Sternarchorhynchus goeldii, Santana & Vari, 2010, Santana & Vari, 2010
Santana, Carlos David De & Vari, Richard P., 2010, Electric fishes of the genus Sternarchorhynchus (Teleostei, Ostariophysi, Gymnotiformes); phylogenetic and revisionary studies, Zoological Journal of the Linnean Society 159 (1), pp. 223-371: 301-305
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STERNARCHORHYNCHUS GOELDII SP. NOV.
Diagnosis: Sternarchorhynchus goeldii is distinguished from all congeners with the exception of S. oxyrhynchus by having the gape of the mouth aligned with main axis of snout, with the gape elongate and extending posteriorly distinctly beyond the vertical through posterior naris contrary to a shorter gape that terminates posteriorly at, or slightly short of, the vertical through anterior nares. Sternarchorhynchus goeldii differs from S. oxyrhynchus in the number of total vertebrae (92–94 versus 97–108, respectively), the greatest body depth (8.2–10.8 versus 6.3–8.2% of TL, respectively), and to a large degree in the head depth at the nape (35.0–44.8 versus 26.8–37.7% of SL, respectively).
Description: Morphometric data for holotype and paratypes specimens in Table 7.
Lateral line extending posteriorly to base of caudal fin, but not extending onto fin. Snout elongate, compressed and very slightly curved ventrally along its distal portion, but having overall anteroventral orientation. Anus and urogenital papilla located ventral to head, with position ranging from slightly anterior of vertical through anterior margin of orbit to vertical located two orbital diameters posterior of vertical through rear of orbit. Anus and urogenital papilla generally more anteriorly positioned in larger specimens. Combined opening for anus and urogenital papilla longitudinally ovoid.
Premaxilla with ten to 11 teeth with six replacement teeth in cleared and stained specimen (N = 6). No sexual dimorphism in form of dentary or dentary dentition apparent in examined samples. Dentary with two rows of teeth. Outer row consisting of 13–20 curved conical teeth and inner row with three to five teeth (N = 7). Mouth terminal. Gape of mouth aligned with main axis of snout, elongate and extending posteriorly distinctly beyond vertical through posterior naris ( Fig. 1A View Figure 1 ). Lower jaw with terminal fleshy pad that extends anteriorly beyond vertical through anterior limit of snout. Fleshy pad directed dorsally and overlaps tip of snout when mouth closed.
Branchiostegal rays five; with first and second ray narrow and elongate, third to fifth rays becoming progressively wider. Precaudal vertebrae 16–17 (three anterior; three to four transitional; N = 15). Total vertebrae 92–94 (N = 10).
Pectoral-fin rays ii + 12–14 [ii + 13] (N = 29). Analfin origin located anterior to vertical through opercle. Anterior unbranched anal-fin rays 21–40  (N = 17). Total anal-fin rays 204–237  (N = 29). Scales above lateral line at midbody three to six  (N = 21). Scales absent along mid-dorsal line from rear of head to origin of electroreceptive filament. Origin of midsaggital electroreceptive filament located approximately at 62% of TL. Filament extending posteriorly beyond vertical through posterior terminus of base of anal fin for distance of approximately five scales. Tail compressed and short, ending in small, elongate caudal fin with rounded posterior margin. Caudal-fin rays 16–22  (N = 13).
Coloration in alcohol: Overall ground coloration tan to dark brown. Head and body with small dark chromatophores relatively densely scattered over surfaces. Chromatophores more densely packed and more intensely pigmented in darker specimens. Portion of head anterior of orbit somewhat darker than remaining region of head in some specimens. Some specimens with posteriormost portion of body and all of tail distinctly darker than remainder of body.
Pectoral fin ranging from nearly completely hyaline to overall darkly pigmented, but with dark pigmentation most developed on distal portions and along dorsal margin of fin. Very lightly pigmented specimens with dark pigmentation limited to distalmost portions and dorsal margin of fin. Overall darkly pigmented specimens with dark pigmentation covering distal half to two-thirds of pectoral fin. Distal portions of anal fin variably dark. Overall more lightly pigmented specimens often with distal dark pigmentation barely apparent on anteriormost portion of anal fin and with obvious dark coloration present only as narrow band along distal portion of fin. Some other individuals with distal dark pigmentation extending forward to anterior limit of fin and with broad irregular band of dark pigmentation extending along most of distal portion of fin. Caudal fin dark even in overall lightly pigmented individuals and very dark in most specimens.
Distribution: Sternarchorhynchus goeldii is distributed along the main stream of the Amazon from the region of Óbidos, Brazil, in the eastern portions of the Amazon basin westwards to north-eastern Peru. The species also occurs to varying degrees in the lower courses of tributary rivers of the main Amazon ( Fig. 42 View Figure 42 ).
Electrical organ discharge: Crampton (1998) and Crampton & Albert (2006) reported that individuals of S. goeldii (identified therein as Sternarchorhynchus oxyrhynchus ) have a type D EOD pattern with a fundamental frequency of 1321–1390 Hz.
Habits: Crampton (2007: 330) reported on the activity pattern of S. goeldii (identified by that author as S. oxyrhynchus ) in an aquarium setting under subdued natural light. In that setting the species demonstrated increased activity levels at night, but only sporadic foraging activities in the course of the day.
Secondary sexual dimorphism: No secondary sexual dimorphism comparable to that found in many congeners was apparent in exampled samples of S. goeldii .
Etymology: The species name, goeldii , is in honour of Emilio Goeldi, who made many contributions to our knowledge of many groups of Amazonian animals including fishes.
Paratypes: – BRAZIL. Amazonas: Rio Solimões , downstream from mouth of Río Purus , upstream from town of Manacapuru (3°27′22″S, 60°45′21″W) FMNH 115520, 1 (193). Rio Purus (4°53′47″S, 62°54′53″W); INPA 17104, 2 (175–202). Rio Amazonas, 20.6 km above Itacoatiara, 35.5 km below Santa Antonia (3°15′46″S, 58°36′02″W), collected by F. Langeani et al., 20.x.1994; USNM 373081, 1 (212). Rio Solimões , Costa do Marimba, Ilha do Careiro, collected by C. Cox-Fernandes et al.; INPA 17633, 4 (285–336). Rio Solimões , near ‘encontro das águas’ (area of mixing of waters of Rio Negro and Rio Amazonas, collected by C. Cox-Fernandes et al.; INPA 24109, 5 (335–367).
Nontype specimens: – BRAZIL. Amazonas: Rio Negro , between tributary Rios Cuieras and Taruma-Açu, between towns of Santa Maria and Leprosário (3°01′45″S, 60°24′7″W); FMNH 115505, 4 (213–263), FMNH 115506, 4 (162–244). Rio Jaú , curve of Jaú, Novo Airão; INPA 11355, 1 (184). Rio Jaú , mouth of Río Preto, Novo Airão ; INPA 12548, 1 (133), INPA 12551, 2 (176–217), INPA 12656, 1 (194). Rio Negro , 12 km above Leprosário, 16.3 km below Santa Maria (3°02′58″S, 60°22′10″W); USNM 373069, 3 (221–257). Rio Negro 4 km above Manaus (3°08′S, 60°03′W); USNM 373044, 2 (231–251). Rio Negro , between Paraná da Floresta and Paraná da Cotia, between towns of Moura and São Francisco (1°33′48″S, 61°33′3″W); FMNH 115507, 1 (231). Rio Negro , 18.5 km above São Francisco (1°33′45″S, 61°33′01″W); USNM 373075, 1 (221). Rio Negro, USNM 373046, 2 (225–243). Rio Negro , above Manaus; MCZ 98360 View Materials , 1 (210). Rio Negro , between tributary drainages Curidique and Paraná Jacaré, between towns of Novo Caioe and São Francisco de Assis (1°58′30″S, 61°14′20″W); FMNH 115508, 4 (180–256). Rio Negro , upstream from tributary drainage Tarumã-Mirim and upstream from city of Manaus (3°04′11″S, 60°11′03″W); FMNH 115517, 1 (272). Rio Negro , upstream from Manaus (3°1′18″S, 60°23′29″W); FMNH 115516, 1 (326). Rio Negro, Praia Grande, Manaus ; INPA 27495 1 (235). Rio Solimões, Manaus ; INPA 24111, 2 (335–339). Rio Negro , near Manaus; INPA 4435, 3 (180–303). Rio Negro , 5.6 km below São Francisco de Assis (1°42′42″S 61°24′27″W); USNM 373106, 3 (173–207). Rio Negro , 33 km below Novo Caioe, 7 km above São Francisco de Assis (1°58′24″S, 61°14′30″W); USNM 373886, 1 (214). Rio Jaú , mouth of Jaú; INPA 12551, 2 (176–217). Rio Jaú , mouth of Rio Preto ; INPA 11355, 1 (184), INPA 12656, 1 (191). Rio Amazonas, Paraná do Tapará; INPA 19991, 1 (203). Rio Solimões , Paraná do Xiborena, INPA 17636, 1 (354). Rio Solimões , Paraná do Xiborena; INPA 24110 1 (285). Rio Solimões , Ilha do Careiro, Paraná do Rei; INPA 27497, 1 (353). Rio Solimoes, Lago Januacá, Manaquiri, INPA 27499, 5 (345–360). Rio Solimões , Paraná do Tapará, Autazes; INPA 19991, 1 (200). Rio Purus, Beabá (4°53′47″S, 62°54′51″W); INPA 17104, 2 (173–211). Rio Solimões , Ilha do Careiro, Paraná do Rei; INPA 17634 1 (288), INPA 17637, 1 (347), INPA uncat., 1 (353), INPA uncat., 1 (370). Rio Japurá between mouth of Lagos Mamirauá and Joaquim; INPA 18274, 1 (334). Rio Japurá , at mouth of Lago Mamirauá; INPA uncat., 1 (214). Rio Tefé at Tefé; INPA 15821, 6 (315–370). Rio Tefé, Toco Preto ; INPA 15821, 6 (311–369). Rio Amazonas, upstream from mouth of Rio Madeira / Paraná da Eva, upstream from town of Novo Oriente (3°13′37″S, 59°3′32″W); FMNH 115519, 7 (193–295). Rio Solimões , below mouth of Rio Madeira ; INPA 20221, 28 (230–313). Rio Solimões , Paraná Xiborena; INPA 16636, 1 (357). Rio Amazonas downstream from Rio Madeira , upstream from town of Itacoatiara (3°20′9″S, 58°36′11″W); FMNH 115518, 1 (289). Rio Uatumã, Presidente Figueiredo at Balbina Dam; INPA 4833, 1 (341). Rio Juruá , tributaries Lago Pauapixuna and Rio Solimões , between towns of Pauapixuna and Vitória (2°41′11″S, 65°48′30″W); FMNH 115503, 2 (257–282). Rio Juruá between Lago Pauapixuna and Rio Solimões , between towns of Pauapixuna and Vitória (2°41′11″S, 65°48′30″W); FMNH 115503, 2 (257–282). Rio Juruá, Lago Pauapixuna and Lago Meneroa , between towns of Pauapixuna and Tamanicoa (2°46′31″S, 65°50′00″W); FMNH 115509, 1 (283). Rio Juruá , between Lago Pauapixuna and Rio Solimões , between towns of Pauapixuna and Vitória (2°41′08″S, 65°48′29″W); FMNH 115502, 1 (289). Rio Jutaí , between mouths of Rio Zinho and Rio Solimões , between towns of Porto Antunes and Copatana (2°51′16″S, 66°57′23″W); FMNH 115510, 1 (257). Rio Juruá tributaries Lago Pauapixuna and Meneroa, between towns of Pauapixuna and Tamanicoa (2°46′31″S, 65°50′00″W); FMNH 115509, 1 (283). Rio Juruá , between Lago Pauapixuna and Rio Solimões , between towns of Pauapixuna and Vitória (2°41′08″S, 65°48′29″W); FMNH 115502, 1 (289). Rio Solimões , downstream from mouth of Rio Purus , upstream from Manacapuru (3°27′22″S, 60°45′21″W); FMNH 115520, 1 (193). Rio Solimões, Lago Manacapuru ; MCZ 9340, 2 (200–355), MCZ 24934 View Materials , 1 (350). Rio Jutaí , between Rio Zinho and Rio Solimões , between towns of Porto Antunes and Copatana (2°51′16″S, 66°57′23″W); FMNH 115510, 1 (257). Rio Jutaí , between Porto Antunes and Foz do Jutaí (2°53′00″S, 66°58′22″W); USNM 375482, 2 (351–353). Rio Solimões (3°36′19″S, 61°18′39″W); USNM 375398, 2 (210–216). Rio Solimões (3°35′43″S, 61°07′16″W); USNM 375399, 1 (261). Pará: Rio Tocantins, Tucuruí; INPA 1501, 1 (220). Rio Amazonas between tributaries Paraná de Jurutí and Trombetas, between towns of Jurutí and Óbidos (2°00′39″S, 55°55′17″W); FMNH 115511, 1 (259). Rio Trombetas between tributaries Furo Maria Tereza and Amazonas, between towns of Fazenda Santana and Óbidos (1°52′53″S, 55°38′13″W); FMNH 115512, 1 (183). Rio Trombetas , between tributaries Lago Bacabal and Lago Samauma (1°31′3″S, 56°9′57″W); FMNH 115513, 2 (not measured). Rio Trombetas , between Rio Cumina and Lago Axipica , between towns of Bom Jesus and Santa Cecilia (1°32′40″S; 56°01′07″W); FMNH 115514, 1 (245). Rio Amazonas, 58.5 km below Jurutí, 21.1 km above Óbidos (1°55′48″S, 55°40′41″W); USNM 373040, 4 (329–368). Roraima: Rio Negro , at confluence with Rio Branco or along lower 30 mi (48 km) below Rio Branco (approximately 1°24′S, 61°27′W); MCZ 46887 View Materials , 3 (1 CS, 190–215).
PERU. Loreto: Rio Amazonas, beach along east bank of east channel of river, opposite Iquitos; INHS 55418, 3 (224–283).
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