Hemigrammus durbinae, Ota, Rafaela P., Lima, Flávio C. T. & Pavanelli, Carla S., 2015

Ota, Rafaela P., Lima, Flávio C. T. & Pavanelli, Carla S., 2015, A new species of Hemigrammus Gill, 1858 (Characiformes: Characidae) from the central and western Amazon and rio Paraná-Paraguai basins, Zootaxa 3948 (2), pp. 218-232 : 218-232

Hemigrammus durbinae , new species

( Figs. 1–4 )

Hemigrammus marginatus (not Ellis, 1911) ― Veríssimo et al., 2005: 4 [ Brazil, Mato Grosso, rio Cuiabá, Manso Reservoir]. Hemigrammus sp. “falso marginatus ” Lima et al., 2013: 270–271 [ Brazil, rio Madeira basin: photo, short description, diagnosis, habitat preferences, distribution in the rio Madeira basin].

Holotype. MZUSP 115984, 23.1 mm SL: Brazil, Amazonas, Careiro, lago Castanho, lago Janauacá complex, rio Solimões basin, c. 3º48'S, 60º23'W, P. Bayley, 5 Jul 1977.

Paratypes. Brazil, Amazonas, rio Solimões basin: MZUSP 102967, 282, 18.1–28.0 mm SL, same data as holotype; MZUSP 102732, 60, 14.0– 27.1 mm SL, Careiro, Lago do Castanho, São José, rio Solimões basin, c. 3º48'S, 60º23'W, P. Bayley, 27 Apr 1977; MZUSP 102433, 240, 14.6–27.0 mm SL; ZUEC 7774, 40, 19.3–27.7 mm SL, Careiro, Lago do Castanho, Lago Janauacá complex, c. 3º48'S, 60º23'W, P. Bayley, 13 Apr 1977; MZUSP 100610, 422, 19.1–27.1 mm SL, Careiro, Lago Castanho, lago Janauacá complex, c. 3º48'S, 60º23'W, P. Bayley, 1 Mar 1977; ZUEC 8392, 318, 14.4–22.5 mm SL, Manaquiri, Lago Murumuru, Lago Janauacá complex, c. 3º24'S, 60º16'W, P. Bayley, 7 Dec 1977; MZUSP 102978, 2, 23.5–23.8 mm SL, “furo” between Lago Murumuru and Paraná de Janauacá, c. 3º24'S, 60º16'W, P. Bayley, 6 Jul 1977; MZUSP 102759, 2, 20.4–21.4 mm SL, “furo” between Lago Murumuru and Paraná de Janauacá, c. 3º24'S, 60º16'W, P. Bayley, 22 Jun 1977; MZUSP 102765, 1, 23.5 mm SL, Manaquiri, Lago Murumuru, Lago Janauacá, c. 3º24'S, 60º16'W, P. Bayley, 11 May 1977; MZUSP 27113, 641, 15.1–27.6 mm SL; MCP 48335, 30, 19.5–26.0 mm SL; CAS 237761, 20, 20.0– 25.4 mm SL; ANSP 197274, 30, 19.0– 25.7 mm SL, Manaquiri, lago Janauacá, c. 3º24'S, 60º16'W, Alpha Helix Expedition, 7–25 Jan 1977; ZUEC 8323, 31, 16.7–25.9 mm SL, Iranduba, Lago Cantagalo, Lago Janauari complex, c. 3º12'S, 60º13'W, P. Bayley, 24 Jan 1979; MZUSP 102446, 934, 18.8–26.2 mm SL, Iranduba, lago Janauari, Olaria, c. 3º12'S 60º01'W, P. Bayley, 14 Apr 1977. Rio Purus basin: INPA 17482, 9, 22.1–24.4 mm SL, Beruri, igarapé Duas Bocas, Paraná do Jari, tributary of rio Purus, 4º53'07''S 62º20'11''W, L. H. Rapp Py-Daniel & C. P. Deus, 7 Jul 2001. Rondônia, rio Madeira basin: INPA 39505, 5, 2 c&s, 22.7–24.9 mm SL, Porto Velho, lago Xodó, near comunidade São Carlos, 8º26'15''S 63º29'56''W, Lúcia H. R. Py-Daniel, 19 Apr 2005; UFRO-I 685, 14, 23.4–26.5 mm SL, Humaitá, lago Puruzinho, rio Madeira, 7º22’04”S 63º03’40”W, 10 Feb 2012, A. Cella-Ribeiro UFRO-I 10619, 7, 19.2–20.3 mm SL; UFRO-I 10620, 13, 18.3–24.8 mm SL, Porto Velho, lago Cuniã, rio Madeira, 8º19'11''S 63º30'01''W, E. R. Silva, 10 Mar 2010; UFRO-I 11580, 20, 15.2–18.6 mm SL, Cerejeiras, igarapé Azul, 10 km on road RO-399, 13º19'10''S 61º03'16''W, Equipe LIP/ UNIR, 2 Sep 2011. Mato Grosso, rio Paraguai basin: NUP 6265, 10, 19.1–21.7 mm SL; NUP 9547, 1 c&s, 26.1 mm SL, Chapada dos Guimarães boundary with Nobres, córrego Forquilha, tributary of rio Cuiabá, 14º41'00''S 55º32'00''W, Nupélia staff, 24 Apr 2000; NUP 2153, 158, 21.5–25.4 mm SL, Barão de Melgaço, baía de Chacororé, tributary of rio Cuiabá, 14º57'07''S 55º42'59''W, Nupélia staff, 24 Feb 2003; NUP 6260, 19, 19.1–21.3 mm SL, Nupélia staff, 26 Apr 2003; NUP 9543, 22 c&s, 21.6–24.1 mm SL, Nupélia staff, 24 Feb 2003; NUP 6261, 50, 19.4–22.5 mm SL, Barão de Melgaço, baía Sinhá Mariana, tributary of rio Cuiabá, 16º20'20''S 55º54'10''W, Nupélia staff, 20 Mar 2002. Paraguay, Ñeembucu, río Paraguay basin: CZFCEN 323, 5, 19.6–23.7 mm SL, Mburicá, arroio Yacaré, tributary of río Paraguay, 26º39'S 58º05'W, H. V. Alcaraz et al., 17 Nov 2006. Concepción: MNHNP 3679, 31, 18.8–20.7 mm SL, San Carlos, Arroyo Blandengue, next to the rio Apa mouth, 22º14'15''S 57º22'19''W, J. Sarmiento et al., 15 Sep 1997. Itapúa, río Paraná basin: MNHNP 3683, 3, 29.0– 21.9 mm SL, Carmen del Paraná, arroyo Tacuary (on route 1 bridge), tributary of río Paraná, 27º13'11''S 56º09'53''W, M. Medina & S. Kullander, 20 Nov 1998.

Non types. Brazil, Amazonas, rio Solimões basin: ZUEC 8255, 95, 16.3–25.6 mm SL, Careiro, Lago Castanho (Lago Janauacá complex), São José, c. 3º48'S, 60º23'W, P. Bayley, 15 Feb 1978; MZUSP 100458, 101, 15.2–26.8 mm SL, Careiro, Lago do Castanho (Lago Janauacá complex), São José, c. 3º48'S, 60º23'W, P. Bayley, 10 Feb 1977; MCP 43962, 49, 15.5–23.4 mm SL, Manaquiri, Paraná de Janauacá, mouth of Lago Castanho, c. 3º24'S, 60º16'W, P. Bayley 24 Nov 1977; MZUSP 50074, 50, 17.7–27.1 mm SL, Careiro, Lago Castanho, lago Janauacá complex, c. 3º48'S, 60º23'W, Alpha Helix Amazon Expedition, 7–25 Jan 1977; ZUEC 6751, 1, 14.1 mm SL, Careiro, Lago Castanho, c. 3º48'S, 60º23'W, K. Okushigue, 6 Aug 1977; ZUEC 8470, 224, 14.5–21.2 mm SL, Manaquiri, Lago Murumuru (Lago Janauacá complex), c. 3º24'S, 60º16'W, P. Bayley, 21 Dec 1977; ZUEC 8459, 95, 14.2–21.5 mm SL, Manaquiri, Lago Murumuru (Lago Janauacá complex), c. 3º24'S, 60º16'W, P. Bayley, 7 Dec 1977; MZUSP 102738, 1, 26.3 mm SL, Manaquiri, Paraná de Janauacá, entrance of Lago Castanho, c. 3º28'S, 60º17'W, P. Bayley, 27 Apr 1977; ZUEC 8382, 141, 17.1–22.3 mm SL, Iranduba, Lago Janauari, Olaria, c. 3º12'S, 60º13'W, P. Bayley, 19 Jan 1978; ZUEC 8373, 252, 14.4–21.0 mm SL, Iranduba, Lago Janauari, near mouth, c. 3º12'S, 60º13'W; P. Bayley 21 Nov 1977; ZUEC 8316, 58, 13.7–19.8 mm SL, Iranduba, Lago Janauari, Olaria, c. 3º12'S, 60º13'W, P. Bayley, 22 Nov 1977; ZUEC 8400, 53, 17.5–21.9 mm SL, Iranduba, Lago Cantagalo, Lago Janauari complex, c. 3º12'S, 60º13'W, P. Bayley, 5 Jan 1978; ZUEC 8335, 453, 13.2–20.2 mm SL, Iranduba, Lago Janauari, c. 3º12'S, 60º13'W, P. Bayley, 10 Nov 1977; ZUEC 8454, 96, 17.3–23.2 mm SL, Iranduba, Lago Janauari, c. 3º12'S, 60º13'W, P. Bayley, 2 Feb 1978; MZUSP 102439, 461, 11.4–20.9 mm SL, Iranduba, Lago Janauari, near Canta Galo, c. 3º12'S, 60º13'W, P. Bayley, 14 Apr 1977; MZUSP 102744, 478, 14.9–22.6 mm SL, Iranduba, Lago Janauari, c. 3º12'S, 60º13'W, P. Bayley, 28 Apr 1977; MCP 43955, 340, 13.4–21.0 mm SL, Iranduba, rio Negro, lago Janauari, c. 3°13'S, 60°01'W, P. Bayley, 22 Nov 1977; MZUSP 100785, 17, 21.6–25.1 mm SL, Iranduba, Lago Janauari, at mouth, between Furo de Paracuuba and Lagoa Terra Preta, c. 3º12'S, 60º13'W, P. Bayley, 3 March 1977; MZUSP 102744, 478, 14.9–22.7 mm SL, Iranduba, Lagoa Janauari, Olaria, c. 3°13'S, 60°01'W, P. Bayley, 28 Apr 1977; MZUSP 63246, 47, 15.9–18.9 mm SL, Tefé, igarapé Cacau, 3°19'14''S 64°43'24''W, M. Goulding, 9 Sep 1979; INPA 17441, 6, 14.5–17.9 mm SL, Beruri, lago Ayapuá, tributary of rio Purus, 4º26'17''S 62º07'24''W, L. H. Rapp Py-Daniel & C. P. Deus, 10 Jun 2001; MZUSP 6012, 32, 15.6–17.3 mm SL, Beruri, lago Beruri, rio Purus basin, 3º50'S 61º20'W, Expedição Permanente à Amazônia. Pará, rio Amazonas basin: MZUSP 9156, 107, 12.1– 15.6 mm SL; MZUSP 50079, 25, 9.9–23.3 mm SL, Santarém, rio Maicá, tributary of rio Amazonas, 2º27'S 54º40'W, Expedição Permanente a Amazônia, 19–27 Oct 1971. Rondônia, rio Madeira basin: UFRO-I 10818, 19, 11.8–14.8 mm SL, Porto Velho, lago Cuniã, tributary of rio Madeira, 8º19'17''S 63º30'29''W, D. S. Souza, 16 Jun 2010; UFRO-I 10822, 2, 11.2–11.5 mm SL, Porto Velho, lago do Cuniã, 8º19'40''S 63º29'50''W, F. G. Vieira, 12 May 2009; UFRO-I 11132, 3, 11.6–11.7 mm SL, Pimenteiras do Oeste, rio Guaporé, 13º19'03''S 62º01'37''W, G. Torrente-Vilara, 25 May 2010; UFRO-I 10623, 3, 12.2–12.3 mm SL, Pimenteiras do Oeste, rio Guaporé, near ECOVALE, 12º29'59''S 63º33'51''W, T. H. S. Pires, 26 May 2010. Mato Grosso, rio Guaporé basin: MZUSP 37455, 40, 15.0– 19.3 mm SL, Vila Bela da Santíssima Trindade, rio Alegre, trib. Rio Guaporé, 30 km from Vila Bela da Santíssima Trindade, c. 15º2’ S, 59º58’W; MZ/Polonoroeste, 28–30 Sept 1984; MZUSP 18686, 2, 19.2– 20.4 mm SL, Vila Bela da Santíssima Trindade, rio Guaporé, c. 15º0’ S, 59º57’W, P.E. Vanzolini, 16 Dec 1976. Mato Grosso, rio Paraguai basin: NUP 9547, 1 c&s, 26.1 mm SL, Chapada dos Guimarães boundary with Nobres, córrego Forquilha, tributary of rio Cuiabá, 14º41'00''S 55º32'00''W, Nupélia staff, 24 Apr 2000. Following lots from Barão de Melgaço, baía Sinhá Mariana, tributary of rio Cuiabá, 16º20'20''S 55º54'10''W: NUP 6262, 19, 21.1–22.3 mm SL, Nupélia staff, 24 Mar 2003; NUP 6264, 20, 18.9–22.4 mm SL, Nupélia staff, 21 Mar 2002; NUP 6259, 1, 26.8 mm SL, Nupélia staff, 22 Apr 2004; NUP 6263, 27, 18.6–21.9 mm SL, Nupélia staff, 19–20 Mar 2002; NUP 9545, 8 c&s, 20.1–21.3 mm SL, 24 Mar 2003; NUP 9546, 2 c&s, 19.1–20.4 mm SL, Nupélia staff, 20 Mar 2002; NUP 9647, 18.3–20.7 mm SL, Nupélia staff, 24 Mar 2003.

Diagnosis. Hemigrammus durbinae differs from most congeners, with the exception of He. marginatus , by the absence of a conspicuous humeral spot and by possessing two dark patches of pigmentation on caudal-fin lobes. The new species can be distinguished from He. marginatus by possessing two conspicuous patches of dark pigmentation occupying most of the caudal-fin lobes, except the tips, which are hyaline (vs. relatively faint dark pigmentation along caudal-fin distal portion, tips of caudal fin dark), by having two dark narrow stripes along analfin base, the first sub-parallel to anal-fin base, extending approximately along region where hypaxial musculature and the muscles of anal fin meet, and the second along anal-fin base (vs. only an inconspicuous dark stripe along anal-fin base present). Additionally, He. durbinae can be diagnosed from He. marginatus by possessing 5–8 pored lateral line scales (vs. 8–14), upper jaw length 32.1–41.6% in head length (vs. 42.3–46.0%), dorsal-fin base length 9.9–13.1% of SL (vs.13.6–15.1% of SL), dorsal-fin length 22.7–27.1% of SL (vs. 27.6–32.6% of SL), and distance from eye to dorsal-fin origin 38.7–45.9% of SL (vs. 34.6–37.8% of SL). For a diagnosis from the similar-looking Hyphessobrycon diancistrus , see the Discussion, below.

Description. Morphometric data summarized in Table 1. Body compressed, moderately elongate; greatest body depth located anteriorly to dorsal-fin origin. Dorsal profile of head convex from premaxilla through anterior nostril, straight to slightly concave from latter point to tip of supraoccipital spine. Dorsal profile of trunk moderately convex from tip of supraoccipital spine through dorsal-fin origin; tilted down from latter point to adipose-fin origin and slightly concave along caudal peduncle. Ventral profile of body convex from tip of lower jaw to pelvic-fin origin; straight or slightly convex between pelvic-fin and anal-fin origin; tilted up along anal-fin base. Ventral profile of caudal peduncle slightly concave.

N Holotype Paratypes Mean SD Standard length (mm) 154 23.1 14.3–28.0 22.6 -

Percents of Standard length

Depth at dorsal-fin origin 150 29.1 25.2–35.6 29.1 1.80 Snout to dorsal-fin origin 149 52.8 49.6–56.1 53.0 1.15 Snout to pectoral-fin origin 149 28.8 26.7–34.7 29.2 1.33 Snout to pelvic-fin origin 149 45.7 44.2–51.0 47.5 1.29 Snout to anal-fin origin 149 61.7 59.5–65.6 62.8 1.49 Caudal-peduncle depth 148 10.0 7.2–11.7 9.6 0.82 Caudal-peduncle length 148 11.2 8.6–14.0 11.5 0.99 Pectoral-fin length 149 19.8 18.4–25.3 21.3 1.27 Pelvic-fin length 147 16.6 14.6–17.8 16.5 0.70 Dorsal-fin base length 149 12.2 9.9–13.1 12.1 0.58 Dorsal-fin length 148 25.4 22.7–27.1 25.6 1.03 Anal-fin base length 149 25.7 22.4–29.9 25.5 1.27 Anal-fin lobe length 148 20.1 17.9–23.8 20.7 1.06 Eye to dorsal-fin origin 149 42.0 38.7–45.9 42.1 1.31 Dorsal-fin origin to caudal-fin base 148 49.0 45.6–51.4 48.6 1.27 Bony head depth 149 23.4 21.3–27.5 23.8 1.23 Bony head length 149 25.1 23.0–30.4 25.0 1.06 End of dorsal-fin base to adipose-fin origin 149 21.5 19.2–24.1 22.0 0.90 Pelvic-fin origin to anal-fin origin 151 17.9 15.2–20.9 18.3 1.15 Supraoccipital spine to dorsal-fin origin 151 30.0 25.2–33.9 29.7 1.67 Snout to supraoccipital spine tip 151 23.3 21.3–27.3 23.4 1.12

Percents of Head length

Horizontal eye diameter 149 40.1 36.8–46.4 40.3 2.00 Snout length 149 28.0 21.3–30.9 27.4 2.45 Least interorbital distance 149 34.6 27.1–36.4 32.6 2.53 Upper jaw length 149 35.5 32.1–41.6 38.0 1.55 Jaws unequal, heterognathous, lower jaw protruding slightly ahead of upper jaw; mouth slightly superior. Maxillary slightly curved; posterior terminus slightly surpassing vertical through anterior margin of eye. Premaxillary teeth in two rows, outer row composed of 1*(95), 2(66), or 3(27) tricuspid teeth, central cusp longer; inner row with 5*(178) or 6(8) tri- to pentacuspid teeth, central cusp longer and broader. Maxilla with 0*(119), 1(40), 2(6) or rarely 3(2) uni- or tricuspid teeth along anteroventral margin, all equal in size. Dentary with 7–12 teeth, anteriormost four teeth larger than remaining, with 3–5 cusps, central cusp longer and broader, followed by a series decreasing gradually of size of 1(27) tricuspid teeth, and remaining two to nine unicuspid, smaller teeth ( Fig. 2 ).

Scales cycloid, with two to four radii; circuli marked anteriorly, but absent distally (‘ Hemigrammus type ’ according to Cockerell (1914)). Lateral line incomplete, slightly curved ventrally, with 5(27), 6(64), 7(33), or 8*(19) pored scales; longitudinal series including perforated scales, 27(11), 28(22), 29(46), 30(41), 31(15), 32*(11), or 33(2) scales; 4*(113) or 5(42) scales rows between dorsal-fin origin and lateral line; 3*(150) scales rows between lateral line and pelvic-fin origin. Predorsal scales 10(81), 11*(56), 12(13), or 13(3). Anal sheath along anal-fin base composed of 3(4), 4*(18), or 5(5) scales in a single row, covering the base of first unbranched rays to third to sixth branched anal-fin rays. Circumpeduncular scales 10(108), 11*(40) or 12(5). Caudal-fin scales covering about basal third of upper and lower caudal-fin lobes, mainly on upper and lower caudal lobes margins, gradually decreasing in size.

Dorsal-fin rays ii,8(60) or 9*(125); first unbranched ray approximately one-third of second unbranched ray; small ossification anterior to first unbranched ray present in all 35 c&s specimens examined. Distal margin of dorsal fin straight. Dorsal-fin origin at midbody or slightly behind this point; base of posteriormost dorsal-fin ray slightly behind vertical through anal-fin origin. First dorsal-fin pterygiophore inserting posterior to neural spine of eleventh vertebra. Pectoral-fin rays i,9(91), 10*(72), or 11(22). Pelvic-fin rays i,6*(139) or 7(46); its origin ahead of vertical through dorsal-fin origin; tip of longest ray surpassing anal-fin origin. Adipose fin small. Anal-fin rays iv,16(56), 17*(50), 18(39), 19(34), 20(6), or 21(1); anal fin falcated, last unbranched ray to fourth branched ray longest, with remaining rays decreasing gradually in size towards anal-fin end; last anal-fin pterygiophore inserting behind hemal spine of fourteenth caudal vertebrae (35). Caudal fin bifurcated; lobes slightly pointed, almost equal in size, inferior lobe slightly longer than superior. Principal caudal-fin rays i,17,i*(186); dorsal procurrent caudalfin rays 9(8), 10(15), or 11(12); ventral procurrent caudal-fin rays 7(3), 8(31), or 9(1). Precaudal vertebrae 12(19) or 13(16); caudal vertebrae 19(2), 20(15), 21(17), or 22(1); total vertebrae 32(5), 33(27), or 34(3). Supraneurals 4(9) or 5(26). Branchiostegal rays 4(35). First gill arch with 6(15) or 7(20) gill rakers on epibranchial, one at angle (35), 11(12), or 12(23) in ceratobranchial, and 2(12) or 3(23) on hypobranchial.

Color in alcohol. Overall ground coloration of body light tan. Anterior portion of lower jaw, snout and dorsal portion of head covered by relatively dense concentration of small dark chromatophores, imparting an overall darker color. Opercle and fourth and fifth infraorbital with scattered relatively large dark chromatophores. Third infraorbital and opercle silvery in specimens retaining guanine pigmentation. Narrow dark midlateral stripe formed by chromatophores at myosepta between hypaxial and epaxial bundles of muscles, more conspicuous posteriorly to dorsal-fin base. Faint longitudinal dark stripe along midline of body originating at vertical through dorsal-fin origin, becoming wider and more conspicuous at caudal peduncle. Scales from predorsal row to second or third row above lateral line posteriorly bordered with dark chromatophores, forming a subtle reticulated pattern. Dark humeral spot absent. Two dark narrow stripes situated along anal-fin base, the first extending approximately along region where hypaxial musculature and muscles of anal fin meet, sub-parallel to anal-fin base, second along analfin base; subjacent dark chromatophores forming thin lines over myomere margins above anal-fin base. Dorsal fin mostly hyaline, with few dark chromatophores concentrated along inferior third of unbranched rays to second or third branched rays and interradial membranes. Adipose, pectoral and pelvic fins hyaline, with few dark chromatophores scattered mainly along their distal tips. Anal fin hyaline, with dark chromatophores scattered on proximal region, mainly on third to fourth branched rays and interradial membranes. Caudal fin hyaline at its basal half with conspicuous patches of black pigmentation occupying most of the fin lobes except the tips, which are hyaline. Dark patches typically not continuous, continuous in some specimens through darkened tips of middle caudal-fin rays (e.g., CZFCEN 323, NUP 2153, NUP 9546).

Sexual dimorphism. None was found. Bony fin hooks, a common dimorphic feature of mature characid males ( Malabarba & Weitzman, 2003) were not found in any of the specimens examined, including 15 c&s male specimens (INPA 39505, 1 ex.; NUP 9543, 10 ex.; NUP 9545, 3 ex.; NUP 9546, 1 ex.) and several dissected males presenting mature testes (see “Ecological notes”, below).

Distribution. Hemigrammus durbinae is known from the central and western portions of the Amazon basins, at the middle and upper portions of the rio Madeira, lower rio Purus, middle rio Solimões/Amazonas, and lower rio Tapajós in Brazil, from the rio Paraguai basin in Brazil and Paraguay, and from the rio Paraná basin in Paraguay ( Fig. 4 ). The comparison of specimens collected throughout its range did not revealed morphometric or meristic differences between the different populations ( Fig. 2 ).

Ecological notes. Hemigrammus durbinae is typically found in large floodplain lakes, both in the Amazon basin (e.g., Lago Janauacá at the rio Solimões, Lago Janauari at the lower rio Negro, Lago Cuniã and Lago Puruzinho at the rio Madeira) and rio Paraguai basin (e.g., Baía de Chacororé and Baía Sinhá Mariana). Stomach contents of five specimens from the rio Paraguai basin in Brazil were analyzed, and consisted mainly in terrestrial insects. Four dissected females ranging between 18.3–26.3 mm SL (NUP 2153, 2; NUP 6263, 1; NUP 9647, 1; MZUSP 27113, 1) possessed large yellowish oocytes and five dissected males between 17.7–22.8 mm SL (CZCEN 323, MHNP 3679, NUP 2153, and NUP 9647) possessed well-developed, lobular, whitish-colored testes, and consequently all were mature. All dissected specimens cited above were from the rio Paraguai basin and were collected in January, February, April, September, and November, indicating an extensive breeding period for the species, at least for that river basin. The single dissected breeding female from the Amazon basin (MZUSP 27113) was collected in January.

Etymology. The specific epithet honors Marion Durbin Ellis (née Marion Lee Durbin) (born 1887, deceased apparently in 1972), Carl Eigenmann´s student and latter a limnologist and environmental toxicologist working at the University of Missouri in Columbia, who devoted herself diligently into the most comprehensive study on Hemigrammus so far. A genitive noun.

Figures

FIGURE 1. Hemigrammus durbinae, new species, MZUSP 115984, holotype, 23.1 mm SL, Brazil, Amazonas, Careiro, lago Castanho, rio Solimões basin.

FIGURE 2. A. UFRO-I 685, paratype, 26.5 mm SL, Brazil, Rondônia, lago Puruzinho, rio Madeira basin. B. CZEN 323, paratype, 23.7 mm SL, Paraguay, Ñeembucu Departament, Mburicá, Arroyo Yacaré, rio Paraguai / Paraná basin.

FIGURE 3. Hemigrammus durbinae, new species, scanning electron micrographs (SEM) showing mesial view of left premaxillary and lateral view of left maxillary (NUP 9543, 20.1 mm SL, paratype); mesial view of left dentary (NUP 9543, 20.2 mm SL, paratype).

FIGURE 4. Map of Central South America showing distribution of Hemigrammus durbinae (red dots; red star, type locality).