Brachyhypopomus draco Giora, Malabarba & Crampton, 2008

Crampton, William G. R., Santana, Carlos D. de, Waddell, Joseph C. & Lovejoy, Nathan R., 2016, A taxonomic revision of the Neotropical electric fish genus Brachyhypopomus (Ostariophysi: Gymnotiformes: Hypopomidae), with descriptions of 15 new species, Neotropical Ichthyology (e 150146) 14 (4), pp. 639-790 : 712-716

Brachyhypopomus draco Giora, Malabarba & Crampton, 2008

( Fig. 22 ; Tables 2-5, 12)

Brachyhypopomus beebei . - Sullivan, 1997: 306, fig. 41; 235-241, table 39 (Paraná-Paraguay basin and coastal drainages of southern Brazil, redescription of B. beebei ).

Brachyhypopomus sp. - Cognato et al., 2007: 244, fig. 1b, color photograph; fig. 2b, caudal filament damage, fig. 2d caudal filament regeneration (S Brazil, damage and regeneration in gymnotiform fishes).

Brachyhypopomus draco Giora et al., 2008: 161 , fig. 1, color photograph of male holotype and female paratype; fig. 2, color photograph of head and tip of caudal filament of holotype (original description, type locality – Brazil, Rio Grande do Sul, Patos-Mirim lagoon system). - Almirón et al., 2010: 573, fig. 5, color photograph of live male ( Argentina, Entre Rios, Paraná dr., listing of Brachyhypopomus ). - Claudino et al., 2010: 358, fig. 1, color photograph of live female ( Brazil, Rio Grande do Sul, Lagoa do Peixe National Park, range extension). -Crampton, 2011: 176, table 10.2, species list; 179, figs. 10.2-10.3, phylogeny, geographical and ecological distributions (gymnotiform biology). - Koerber, 2011: 7 ( Argentina, species list]. - Malabarba et al., 2013: 96, color photograph of live individual ( Brazil, Rio Grande do Sul, rio Tramandaí, catalog of fishes]. - Carvalho, 2013: 143, fig.3C outline of head; 181-185, figs. 41-43, position in phylogeny (phylogenetic systematics of Rhamphichthyoidea ). -Mirande & Koerber, 2015: 48 ( Argentina, catalog of fishes). - Tagliacollo et al., 2016: 28, fig. 5 (phylogeny of Gymnotiformes ). - Crampton et al., 2016: 1-66 , table 1, 3-4, figs. 1-7, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Diagnosis. Brachyhypopomus draco is diagnosed from congeners by the following combination of characters: precaudal vertebrae 21-25, vs. 15-20 in B. batesi , B. benjamini , B. bennetti , B. bombilla , B. bullocki , B. cunia , B. diazi , B. flavipomus , B. hendersoni , B. janeiroensis , B. jureiae , B. menezesi , B. occidentalis , B. provenzanoi , B. regani , B. sullivani , and B.walteri ; pale stripe along middorsal region of body absent, vs. prominent pale uninterrupted middorsal stripe from occipital region to base of caudal filament present in B. arrayae , B. beebei , B. belindae , B. gauderio , B. pinnicaudatus , and B. verdii ; anal-fin rays 155- 204, vs. 226-293 in B. brevirostris ; caudal filament length 15.7-35.0% LEA, vs. 7.4-14.0% in B. palenque ; absence of oblique stripes or saddles on body surface, vs. presence of continuous or discontinuous dark vertical or diagonally oriented stripes or saddles absent on body surface dorsal to lateral line, and often extending across lateral line into ventral lateral surface, in B. alberti and B. hamiltoni .

Description. Head and body shape, and pigmentation illustrated in Fig. 22 , and in original description. Meristic and morphometric data for examined specimens are presented in Tables 2-5 and 12. Body moderate in depth. Head short to moderate in length and moderate to broad in depth. Dorsal profile of head straight to slightly convex from occiput to snout, ventral profile of head approximately straight with areas of concavity and convexity between operculum and snout, snout truncate to rounded. Eye small to moderate in size. Upper jaw with moderate to acute sigmoidal angle between premaxillary and maxillary portions in lateral view. No accessory electric organ over operculum. Gill filaments on first gill arch 36 (n = 1). Pectoral fin moderate to broad in width, pectoral-fin rays 14-17 (mode of 16 in populations from Uruguay dr. and coastal drainages of southern Brazil, and 15 in populations from río Paraguay). Precaudal vertebrae 21-25 (mode of 23 in populations from Uruguay dr. and coastal drainages of southern Brazil, and 22 in populations from río Paraguay), including 1-3 (mode 2) transitional vertebrae. Anal-fin origin slightly (<0.25 HL distance) posterior to, or near, tip of pectoral fin. Anal-fin rays 155- 200, with somewhat higher median value in populations from the río Paraguay (189-197, median 195) than in populations from Uruguay dr. and coastal drainages of southern Brazil (168-200, median 179) ( Table 2). Dorsal rami of recurrent branch of anterior lateral line nerve not visible. Middorsal region of body scaled. Rows of scales above lateral line 4-6 (mode 5). Lateral line continuous. Sparse depigmented epidermal canals; as an irregular interrupted single groove either side of dorsal midline along most of posterior half body, and as sparse scratch like marks dorsal to and near lateral line in posterior third of body. Three bilateral electrocyte columns at anal-fin terminus in immature, mature female, and mature male specimens. Three columns of electrocytes at or near a mid-point between anal-fin terminus and tip of caudal filament in mature females, and three or four (or three alternating with four) in immature specimens and mature males. Number of columns tapering from 3 or 4 to 2-3 in distal portion of caudal filament. Caudal filament short to moderate in length.

Coloration. ( Fig. 22 ). Background tan to dark brown. Dorsal region without prominent depigmented pale stripe extending along midline from occipital region to base of caudal filament (although in some specimens dorsal midline is somewhat paler than areas adjacent to midline). Dorsal surface without dark markings, or with irregular dark marks or flecks that are sometimes vertically elongated but never form distinct bands. Series of diffuse horizontal dash-like dark markings often present along lateral line in posterior third of body, anterior to anal-fin terminus. Flank below lateral line over body cavity with irregular dark flecks, but rarely vertically elongated bands. Multiple vertically elongated incomplete bands usually, but not always, present over pterygiophores. Caudal filament darker than body, especially dorsally, ventrally, and near tip; with or without irregular, incomplete dark bands. Head with evenly scattered dark chromatophores, darker dorsally. Eye without prominent suborbital patch, or stripe, of chromatophores/subcutaneous pigmentation. Pectoral and anal-fin membranes hyaline. Pectoral-fin rays hyaline with light scattering of brown chromatophores.Anal-fin rays with scattered or uniform dark pigmentation; darker in posterior half of fin. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. Moderate adult size, largest specimen examined 182 mm TL ( LEA of this specimen not available) (n = 264). Largest male specimen examined 177 mm TL, 137 mm LEA (n = 27). Largest female examined 134 mm, 109 mm LEA (n = 14). Maximum male size in type series 151.8 mm LEA vs. 128.4 mm LEA for females ( Giora et al., 2008) .

Sexual dimorphism. Sexually mature males attain larger sizes than females. Breeding mature males exhibit longer and deeper caudal filaments than immature individuals and breeding females, and reach slightly larger sizes ( Figs. 22 a-b) but do not exhibit an elevated number of bilateral horizontal columns or vertical rows of electrocytes. Instead breeding males exhibit clearly enlarged electrocytes relative to immature specimens and females. Tip of caudal filament in breeding males often with paddle-like lateral compression (sometimes very widened), with electrocytes reaching near tip or terminating as far as around half-way along paddle-like structure. No known sexual dimorphism in pigmentation.

Geographic distribution. Argentina, Brazil, Paraguay, and Uruguay ( Fig. 23 ). Widely distributed through lower portions of the Paraguay, Paraná , and Uruguay drainages as far north as 25°S, the Patos-Mirim lagoon system of southeast Brazil /northeast Uruguay, and some other coastal drainages of Brazil north of Lagoa dos Patos .

Population variation: We found complete overlap in the range of meristics ( Tables 2-5) and morphometric proportions ( Table 12), and observed similar pigmentation among populations of B. draco from Uruguay dr./coastal drainages of southern Brazil, and from the río Paraguay. These observations, in combination with molecular data ( Crampton et al., 2016), support the hypothesis that all populations we have assigned to B. draco are members of a single geographically widespread species, which is morphologically and genetically distinct from all congeners. Ecological notes. The original description of B. draco notes that it occurs most commonly in “river edges, slow moving creeks, lagoons and flooded areas with muddy or sandy bottom and abundant emergent or floating vegetation”. Schaan et al. (2009) provides a detailed account of the natural history and reproductive biology of B. draco . Breeding occurs primarily during the late austral winter and austral summer, which corresponds to a period of higher temperature and rainfall, and substantially longer photoperiod. At this time the sex ratio approximates 1:1. During the austral winter B. draco exhibits gonadal quiescence, a general reduction in activity and feeding, and an accompanying reduction of the EOD pulse-rate (Giora et al., 2011; Schaan et al., 2009). Stomach contents of specimens from the type locality comprise aquatic insect larvae and other small aquatic invertebrates (WGRC unpublished data).

Co-occurring congeners: Through most of its range, B. draco occurs in geographical sympatry and in ecological syntopy with B. bombilla and B. gauderio . Brachyhypopomus draco probably also co-occurs with B. walteri in the northern part of the former’s distribution in the Paraguay-Paraná system (see distribution for B. walteri , Fig. 47 ), but not with B. brevirostris , which occurs as far south as 19°S ( Fig. 18 ) (compared to 25°S for the highest known latitude for B. draco , Fig. 23 ).

Local names. Argentina, Paraguay: morenita; Brazil: tuvira, moreninha, tuvira dragão ( Malabarba et al., 2013); Uruguay: morenita, limpiavidrio ( Nion et al., 2002).

Material examined. 264 specimens. Argentina. Entre ríos. AI 268, 2, 118-129 mm, Pre-Delta National Park, Pozo Hondo, Arroyo las Tortugas , Paraná dr., 32°08′40″S, 060°39′02″W . Brazil. Rio Grande do Sul. FURG 2186, 3, 42-80 mm, wetlands draining into Parque Nacional Lagoa do Peixe, 6 km W Mostardas, Patos-Mirim dr., 31°06′05″S, 050°51′17″W . MCP 9487 , 3 , 64-96 mm, Vila Itapevi, Cecequi-São Francisco de Assis rd., rio Uruguai, Uruguay dr., ca. 29°47′S, 55°07′W . MCP 13643 , 3 (1 immature, 71 mm, 1 female, 134 mm, 1 male, 96 mm), stream, affl. of Lagoa dos Quadros, nr. Praia do Barco, rio Tramandaí dr., ca. 29°42′S, 050°05′W . MCP 19546 , 1 , male, 149 mm, Fazenda Pirai rd., 4.5 km São Gabriel, rio Vacacaí , affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°18′51″S, 054°21′35″W . MCP 19846 , 1 , female ( CS), 130 mm , MCP 19847 (part), 1, male, 139 mm, Banhado do Inhatium, hwy. BR- 290, 21 km São Gabriel, affl. rio Ibicuí, Uruguay dr., 30°15′43″S, 054°31′33″W . MCP 20215 , 5 , 64-80 mm, Eldorado do Sul, BR-290, affl. rio Jacuí, affl. rio Guaíba, Patos-Mirim dr., 30°02′36″S, 051°20′56″W . MCP 20217 , 3 , 58-68 mm, arroio Passos dos Carros, rd. linking BR16 to Guaíba, affl. rio Jacuí, affl. rio Guaíba , Patos-Mirim dr., 30°05′55″S, 051°23′15″W . MCP 20711 , 1 , 73 mm, Osório, channel linking Lagoa Emboaba and Emboabinha, rio Tramandaí dr., 29°57′57″S, 050°13′45″W . MCP 23795 , 2 (1 immature, 44 mm, 1 female, 90 mm), mun. Tapes, arroio Teixeira on BR-16 E, Patos-Mirim dr., 30°38′34″S, 051°32′45″W . MCP 41537 (paratype), 1, female, 108 mm LEA, MCP 41538 , 2 (paratypes) (1 female, 92 mm LEA, 1 male, 88 mm LEA) , MCP 41539 , 1 (paratype), male, 147 mm LEA, MCP 41540 , 1 (holotype), male, 177 mm TL, 137 mm LEA, MNRJ 30916 , 2 (paratypes) (1 female, 128 mm LEA, 1 male, 152 mm LEA) , MNRJ 30917 , 1 (paratypes) male, 150 mm LEA, MNRJ 30918 , 1 (paratype) male, 138 mm LEA, MZUSP 94429 , 1 (paratype) male, 139 mm LEA, UFRGS 6515 , 1 , male, 135 mm , UFRGS 6521 , 1 , female, 114 mm , UFRGS 6522 , 1 , female, 127 mm , UFRGS 6523 , 1 , male, 117 mm , UFRGS 8888 , 1 (paratype), male, 126 mm LEA, mun. Viamão, Lagoa Verde, Parque Estadual de Itapuã, Patos-Mirim dr., 30°22′52″S, 051°01′25″W . MCP 41938 , 2 (1 female, 110 mm, 1 male, 80 mm), mun. Cacequi, stream, affl. rio Ibicuízinho, on hwy. Cacequi-Estação São Lucas, Uruguay dr., 29°50′12″S , 054°27′423″W. MCP 41961 , 2 (1 female, 112 mm, 1 male, 95 mm), mun. Cacequi, Fazenda da Convenção, affl. rio Ibicuí , Uruguay dr., 29°50′58″S, 054°53′02″W . MCP 45352 , 1, 134 mm, mun. Pelotas, nr. bridge to Pelotas, rio São Gonçalo, Patos-Mirim dr., 31°46′19″S, 52°20′33″W . MCP 45353 , 1 , 57 mm, mun. Eldorado do Sul, arroio Passos dos Carros on hwy. connecting hwy. BR-16 to Guaíba, rio Jacuí, affl. rio Guaíba , Patos-Mirim dr., 30°05′55″S, 051°23′15″W . UFRGS 732 , 1 (paratype), female, 86 mm LEA, mun. Viamão, arroio Alexandrina, Patos-Mirim dr., ca. 30°06′S, 050°57′W . UFRGS 820 , 1 (paratype), male, 117 mm LEA, mun. Guaíba, BR-290 hwy., Patos-Mirim dr., ca. 30°07′S, 051°20′W . UFRGS 821 , 1, 110 mm , UFRGS 822 , 1 (paratype), male, 119 mm, mun. Viamão, stream flowing into Praia de Fora, Lagoa dos Patos, Parque Itapuã, Patos-Mirim dr., 30°23′09″S, 051°01′00″W . UFRGS 3938 , 1 , 27 mm, mun. Osório, Lagoa Emboaba, rio Tramandaí dr., 29°57′00″S, 050°13′00″W . UFRGS 4096 , 7 , 56-130 mm, mun. Tramandaí, Lagoa do Passo, rio Tramandaí dr., 29°52′01″S, 050°06′W . UFRGS 4236 , 2 , 86-99 mm, mun. Viamão, Lomba do Pinheiro, affl. rio Guaíba, Patos-Mirim dr., 30°05′00″S, 051°07′59″W . UFRGS 4317 , 1 (paratype), 59 mm, mun. Viamão, arroio Itapuã, Patos-Mirim dr., ca. 30°15′S, 051°02′W . UFRGS 4503 , 1 , 50 mm, mun. lago Emboaba, rio Tramandaí dr., 29°57′S, 050°13′W . UFRGS 4802 , 23 , 2169 mm , UFRGS 4812 , 7 , 75-170 mm , UFRGS 4814 , 3 , 57-82 mm, mun. Viamão, Parque Estadual de Itapuã, Patos-Mirim dr., ca. 30°20′S, 051°00′W . UFRGS 5887 , 1 , 62 mm, mun. Arambaré, unnamed stream, Arambaré - Santa Rita do Sul hwy. Lagoa dos Patos, Patos-Mirim dr., 30°57′09″S, 051°30′04″W . UFRGS 6486 , 1 (paratype), male, 113 mm , UFRGS 6487 , 1 , female, 104 mm , UFRGS 6488 , 1 (paratype), male, 113 mm , UFGRS 6489 , 1 (paratype), male, 112 mm , UFRGS 6490 , 1 (paratype), female, 111 mm , UFRGS 6491 , 1 (paratype), male, 93 mm , UFRGS 6492 , 1 , female, 96 mm, mun. Capão da Canoa, stream, Estrada do Mar (hwy. RS-389) km 38, rio Tramandaí dr., 29°43′09″S, 050°00′56″W . UFRGS 6493 , 1 , male, 100 mm , UFRGS 6494 , 1 (paratype), male, 100 mm , UFRGS 6497 , 1 (paratype), male, 106 mm , UFRGS 6785 , 4 (paratypes) (2 females, 84-85 mm LEA, 2 male, 79-105 mm LEA), mun. Rosário do Sul, stream, hwy. BR-290, affl. rio Santa Maria, affl. rio Ibicuí, Uruguay dr., 30°12′42″S, 055°03′17″W . UFRGS 6507 , 1 (paratype), male, 109 mm , UFRGS 6508 , 1 , male, 126 mm , UFRGS 6509 , 1 (paratype), female, 102 mm , UFRGS 6510 , 1 , female, 86 mm , UFRGS 6511 , 1 (paratype), male, 126 mm , UFRGS 6513 , 1 , female, 113 mm , UFRGS 6514 , 1 , male, 107 mm, mun. São Gabriel, stream on margin hwy. BR-290, affl. rio Cacequí, affl. rio Santa Maria , affl. rio Ibicuí , Uruguay dr., 30°18′57″S, 054°24′23″W . UFRGS 6525 , 1 , male, 130 mm , UFRGS 6526 , 1 (paratype), male, 129 mm , UFRGS 6527 , 1 , immature, 100 mm, mun. El Dorado do Sul, rd. hwy. BR-290, affl. rio Jacuí, affl. rio Guaíba, Patos-Mirim dr., 30°02′56″S, 051°23′33″W . UFRGS 6671 , 3 (paratypes) (1 female, 96 mm LEA, 2 male, 86-107 mm LEA), mun. Terra de Areia, creek affl. rio Três Forquilhas, hwy. RS 486, rio Tramandaí dr., 29°33′22″S, 050°04′19″W . UFGRS 6748 , 1 (paratype) male, 91 mm LEA, UFRGS 6750 , 14 , 46-128 mm LEA, mun. Alegrete, Sanga do Jacaré, stream crossing BR-290, affl. rio Ibicuí, Uruguay dr., 30°12′42″S, 055°03′19″W . MZUSP 94428 , 8 (paratypes) (2 male, 96-127 mm LEA, 6 female, 52-104 mm LEA) , UFRGS 6752 , 1, 100 mm , UFRGS 6753 (paratype), 1 male, 88 mm LEA, UFGRS 6754 , 1 , 61 mm , UFRGS 6789 , 4 (paratypes) (2 females, 72-80 mm LEA, 2 male, 106-126 mm LEA), mun. Rosário do Sul, stream at margin hwy. BR-290, affl. arroio Gueromana, affl. rio Ibirapuitã, affl. rio Ibicuí , Uruguay dr., 30°01′00″S, 055°23′18″W . UFRGS 6780 , 11 , São Gabriel, rio Vacacaí system, Patos-Mirim dr., ca. 30°20′S, 054°19′W . UFRGS 7686 , 30 , UFRGS 7707 , 3 , Viamão, Patos-Mirim dr., ca. 30°05′S, 051°01′W . UFRGS 8263 , 28 , Charqueadas, rio Jacuí , Patos-Mirim dr., ca. 29°57′S, 051°37′W . UFRGS 8475 , 4 , Pantano Grande, rio Pardo , Patos-Mirim dr., ca. 30°15′S, 052°20′W . UFRGS 8938 , 1 , rio Tramandaí dr., no coordinates . UFRGS 14562 , 2 , 136-137 mm, mun. Águas Claras, Refúgio da Vida Silvestre, Banhado dos Pachecos , rio Tramandaí dr., 30°04′40″S, 050°50′59″W . UFRGS 15292 , 2 , 103-114 mm, mun. Arambaré, Patos-Mirim dr., no coordinates. UMMZ 143283, 2, 48-100 mm, Conceição do arroio, ca. 20 mi. N Tramandaí, rio Maquiné, rio Tramandaí dr., ca. 29°43′S, 050°08′W . Paraguay (localities from Paraná dr.). Alto Paraná. UMMZ 206908, 1, female, 103 mm, stream, ca. 30 km NW Hernandarias, rd. to Itakyry , affl. río Paraguay, 25°14′12″S, 054°52′48″W . Caaguazú. UMMZ 206252, 5, 33- 14 mm, Estancia San Ignacio, 24 km Carayao, río Hondo , affl. río Paraguay, 25°01′36″S, 056°25′48″W . Central. UMMZ 205706, 2, 110-115 mm, río Paraguay, NW Asunción, ca. 25°17′S, 057°39′W . UMMZ 206001 (part), 1, male, 132 mm, río Salado (nr. mouth) nr. N Limpio, affl. río Paraguay, 25°08′42″S, 057°25′12″W . UMMZ 208106, 2, 84-100 mm, ca. 1.0 km S Puente Remanso bridge, río Paraguay, 25°17′36″S, 057°33′00″W . Cordillera. ANSP 185112, 1, female, 105 mm, ANSP 185119, 2, 76-79 mm, stream crossing Caacupe-Tobati rd., 7.0 km Route 2 in direction of Tobati , affl. río Paraguay, ca. 25°22′S, 057°13′W . UMMZ 205767, 1, 107 mm, Arroyo Tobati, 1.6 km S Tobati, affl. río Piribebuy , affl. río Paraguay, 25°18′30″S, 057°04′12″W . Misiones. ANSP 170412, 1, 118 mm, bridge on Ayolas-Asunción-Encarnacíon hwy. (Ruta 1) at km 4/A262, affl. río Paraná , ca. 27°24′S, 056°48′W . ANSP 175180, 1, 85 mm, stream crossing rd. to Ayolas, affl. río Paraná , 27°03′29″S, 056°47′22″W . ANSP 185113, 1, 45 mm, marshes, rd. from Ayolas to Asunción-Encarnacíon hwy, affl. río Paraná , ca. 27°23′S, 056°47′W . Paraguarí. USNM 181483 , 5 , 88-138 mm, nr. Pueblo Ybytymí, Arroyo Pachongo , affl. río Paraguay, ca. 25°46′S, 056°47′W . Presidente Hayes. ANSP 185111, 2 (1 female, 103 mm, 1 male, 114 mm), Puente Remanso , affl. río Paraguay, 25°10′S, 057°33′W . Uruguay. Artigas. ZVC-P 2727, 1, Laguna Redonda on margin of río Uruguay, Franquia, nr. Bella Unión, Uruguay dr., 30º14′46″S, 057º36′22″W .

Figures

Fig. 22. Brachyhypopomus draco. a. MCP 19847 (part), male, 138 mm TL (head in lateral view, body in lateral and dorsal view); Brazil, rio Ibicuí, Uruguay dr. b. MCP 13643, female, 132 mm TL (body in lateral view); Brazil, rio Sanga, rio Tramandaí dr. Note sexual dimorphism in caudal filament height. Specimens fixed in formalin and preserved in EtOH. Scale bars = 5 mm.

Fig. 23. Collection records for Brachyhypopomus draco (circles), B. janeiroensis (squares), and B. jureiae (triangles). Holotype locations are marked with open symbols. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).

Fig. 47. Collection records for Brachyhypopomus walteri (circles). Holotype location is marked with an open symbol. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).

Fig. 18. Collection records for Brachyhypopomus brevirostris (circles). Precise locality of the lectotype is not known. Elevation data refers to altitude above mean sea level (see Fig. 2 for legend).