Brachyhypopomus gauderio Giora & Malabarba, 2009

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 : 721-726

Brachyhypopomus gauderio Giora & Malabarba, 2009

( Fig. 26 ; Tables 2-5, 14)

Rhamphichthys brevirostris . - Perugia, 1891: 56 ( Argentina, Chaco, Resistencia, based on three specimens collected by Spegazzini (MSNG 27458); one of the three was identified as Eigenmannia trilineata , and two, incorrectly, as Brachyhypopomus bombilla by Azpelicueta & Koerber, 2015: 40-42, fig. 3, color photograph of specimens [in discussion of Perugia listings]).- Ringuelet et al., 1967: 253; Lopez et al., 2003: 65 (repeat listings from Perugia, 1891). - Boulenger, 1896: 38 ( Brazil, Mato Grosso, Descalvados, list of fishes collected in río Paraguay by C. Ternetz, record corresponds to BMNH 1895.5.17.265-268; identified herein as B. gauderio (part, n = 1), B. bombilla (part, n = 3).

Hypopomus brevirostris . - Eigenmann & Kennedy, 1903: 530 ( Paraguay, listing of fishes collected by J. Daniel Anisits, “ Four specimens (108, 158, 220), Mato Grosso or Asunción. Campo Grande and Arroyo Chagalalina.”; we identified these four specimens as AMNH 1009, CAS 72215, FMNH 5251, all B. gauderio ). -Carter & Beadle, 1931: 337, pl. 21, fig. 7, transverse section of the mouth and gill chamber; pl.31, fig.8, illustrations of gill-lamellae morphology ( Paraguay, ecology with discussion of respiratory adaptations; identified from context as B. gauderio ). - Casciotta et al., 2005: 71, line-drawing; 237, fig. 108, color photograph ( Argentina, Iberá wetlands, catalog of fishes).

Brachyhypopomus pinnicaudatus . - Franchina, 1997: 115, figs. 7-10, black and white photographs of electrocyte arrangements in caudal filament (electric organ ontogeny). -Stoddard, 1999: 255, fig. 4, color photograph of mature female (EOD evolution). -Stoddard et al., 1999: 610, fig. 1, black and white photograph of mature male and female (EOD evolution). -Albert & Crampton, 2003: 494 (rio de la Plata basin, Paraguay, Brazil, Uruguay, catalog of hypopomids). -Curtis & Stoddard, 2003: 330, fig. 1, black and white photographs of mature male and female (communication). - Crampton &Albert, 2006: 672, fig.23.8, position in phylogenetic tree; 681, notes on EODs (gymnotiform species and EOD diversity). -Graça & Pavanelli, 2007: 168, color photograph of live individual ( Brazil, upper rio Paraná, species lists - presumed to be an introduced species, see ‘Remarks′, below).

Brachyhypopomus sp. - Giora et al., 2008: 167 ( Brazil, Rio Grande do Sul, listed in comparative material for description of B. draco ).

Brachyhypopomus gauderio Giora & Malabarba, 2009: 62 , fig. 1, color photograph of male holotype (original description, type locality – Brazil, Rio Grande do Sul, Palmares do Sul, Patos-Mirim dr.). - Almirón et al., 2010: 573, fig. 7, color photograph ( Argentina, Entre Rios, Pre-Delta Matinal Park, Paraná dr., listing of Brachyhypopomus ). -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, phylogeny, geographical and ecological distributions, gymnotiform biology). - Malabarba et al., 2013: 97, color photograph of live individual ( Brazil, Rio Grande do Sul, rio Tramandaí, catalog of fishes). - Carvalho, 2013: 168, fig. 25a, color photograph of head; 181-185, figs. 41-43, position in phylogeny (phylogenetic systematics of Rhamphichthyoidea ). -Mirande & Koerber, 2015: 48 ( Argentina, catalog of fishes). - Crampton et al., 2016: 1-66, table 1, 3-4, figs. 1-7, 18-20 (phylogeny, biogeography and ecology of Brachyhypopomus ).

Brachyhypopomus bombilla . -Azpelicueta & Koerber: 2015, 40- 42, fig. 3, color photograph of two specimens, MSNG 27458 (discussion of fish specimens listed in Perugia, 1891).

Diagnosis. Brachyhypopomus gauderio is diagnosed from congeners by the following combination of characters: prominent pale stripe along middorsal region of present, vs. absent in all congeners except B. arrayae , B. beebei , B. belindae , B. pinnicaudatus , and B. verdii ; longest anal-fin ray 3.9-5.4% LEA, vs. 1.6-3.9% in B. beebei ; precaudal vertebrae 18-21, vs. 24-26 in B. belindae and B. verdii . Brachyhypopomus gauderio exhibits similar pigmentation and overlapping meristic counts and morphometric proportions with some populations of B. arrayae and B. pinnicaudatus . Brachyhypopomus gauderio can be distinguished from B. arrayae by the absence of a contact between a small ascending process on the endopterygoid and the orbitosphenoid vs. a contact between these two bones in B. arrayae (see diagnosis for B. arrayae for details). Brachyhypopomus gauderio can be distinguished from B. pinnicaudatus by the absence of a medial bridge on the posterior portion of the basihyal (de Santana & Vari, 2010: 250. fig. 15; Fernandes et al., 2014: 104, fig. 7), vs. presence in B. pinnicaudatus .

Description. Head and body shape, and pigmentation illustrated in Fig. 26 and in original description. Meristic and morphometric data for examined specimens presented in Tables 2-5 and 14. Body moderate to broad in depth. Head short to moderate in length and moderate to broad in depth. Dorsal profile of head approximately straight from occiput to snout, ventral profile of head approximately straight between operculum and snout, snout 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 35-45 (median 40, n = 6). Pectoral fin moderate in width, pectoral-fin rays 12-17; range and mode higher in populations from Patos-Mirim lagoon system and Uruguay drainage (14- 17, mode 15) than from Paraguay drainage (12-15, mode 13). Precaudal vertebrae 18-21; range and mode slightly higher in populations from Lagoa dos Patos and Uruguay drainages (20-21, mode 21) than from Paraguay drainage (18-21, mode 20); transitional vertebrae 1-2 (mode 2) in populations from Lagoa dos Patos and Uruguay drainages and 2-3 (mode 2) in populations from the Paraguay drainage. Anal-fin origin slightly (<0.25 HL distance) anterior to, or near, tip of pectoral fin. Anal-fin rays 180- 216; ranges and median values very similar in populations from Lagoa dos Patos and Uruguay drainages (187-206, median 200 in examined specimens) and from Paraguay drainage (183-211, median 201). Dorsal rami of recurrent branch of anterior lateral line nerve not visible. Middorsal region of body scaled. Rows of scales above lateral line 4-7 (mode 5). Lateral line continuous. Epidermal canals not conspicuous, but present in form of single bifurcating and sometimes branched horizontal depigmented groove, with darkened margins, on either side of dorsal surface in dorsal portions of flank, beginning approximately two head lengths posterior to occiput and extending to approximately two head lengths anterior to anal-fin terminus. Epidermal canals also variably present in posterior half of body as very sparse single or sometimes parallel double depigmented grooves either side of, but mostly dorsal to, lateral line. Three bilateral horizontal columns at anal-fin terminus, and three or sometimes three alternating with four at or near a mid-point between anal-fin terminus and tip of caudal filament in immature, mature female, and mature male specimens. Some regenerated specimens exhibit four columns of electrocytes in regenerated portions of caudal filament. Caudal filament short to moderate in length.

Coloration. ( Fig. 26 ). Background pale tan to dark brown. Pigmentation highly variable. Dorsal region with prominent depigmented or lightly pigmented stripe extending along midline from occipital region to base of caudal filament, or deep into caudal filament, bordered by prominent dark horizontal wavy reticulated lines from which short irregular patches extend ventrally. Dorsal pigmentation pattern strongly resembles that of B. pinnicaudatus , but pale depigmented stripe is not as conspicuous (and in some specimens the depigmented stripe is obscured). Irregular small dark patches or horizontally elongated spots often extend along lateral line. Ventral flank with irregular broken vertical bands and vertically elongated spots, especially over anal-fin pterygiophores. Caudal filament darker than body, with irregular dark markings or bands along entire length. 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 with light scattering of brown chromatophores. Anal-fin rays with light or dark patches of chromatophores, with overall anal-fin pigmentation varying greatly, from almost unpigmented to dark mottled pattern. Color in live individuals similar to preserved specimens, with opercular region usually rosy due to underlying gills.

Size. Moderate adult size, largest specimen examined 200 mm (n = 754). Largest male specimen examined 181 mm TL, 139 mm LEA (n = 25). Largest female specimen examined 172 mm TL, 137 mm LEA (n = 37). Maximum male size in type series 149.0 mm LEA vs. 133.3 mm LEA for females (Giora & Malabarba, 2009).

Sexual dimorphism. Sexually mature males attain slightly larger sizes, and develop longer and deeper caudal filaments than immature individuals and breeding females ( Figs. 26 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 large breeding males usually with paddle-like compression, sometimes free of electrocytes in tip. No known sexual dimorphism in pigmentation.

Geographic distribution. Argentina, Bolivia, Brazil, Paraguay, and Uruguay ( Fig. 27 ). Widely distributed through Patos-Mirim lagoon system, some coastal drainages of Rio Grande do Sul north of Lagoa dos Patos , Uruguay drainage, Paraná downstream of the former Guaíra Falls , and lower to upper Paraguay to as far north as 14°45′S .

Population variation: The osteological diagnostic characters listed in the differential diagnoses that distinguish B. gauderio from B. pinnicaudatus were observed in cleared and stained specimens of B. gauderio from both the Uruguay and Paraná drainages. We also found complete overlap in the range of meristics ( Tables 2-5) and morphometric proportions ( Table 14), and observed similar pigmentation among populations of B. gauderio from the Patos-Mirim lagoon system, Uruguay drainage, and Paraguay drainage. These observations, in combination with molecular data ( Crampton et al., 2016), support the hypothesis that all populations we have assigned to B. gauderio are members of a single geographically widespread species, which is morphologically and genetically distinct from its allopatric sister species B. pinnicaudatus , known from the Amazon basin and coastal drainages of French Guiana, and from all other congeners.

Ecological notes. Brachyhypopomus gauderio inhabits vegetated river banks, slow-moving creeks, swamps, lagoons, and flooded areas, often with low dissolved oxygen concentrations (<0.5 mgl-1) (Giora & Malabarba, 2009). It is typically the most locally abundant congener throughout its range, and is often one of the most common fishes in aquatic vegetation. Brachyhypopomus gauderio is typically found in systems with relatively high electrical conductivity (50-250 μScm-1) and pH values ranging from 6.5 to 8.5, but is also found in higher conductivity systems (250-750 μScm- 1), and less commonly in lower conductivity systems (<50 μScm-1) ( Silva et al., 2003: 333, fig.2). Silva et al. (2003) report large seasonal variations in temperature, conductivity, and pH from collecting sites in Uruguay. Populations from high latitudes are exposed to a colder, drier austral winter and most foraging and breeding occurs during the warmer summer months ( Giora et al., 2014). Respiratory adaptations associated with hypoxia tolerance are discussed by Carter & Beadle (1931).

Reproductive seasonality, life history, and ecology in B. gauderio are documented by several authors ( Gavassa et al., 2012; Giora et al., 2014; Miranda et al., 2008; Quintana et al., 2004; Silva et al., 2003). It breeds during the austral summer, with maturation probably triggered by rising temperature and a change in photoperiod. During the breeding season it lives in dense social groups, and exhibits a sex ratio of mature individuals highly skewed towards females (around 3:1, despite observations of a primary sex ratio close to unity in a long-term laboratory population), possibly due to elevated male mortality related to stress from intrasexual competition ( Gavassa et al., 2012; Miranda et al., 2008). Males exhibit a wider spacing, and move less than females – consistent with a polygynous or polygynandrous mating strategy resembling exploded lek polygyny ( Miranda et al., 2008). During the austral winter B. gauderio exhibits gonadal quiescence, reduced activity and feeding, and a slower EOD rate ( Giora et al., 2014; Silva et al., 2002; Silva et al., 2003). Sullivan (1997) cites a personal communication from D. Stewart (State University of New York, Syracuse) reporting that five specimens from FMNH lot 86684 from the Pantanal of Mato Grosso, Brazil (listed below) were “found aestivating in dry soil”.

The spawning behavior of B. gauderio has been observed from infra-red video recordings in aquaria (pers. comm., P. Stoddard). Females usually spawn in the presence of one or more males, which fertilize the eggs as they leave the ovipositor. This species also deposits individual fertilized eggs in water hyacinth leaf bracts above the surface. Here trapped pools of rain water presumably form a favorable, predator-free environment for the larva. Parental care of eggs or larvae is unknown in both males and females ( Miranda et al., 2008), although see Giora et al. (2014). As in B. occidentalis , adult size classes of B. gauderio more or less disappear subsequent to the breeding season, a pattern consistent with an annual life cycle ( Silva et al., 2003).

The diet of B. gauderio is dominated by small aquatic insect larvae and microcrustacea, with some (likely incidental) consumption of vegetable matter ( Giora et al., 2014).

Co-occurring congeners: Through most of its range, B. gauderio occurs in geographical sympatry and in ecological syntopy with B. bombilla and B. gauderio . Brachyhypopomus gauderio also co-occurs with B. brevirostris and B. walteri in the upper río Paraguay.

Local names. Argentina, Paraguay: morenita; Bolivia: cuchillo; Brazil: tuvira, moreninha, tuvira-de-sela ( Malabarba et al., 2013) (south), sarapó (north); Uruguay: morenita, limpiavidrio.

Remarks: Identity of the neurobiology model species: B. gauderio is a model species for studies of the electrosensory system, and is the subject of multiple papers on neurobiology, neuroethology, EOD plasticity, and ecology – many of which stem from research at the laboratories of Angel Caputi, Omar Macadar, and Ana Silva (Instituto de Investigaciones Biológicas Clemente Estable, Uruguay), Carl Hopkins (Cornell University), Michael Markham (University of Oklahoma), and Philip Stoddard (Florida International University) (see Introduction). Laboratory studies of B. gauderio at the Hopkins and Stoddard labs have been based on captive populations that derive from Uruguayan stock (pers. comm., P. Stoddard). We confirmed from cleared and stained specimens that populations from the Stoddard Lab exhibit the osteological characters diagnostic of B. gauderio . Multiple studies prior to ca. 2010 refer to B. gauderio as B. pinnicaudatus (or Hypopomus pinnicaudatus ). Prior to Giora & Malabarba’s (2009) description of B. gauderio , which we confirm here as a valid species, B. pinnicaudatus was thought to constitute a single species distributed through much of northern and southern South America.

Invasive populations: We examined three MZUSP lots of B. gauderio collected at sites in the upper Paraná drainage, well upstream of the former Guaíra Falls (drowned by the Itaipu hydroelectric dam since 1982), and also upstream of additional hydroelectric dams (see ‘Suspected introduced records′ in Material examined). These were collected in 1995 and 2003. Graça & Pavanelli (2007) and Meschiatti & Arcifa (2009) list B. gauderio (therein listed as B. pinnicaudatus ) as an introduced species in the upper Paraná. Citing R. Campos-da-Paz of the Universidade Federal do Rio de Janeiro by personal communication, Graça & Pavanelli (Graça & Pavanelli, 2007) suggest that B. gauderio was likely introduced by sport fishermen, who use the species as live bait. They also report that B. gauderio is now common in various floodplain lakes in the upper Paraná basin. The sale of live B. pinnicaudatus and species of Gymnotus for sport fishing is very common throughout southern Brazil (pers. comm., F. C. T. Lima, ZUEC), and is also common in the lower Paraguay basin (WGRC pers. obs. from Entre Ríos, Argentina) and upper rio Xingu (pers. comm., R. E. Reis, MCP). Galves et al. (2009), and Meschiatti & Arcifa (2009) comment on the prevalence of introduced fish species in the upper Paraná. We illustrate the occurrence of these introductions in Fig. 27 (with grey circles) but omit them from the range of the genus presented in Fig. 2 .

Material examined. 753 specimens. Argentina (localities from Paraná dr.). Chaco. MSNG 27458, 2, 98-102 mm LEA, Resistencia, Paraná dr., ca. 27°27′S, 058°59′W (from photograph). Corrientes. MACN-ict 9459, 9, 109-134 mm, Iberá wetlands, Laguna Galarza, Paraná dr., 28°04′56″S, 056°42′04″W. Entre Ríos. MACN-ict 9460, 1, 92 mm, Pre-Delta National Park, Arroyo Los Dorados, río Paraná floodplain, Paraná dr. 32°08′08″S, 060°37′26″W. UF 177364 , 5 (1 CS), 135-175 mm, nr. La Paz, río Paraná floodplain, Paraná dr., ca. 30°42′S, 059°39′W. Bolivia. Santa Cruz. FMNH 54542, 1, 77 mm, Puerto Suárez, río Paraguay , Paraná dr., ca. 18°55′S, 057°47′W. Brazil. Mato Grosso (localities from rio Paraguai [Paraguay] dr., Paraná dr.). AMNH 97895, 2, 55-117 mm, rio Pixaim [Pixaime], ca. 16°44′S, 056°51′W. BMNH 1895.5.17.265-268 (part), 1, 64 mm, mun. Cácares, Descalvados, 16°43′59″S, 057°44′54″W. BMNH 1900.4.14.91-94 (part), 2, 75-79 mm, mun. Carandàzinho, rio Cuiabá , ca. 16°27′S, 056°08′W. CAS 72225, 1, 82 mm, “Mato Grosso, Brazil or Asunción , Paraguay [or río Paraguay], no coordinates. FMNH 86684, 5, 79-127 mm, Porto Cercado, side of Poconé-Porto Cercado rd. , rio Cuiabá , affl. rio Piquiri , 16°30′S, 056°22′W. FMNH 108541, 12, 55-100 mm, mun. Corumbá, on hwy. MS-184, swamp, lower rio Negro , 19°20′17″S, 056°57′42″W. FMNH 120674, 1, 115 mm, mun. Cáceres, nr. Cáceres, ca. 16°05′S, 057°41′W. MZUSP 4460 , 1 , 45 mm, mun. Santo Antônio de Leverger , lake nr. Santo Antônio de Leverger , rio Cuiabá , ca. 15°51′S, 056°04′W. MZUSP 19224 , 1 , Poconé, rio Cuiabá , ca. 16°15′S, 056°37′W. MZUSP 25149 , 2 , 67-70 mm, mun. Cáceres, Ilha da Taiamã [Estação Ecológica Taiamã], 16°53′S, 057°27′W [coordinates from center of island]. MZUSP 35910 , 1 , 67 mm, mun. Itiquira, Fazenda Santo Antônio do Paraíso , lakes between rio Piquiri and rio Itiquiri, ca. 17°12′S, 054°09′W. MZUSP 77202 , 5 , 25-134 mm, Nobres Paraguai, Represa da Fazenda Pé de Serra , rio Cuiabá , 14°45′S, 056°40′W. MZUSP 83562 , 3 , immature, 55-67 mm, MZUSP 83603 , 1, 124 mm, temporary lake, rio Itiquira /Piquiri, 17°28′13″S, 055°14′46″W. MZUSP 83607 (part), 3, immature, 50-76 mm, mun. Coxim, Paraguai Lagoa, source of Ribeirao dos Veados, affl. rio Coxim ( rio Taquari ), 18°25′21″S, 054°50′06″W. MZUSP 96652 , 2 , 66-67 mm, Pantanal de Paiaguás , swamp 1 km Vila de Mimoso, 16°17′S, 055°48′W. MZUSP 96703 , 2 , immature, 63-69 mm, mun. Barão de Melgaço , Pantanal de Paiaguás , rio Mutum , between Vila de Mimoso and Joselândia, 16°19′30″S, 055°49′59″W. ZUEC 3697, 2, 86-101 mm, ZUEC 5146, 3, 74-106 mm, ZUEC 5726, 15, 80-115 mm, mun. Poconé, Porto Cercado, rio Cuiabá , 16°31′S, 056°23′W.ZUEC 4473, 2, 42-49 mm, mun. Poconé, Transpantaneira hwy, km 24, rio Claro , 16°33′S, 056°42′W. ZUEC 5466, 1, 74 mm, mun. Poconé, rio Piraputanga , affl. rio Vermelho , affl. rio Cuiabá , ca. 16°20′S, 053°56′W. Mato Grosso do Sul. MUSM 17129 , 2 (1 immature, 80 mm, 1 female, 101 mm), rio Negro on rd. between “NHE Colandia and Brazcs”, 19°12′09″S, 055°03′23″W [longitude reported incorrectly on label as 052°03′23″W]. MZUSP 36386 , 5 , 36-98 mm, mun. Corumbá, Fazenda Nhumirim, Nhecolândia, 19°15′S, 057°02′W. MZUSP 59442 (part), 10 (4 immature, 67-92 mm, 6 female, 62-113 mm), rio Vermelho , rio Miranda , 19°37′22″S, 056°57′27″W. MZUSP 59646 , 29 (1 CS), 45-172 mm (14 sexed: 2 immature, 67-81 mm, 5 female, 108-172 mm, 7 male, 96-168 mm), Baía da Passagem , at Fazenda Caceres, Nhecolândia, 19°08′17″S, 056°49′14″W. Rio Grande do Sul. FMNH 54538, 1, 101 mm, Cacequy [Cacequi], rio Ibicuí , Uruguay dr., ca. 29°53′S, 054°49′W. FMNH 54546, 1, male, 180 mm, Uruguiana, rio Uruguai , Uruguay dr., ca. 29°45′S, 057°05′W. MCP 9710 , 1 , male, 164 mm, mouth of the arroio da Faxina, affl. rio Guaíba , Patos-Mirim dr., no coordinates. MCP 11135 , 1 , male, 144 mm, mun. Santo Angelo, Fazenda dos Hinz, rio Piratini , Uruguay dr., ca. 28°42′S, 054°25′W. MCP 13956 , 2 , 83-94 mm, hwy. BR-290, ca. 10 km BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°03′13″S, 051°26′17″W. MCP 14177 , 1, 168 mm, channel, hwy. BR-290, ca. 12 km BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°03′19″S, 051°27′17″W. MCP 14459 , 2 (1 female, 138 mm, 1 male, 140 mm), BR-290, channel, ca. 2 km BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°02′39″S, 051°21′20″W. MCP 14606 , 5 (1 CS) (2 female, 139-147 mm, 3 male, 128-156 mm), channel, hwy. BR-290, ca. 2 km BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°02′46″S, 051°21′07″W. MCP 14775 , 2 , male, 142-178 mm, mun. Uruguaiana, Sanga Bárbara, Uruguaiana, affl. rio Uruguai , Uruguay dr., 29°48′00″S, 057°06′00″W. MCP 15326 (part), 2, 101-114, canals along hwy. BR-290 between 1 and 6 km junction with hwy. BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., between 30°02′39″S, 051°21′20″W and 30°02′48″S, 051°23′27″W. MCP 19547 , 2 , 140-200 mm, bridge on São Gabriel-Tiaraju hwy., affl. rio Vacacaí , affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°17′29″S, 054°20′18″W. MCP 19549 , 6 , 48-156 mm, MCP 19553 , 2 , 35-60 mm, bridge over Banhado do Inhatium , hwy. BR- 290, 21 km São Gabriel, affl. rio Ibicuí , Uruguay dr., 30°15′43″S, 054°31′33″W. MCP 20216 , 3 , 70-100 mm, mun. Eldorado do Sul, on hwy. BR-290, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°02′36″S, 051°20′56″W. MCP 20218 , 3 , 109-157 mm, arroio Passos dos Carros, on rd. linking hwy. BR-116 to Guaíba, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°05′55″S, 051°23′15″W. MCP 21168 , 1 , female, 104 mm, MCP 21169 , 1, 115 mm, channel on margin hwy. BR-290, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., 30°02′36″S, 051°20′56″W. MCP 21726 , 5 , 87-134 mm, mun. Eldorado do Sul, channel on margin hwy. BR-290 ca. 5 km junction with BR-116, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., ca. 30°03′S, 051°24′W. MCP 37086 , 1, 100 mm, mun. Cerro Largo, arroio Brum Lageado, affl. rio Ijuí , Uruguay dr., 28°12′50″S, 054°49′36″W. MCP 37580 , 1, 131 mm, mun. Pelotas, nr. bridge to Pelotas, rio São Gonçalo , Patos-Mirim dr., 31°46′19″S, 52°20′33″W. MCP 43280 , 1 (holotype), male, 180 mm TL, 149 mm LEA, mun. Palmares do Sul, channel connecting Lagoa do Casamento and Lagoa dos Gateados, Patos-Mirim dr., ca. 30°28′S, 050°40′W. MCP 43281 , 1 (paratype), female, 124 mm LEA, MCP 43282 , 1 (paratype), female, 133 mm LEA, mun. Viamão, Lagoa Negra, Parque Estadual de Itapuã , Patos-Mirim dr. MCP 43283 , 2 (paratypes) (1 female, 83 mm LEA, 1 male, 92 mm LEA), mun. Capão da Canoa , Lagoa dos Quadros, rio Tramandaí dr., ca. 29°42′S, 050°06′W. MNRJ 30915 , 2 (paratypes) (1 female, 85 mm LEA, 1 male, 70 mm LEA), UFRGS 8874 , 1, 154 mm, mun. Cidreira, Lagoa Fortaleza, rio Tramandaí dr., 30°08′58″S, 050°14′30″W. MNRJ 32792 , 5 (paratypes) (2 female, 75-78 mm LEA, 3 male, 74-97 mm LEA), UFRGS 4240 , 10 , 42-134 mm, mun. Barra do Ribeiro , lake on hwy. linking BR-116 to Barra do Ribeiro , Patos Mirim dr., ca. 30°17′S, 051°21′W. MNRJ 32793 , 1 (paratype) male, 136 mm LEA, MCP 43284 , 1 (paratype) male, 123 mm LEA, MZUSP 100309 , 15 (paratypes) (7 female, 78-127 mm, 8 male, 60-127 mm), UFRGS 6499 , 1 (paratype), male, 123 mm, UFRGS 6500 , 1 , female, 123 mm, UFGRS 6501 , 1 , female, 125 mm, UFRGS 6502 , 1 , female, 162 mm, UFRGS 6503 , 1 , (paratype), male, 103 mm, UFRGS 6504 , 1 , male, 152 mm, UFGRS 6505 , 1 , male, 178 mm, UFRGS 6506 , 1 , male, 185 mm, UFRGS 6512 , 1 , female, 131 mm, mun. São Gabriel , stream, affl. arroio Piraí , 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. MZUSP 100308 , 1 male (paratype), 140 mm LEA, UFRGS 9581 , 2 (paratypes) (1 female, 126 mm LEA, 1 male, 129 mm LEA), UFRGS 10032 , 1 (paratype), female, 102 mm LEA, UFRGS 10035 , 1 (paratype), female, 106 mm LEA, UFRGS 10042 , 1 (paratype), male ( CS), 120 mm LEA, UFRGS 10048 , 1 (paratype), male ( CS), 118 mm LEA, mun. Charqueadas, flooded area nr. Arroio dos Ratos, rio Jacuí, Patos-Mirim dr., 29°57′32″S, 051°33′10″W. MZUSP 23167 , 1 , 52 mm, km 124, Camaquá-Pelotas hwy. BR-116, Patos-Mirim dr., ca. 31°45′S, 052°20′W. MZUSP 23169 , 1 , 43 mm, Porto Alegre, rio Jacuí, Patos-Mirim dr., ca. 30°02′S, 051°13′W. MZUSP 23630 , 3 (1 immature, 87 mm, 1 female, 127 mm, 1 male, 118 mm), São Leopoldo, Banhado Schreck, affl. rio dos Sinos, affl. rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., ca. 29°45′S, 051°09′W. MZUSP 25165 (part), 3, 97-132 mm, Camaquã, rio Jacuí , affl. rio Guaíba , Patos-Mirim dr., ca. 30°50′S, 051°49′W. NRM 27641, 2, 75-103 mm, stream, affl. Lagoa dos Quadros, nr. Praia do Barco , rio Tramandaí dr., ca. 29°42′S, 050°05′W. UFRGS 187 , 1 , 97 mm, UFRGS 719 , 2 , 137-141 mm, mun. Guaíba, Praia de Sans-Souci , rio Guaíba , Patos-Mirim dr., 30°03′05″S, 051°18′35″W. UFRGS 733 , 1 , 53 mm, mun. Guaíba, stream on hwy. BR- 290, 2 km junction with BR-116, affl. rio Guaíba , Patos-Mirim dr., 30°03′00″S, 051°20′59″W. UFRGS 2219 , 2 (paratypes), 100-152 mm, mun. Santo Antônio da Patrulha , creek between BR-290 and Santo Antônio da Patrulha , Patos-Mirim dr., ca. 29°52′S, 050°35′W. UFRGS 5641 , 3 (paratypes), 101-158 mm, mun. Viamão, Lagoa do Palácio , Patos-Mirim dr., 30°24′10″S, 050°57′25″W. UFRGS 3845 , 1 , 84 mm, mun. Palmares do Sul, Lagoa dos Barros, 1st canal, hwy. to Capivarí, Patos-Mirim dr., ca. 29°53′S, 050°18′W. UFRGS 3895 , 2 , 78-86 mm, mun. Guaíba, mun. Barra do Ribeiro , arroio Ribeirinho, affl. rio Guaíba , Patos-Mirim dr., 30°21′00″S, 051°24′59″W. UFRGS 4003 , 3 , 51-72 mm, mun. Cidreira, Lagoa do Lessa , at bridge, rio Tramandaí dr., 29°50′00″S, 050°10′00″W. UFRGS 4061 , 2 , 26-85 mm, 2nd canal to Lagoa dos Índios, km 10, rio Tramandaí dr., ca. 29°59′S, 050°17′W. UFRGS 5015 , 1, 132mm, mun. Arambaré, Patos-Mirim dr., no coordinates. UFRGS 6516 , 1 , female, 132 mm, UFRGS 6517 , 1 , female, 143 mm, UFRGS 6518 , 1 , female, 151 mm, UFRGS 6519 , 1 , female, 136 mm, UFRGS 6520 , 1 , female, 144 mm, UFRGS 6524 , 1 (paratype) male, 160 mm, UFRGS 10036 , 1 (paratype), male ( CS), 133 mm LEA, mun. Viamão, Lagoa Negra, Parque Estadual de Itapuã , Patos-Mirim dr., 30°22′52″S, 051°01′25″W. UFRGS 6765 , 1, 141 mm, UFRGS 6768 , 1, 149 mm, mun. Uruguiana, stream, affl. Uruguay dr., 29°45′56″S, 057°02′01″W. UFRGS 8933 , 1 (paratype), female, 102 mm LEA, arroio do Sal, creek on Estrada do Mar rd. , rio Tramandaí dr., 29°30′33″S, 049°53′34″W. UFRGS 14563 , 1 , 88 mm, mun. Maquiné, mouth of rio Maquiné , Lagoa dos Quadros, rio Tramandaí dr., 29°43′38″S, 050°08′36″W. UFRGS 14963 , 6 , 92-135 mm, mun.Tramandaí, Lagoa do Passo , rio Tramandaí dr., 29°52′01″S, 050°06′00″W. USNM 191645 , 1 , 77 mm, Porto Alegre, rio Guaíba , Patos-Mirim dr., ca. 30°02′S, 051°07′W. Paraguay (localities from Paraná dr.). Alto Paraguay (localities from río Paraguay dr.). FMNH 108059, 3, 93-130 mm, lagoon nr. Estância Cerrito, 21°27′S, 057°55′W. FMNH 108060, 1, 140 mm, flooded palm forest, riacho Coeyú, affl. río Paraguayin , ca. 21°26′S, 057°58′W. FMNH 117751, 1, 59 mm, río Negro , at confl. with río Paraguay , ca. 20°09′S, 058°10′W. MZUSP 54332 , 1 , female, 104 mm, Puerto 14 de Maio, ca. 20°18′S, 058°06′W. Boquerón (localities from río Paraguay dr.). ANSP 185115, 1, 132 mm, pond, N side TransChaco hwy. at km 464.1, ca. 22°15′S, 060°30′W. ANSP 185116, 5, 84-134 mm, marsh at Mariscal Estigarribia, ca. 22°00′S, 060°37′W. NRM 35483, 1, 181 mm, Estancia Água de Sidia , ca. km 100 on Filadelfia-Madrejon hwy. (5.2 km off rd.), ca. 21°27′S, 059°53′W. Caaguazú. NRM 42920, 1, 47 mm, stream crossing Colonia Sommerfeld-Repatriación rd. , affl. río Paraguay , 25°36′02″S, 055°47′11″W. Central (localities from río Paraguay dr.). AMNH 1009, 1, CAS 72215, 2, 143-152 mm, Campo Grande, lagoons 5 km Asunción, ca. 25°19′S, 057°31′W. MZUSP 77990 , 1 , 34 mm, Balneário Joly, Zona de Pirayú , ca. 25°29′S, 057°14′W. NRM 42400, 1, 123 mm, swamp nr. lago Ypacaraí, N Areguá, 25°16′16″S, 057°23′51″W. UMMZ 205591, 2, 102-103 mm, ca. 1 km S Puente Remanso, E shore río Paraguay , 25°12′30″S, 057°33′00″W. UMMZ 205874, 11, 41-125 mm, ca. 1 km S Puente Remanso, flooded pasture at margin río Paraguay , 25°12′30″S, 057°33′00″W. UMMZ 205912, 5, 27-78 mm, Arroyo Pirayú, 13 km W Caacupe, affl. lago Yparcaraí, río Salado , 25°23′12″S, 057°14′42″W. UMMZ 206001, 4 (part), 97-144 mm, río Salado (nr. mouth) at bridges 5.4-5.85 km N Limpio, ca. 25°08′S, 057°25′W. Concepción (localities from río Paraguay dr.). NRM 43362, 1, 90 mm, NRM 44254, 3, 19-31 mm, NRM 44259, 23, 30- 140 mm, Isla Peña Hermosa, río Paraguay , S mouth riacho La Paz, 22°24′09″S, 057°51′13″W. UMMZ 207817, 1, 126 mm, Paso Horqueta, río Aquidabán , 23°03′48″S, 057°23′24″W. ZMH 11631, 1, 113 mm, Puerto Max, Arroyo Postillón, ca. 22°41′S, 057°44′W. Misiones. ANSP 175178, 3, 110-149 mm, pool (rd. to Ayolas ?), affl. río Paraná , 27°19′40″S, 056°43′54″W. ANSP 185118, 2, 32-79 mm, marshes on rd. from Ayolas to main Asunción-Encarnación hwy. (Ruta 1), 200 m S km 18/A276, affl. río Paraná , ca. 27°23′S, 056°47′W. UMMZ 207463, 1, 151 mm, río Paraná ca. 2 km E Ayolas, río Paraná , 27°24′00″S, 056°46′12″W. Ñeembucú (localities from río Paraguay dr.). NRM 32801, 1, 48 mm, NRM 32829, 9, 53-102 mm, NRM 32852, 1, 42 mm, Paso Cornelio , swamp, Pilar-Humaitá rd. , nr. Humaitá , 27°03′09″S, 058°25′39″W. NRM 32870, 1, 103 mm, km 17 on Pilar-Humaitá rd. , 26°58′44″S, 058°18′00″W. Presidente Hayes (localities from río Paraguay dr.). AMNH 99960, 50, 51-130 mm, AMNH 99977, 1, 154 mm, Estancia la Golondrina , 140 km NW Asunción, marshlands affl. río Confuso , ca. 24°36′S, 058°07′W. ANSP 170413, 3, 85-96 mm, pool, km 15, Ruta General Bruguez , ca. 24°45′S, 058′49′W [coordinates for Fortín General Bruguez]. ANSP 185114, 1, 63 mm, pools on Rancho Salmo 23, ca. 8 km towards Clorinda from Puente Remanso , affl. río Negro , ca. 25°11′S, 057′34′W. ANSP 185117, 1, 129 mm, pools nr. Puente Remanso , ca. 25°10′S, 057°33′W. FMNH 54540, 2, 66-125 mm, Villa Hayes , ca. 25°05′S, 057°31′W. NRM 22601, 1, 32 mm, military post at General Bruguez , río Pilcomayo , 24°44′33″S, 058°50′07″W. NRM 27919, 1, 140 mm, NRM 32525, 4, 61-135 mm, infantry regiment Pedro Juan Caballero , río Pilcomayo , 24°38′56″S, 058°48′18″W. NRM 32524, 10, 81-105 mm, General Bruguez , ca. 1 km N military camp, río Pilcomayo , 24°43′38″S, 058°49′10″W. NRM 32526, 11, 57-156 mm, military post at general Bruguez , río Pilcomayo , 24°44′43″S, 058°50′10″W. NRM 32528, 6, 69-104 mm, Estancia la Rural , pool nr. río Confuso , 24°50′47″S, 057°46′44″W. NRM 35257, 39, 92-144 mm, Tajamar , km 78, trans-Chaco rd., 24°48′32″S, 057°46′57″W. NRM 35349, 101, 21-172 mm (1 sexed: 1 male, 172 mm), Estero Guazú at Estancia Loma Verde , ca. 10 km Concepción-Pozo Colorado rd., 23°34′53″S, 058°01′53″W. NRM 35447, 5, 26-117 mm, NRM 35830, 8, 38-106 mm, N branch riacho Negro at Makthlawayia , 23°15′58″S, 057°37′42″W. NRM 35668, 7, 58-106 mm, km 37, Pozo Colorado-Concepción rd. , riacho Negro , 23°30′53″S, 057°49′17″W. UMMZ 206972, 3, 95-120 mm, Puente Remanso bridge [nr. Remansito], ca. 25°10′S, 057°32′W. UMMZ 207026, 24, 45-145, marsh, 34.3 km NW toll booth on puente Remanso , río Confuso , 25°04′54″S, 057°36′00″W. UMMZ 207098, 4, 106-138 mm, small stream ca. 33.7 km NW toll booth on Puente Remanso bridge ( Estancia La Golondrina ), affl. río Confuso , 25°04′54″S, 057°36′00″W. UMMZ 207369, 6, 127-154 mm, Trans-Chaco hwy., E side, 0.2 km, 1.0 km SE entrance to Estancia Juan de Zalazar , riacho San Carlos , 23°01′36″S, 059°15′00″W. UMMZ 207381, 11, 118-171 mm, pond E rd. ca. 6.6 km N Trans-Chaco hwy., ca. 46 km SE Filadelfia, ca. 22°38′S, 059°43′W. UMMZ 207565, 4, 151-188 mm, UMMZ 207598, 9, 55-140 mm, pools at bridge ( Puerto Falcón to Argentina ), ca. 12 km WSW Chaco-I, río Pilcomayo , 25°15′48″S, 057°42′36″W. UMMZ 207588, 1, 88 mm, pools ca. 83.2 km Puerto Falcon , 24°52′54″S, 058°18′36″W. UMMZ 207620, 1, 120 mm LEA, riacho Pilco , ca. 25°06′S, 057°46′W. UMMZ 216612, 4, 72-93 mm, Estancia La Golondrina , marshlands, affl. río Confuso , ca. 24°36′S, 058°07′W. USNM 232235 , 4 , 78-106 mm, río Confusa [Confuso], ca. 25 km E Trans-Chaco, ca. 25°06′S, 057°34′W. San Pedro (localities from río Paraguay dr.). NRM 33612, 1, 48 mm, km 20 on San Pedro-Nuevo Germania rd. , 23°59′23″S, 056°57′13″W. UMMZ 206572, 1, 122 mm, río Corrientes , affl. río Jejuí Guazú , 24°22′54″S, 055°56′24″W. Region not specified. BMNH 1927.11.23.31, 1, 117 mm, swamp at Makthalawaiya , Paraguayan Chaco , no coordinates. CAS 72224, 2, 38-56 mm, FMNH 52591, 1, 140 mm, Arroyo Chagalalina , affl. río Aquido Canigi , no coordinates. NRM 33632, 1, 132 mm, NRM 33634, 1, 27 mm, listed “labels lost, but known to come from S. Kullander’s or B. Delling’s collection efforts [in Paraguay]”. Uruguay. Artigas (localities from Uruguay dr.). MNHN-Uruguay 1746, 1, río Cuareim , Laguna de las Lavanderas , 30º23′34″S, 056º27′33″W. MNHN-Uruguay 2823, 1, Arrocera Conti , island in río Uruguay , 30º29′27″S, 057º51′55″W. NRM 56105, 5, 55-79 mm, NRM 56106, 1, 95 mm, N Bella Unión, lagoon on río Uruguay , 30º13′03″S, 057º37′18″W. ZVC-P 19, 4, ZVC-P 2925, 14, ZVC-P 3518, 1, ZVC-P 7984, 2, Estancia El Ombú , Barra del Yucutuyá , río Cuareim , 30º18′09″S, 057º23′21″W. ZVC-P 2923, 1, ZVC-P 7983, 1, Franquia , Bella Unión , Laguna Redonda , 30º14′46″S, 057º36′22″W. Cerro Largo. ZVC-P 5002, 1, Paso Mazangano , Route 44, río Negro , Uruguay dr., 32º06′36″S, 054º40′06″W. Durazno. UF 183774 , 2 ( CS), 118-155 mm, Laguna Lavalle , río Negro , Uruguay dr., 33°01′16″S, 055°22′30″W. Paysandú. USNM 86173 , 1, 101 mm, Paysandú , Uruguay dr., ca. 32°19′S, 58°03′W. Río Negro (localities from Uruguay dr.). ZVC-P 4658, 1, Estero de Farrapos S side San Javier , 32º40′34″S, 058º07′49″W. ZVC-P 4696, 1, Estero de Farrapos , mouth of Arroyo Román Grande , 32º50′35″S, 058º05′05″W. Rocha (localities from Patos-Mirim dr.). CU 77186, 1, bañado, Route 19, no coordinates. CU 77187, 1, cañada, Route 19, no coordinates. ZVC-P 5917, 1, Potrerillo , Laguna Negra , 33º58′39″S, 053º38′29″W. ZVC-P 5919, 1, Arroyo de las Negras , Route 19, km 22, Laguna Mirín , 33º35′53″S, 053º41′00″W. ZVC-P 5920, 2, río San Luis , Route 19, km 30.65, affl. Laguna Merín , 33º36′06″S, 053º43′32″W. Salto (localities from Uruguay dr.). NRM 52215, 6, 106-144 mm, embayment of río Uruguay , Constitución , 31º03′57″S, 057º50′20″W. NRM 56068, 1, 141 mm, Constitución , río Uruguay , 31º04′03″S, 057º50′45″W. Tacuarembó. ZVC-P 1992, 4, Paso del Sauce above Arroyo Yaguarí , 29 km S Pueblo Ansina, affl. río Negro , Uruguay dr., 32º02′00″S, 055º22′01″W. Treinta y Tres (localities from Patos-Mirim dr.). NRM 61393, 1, 86 mm, affl. Arroyo del Parao , Ruta 18, W Vergara, río Olimar Grande , 32º55′12″S, 053º55′18″W. NRM 61473, 3, 49-63 mm, Arroyo Corrales del Parao , Ruta 91, S Vergara, río Olimar Grande , 33º01′46″S, 053º52′57″W. ZVC-P 5918, 2, Arroyo El Tigre, Ruta 17, km 322, affl. río Olimar , affl. río Cebollati , affl. Laguna Mirim , 33º14′50″S, 053º54′40″W. Region not specified. UF 183779 , 1 ( CS), 153 mm, aquarium specimen bred in captivity by P. Stoddard, Florida International University , from specimens exported from Uruguay. Suspected introduced records (15 specimens, grey circles in Fig. 27 ). Brazil. São Paulo (localities from rio Tietê dr., Paraná dr.). MZUSP 49201 , 9 , mun. Americana , Represa Santa Maria da Serra , ca. 22°45′S, 047°19′W [coordinates for town of Americana], coll. 7 Feb 1995, museum record states: “purchased from fishermen that sell bait in Praia Azul, Americana”. MZUSP 53862 , 4 , 121-176 mm, mun. Santa Maria da Serra , Represa de Barra Bonita , nr. Santa Maria da Serra , rio Piracicaba , ca. 22°34′S, 048°08′W, coll. 1995. MZUSP 83410 , 2 , 175-175 , mun. Bariri , downstream of hydroelectric barrage UHE Bariri , margin rio Tietê , ca. 22°08′S, 048°45′W, coll. 4 Apr 2003 .

Figures

Fig. 26. Brachyhypopomus gauderio. a. MZUSP 59646, female, 138 mm TL (head in lateral view, body in lateral and dorsal view); Brazil, rio Miranda, Paraguay dr. b. NRM 35349, male, 171 mm TL (body in lateral view); Paraguay, río Negro, Paraguay dr. Note sexual dimorphism in caudal filament height. Specimens fixed in formalin and preserved in EtOH. Scale bars = 5 mm.

Fig. 27. Collection records for Brachyhypopomus gauderio (circles) and B. menezesi (squares). Holotype locations are marked with open symbols. Grey circles refer to suspected anthropogenic introductions of B. gauderio to upper Paraná dr. (see species redescription in text). Elevation data refers to altitude above mean sea level (see Fig. 2 for legend). Note that the most southerly record for B. menezesi is in a headwater of the rio São Francisco, near the drainage divide with rio Paraná headwaters.

Fig. 2. Collection records for Brachyhypopomus based on 11,750 specimens from 2,642 georeferenced museum lots. Map of South and southern Central America based on HydroSHEDS data. Elevation data refers to altitude above mean sea level.