Brachyhypopomus gauderio, Giora, Julia & Malabarba, Luiz R., 2009

Giora, Julia & Malabarba, Luiz R., 2009, Brachyhypopomus gauderio, new species, a new example of underestimated species diversity of electric fishes in the southern South America (Gymnotiformes: Hypopomidae), Zootaxa 2093, pp. 60-68 : 62-66

Brachyhypopomus gauderio , new species

( Fig. 1 )

Brachyhypopomus sp. Giora et al. (2008) [listed in comparative material of B. draco ].

Holotype: MCP 43280 (male, 149.0 mm LEA), Palmares do Sul, channel connecting Lagoa do Casamento and Lagoa dos Gateados (30°28’S, 50°40’W), 28 Sep 2006, F. Becker.

Paratypes: All from Brazil, Rio Grande do Sul. Laguna dos Patos drainage: MZUSP 100308, 1 (male, 139.6 mm LEA), Charqueadas, flooded area near Arroio dos Ratos creek (29°57’31.9”S, 51°33’10.1”W), 28 Nov 2005, J. Giora, D. Rocha & A. Ribeiro. UFRGS 10032, 1 (female c&s, 102.3 mm LEA), Charqueadas, flooded area near Arroio dos Ratos creek (29°57’31.9”S, 51°33’10.1”W), 24 Mar 2006, J. Giora, D. Rocha & C. E. Machado. UFRGS 9581, 2 (1 male, 128.6 mm LEA, 1 female, 126.3 mm LEA), UFGRS 10042, 1 (male c&s, 119.6 mm LEA), UFGRS 10035, 1 (female c&s, 105,9 mm LEA),Charqueadas, flooded area near Arroio dos Ratos creek (29°57’31.9”S, 51°33’10.1”W), 22 Sep 2005, J. Giora, D. Rocha & R. Hirano. UFRGS 10048, 1 (male c&s, 118.4 mm LEA), Charqueadas, flooded area near Arroio dos Ratos creek (29°57’31.9”S, 51°33’10.1”W), 26 Jan 2006, J. Giora, D. Rocha & T. Giora. MCP 43281, 1 (female, 124.3 mm LEA), UFRGS 6524, 1 (male, 125.8 mm LEA), Viamão, Parque Estadual de Itapuã, Lagoa Negra (30°21’35”S, 50°58’34”W), 11 Nov 2003, J. Anza, D. Cognato, A. Dufech & J. Giora. UFRGS 10036, 1 (male c&s, 132.5 mm LEA), Viamão, Parque Estadual de Itapuã, Lagoa Negra (30°21’35”S, 50°58’34”W), 11 Apr 2002, J. Anza, M. Azevedo, A. Dufech & J. Giora. MCP 43282, 1 (female, 133.3 mm LEA), Viamão, Parque Estadual de Itapuã, Lagoa Negra (30°21’35”S, 50°58’34”W), 6 Jan 2003, D. Cognato, T. Dias & J. Giora. MNRJ 32792, 5 (3 males, 74.4–97.2 mm LEA, 2 females, 75.0–78.0 mm LEA), Barra do Ribeiro, along the road between BR 116 and Barra do Ribeiro town (30°17’00”S, 51°21’00”W), 21 Oct 1987, L. Malabarba, F. Becker & M. Schneider. UFRGS 5641, 2 (males, 81.7–126.2 mm LEA), Viamão, Parque Estadual de Itapuã, Lagoa do Palácio (30°24’10”S, 50°57’25”W), 26 Nov 2002, J. Anza, L. Malabarba, T. Gonçalves & T. Hasper. UFRGS 2219, 2 (1 male, 120.8 mm LEA, 1 female, 80.0 mm LEA), Santo Antônio da Patrulha, creek between BR 290 and Santo Antônio da Patrulha city (29°52’00”S, 50°35’00”W), 3 Mar 1983, L. Malabarba, C. M. Malabarba & R. Reis. Rio Tramandaí drainage: UFRGS 8933, 1 (female, 101.6 mm LEA), Arroio do Sal, creek parallel to Estrada do Mar road (29°30’33”S, 49°53’34”W), 11 Mar 2005, J. Anza, J. Giora, L. R. Malabarba. MCP 43283, 2 (1 male, 91.6 mm LEA, 1 female, 83.1 mm LEA), Capão da Canoa, Lagoa dos Quadros (29°42’00”S, 50°06’00”W), 14 Nov 1988, L. Malabarba. Rio Uruguay drainage: UFRGS 6499, 1 (male, 102.1 mm LEA), UFRGS 6503, 1 (female, 84.1 mm LEA), MCP 43284, 1 (male, 123.1 mm LEA), MNRJ 32793, 1 (male, 135.7 mm LEA), MZUSP 100309, 15 (8 males, 59.8–127.1 mm LEA, 7 females, 78.0– 127.1 mm LEA), São Gabriel, stream tributary of Arroio Piraí, BR290 (30°18’56”S, 54°24’22”W), 26 Nov 2003, L. Malabarba, J. Giora, D. Cognato, G. Neves & J. Ferrer.

Non-type material: The following specimens were used to record the distribution of the new species, but are not used in the species description and are not part of the type series. However, they do not differ in morphometric or meristic characteristics from the type specimens. Brazil, Rio Grande do Sul: MCP 9710, 1, Porto Alegre, mouth of Arroio da Faxina; MCP 14177, 1, Eldorado do Sul; MCP 14459, 2, Eldorado do Sul; MCP 14606, 2, Guaíba; MCP 15326, 2, Eldorado do Sul; MCP 11135, 1, Santo Ângelo; USNM 191645, 1, Porto Alegre. Uruguay: ZVC –P 5002, 1, Paso Manzagano, Rio Negro; ZVC –P 1992, 1, Paso del Sauce. Paraguay: ANSP 185112, 1, Departamiento Cordillera; ANSP 185116, 5, Departamiento Boqueron; ANSP 185114, 1, Presidente Haynes; UMMZ 207817, 1, Concepcion; USNM 232235, 3, Presidente Haynes.

Diagnosis: Brachyhypopomus gauderio is diagnosed by the following features: body depth 11.0–14.1% of LEA (vs. 10.9–11.0% in B. jureiae , 10.1–10.9% in B. janeiroensis ); branchial aperture 20.4–28.1% of LEA (vs. 19.0–19.8% in B. jureiae ); caudal filament length 19.6–32.2% of LEA (vs. 42.3–45.8% in B. jureiae , 34.0–39.6% in B. janeiroensis ); anal-fin ray length 3.6–5.1% of LEA (vs. 3.3–3.4% in B. jureiae ); pectoral-fin length 4.9–6.4% of LEA (vs. 4.3–4.6% in B. jureiae ); snout to anal-fin origin 17.0–21.2% of LEA (vs. 16.1–17.4% in B. beebei ); number of anal-fin rays 180–216 (vs. 214–228 in B. beebei , 200–240 in B. occidentalis , 251–295 in B. brevirostris ); upper jaw equal to lower jaw (vs. upper jaw slightly longer than lower jaw in B. occidentalis , B. diazi , B. brevirostris and B. jureiae ).

Brachyhypopomus gauderio is diagnosed from B. pinnicaudatus by the following characters: caudal filament length 19.6–32.2% of LEA (vs. 32.3–42.3%); pectoral-fin length 4.9–6.4% of LEA (vs. 6.7–7.9%); head length 10.0–12.7% of LEA (vs. 12.4–15.6%); number of anal fin rays 180–216 (vs. 176–185).

Brachyhypopomus gauderio is diagnosed from the syntopic species B. draco and B. bombilla by the following characters: dorsal surface of the body with chocolate-brown stains that are connected forming a reticulated drawing contrasting with the yellow background, vs. dark brown dorsal surface with a variable number darker bands, nearly perpendicular or oblique to longitudinal body axis, never being interconnected in B. draco , and body background light brown with an irregularly scattered darker brown pigmentation more dense in dorsal half of body in B. bombilla ; anal-fin origin located at same line of posterior edge of pectoralfin, vs. anal-fin origin located posterior to posterior edge of pectoral-fin in B. draco ; distal portion of caudal filament moderately broadened vertically and laterally compressed in sexually mature males, vs. extreme broadened and forming a distinct paddle shaped structure in mature males of B. draco , and not broadened in B. bombilla ; body depth 11.0–14.1% of LEA (vs. 8.8–12.2% in B. draco , 9.4–11.0% in B. bombilla ); branchial aperture 20.4–28.1% of LEA (vs. 13.8–18.3% in B. bombilla ); mouth gape 14.4–18.5% of HL (vs. 9.5–16.5% in B. draco ); head width at operculum 52.4–73.2% of HL (vs. 48.4–65.0% in B. draco , 43.6–51% in B. bombilla ); head width at center of eyes 31.1–48.1% of HL (vs. 24.7–31.7% in B. bombilla ); interorbital distance 23.3–30.4% of HL (vs. 14.9–20.5% in B. bombilla ); number of anal-fin rays 180–216 (vs. 155–198 in B. draco ); upper jaw equal to lower jaw (vs. upper jaw slightly longer than lower jaw in B. bombilla ); precaudal vertebrae 20–21, 18–19 anterior and 1–2 transitional (vs. 21–23 vertebrae, 20–22 anterior and 1–2 transitional in B. draco ).

Description: Morphometric data are presented in Table 1. Head conical, nearly triangular in lateral view, snout short and blunt, eyes small, mouth terminal with upper jaw length equal to lower jaw, no teeth in both jaws. Body laterally compressed. Dorsal profile convex from snout to caudal filament, most notably at anterior half of body. Ventral profile convex from lower jaw to anterior anal-fin base; nearly straight from that point to caudal filament. Highest body depth located at anal-fin origin. Body depth increasing from head to anal-fin origin, remaining nearly same depth to close to 40th anal-fin ray, sharply decreasing from that point to caudal filament. Caudal filament moderately short in all specimens; caudal filament slender and nearly cylindrical in females, juveniles and males in non-reproductive period; caudal filament vertically broadened and laterally compressed in sexually mature males (see sexual dimorphism, below). Cycloid scales covering body, except head and fins. Scales smaller on anterior portion of body; five to seven series of large scales along mid-lateral portion of body, reducing to two or three series posteriorly. Mid-lateral scales nearly twice larger than dorso-lateral and dorsal scales and four times larger in diameter than anterior ones; smallest scales covering region of anal-fin pterygiophores. First anterior perforated scale of lateral line above pectoral-fin origin; lateral line irregular, not extending to caudal filament. Branchial aperture small and slightly anterior to pectoral-fin origin. Pectoral fins rounded and with perpendicular insertion; pectoral-fin rays i–ii + 13–15 (15–17 total pectoral-fin rays, n = 38, mode = 16). Anal-fin relatively long with vi–x + 173–206 rays (180–216 total anal-fin rays, n = 38, mode = 198). Anal-fin origin located at same line of posterior edge of pectoral fin. Precaudal vertebrae 20–21 (18–19 anterior, 1–2 transitional; n= 5).

95% confidence limit

LEA (mm) 149.0 38 50 151.9 96.9 24.56

Percentage of LEA

HL 10.5 38 10.0 12.7 11.3 11.10 11.57 0.71 Caudal filament length 20.1 36 19.6 32.2 24.7 23.64 25.77 3.14 Snout to anal fin origin 17.6 38 17.0 21.2 18.9 18.59 19.26 1.03 Depth of caudal filament 2.3 38 1.6 2.4 2.0 1.97 2.11 0.22 Longest anal fin ray 4.1 38 3.6 5.1 4.5 4.39 4.59 0.30 Longest pectoral fin ray 5.0 38 4.9 6.4 5.6 5.49 5.69 0.30 Body depth 13.1 38 11.0 14.1 12.9 12.59 13.16 0.86

Percentage of HL

Snout length 25.0 38 23.3 28.2 26.4 25.99 26.72 1.12 Gape width 18.3 38 14.4 18.5 16.2 15.84 16.59 1.14 Orbital diameter 9.6 38 9.0 12.1 10.8 10.50 11.01 0.77 Interorbital distance 30.3 38 23.3 30.4 26.4 25.87 26.90 1.57 Posterior nare to eye 6.3 37 3.4 6.3 5.0 4.76 5.22 0.69 Branchial aperture 27.8 38 20.4 28.1 25.5 24.80 26.25 2.21 Head width at operculum 67.2 38 52.4 73.2 64.9 63.23 66.65 5.20 Head width at eyes 46.2 38 31.1 48.1 41.2 38.90 42.40 3.81 Color in Life: General body color varying from light brown to yellow. Head darker than rest of body. Dorsal surface with chocolate-brown stains that are connected forming reticulated drawing contrasting with yellow background. Variable number of brown stripes running from dorsal stains to base of anal fin, roughly defined in middle of body and occurring from head to tip of caudal filament. Anal and pectoral fins speckled with dark brown pigment, with hyaline inter-radial membranes.

Secondary Sexual Dimorphism: The caudal filament of dominant mature males is laterally compressed, especially on its distal portion, differing from that of females, juveniles and non-dominant males, which is usually cylindrical (J. Giora & C. Fialho, in preparation). However, there is no sexual dimorphism in the caudal filament length of B. gauderio during any of its maturation stages.

Distribution: Brachyhypopomus gauderio is known from the Laguna dos Patos, Rio Uruguay and Rio Tramandaí drainages in the Rio Grande do Sul state, Brazil, being widely distributed from the central, southern and coastal regions of the state. It also occurs in the Rio Uruguay basin in Uruguay (ZVC–P 5002; ZVC–P 1992) and in the Rio Paraguay basin in Paraguay (ANSP 185112; ANSP 185116; ANSP 185114; UMMZ 207817; USNM 232235).

Habitat: Brachyhypopomus gauderio inhabits river banks, slow-moving creeks, lagoons, and flooded areas with muddy or sandy bottom; the occurrence of the species is always associated with abundant emergent or floating vegetation. Brachyhypopomus gauderio is sympatric and commonly syntopic with B. draco , and more rarely syntopic with B. bombilla . Throughout Rio Grande do Sul state the species was also collected along with the gymnotiforms Eigenmannia trilineata and Gymnotus sp.

Etymology: “ Gaudério ”, from the Brazilian folk traditions a synonym for “gaúcho”, meaning the person who lives in the countryside (pampas) of Rio Grande do Sul state, southern Brazil, Uruguay and Argentina, named in reference to the geographic distribution of the species.

Figures

FIGURE 1. Holotype (MCP 43280, male, 149.0 mm LEA) of Brachyhypopomus gauderio, Palmares do Sul, Rio Grande do Sul, Brazil.