Moenkhausia melogramma Eigenmann, 1908

Soares, Isabel M., Ota, Rafaela P., Lima, Flávio C. T. & Benine, Ricardo C., 2020, Redescription of Moenkhausia melogramma (Characiformes: Characidae), a poorly known tetra from the western Amazon basin, Neotropical Ichthyology 18 (3), pp. 1-17 : 3-10

Moenkhausia melogramma Eigenmann, 1908

( Figs. 1–3 ; Tab. 1 )

Moenkhausia melogrammus Eigenmann, 1908:102–103 [original description; type locality: “ Tabatinga ” (= Brazil, Amazonas State)] .

Moenkhausia melogramma . — Eigenmann, 1910:437 [listed; adequacy of the specific epithet to the gender]. — Eigenmann, 1917:44; 67; 78–79; plates 6, 10 [diagnosis in key, redescription]. — Fowler, 1948:153 [listed]. — Géry, 1977:446 [diagnosis in key; allocation in the M. grandisquamis group]. — Axelrod et al., 1995:282 [photo in life]. — Lima et al., 2003:148 [listed]. — Arbeláez et al., 2004:102 [ Colombia, Leticia, Quebrada La Arenosa]. — Galvis et al., 2006:221, 468 [short description, photo in life (pl. 43 b), ecological notes; Colombia, Amazonas, Leticia].

Moenkhausia melanogramma (spelling error). — Eigenmann, 1917:40 [comments about the third tooth on premaxilla].

Hemigrammus lunatus (not Durbin). — Ibarra, Stewart, 1989:369, 377 [in part; Ecuador, río Napo basin; abundance].

Hemigrammus cf. lunatus (not Durbin). — Galacatos et al., 1996:881, 889 [in part; Ecuador, río Napo basin; abundance]. — Galacatos et al., 2004:40–41, 44, 48 [in part; Ecuador, río Yasuni basin; abundance, habitat preference].

Moenkhausia sp. — Ota et al., 2019:345 [comparison with Hemigrammus changae ; Ecuador, Sucumbíos, río Putamayo basin].

Diagnosis. Moenkhausia melogramma differs from all congeners, except M. collettii , M. copei , M. venerei Petroli, Azevedo-Santos, Benine, 2016 , M. conspicua Soares, Bührnheim, 2016 , and M. flava Britzke, Troy, Oliveira, Benine, 2018 , by the presence of a broad dark longitudinal stripe across the eye (vs. absent) and a well-defined dark longitudinal stripe on the anal-fin base vs. absent). Moenkhausia melogramma is promptly distinguished from M. collettii , M. copei , M. venerei , M. conspicua , and M. flava by having two humeral blotches (vs. a single humeral blotch). It differs from M. flava by the overall body coloration clear in live specimens (vs. pale-yellowish). Moenkhausia melogramma can be distinguished from M. collettii by having the first humeral blotch approximately triangular (vs. oval, horizontally elongated). It is further distinguished from M. conspicua , M. copei , and M. venerei by having a narrow, longitudinal, midlateral stripe, occupying one longitudinal series of scales (vs. longitudinal stripe wide, occupying two longitudinal series of scales).

Description. Morphometric data summarized in Tab. 1 . Body compressed, moderately deep; greatest body depth anterior to dorsal-fin origin. Dorsal profile of head convex from tip of snout to anterior nostrils, straight to slightly concave from anterior nostrils to tip of supraoccipital spine. Dorsal profile of body moderately convex from tip of supraoccipital spine to dorsal-fin origin, posteroventrally slanted and straight from latter point to adipose fin, and slightly concave to straight along caudal peduncle. Ventral profile of body convex from anterior tip of lower jaw to pelvic fin; straight to slightly convex from pelvic-fin origin to anal-fin origin; posterodorsally slanted and straight along anal-fin base, and slightly to moderately concave along caudal peduncle.

Mouth terminal, isognathous. Two tooth rows in premaxilla: outer with three (42), four (211), or five* (22) tricuspid teeth; only specimens with five teeth have third tooth misaligned. Inner row with four (6), five*(265), or six (4) penta- to heptacuspid teeth. Maxilla with one (11), two *(139), three (104), or four (21) tri- to pentacuspid teeth. Dentary with anteriormost four* (270) or five (5) teeth penta- to heptacuspid, followed by middle-sized tricuspid tooth, and posteriormost five (3), six (1), 10 (1), or 11 (1) smaller, tricuspid or conical teeth. Central cusp of all teeth larger than lateral cusps.

Scales cycloid. Lateral line completely pored, slightly curved anteriorly, with 32 (34), 33 (71), 34* (84) 35 (30), or 36 (3) perforated scales. Six specimens with discontinuous lateral line, with solely one or two scales lacking pore ( LBP 23758, 3, 33.9–36.0 mm SL; ZUEC 13213, 2, 30.6–41.5 mm SL; ZUEC 15479, 1, 33.1 mm SL). Longitudinal scale rows between dorsal-fin origin and lateral line five (135), six* (137) or seven (2); longitudinal scale rows between lateral line and pelvic-fin origin three (6), four* (246) or five (21). Predorsal scale row with eight (4), nine (154) or 10 scales (105). Circumpeduncular scales 14 (221). Scale sheath along anal-fin base with up to seven small scales, in single row, overlying proximal portion of anteriormost anal-fin rays. Caudal fin scaled, scales covering proximal half of caudal-fin lobes.

Dorsal-fin rays ii (311), eight (7), nine* (302) or 10 (2). Dorsal-fin origin at midbody or slightly behind this point, slightly posterior to vertical through pelvic-fin origin. First unbranched ray shorter than second ray. Adipose fin at vertical through 12 th or 13 th caudal vertebrae. Pectoral-fin rays i (310), 10 (22), 11 (160), 12* (116) or 13 (12); tip of adpressed longest rays usually reaching pelvic-fin insertion. Pelvic-fin rays i (311), 6 (3), 7* (299) or 8 (9); tip of adpressed longest rays usually reaching anal-fin insertion. Anal-fin rays iv* (6), 20 (11), 21 (53), 22 (73), 23* (82), 24 (55), 25 (25) or 26 (6); anteriormost rays slightly longer, subsequent rays gradually decreasing in size. Principal caudal-fin rays i (278), eight (4) or nine* (274) + seven (2) or eight (276), i*(278). Dorsal procurrent caudal-fin rays 10 (3) or 11* (3) and ventral procurrent caudal-fin rays seven (2), eight (3) or nine* (1). Caudal fin forked; lobes similar in size.

Supraneurals four* (6), “I” or “Y” shaped with laminar bone almost along entire length. Precaudal vertebrae 15* (6); caudal vertebrae 18* (3) or 19 (3); total vertebrae 33* (3) or 34 (3). First gill arch with five (68), six (161) or seven (34) gill rakers on upper limb and 10 (59), 11 (151) or 12 (53) gill rakers on lower limb.

Color in alcohol. Overall ground color pale beige. Upper and lower lips, anterior portion of maxilla, snout, top of head and dorsal portion of opercle with scattered small dark chromatophores. Scales from two or three first longitudinal series of dorsal region posteriorly bordered by dark chromatophores, forming slightly reticulate pattern; scattered dark chromatophores concentrated along margins of myosepta of posterior half of lower portion of body, between lateral line and anal-fin base. Broad, dark longitudinal stripe crossing middle portion of eye, inconspicuous in specimens stored for long time in formalin. Two humeral blotches formed by brown chromatophores. First humeral blotch vertically elongated, slightly oblique, approximately triangular, roughly rounded in its upper portion and with irregular projections in its lower portion, extending vertically through two longitudinal scales series above lateral line and two series below it, more pigmented in the two series above lateral line. First humeral blotch followed posteriorly by clear area. Second humeral blotch inconspicuous, irregular, roughly oblique, comma-shaped, or a narrow vertical stripe, more concentrated above lateral line, with its limits well-defined ( Figs. 2A, D, F ) or progressively fading posteriorly as a longitudinal stripe ( Figs. 2B, C, E ). Few chromatophores scattered on region of hypural plate. Conspicuous longitudinal dark line along anal-fin base, formed by melanophores, covering base of anal-fin rays and proximal portion of interradial membranes. Dorsal fin with scattered dark chromatophores on interradial membranes. Adipose fin with few scattered dark chromatophores concentrated on anterior margin. Pectoral, pelvic, and caudal fins with few scattered dark chromatophores on interradial membranes ( Fig. 2 ).

Color in life. Based on pictures of five specimens photographed in life ( ZUEC 14944, ZUEC 15479; Fig. 3 ) and in the photo of one specimen provided by Galvis et al. (2006: 468, pl. 43 b). Overall color pattern clear, dorsum light grey, with an olive hue; top of head with metallic green-coppery color; midline with metallic green color, especially intense in area immediately before first humeral blotch. Lower portion of head and abdominal region clear, with silvery hue. Area immediately above anal fin slightly translucent. Fins mostly hyaline, yellowish pigmentation on anterior portion of dorsal, anal, and pelvic fins; tip of dorsal and anal fins whitish in some specimens. Black markings as in preserved specimens.

Sexual dimorphism. Mature males possess bony hooks on pelvic- and anal-fin rays or only on anal-fin rays. Pelvic fin with one small and slender bony hook per lepidotrichium segment, arranged along the middle portion of the unbranched ray and anteriormost first to second branched fin rays. Anal fin with one or two (rarely three) pairs or unpaired bony hooks per lepidotrichium segment, arranged along distal half of last unbranched ray and from first to fourth branched rays, larger on middle portion of ray.

Geographic distribution. Moenkhausia melogramma is distributed across the western portion of the Amazon basin in Brazil, Colombia, Peru, and Ecuador, with its easternmost records for the rio Curuá and rio Tapajós basins on the lower Amazon basin ( Fig. 4 ). Although we have examined only two lots of M. melogramma from Ecuador in the present study, a cursory examination of the material identified as Hemigrammus lunatus from both the Napo and Putumayo basins in Ecuador, deposited at FMNH and MEPN, by one of the authors ( FCTL), showed it to belong mostly to M. melogramma (see also comments in Ota et al., 2019: 343). Records in the literature for the species, outside the range discussed above ( Lasso et al., 2004) are discussed in the “Remarks” below.

Ecological notes. Moenkhausia melogramma was collected in moderate to relatively large clearwater terra firme streams, in the area of Tabatinga and Benjamin Constant, Amazon State, western Amazon basin of Brazil, and both black and slightly muddy water terra firme streams in the rio Juruá basin, Acre State (Flávio C. T. Lima, 2016- 2017, pers. obs.). The species was collected in the same type of habitat in the region of Leticia, Colombia ( Galvis et al., 2006: 221). Moenkhausia melogramma was considered to be ubiquitous in both piedmont (235–295 m asl) and lowland (below 220 m asl) areas in the río Napo basin ( Galacatos et al., 1996; as Hemigrammus cf. lunatus , in part). Moenkhausia melogramma was collected in syntopy with M. collettii at the lago Amanã, rio Solimões basin ( INPA 32161) and in a tributary of the middle rio Madeira ( ZUEC 6736). The species was found to be an omnivore, ingesting terrestrial invertebrates and aquatic vegetation ( Galvis et al., 2006: 221).

Conservation status. Moenkhausia melogramma is broadly distributed across the western Amazon basin, in relatively little disturbed areas, and it is considerably abundant at several sites. The species is known to occur in at least three Conservation Units: Canutama State Forest and Canutama Extractive Forest (rio Purus), both in Brazil, and at the Yasuní National Park in Ecuador. Due to broad geographical distribution, relatively high abundance, and relatively little impact from anthropogenic activities in the areas inhabited by the species, M. melogramma is herein categorized as Least Concern ( LC), according to the International Union for Conservation of Nature ( IUCN) categories and criteria ( IUCN Standards and Petitions Subcommittee, 2017).

Remarks. Despite recorded in the literature, we were unable to confirm the occurrence of Moenkhausia melogramma from the río Orinoco basin ( Lasso et al., 2004: 115). We consider this record as very likely the result of a misidentification of a similar-looking species occurring in that basin, such as Hemigrammus barrigonae Eigenmann, Henn, 1914 or M. collettii . The only previous records for the species in the literature that we were able to confirm were those by Arbeláez et al. (2004) and Galvis et al. (2006), from the region of Leticia in Departamento Amazonas, Colombia, from which the voucher material (not cited in the Material Examined) was cursorily examined by one of the authors ( FCTL) during a visit to the ICN-MHN and IAvH-P collections.

Material examined. Holotype of Moenkhausia melogramma : MCZ 20825 , 38.3 mm SL, Brazil, Amazonas State, Tabatinga, Sep–Oct 1865, D. Bourget (Thayer Expedition) (photos and radiographs only). Non-type specimens: Brazil: Rio Juruá basin: LBP 4112 , 3 , 26.2–31.4 mm SL, Acre, Mâncio Lima, rio Japiim, tributary of rio Moa , 7°34’28.8”S 72°55’24.9”W, 24 Oct 2006, C. Oliveira, R. C. Benine & C. S. Silva ; LBP 4133 , 12 , 21.9–28.5 mm SL, Acre, Mâncio Lima, rio Moa , 7°26’35.5”S 73°3’33.5”W, 24 Oct 2006, C. Oliveira, R. C. Benine & C. S. Silva ; LBP 4148 , 3 , 31.9–38.8 mm SL, same data as LBP 4133 ; ZUEC 13414 , 271 , 23.5–41.5 mm SL, Acre, Mâncio Lima, igarapé Branco, 7º38’43”S 72º52’55”W, 30 Sep 2016, T. C. Pessali , T. R. F. Jacó , T. L. Silva, A. Casas & F. C. T. Lima ; ZUEC 13314 , 87 , 20.8–31.6 mm SL, Mâncio Lima, Paraná de Pentecostes (trib. rio Moa ), 7º28’2”S 72º57’38”W, 29 Sep 2016, F. C. T. Lima , T. C. Pessali , T. R. F. Jacó & T. L. Silva ; ZUEC 13213 , 36 , 22.3–46.3 mm SL (2 c&s 34.4–34.5 mm SL), Acre, Cruzeiro do Sul, igarapé Paleral, affluent of rio Moa , 7°31’48”S 72°51’08”W, 29 Sep 2016, F. C. T. Lima , T. C. Pessali & T. R. F. Jacó ; ZUEC 13188 , 189 , 19.9–30.1 mm SL, Cruzeiro do Sul, lago Vermelho, rio Moa , 7º36’48”S 72º48’10”W, 23 Sep 2006, F. C. T. Lima , T. C. Pessali , T. R. F. Jacó , T. L. Silva & R. Rubens ; ZUEC 13221 , 52 , 26.6–35.8 mm SL, Acre, Cruzeiro do Sul, rio Croa , near BR-364, 7°44’16”S 72°32’59”W, 26 Sep 2016, F. C. T. Lima , T. C. Pessali , T. R. F. Jacó & A. Casas . ZUEC 13555 , 100 , 23.2–30.4 mm SL, Cruzeiro do Sul , igarapé Preto, 7º36’15”S 72º44’59”W, 24–26 Oct 2016, T. Jacó , T. Souza , R. Souza, J. Souza & T. Nascimento ; ZUEC 13102 , 117 , 21.5–28.9 mm SL, same locality as previous, 22 Sep 2016, F. C. T. Lima , T. C. Pessali , T. R. F. Jacó, A. Casas & T. L. Silva ; ZUEC 13819 , 750 , 24.5–39.9 mm SL, Amazonas, rio Gama , village of Gama, 7º17’38”S 72º38’36”W, 24 Nov 2016, T. Jacó, A. Casas, J. Souza & T. Souza ; Amazonas: Rio Javari basin: ZUEC 15436 , 2 , 33.1–38.3 mm SL, Benjamin Constant, igarapé do Negão, road Benjamin Constant / Atalaia do Norte , 4º25’50”S 70º4’10”W, 17 Nov 2017, F. C. T. Lima, G. N. Salvador & N. Flausino Jr ; ZUEC 15479 , 26 , 31.9–39.3 mm SL, Atalaia do Norte, igarapé do Adolfo, road Benjamin Constant / Atalaia do Norte , 4°26’5”S 70°7’19”W, 11 Nov 2017, F. C. T. Lima, C. R. Moreira, G. N. Salvador & N. Flausino Jr. ; ZUEC 15625 , 1 , 35.7 mm SL, Atalaia do Norte, igarapé Branco, road Benjamin Constant / Atalaia do Norte , 4º25’1”S 70º8’37”W, 9 Nov 2017, F. C. T. Lima, G. N. Salvador & N. Flausino Jr. Rio Madeira basin: MZUSP 117596 , 44 , 16.0– 44.3 mm SL (10, 27.8–44.3 mm SL), rio Juma, affluent of rio Aripuanã at BR-230 between Vila dos 180 and Apuí , 7°12’43”S 59°55’18”W, 22 Jun 2015, W. M. Ohara & V. Abrahão ; MZUSP 122033 , 13 , 26.0– 35.1 mm SL, Manicoré, igarapé on side road S of Santo Antônio do Matupi district, km 180 of Transamazônica road (BR-230), 7°57’20.8”S 61°34’2.3”W, 3 Oct 2016, O. Oyakawa, W. Ohara , T. Teixeira & M. Pastana ; MZUSP 122525 , 7 , 21.8–35.4 mm SL (5, 28.9– 35.4 mm SL), igarapé affluent of rio Juma, left to Transamazônica (BR-230), 7°15’16”S 59°56’14.4”W, 8 Oct 2016, O. Oyakawa, W. Ohara , T. Teixeira & M. Pastana ; MZUSP 122544 , 5 , 27.6–32.9 mm SL, Apuí, rio Juma, igarapé affluent of rio Coruja , 7°13’35.1”S 59°52’16.7”W, 8 Oct 2016, O. Oyakawa, W. Ohara , T. Teixeira & M. Pastana. Rio Purus basin: INPA 23564 , 1 , 21.5 mm SL, Canutama, Canutama State Forest, rio Paisé , igarapé da Flor, 6°32’28.7”S 64°32’49.8”W, 27 May 2013, G. G. Barros ; INPA 23577 , 1 , 25.1 mm SL, Canutama, Canutama State Forest, rio Paisé , 6°30’56.7”S 64°32’18.2”W, 28 Apr 2013, G. G. Barros ; INPA 23774 , 1 , 20.3 mm SL, Canutama, Canutama State Forest, rio Paisé , 6°30’23.2”S 64°32’10.3”W, 11 May 2013, T. B. A. Couto ; INPA 23801 , 3 , 23.9–26.2 mm SL, Canutama, Canutama Extractive Reserve, rio Paisé , 6°33’45.7”S 64°33’34.2”W, 11 May 2013, G. G. Barros ; INPA 35017 , 3 , 26.4–30.1 mm SL, Canutama, igarapé at Canutama Extractive Reserve , 6°39’59”S 64°37’3”W, 2 Sep 2010, S. Arrolho & R. Rosa ; INPA 35028 , 16 , 22.6–28.9 mm SL, Canutama, igarapé at Canutama Extractive Reserve , 6°40’34”S 64°36’47”W, 2 Sep 2010, S. Arrolho & R. Rosa ; INPA 36442 , 19 , 21.3 –29.0 mm SL, Canutama, igarapé at Canutama Extractive Reserve , 6°40’19”S 64°36’5”W, 2 Sep 2010, S. Arrolho & R. Rosa ; INPA 53275 , 1 , 30.1 mm SL, Tapauá, Turiaçu community, igarapé do Cemitério, 5°0’24”S 63°0’3”W, 12 Aug 2012, T. B. A. Couto ; LBP 12017 , 6 , 26.3–31.7 mm SL, Lábrea, tributary of rio Purus , 7°56’6.6”S 63°27’21.2”W, 24 Aug 2010, C. Oliveira, M. Alexandrou, G. J. C. Silva & M. Taylor ; MCP 54148 , 3 , 23.6–25.6 mm SL, Canutama, igarapé São João, tributary of rio Ipixuna, BR-319, about 60 km south of Humaitá , 7°55’53”S 63°20’3”W, 28 Jul 2004, P. Buckup, P. Lehman, F. Lima & J. Pezzi. Rio Solimões basin: INPA 32161 , 24 , 31.9–52.4 mm SL (1 c&s 40.7 mm SL), Tefé, igarapé Baré, lago Amanã , 2°17’50”S 64°42’2”W, 6 Nov 2002, M. Catarino ; ZUEC 15150 , 6 , 32.9–41.1 mm SL, Tefé, igarapé of Miriti (trib. rio Tefé), road of Agrovila , 3°26’55”S 64°45’23”W, 30 Nov 2017, F. C. T. Lima, G. N. Salvador & N. Flausino Jr.; LBP 22682 , 2 , 34.7–37.9 mm SL; LBP 22683 , 7 , 30.7–37.9 mm SL, Tabatinga, igarapé Xingu, 4°12’02.7”S 69°55’35.3”W, 16 Nov 2016, C. Oliveira, B. F. Melo, J. M. Marin & G. Aricari; LBP 23758 , 59 , 31.6– 42.1 mm SL (1 c&s 34.2 mm SL), Tabatinga, igarapé Xingu , 4°11’25.5”S 69°55’40.3”W, 17 Nov 2016, C. Oliveira, B. F. Melo, J. M. Marin & G. Aricari; ZUEC 14944 , 85 , 24.8–42.3 mm SL (3 c&s 27.2–35.6 mm SL); MCZ 173933 , 10 , 27.7–34.6 mm SL; LBP 26160 , 5 , 26.6–28.8 mm SL, Tabatinga, igarapé do Urumutum, 4°12’34”S 69°54’47”W, 21 Nov 2017, F. C. T. Lima, C. R. Moreira, G. N. Salvador & N. Flausino Jr.; ZUEC 14912 , 49 , 22.9–39.8 mm SL, Tabatinga, same locality as previous lot, 3 May 2017, F. C. T. Lima, A. Acosta & J. D. Bogotá-Gregory; ZUEC 14879 , 13 , 30.2–35.4 mm SL, Tabatinga, igarapé do Olivério, ramal do Urumutum, 4º10’58”S 69º54’22”W, 3 May 2017, F. C. T. Lima, A. Acosta & J. D. Bogotá-Gregory; ZUEC 15331 , 6 , 38.5–41.2 mm, Tabatinga, stream at Ramal do Urumutum , 4º10’3”S 69º54’15”W, 20 Nov 2017, F. C. T. Lima, C. R. Moreira, G. N. Salvador & N. Flausino Jr.; ZUEC 15068 , 2 , 30.2–33.7 mm SL, Benjamin Constant, igarapé Cajarizinho, 4º26’41”S 69º59’56”W, 17 Nov 2017, F. C. T. Lima, C. R. Moreira, G. N. Salvador & N. Flausino Jr. Mato Grosso: Rio Guaporé basin: MCP 39927 , 19 , 24.8–35.5 mm SL (12, 27.0– 35.5 mm SL), Comodoro, stream affluent of rio Novo, at road BR-174, between Pontes e Lacerda and Comodoro , 14°13’26”S 59°41’27”W, 12 Jul 2004, V. Bertaco, F. Lima, J. P. Silva & P. Lehmann ; MCP 44561 , 18 , 25.1–36.1 mm SL (10, 27.3–36.1 mm SL), Pontes e Lacerda, rio Pindaituba, at road BR-174, between Pontes e Lacerda and Comodoro , 15°0’41”S 59°17’18”W, 12 Jul 2004, V. Bertaco, F. Lima, J. P. Silva & P. Lehmann. Pará: Rio Curuá basin: UFOPA 968 , 12 , 28.2–38.4 mm SL, Alenquer, tributary of rio Curuá , 1°39’57.5”S 54°53’37.8”W, 6 Jan 2017, A. Silva, A. Canto, C. Silva, F. Ribeiro & J. Souza. Rio Tapajós basin: ZUEC 12094 , 11 , 21.4–43.2 mm SL, Santarém, rio Mentaí , Cachoeirinha community, 2°43’49”S 55°35’34”W, 27 Nov 2015, F. C. T. Lima, B. B. Calegari , W. G. R. Crampton & E. Cerdeira. Rondônia: Rio Guaporé basin: INPA 44330 , 11 , 25.0–38.6 (9, 30.7–38.6 mm SL), middle rio Cautário , 14 Jul 2003, G. Torrente-Vilara. Rio Jamari basin: NUP 20808, 1, 43.8 mm SL, Ariquemes, rio Jamari , 9°56’20.7”S 63°4’8.1”W, Jan 2016, J. R. Gonçalves ; NUP 20809, 5, 30.0–38.0 mm SL, Ariquemes, rio Canaã , 10°12’27.5”S 63°6’40.5”W, Dec 2016, J. R. Gonçalves ; NUP 20811, 1, 38.5 mm SL, Ariquemes, rio Canaã, affluent of rio Jamari , 10°12’27.5”S 63°6’40.5”W, Nov 2015, J. R. Gonçalves ; NUP 20812, 3, 29.0– 36.7 mm SL, Ariquemes, rio Itapoana , 9°57’22.8”S 63°5’45.7”W, Dec 2016, J. R. Gonçalves . ZUEC 6736 , 5 , 26.2–32.3 mm SL, Porto Velho, stream at Balneário Cachoeirinha, 8º54’50”S 63º55’52”W, 12 Jul 2012, W. M. Ohara, T. H. S. Pires & F. C. T. Lima. Colombia: Río Amazonas basin: LBP 22468 , 1 , 34.0 mm SL, Leticia, quebrada La Ponderosa, 4°8’24.4”S 69°56’53.4”W, 11 Nov 2016, C. Oliveira, B. F. Melo, J. M. Marin & G. Aricari. Ecuador: Sucumbíos: Río Putumayo basin: ZUEC 11327 , 15 , 26.4–37.5 mm SL, río Gueppi , 0°18’59”S 75°17’13”W, 8–11 Aug 2000, R. Barriga & A. Machado. Peru: Loreto: Río Amazonas basin: MUSM 30440 , 37 , 21.7–39.7 mm SL (20, 29.1– 39.4 mm SL; 2 c&s 33.8–34.7 mm SL), Maynas, Iquitos, quebrada San Lucas , 4°8’14.9”S 73°27’48.2”W, 15 Feb 1998, H. Ortega & F. Chang ; ZUEC 17118 , 1 , 34.7 mm SL, Iquitos, quebrada Lindero, road Iquitos / Nauta, 4º9’3”S 73º28’23”W, 7 Jan 2004, W. G. R. Crampton, H. Ortega , R. E. Reis & F. C. T. Lima. Río Madre de Dios basin: MZUSP 106697 , 11 , 21.2–44.6 mm SL (8, 21.2–44.6 mm SL), Mazuko, río Planchon , 36.3 km N of Puerto Maldonado, 12°16’38”S 69°9’9”W, 28 Jul 2010, J. L. Birindelli, N. Lujan, D. Taphorn & D. Brooks. Río Marañón basin: MUSM 25616 , 8 , 17.6 –33.0 mm SL, Andoas, near río Corrientes , 2°33’53.7”S 76°11’53.1”W, 18 Aug 2005, B. Rengifo ; MUSM 38008 , 9 , 29.6–37.6 mm SL, Andoas, río Plantayacu , 3°8’8.4”S 75°45’43.5”W, 18 Aug 2008, R. Quispe.

Figures

FIGURE 1 | Moenkhausia melogramma, holotype, MCZ 20285, 38.3 mm SL, Brazil, Amazonas, Tabatinga. A. recent photograph, available on MCZ website (all rights reserved); B. after Eigenmann, 1917 (pl. 6, fig. 1).

FIGURE 2 | Moenkhausia melogramma. A. ZUEC 14912, female, 39.9 mm SL, Brazil, Amazonas, Tabatinga, rio Solimões basin. B. ZUEC 15479, female, 38.1 mm SL, Brazil, Amazonas, Atalaia do Norte, rio Javari. C. MZUSP 122033, male, 33.2 mm SL, Brazil, Amazonas, Manicoré, rio Madeira basin. D. ZUEC 11327, female, 30.2 mm SL, Ecuador, Sucumbíos, río Gueppi, río Putumayo basin. E. MUSM 30440, male, 34.0 mm SL, Peru, Loreto, Maynas, Iquitos, quebrada San Lucas. F. MZUSP 106697, female, 43.2 mm SL, Peru, Madre de Dios, Mazuko, río Planchón.

FIGURE 3 | Moenkhausia melogramma, immediately before preservation. A. ZUEC 15479, female, 37.6 mm SL, Brazil, Amazonas, Atalaia do Norte, rio Javari, igarapé do Adolfo. Photo: G. N. Salvador. B. ZUEC 13213, female, 41.5 mm SL, Brazil, Acre, Cruzeiro do Sul, igarapé Paleral, affluent of rio Moa. Photo: T. C. Pessali.

FIGURE 4 | Distribution of Moenkhausia melogramma in the western Amazon basin. Red star represents the type locality; black circles represent remaining known localities (one symbol may represent more than one lot).