Gymnotus rostratus Linnaeus, 1766:428 Bloch, Schneider, 1801:522 Rhamphichthys rostratus (Linnaeus, 1766) Gymnotus longirostratus Lacepède, 1800:145 Rhamphichthys blochii Kaup, 1856:133 Rhamphichthys reinhardti Kaup, 1856:132 Rhamphichthys schneideri Kaup, 1856:136 Rhamphichthys schomburgki Kaup, 1856:135 A taxonomic review of the Neotropical electric fish Rhamphichthys (Gymnotiformes: Rhamphichthyidae) Carvalho, Tiago P. Albert, James S. Neotropical Ichthyology 2023 e 230012 2023-12-11 21 4 1 76 4S2HN (Linnaeus, 1766) Linnaeus 1766 [723,1224,1123,1147] Rhamphichthyidae Rhamphichthys Animalia Gymnotiformes 54 55 Chordata species rostratus  ( Fig. 49–60; Tab. 10)     Gymnotus rostratusLinnaeus, 1766:428(original description, type-locality: America). —  Bloch, Schneider, 1801:522(illustrated).   Rhamphichthys rostratus(Linnaeus, 1766). —Müller, Troschel, 1849: (new combination). —Kaup, 1856:135 (redescription). —Steindachner, 1868:8 (redescription). —Günther, 1870:5 (redescription). —Eigenmann, Ward, 1905:168 (listed). Ihering, 1907:279 (redescription and key). —Ellis, 1913:137; fig.1 (redescription, feeding and skull illustration). —Santos et al., 1984:19 (illustrated and briefly described). —Planquette et al., 1996:400–01 (illustrated, briefly described and distribution in French Guiana). —Frery et al., 2001:453 (mercury contamination). —Maldonado-Ocampo, Albert, 2003:157(listed). —Santos et al., 2004:106 (illustrated and briefly described). —Lasso et al., 2004 (listed). —Lucinda et al., 2007:81 (listed). —Montag et al., 2009:246 (listed). —Vari et al., 2009:46 (listed). —Ortega et al., 2011:41 (listed). —Mol et al., 2012:277 (listed). — Carvalho, Albert, 2015:40(Comparative material examined). —Tagliacollo et al., 2016:29, fig. 5 (phylogenetic relationships). —Ferraris et al., 2017:28 (listed). —DoNascimiento et al., 2017:66 (listed). —Giora, Carvalho, 2018:1060 (accessory electric organ anatomy). —Janzen et al., 2022: tab. 1 (Barcode library). —Taphorn et al., 2022:40 (listed).   Gymnotus longirostratusLacepède, 1800:145, 178 (original description, type-locality: South America).   Rhamphichthys blochii Kaup, 1856:133, fig. 9 (original description: type-locality: No locality stated. Holotype: ZMB 4089). —Günther, 1870:5 (redescription).   Rhamphichthys reinhardti Kaup, 1856:132, fig. 8 (original description: type-locality: No locality. Holotype: MNHN 3956). —Eigenmann, Ward, 1905:169 (listed).   Rhamphichthys schneideri Kaup, 1856:136, fig. 11 (original description: type-locality: Cayenne. Holotype: MHNH 3957).   Rhamphichthys schomburgki Kaup, 1856:135, fig. 10 (original description: type-locality: Rivers of Demerara, British Guiana. Holotype: MNHN 3958). —Steindachner, 1868:10 (redescription).   Diagnosis.  Rhamphichthys rostratusdiffers from all congeners by a greater number of caudal vertebrae (111–117), vs.lower number of vertebrae (90–109).  Rhamphichthys rostratusalso differs from all congeners, except from  R. apurensis, by a longer snout (58.8– 65.1% of HL), vs. shorter snout (46.4–59.1% of HL), and a longer caudal appendage (18.4–35.6% of LEA), vs.shorter caudal appendage (5.8–20.3% of LEA; except in  R.  pantherinus, 9.1–28.8 %).  Rhamphichthys rostratusfurther differs from all congeners except  R. apurensisand  R. pantherinusby the intercalated pattern of the saddles on the mid dorsum, vs.a sickle shaped or absence of saddles.  Rhamphichthys rostratustypically has darkly pigmented distal ends of the anal fin rays, forming a longitudinal stripe ( Fig. 61), vs.anal fin varying in pigmentation but not forming a distal darkened stripe.   Description.Morphometrics and meristics given in Tab. 10. Adult body size large as compared with other congeners, maximum size 850 mmLEA, maturing at about  420–460 mmLEA. Mouth subterminal. Snout very long, more than half of head length. Dorsal profile of snout strongly concave in front of eye, head profile slightly convex posteriorly. Anterior nares positioned terminally; posterior nares located closer to snout than eyes at about one fourth of length. Body profile almost straight to slightly concave dorsally. Ventral body profile slightly concave from anal–fin origin to end of anal fin. Greatest body depth slightly posterior to end of body cavity. Body tapering posterior to mid body. Eyes small, positioned laterally. Urogenital papilla developed and anteriorly positioned below eyes in specimens larger than 400 mmLEA. Urogenital papilla small. Posterior gas bladder small and membranous in between viscera. Caudal appendage long, laterally compressed, its depth about three times its width.   FIGURE 49 |Linear regression of  Rhamphichthys pantherinuspopulations. Blue circles = Amazon Basin (open circle = holotype of  R. pantherinus); red circles = Mearim System (open circle = holotype of  R. atlanticus); black circles = Trombetas basin (open circle = holotype of  R. longior).   FIGURE 50 |Scatter plots of PCA scores. A.PC 1 vs. PC 2; B.PC 1 vs.PC 3. PCA of  Rhamphichthys pantherinusgeographic populations: Red = Amazon; blue = Mearim (including  R. atlanticusholotype); pink = Negro; golden = Tocantins (type-locality of  R. marmoratus); brown = Tombetas (including types of  R. longior); yellow = western Amazon (including  R. pantherinusholotype) and grey = Xingu.   TABLE 10 |Morphometric and meristic data for  Rhamphichthys rostratus. H1= holotype of  Rhamphichthys reinhardti; H2 = holotype of  R. schneideri; H3 = holotype of  R. schomburgki; H4 = holotype of  R. blochii; SD = standard deviation; n = number of specimens.     H1  H2  H3  H4  n  Range  Mean  SD  Length to end of anal fin (LEA) 600 630 700 510 32 270–700 446.9 –   Percents of LEA  Anal-fin length Body depth Pectoral-fin length Head length Caudal filament length Caudal filament depth 90 6.6 4.1 12.4 18.5 1.8 88.9 8.9 4.7 14.0 23.8 1.9 87.5 8.1 3.6 15.7 – 1.4 94.1 8.6 5.3 15.9 23.3 1.5 32 32 32 32 26 32 80.6–94.1 6.1–8.9 3.7–5.6 12.4–15.9 18.4–35.6 1.0–3.0 88.2 7.6 4.8 14.3 26.6 2.0 2.4 0.6 0.5 0.9 4.9 0.4   Percents of head length  Interorbital distance Snout length Postorbital length Eye diameter Post. nares length Branchial opening 10.3 60.7 36.8 4.4 13.3 – 9.7 63.2 36.3 3.4 13.2 15.8 8.1 65.1 34.1 2.9 12.4 12.6 9.3 60.3 37.2 3.7 – 15.5 32 32 32 32 31 31 8.1–12.5 58.8–65.1 33.1–38.2 2.9–5.8 12.5–18.4 12.6–19.6 9.7 62.3 35.6 4.4 14.8 16.0 0.9 1.2 1.1 0.6 1.2 1.6   Meristics  Anal-fin rays Pectoral-fin rays 405 18 403 19 417 22 394 21 28 32 365–455 17–39 400.0 62.9 22.7 119.3 Body entirely covered by scales in adults, anterior and dorsal areas naked in juveniles. Scales cycloid elongate in shape posteriorly, length twice as depth. Lateral line complete with ossified tubules, anterior portion of presenting ventral rami. Pectoral fin with 17–22 (mode 18) rays, dorsal rays longer than ventral rays, distal fin margin slightly rounded. Anal fin with 365–455 (median 395) rays. Unbranched 17–34 anal–fin rays in the anterior portion of the anal fin. Anal–fin origin at vertical of anterior portion of opercle. Precaudal vertebrae 19–20 ( Tab. 5). Vertebrae to end of anal fin 111–117 ( Tab. 5). Displaced hemal spines 13–15 (n = 2). Sexual dimorphism unknown.  Coloration in alcohol.Ground color of dorsal and lateral surfaces of head and body yellow to dark brown ( Figs. 51–62). Head with scattered dark brown blotches of about eye size; snout mostly dark, ventral margin less pigmented. Body presenting dark intercalated saddles, these reaching ventrally the lateral line. Presence of dark lateral pigment bands, slightly diagonally placed along the long axis of the body. Bands sometimes contacting the dorsal saddles; bands diffuse over the pterygiophore region, extending to the proximal region of the anal fin rays. Anal fin mostly clear except for distal portion dark. Pectoral fin clear with broad dark bars. Caudal appendage with dark vertically elongate blotches.   FIGURE 51 |  Rhamphichthys rostratus, ANSP187120, 520 mm LEA, Lawa Lawa River Cataract west of base camp 8 km W of Anapaiake, Sipaliwini, Suriname.   FIGURE 52 |Detail of head of  Rhamphichthys rostratus, ANSP187120, 520 mm LEA, Lawa Lawa River Cataract west of base camp 8 km W of Anapaiake, Sipaliwini, Suriname.   FIGURE 53 |  Rhamphichthys rostratus, holotype of  Rhamphichthys blochii, ZMB4089, 510 mm LEA, South America.   FIGURE 54 |  Rhamphichthys rostratus, holotype of  Rhamphichthys blochii, ZMB4089, 510 mm LEA, South America.   FIGURE 55 |  Rhamphichthys rostratus, holotype of  Rhamphichthys reinhardti, MNHN3956, 600 mm LEA, Brazil.   FIGURE 56 |Detail of the head of  Rhamphichthys rostratus, holotype of  Rhamphichthys reinhardti, MNHN3956, 600 mm LEA, Brazil.   FIGURE 57 |  Rhamphichthys rostratus, holotype of  Rhamphichthys schneideri, MNHN3957, 700 mm LEA, Cayenne, French Guiana.   FIGURE 58 |Detail of the head of  Rhamphichthys rostratus, holotype of  Rhamphichthys schneideriMNHN3957, 700 mm LEA, Cayenne, French Guiana.   FIGURE 59 |  Rhamphichthys rostratus, holotype of  Rhamphichthys schomburgki, MNHN3958, 700 mm LEA, Demerara, Guyana.   FIGURE 60 |Detail of the head of  Rhamphichthys rostratus, holotype of  Rhamphichthys schomburgkiMNHN3958, 700 mm LEA, Demerara, Guyana.   FIGURE 61 |  Rhamphichthys rostratus, ANSP182428, 445 mm LEA, fisherman catch purchased from canoe in Belen, Iquitos, reportedly from Lower Río Itaya, Loreto, Peru.   FIGURE 62 |Detail of the head of  Rhamphichthys rostratus, ANSP182428, 445 mm LEA, fisherman catch purchased from canoe in Belen, Iquitos, reportedly from lower Río Itaya, Loreto, Peru.  Geographical distribution.  Rhamphichthys rostratusis known from the Amazon, Essequibo, Tocantins, and coastal river of Guianas basins ( Fig. 63; Tab. 1). It inhabits river channels of medium to large size rivers. It is also found in flooded forest and oxbow lakes.  Ecological notes.Adult specimens of Wismar Guyanaare reported to feed on mud-inhabiting worms and insects, including annelids, dipteran larvae, and gyrinid amphipods (Ellis, 1913:173).   Remarks on synonym and geographic variation.The synonyms of  Rhamphichthys rostratuswere proposed by several authors (see introduction) and were established by Mago-Leccia (1994). After examining Kaup’s (1856)  Rhamphichthys typematerial we concur to this extensive synonymization. A PCA was done using geographic populations of  R. rostratusand little geographic variation on morphometrics was observed between Amazon, Negro and Guianas populations. The first three principal components (PC 1, PC 2 and PC 3) explain most of the variance (75.3%; Tab. S10). Scores were plotted for PC 1 vs.PC 2 and show large morphometric overlap of geographic populations of  R. rostratus( Fig. 62). Strong loadings separating some of these groups are the interorbital standard length (SL), anal fin length; preorbital length ( PR), pectoral–fin length (PFL); branchial opening (BO) and Eye diameter (BD) (Tab. S11). A Multivariate Analyses of Variance (MANOVA) was done using the PC scores of the first three axes of the PCA. Populations of  R. rostratusfrom Amazon marginally differs statistically from Guianas and Negro basin (Tab. S12; Wilks’ λ: 0.3435; P<0.001; F6,48 = 5.651).  Remarks.The typeof  Gymnotus rostratusis lost (Mago-Leccia, 1994; Ferraris, 2003). Although Linnaeus’ 1766 description of  R. rostratusis very brief and too superficial to distinguish between different species of the genus,  R. rostratusis the only species in the genus inhabiting Surinamese rivers (Mol et al., 2012), the likely type-locality of this species ( Albert, Crampton, 2003).   Material examined. ZMB4089 holotypeof  Rhamphichthys blochiiAmerica. MNHN3956, holotypeof  Rhamphichthys reinhardti, cabinet d’ajuda, probably Amazon basin in Brazil.  Essequibo: UMMZ216489, 1, Guyana, Essequibo River at opposite side of Bartica, 06º24’N 58º35’W. Guianas: ANSP187119, 1 ( 1 specimenmeasured in Tab. 10, 580 mm LEA), Suriname, Sipaliwini, Lawa Lawa river Cataract west of base camp 8 kmwest of Anapaiake. FMNH53293, 1, Guiana, Demerara River at Wismar. ANSP187120, 1 ( 1 specimenmeasured in Tab. 10, 520 mm LEA), Suriname, Sipaliwini, Lawa Lawa river, Cataract west of base camp 8 kmW of Anapaiake, 03º19’31”N 54º03’48”W, 18 Apr 2007. J. Lundberg, M. Sabaj, P. Willink, J. Mol et al. MHNG2316.17, 1, French Guiana, Antecome Pata upper Maroni. MHNG2117.007, 1, Suriname, Sipaliwini, Tapahony River Kumaru Konde Sula, 03º21’N 55º25’W. MNHN3957, holotypeof  Rhamphichthys schneideri, French Guyana, Cayenne. MNHN3958, holotypeof  Rhamphichthys schomburgki, Guyana. MNHN1998.1569, 1, Suriname, Oulemoni, 03º08’N 54º26’W. MNHN2000.5923, 1 ( 1 specimenmeasured in Tab. 10, 270 mm LEA), French Guyana, Maroni, St. Laurent du Maroni, Antecume Pata, camp nivree, rapids in the main channel upstream the village, 03º18’N 54º05’W. MNHN2001.2291, 1 ( 1 specimenmeasured in Tab. 10, 420 mm LEA), French Guyana, Litany, Saint Laurent du Maroni, port of d’antecume pata. MNHN2002.816, 1 ( 1 specimenmeasured in Tab. 10, 670 mm LEA, French Guyana, Litany, St. Laurent du Maroni, Waterfall Alimina-Emen. USNM225654, 1, Suriname, Nickerie, Mataway creek approximately 8 kmfrom its intersection with Corantijn River, 04º47’N 57º45’W. ZMB6433, 1, Suriname, Maroni. Rio Negro: ANSP189560, 1, Brazil, Amazonas, rio Jauaperi 9.2 km above confluence with rio Negro, 01º35’08”S 61º28’35”W. AUM43333, 1, Venezuela, Amazonas, Río Casiquiare at mouth of Caño Caripo 36 kmWSW of La Esmeralda, 03º06’48”N 65º52’40”W. FMNH115524, 1, Brazil, Amazonas, Manaus, rio Negro between tributaries igarapé Taruma-Mirim and rio Solimões, 03º07’36”S 60º07’55”W. INPA4428, 2 ( 2 specimensmeasured in Tab. 10, 480–510 mm LEA(Brazil, Amazonas, Manaus, rio Negro near Manaus. MCP26285, 1, Brazil, Amazonas, rio Jauaperi 9.6 miles upstream São Francisco, 01º34’46”S 61º28’38”W. MCP26286, 2, Brazil, Amazonas, rio Negro about 9.6 miles downstream Novo Caioe, 01º41’13”S 61º29’02”W. MCP27756, 23 ( 5 specimensmeasured in Tab. 10, 380–450 mm LEA, 1 cs), Brazil, Amazonas, rio Negro 15 milesdownstream Moura, 01º33’28”S 61º34’15”W. MCNG37875, 1, Venezuela, Amazonas, Río Casiquiare at Isla Cuamate downstream Caño Solano, 02º00’N 66º57’W. MZUSP32217, 1, Brazil, Amazonas, rio Negro downstream mouth of rio Daraá, 00º28’S 64º46’W. MZUSP32220, 1, Brazil, Amazonas, rio Arira tributary to rio Negro, 00º31’S 63º33’W. MZUSP32223, 1, MZUSP32230, 1, Brazil, Amazonas, rio Negro at Anavilhanas, 02º42’S 60º45’W. MZUSP32231, 1, Brazil, Amazonas, rio Negro at mouth of rio Urubaxi, 00º31’S 64º50’W. MZUSP32232, 1, Brazil, Amazonas, rio Negro in flooded forest at São Gabriel da Cachoeira, 00º07’S 67º05’W. MZUSP32233, 1, Brazil, Amazonas, flooded forest near confluence of rio Negro and rio Marauiá, 00º24’S 65º12’W. MZUSP91650, 1, Brazil, Amazonas, rio Uapés. MZUSP92251, 1 ( 1 specimenmeasured in Tab. 10, 330 mm LEA), Brazil, Amazonas, São Gabriel da Cachoeira, igarapé Curuni 500 mbelow port of comunidade São José II, tributary to rio Tiquié, 00º13’N 69º36’W. MZUSP93446, 1 ( 1 specimenmeasured in Tab. 10, 530 mm LEA), Brazil, Amazonas, São Gabriel da Cachoeira, rio Tiquié near comunidade Serra do Mucura, 00º10’S 69º07’W. USNM, 373070, 1, Brazil, Amazonas, rio Negro 5.6 km below São Francisco, 01º42’22”S 61º24’27”W. Amazonas Lowlands. ANSP182428, Peru, Loreto, fisherman catch purchased from canoe in Belen, Iquitos, reportedly from lower Río Itaya, 03º45’S 73º25’W. ANSP189533, 1, Brazil, Amazonas, rio Amazonas, 162 kmdownriver Manaus, 31 kmupstream Itacoatiara, 03º15’36”S 58º34’12”W. ANSP189552, 2, Brazil, Amazonas, rio Madeira 4.7 km downstream from Rosarinho and 17.9 km from vila Urucurituba 03º39’17”S 59º03’27”W. ANSP189555, 1 ( 1 specimensmeasured in Tab. 10, 370 mm LEA), Brazil, Amazonas, rio Solimões downstream rio Juruá mouth 21.5 km downstream Tamanicoa, 02º34”38’S 65º30’11”W. ANSP189556, 1, Brazil, Amazonas, rio Solimões 9 kmupstream Santo Antonio do Içá, 03º08’53”S 67º53’29”W. ANSP189558, 1, Brazil, Amazonas, rio Juruá 9.2 km of Pauapixuna, 02º40’54”S 65º48’57”W. ANSP189559, 1 ( 1 specimenmeasured in Tab. 10, 375 mm LEA), Brazil, Amazonas, rio Solimões 45.9 km downstream of Codajás and 18.2 km upstream of Anori, 03º52’21”S 61º42’49”W. CAS36690, 1, Peru, Loreto, Caño del Chancho near Pebas, 03º20’S 71º51’W. FMNH114680, 1( 1 specimenmeasured in Tab. 10, 340 mm LEA), Brazil, Amazonas, rio Solimões between tributaries rio Japurá and lago Caimbe, 03º19’32”S 64º32’18”W. FMNH114682, 3, Brazil, Amazonas, rio Madeira between Paraná do Canuma and rio Amazonas, 03º40’14”S 59º04’12”W. FMNH114683, Brazil, Amazonas, rio Solimões between tributaries rio Japurá and lago Caimbe, 03º18’30”S 64º35’25”W. FMNH115521, 1 ( 1 specimenmeasured in Tab. 10, 370 mm LEA, Brazil, Pará, rio Trombetas between tributaries lago Bacabal and lago Samauma, 01º31’03”S 56º09’57”W. FMNH115523, 1 ( 1 specimenmeasured in Tab. 10, 443 mm LEA), Brazil, Pará, rio Trombetas between tributaries lago Bacabal and lago Aracuazinho, 01º31’10”S 56º08’59”W. IAvH-P 3192, 2, Colombia, Amazonas, Letícia, PNN Amacayacu, 03º00’47”S 70º00’01”W. IAvH-P 5342, 2, Colombia, Amazonas, La Chorrera, Lago Grande at río Igará-Paraná, 00º44’S 73º01W. ICNMCN 6671, 1, Colombia, Guiania, San Felipe, Río Negro at San Felipe. INPA9360, 1 ( 1 specimenmeasured in Tab. 10, 640 mm LEA), Brazil, Amazonas, Presidente Figueiredo, igarapé Nazaré tributary to rio Uatuma. INPA17645, 2 (1 cs), Amazonas, Careiro da Varzea, paraná do Rei at ilha do Careiro, 03º09’S59º43”W. INPA27621, 2 ( 2 specimensmeasured in Tab. 10, 330–365 LEA), Brazil, Amazonas, Manaus, rio Solimões at Costa do Catalão. MNHG2552.17, 1, Brazil, Pará, rio Tapajos at Aveiro, 03º36’S 55º19’W. MCP26455, 2, Brazil, Pará, rio Trombetas 6.25 miles usptream vila Aracua, 01º31’13”S 56º09’20”W. MCP33444, 1, Brazil, Amazonas, Alvarães, rio Japurá near mouth of lago Mamirauá, 03º07’40”S 64º46’26”W. MCP33446, 1, Brazil, Amazonas, Alvarães, rio Japurá paraná Maiana. MCP33447, 1, Brazil, Amazonas, rio Tefé at Toco Preto. MPEG1299, 1, Brazil, Pará, rio Amazonas at Óbidos, 01º54’S55º31”W. USNM52552, 1, Brazil, rio Amazonas. Mamoré-Madre de Dios: FMNH54701, 1, Bolivia, Río Mamore. MNHN1988–1029, 1, Bolivia, mouth of Río Ibare. Madeira Brazilian Shield. MZUSP13957, 1, Brazil, Rondônia, rio Machado at igapó Paraíso. Tocantins-Araguaia.MCN 18986, 2, Brazil, Tocantins, Ananás, ribeirão Curicacas left margin tributary of rio Araguaia, 06º09’30”S 48º16’21”W. MCN 18987, 1, Brazil, Pará, Marabá, rio Taurizinho left margin tributary of rio Tocantins, 05º22’40”S 49º00’54”W. MCN 18988, 2, Brazil, Tocantins, rio Tocantins between Vila Nova dos Martirios and Buriti do Tocantins, 05º16’06”S 48 06’52”W. Amazonas estuary and coastal drainages: ANSP189541, 1, Brazil, Pará, rio Acarai upstream from confluence with rio Xingu and Porto de Moz, 02º04’34”S 52º20’42”W. MPEG2300, 1, Brazil, Pará, Gurupá, rio Amazonas downstream Gurupá near Estreito, 01º21’S 51º36’W. MPEG5466, 1, Brazil, Pará, Castanhal, rio Apeu at Boa Vista do Apeu. MPEG18693, 3, Brazil, Pará, Cachoeira do Anari, rio Arari. MZUSP32225, 3, Brazil, Amapá, rio Araguari. [681,824,1836,1856] ZMB 54 55 ZMB 4089 1 holotype [713,858,193,213] MNHN 55 56 MNHN 3956 1 holotype [715,862,268,288] MHNH 55 56 MHNH 3957 1 holotype [735,879,343,362] MNHN Demerara, British Guiana Demerara, British Guiana 55 56 MNHN 3958 1 holotype