. Furthermore, these differences in assemblage composition might be explained by the asymmetrical spatial use of habitats during different seasons, strongly suggesting the importance of the flood-pulse cycle for maintaining diversity in this environment.
... Despite the high number of fish species described for this region, the fish assemblages that inhabit the bottom depths of the main channels of large tropical rivers are among the least known ichthyofauna due to difficulties obtaining samples from this biotope (Duarte et al. 2019a, b). Thereby, studies performed in this type of environment have often led to the discovery of new taxa and records of rare species (e.g., De Santana & Vari 2012, Lundberg et al. 2013, Walsh et al. 2015. ...
... Significance of individual LCBD values was tested for using the permutation procedure of Legendre & de Cáceres (2013). In addition, for investigating the potential importance of floodplains to benthic fish assemblage of the main channel of whitewater rivers, we categorized species with higher SCBD values into resident or migratory based on some studies of fish diversity, description and record of these species in distinct habitats such as floodplain lakes or adjacent wetlands (e.g., Cox-Fernandes 1997, De Santana & Vari 2012, Lundberg et al. 2013, Duarte et al. 2022. ...
... The family Apteronotidae represented 21 species and Doradidae represented 19 (Table S2). Sternarchella calhamazon (Lundberg, Cox Fernandes, Campos da Paz & Sullivan, 2013) was the most abundant species in the Japurá and Purus rivers, representing 45.7% and 16.3%, of the total collected, respectively. For the Madeira River, the doradidae Opsodoras boulengeri (Steindachner, 1915) was the most abundant species, with 19.2% of the total collected in this river (Table S2). ...
... Fish assemblages that inhabit the bottom depths of the main channels of large tropical rivers are among the least known ichthyofauna due to difficulties obtaining samples from this biotope. Studies performed in this type of environment have often led to the discovery of new taxa and records of rare species (Lundberg and Mago-Leccia 1986;Lundberg and Rapp Py-Daniel 1994;Lundberg et al. 1996Lundberg et al. , 2013Ribeiro and Rapp Py-Daniel 2010;de Santana and Vari 2012;Walsh et al. 2015). The ichthyofauna in such environments is composed primarily of benthic fishes (that live at or near the bottom; cf. ...
... In our analysis, the highest number of indicator species was found in the Apteronotidae family (19 species), which did not show a specific depth preference. Lundberg et al. (2013) observed that S. calhamazon, of the Family Apteronotidae, occurs at depths ranging from ,2 to 30 m. This species is one of the most abundant species found in samples from the bottom of the main channel collected from the Amazon Basin, as well as in our samples from the Purus River. ...
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Studies of fish assemblages have demonstrated that the main channels of rivers contain ichthyofauna adapted to this environment. However, information regarding the effects of temporal and spatial variations on this ichthyofauna is scarce. Using data from benthic fish assemblages in a major tributary of the Amazon basin collected during two consecutive receding and two rising water seasons, we tested the hypothesis that there are marked variations in community composition between the receding and rising water seasons. An asymmetry in predictability was detected among samples from the receding and rising seasons. Predictability in terms of species composition was higher for receding than rising seasons. The continual disassembly and reassembly cycles (due to dispersal) of local communities across a spatially heterogeneous landscape could explain this difference. Depth and dissolved oxygen affected the distribution of some benthic fish species during the rising seasons. This study highlights the important contribution of marginal wetlands to the benthic ichthyofauna inhabiting the main channel of the Purus River, as well as other major Amazonian rivers.
... below 250 m elevation) of the Neotropical realm . However, many of these species inhabit remote or largely inaccessible and difficult habitats to reach or sample, and these species′ largely cryptic and nocturnal behaviour makes most gymnotiform fishes difficult to collect on a large scale without using specialist equipment and careful planning Lundberg et al. 2013;Haag et al. 2019). Therefore, gymnotiform fishes have become chronically underreported in most published regional inventories and databases and underrepresented in museum collections (Albert and Reis 2011). ...
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Gymnotiform electric knifefishes are an important yet undersampled component of the Neotropical aquatic biota. We report on the gymnotiform fauna of the Tres Fronteras region located at the triple border of Brazil, Colombia, and Peru in the biodiverse western Amazon. The presence of at least 33 species of gymnotiforms in the Tres Fronteras region is validated from recent sampling efforts and the review of previously collected materials. A key is provided for the identification of the species that have been collected from the region. We comment on the diversity of habitat utilization and intraspecific colour variation of some species.
... asynchrony, benthic fish assemblages, diversity, seasonal, species abundance distributions to the difficulty of obtaining samples from bottom rivers habitats (Cox-Fernandes et al., 2004;Duarte, Espírito-Santo, et al., 2019;Duarte, Magurran, et al., 2019;Thomé-Souza & Chao, 2004). The few studies from this environment have shown that local diversity is very high, underpinned by a small number of very abundant species and many rare species (Albert & Reis, 2011;Duarte, Espírito-Santo, et al., 2019), including several taxa new to science (de Santana & Vari, 2012;Lundberg et al., 2013;Ribeiro & Rapp Py-Daniel, 2010;Walsh et al., 2015). Indeed, studies that seek to identify the species inhabiting a particular environment and the factors that affect their dynamics are fundamental for future management programmes and conservation (Magurran & Dornelas, 2010), as anthropogenic activities, including overexploitation, habitat loss, and climate change, are currently causing profound transformations in ecosystems and unprecedented loss of biological diversity (Frederico et al., 2021;Magurran & Dornelas, 2010;Röpke et al., 2017;Tedesco et al., 2013). ...
Article
1. The seasonality of tropical rivers, induced mainly by water level changes, shapes many interrelated aspects of ecological communities and the populations they contain, including animal movement, feeding, growth, and reproductive activity. However, the role played by seasonality in structuring the diversity of tropical assemblages is not yet fully understood. 2. We examined the effects of seasonality on community structure and composition of benthic fish assemblages comparing two consecutive receding and rising water seasons in a major tributary of the Amazon basin. We quantified seasonal shifts in species abundance distributions and in composition using a multivariate dispersion test, total β diversity and its decomposition into local (LCBD) and species contribution to β diversity (SCBD). Additionally, we tested for relationships between LCBD values and richness, total abundance, and environmental variables. 3. Many benthic fish species were rare in terms of numerical abundance. Rarity was most pronounced in the rising seasons, which had a higher proportion of singletons. A logseries was the best-fit model for both the receding and one of the rising season's species abundance distributions, while a lognormal was selected for the second rising season. We detected variation in species composition between seasons—the rising seasons were distinct from one another in terms of species composition, as well as differing from the receding seasons. LCBD showed strong negative relationships with species richness and total abundance, particularly in the rising seasons, indicating that seasons with high uniqueness in their composition also had low richness and abundance. LCBD was negatively correlated with temperature, while depth presented a positive relationship, as observed mainly in rising seasons with colder temperatures and greater water depth. Approximately one third of the species had higher than average SCBD values and were considered major contributors to β diversity. 4. These significant seasonal differences in both species relative abundances and assemblage composition might be explained by the asymmetrical spatial use of habitats during different seasons, strongly suggesting the importance of the flood–pulse cycle for maintaining diversity in this environment. 5. Studies that seek to identify the species inhabiting a particular environment (e.g. bottom rivers habitats) and the factors that affect the dynamics, structure and composition of these communities are fundamental for future management and conservation. This is particularly urgent for understudied tropical freshwater ecosystems, as human pressures including anthropogenic climate change are expected to become increasingly severe. Rising temperatures and changing precipitation patterns modify water temperature and flow regimes, thus affecting the hydrologic regime that determines the structure and dynamics of the ecological communities, with potential consequences for their integrity.
... Meristic data for species in Apteronotus and other Gymnotiformes genera were taken by direct examination and/or from the literature (Albert, 2001;Bernt & Albert, 2017;Bernt et al., 2018Bernt et al., , 2020Campos-da-Paz, 1995, 1999Evans et al., 2017a;Fernández-Yépez, 1968;Hulen et al., 2005;Hilton et al., 2007;Hilton & Cox Fernandes, 2017;Lundberg et al., 2013;Mago-Leccia, 1994;Maldonado-Ocampo et al., 2011;de Santana, 2002de Santana, , 2003, 2005de Santana & Cox Fernandes, 2012;de Santana & Lehmann, 2006;de Santana & Crampton, 2007, 2010, 2011de Santana & Vari, 2009, 2010Schultz, 1949;Steindachner, 1881;Triques, 2011;. ...
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A new species of ghost knifefish, Apteronotus, is described from high‐energy environments in the Rios Mapuera and Trombetas (at Cachoeira Porteira waterfalls), Brazil. X‐ray microcomputed tomography (μCT scan) was used to access the internal anatomy of the type series. The new species is distinguished from all congeners by the anteriormost position of the anus, with its posterior margin extending less than one eye diameter beyond the vertical through the caudal limit of the posterior nostril, the low number of anal‐fin rays (117–125) and the reduced number of branchiostegal rays (three). A series of modifications associated with secondary sexual dimorphism on the preorbital region of mature males are depicted and discussed. In addition, comments on homologies of the branchiostegal rays in Apteronotidae are provided.
... Apteronotids range from Panama to northern Argentina, and are most diverse in the Amazon basin with at least 40 species in 13 genera. Deep-river channels are challenging to sample, but extensive benthic trawling efforts by Lundberg and colleagues (Lundberg et al., 1996;Lundberg et al., 2013) and Crampton (e.g. Crampton, 1996, 1998, 2007de Santana & Crampton, 2006, 2007, 2010 have contributed to the description of many new apteronotids in the past 20 years. ...
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We describe Melanosternarchus amaru as a new genus and species of Apteronotidae from the deep channels of blackwater and clearwater tributaries of the Amazon River in Brazil and Peru. The new species superficially resembles members of the widespread “Apteronotus” bonapartii species group, from which it can be readily distinguished by expanded bones of the infraorbital laterosensory canal. It can further be distinguished from all other apteronotids by a unique combination of characters: reduced premaxillary dentition, a large gape, and an absence of scales from the entire dorsum. A molecular phylogenetic analysis using three mitochondrial loci and one nuclear locus (~3000 bp) places this genus as sister to Compsaraia, and these two genera together as a clade sister to Pariosternarchus; all nodes with strong statistical support. The clade formed by these three genera includes five species, four of which are restricted to the Amazon basin. The apparent habitat preference of the new species for low-conductivity blackwater and clearwater rivers has not been reported in other apteronotid species.
... The goal of the project was to document the diversity of deep-channel fishes of the Amazon (Cox Fernandes et al., 2004). This endeavor, called the Calhamazon Project, collected thousands of specimens of electric fishes, including several new species within Apteronotidae (Lundberg et al., 1996(Lundberg et al., , 2013Lundberg and Cox Fernandes, 2007). Several additional new apteronotid species (also collected during the Calhamazon Project) were described from separate collections made by William Crampton (1996) from the Central Amazon near Tefé de Santana and Crampton, 2006, 2007de Santana and Vari, 2010). ...
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The deep channels of large rivers throughout the humid Neotropics are occupied by diverse and abundant assemblages of electric knifefishes. Historically this habitat has been poorly sampled, but extensive benthic trawling efforts in the Brazilian Amazon in the 1990s produced large numbers of electric fishes especially in the family Apteronotidae. A large number of these specimens, initially identified as Porotergus, have been found to belong within Compsaraia, a genus with two species described from the Orinoco and western Amazon. From this material we describe a new species, from the Amazon River in Brazil, and provide a new diagnosis for the genus. This species is readily distinguished from congeners by a short, rounded snout and small, subterminal mouth with reduced dentition. This species inhabits large rivers in the Eastern and Central Amazon between Ilha Grande de Gurupá and the mouth of the Rio Içá. This description brings the total number of valid apteronotid species to 95. © 2017 by the American Society of Ichthyologists and Herpetologists.
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The present study reviews the records of occurrences of fish species found in the Mamirauá Sustainable Development Reserve (MSDR). The reserve is located in a large section of the middle Solimões River basin, in its interflow with Japurá River. For the elaboration of the list of fish species occurring in Mamirauá Reserve, we used a database of different studies on fish communities carried out in the area over the last three decades, in addition to the material deposited in the ichthyological collections of three scientific institutions, the National Institute for Amazon Research - INPA, the Mamirauá Sustainable Development Institute - IDSM and the Science and Technology Museum of the Catholic University of Rio Grande do Sul - PUCRS. The ichthyofauna of the MSDR is composed of 541 species, encompassing 45 families and 15 orders. These correspond to 20% of all valid species known for the entire Amazonia so far. As observed in other studies in the Neotropical Region, the more represented orders were Siluriformes (209 species) and Characiformes (185 species), followed by the Gymnotiformes (78 species). The results presented here demonstrate a considerable increase (86%) in the knowledge about the fish diversity found in Mamirauá Reserve, in relation to its first list of fish species, published in the 90's. This increase reflects not only the growth in number of studies on fish diversity in the area, with new surveys, but also the continuous taxonomic work on the collections, and descriptions of twenty-eight new species, with one hundred and ten type series. Further surveys are expected to take place in the Northwestern, more isolated areas of the Reserve, and will allow the identification of new occurrences, and may even unveil new fish species yet to be described to Science..
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We provide a general compilation of the diversity and geographical distribution of Amazonian fishes, updated to the end of 2018. Our database includes documented distributions of 4214 species (both Amazonian and from surrounding basins), compiled from published information plus original data from ichthyological collections. Our results show that the Amazon basin comprises the most diverse regional assemblage of freshwater fishes in the world, with 2716 valid species (1696 of which are endemic) representing 529 genera, 60 families, and 18 orders. These data permit a view of the diversity and distribution of Amazonian fishes on a basinwide scale, which in turn allows the identification of congruent biogeographical patterns, here defined as the overlapping distributions of two or more lineages (species or monophyletic groups). We recognize 20 distinct distributional patterns of Amazonian fishes, which are herein individually delimited, named, and diagnosed. Not all these patterns are associated with identifiable geographical barriers, and some may result from ecological constraints. All the major Amazonian subdrainages fit into more than one biogeographical pattern. This fact reveals the complex history of hydrographical basins and shows that modern basin-defined units contribute relatively little as explanatory factors for the present distributions of Amazonian fishes. An understanding of geomorphological processes and associated paleographic landscape changes provides a far better background for interpreting observed patterns. Our results are expected to provide a framework for future studies on the diversification and historical biogeography of the Amazonian aquatic biota.
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A new group of predaceous apteronotid electric fishes is described from recent trawl collections made in large, white- and black-water river channels of the Amazon Basin in Brazil. Magosternarchus, n. gen., is diagnosed by greatly enlarged jaws and teeth. The type species, Magosternarchus raptor, n. sp., possesses uniquely enlarged premaxillary bones and an associated hypertrophied mesethmoid. Magosternarchus duccis, n. sp., is unique in its strongly projecting lower jaw that includes and often extends dorsal to the upper jaw and snout. The only identifiable stomach contents in specimens of both species of Magosternarchus are tails of other gymnotiform fishes. Shared features of the ethmoid and jaw bones, mesopterygoid, opercle, gillrakers, basibranchials, and infraorbital laterosensory canal suggest that Magosternarchus is most closely related to Sternarchella. /// Um novo grupo de peixes elétricos predadores, capturados recentemente com redes de arrasto, é descrito proveniente de canais de rios da Bacia Amazônica Brasileira. Magosternarchus, gen. nov., é diagnosticado pela presenca de dentes e de mandíbulas bem desenvolvidas. A espécie tipo, Magosternarchus raptor, sp. nov., possui umã expans ão dos premaxilares associada ao mesetmóide hipertrofiadã que é única entre os peixes elétricos. Magosternarchus duccis, sp. nov., é diferenciado por apresentar a mandibula inferior prolongada, a qual se extende dorsalmente sobre a mandibula superior e o focinho. O único material identificado no conteúdo estomacal dos especimens das duas espécies de Magosternarchus foram elementos das nadadeiras caudais e das vértebras de outros peixes elétricos. Caracteres comuns relativos aos ossos etmóide e das mandíbulas, mesopterigóide, opérculo, rastros branquiais, elementos do basibranquial e canal do infraorbital sugerem que Magosternarchus é filogeneticamente mais próximo do gênero Sternarchella.
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