Moenkhausia guaruba Lima & Vita & Dutra & Ohara & Pastana 2023, new species

Moenkhausia guaruba, new species (Figs. 1, 3–4) urn:lsid:zoobank.org:act: 5F05B041-01D8-4E1E-959D-7842A75391AE Holotype. MZUSP 128235, 96.9 mm SL, Brazil, Pará, Novo Progresso, upper rio Braço Norte, tributary of rio Peixoto de Azevedo, rio Tapajós basin, 9°21’47.72”S 54°54’14.44”W, O. Oyakawa, W. Ohara and M. Pastana, 3 August 2015. Paratypes. All from Brazil, Pará, rio Peixoto de Azevedo drainage, rio Tapajós basin: MZUSP 119389 (32, 2 C&S, 44.5–85.1 mm SL), INPA 59895 (5, 48.6–77.5 mm SL), collected with holotype. MZUSP 119401 (1, 67.6 mm SL), Igarapé Olho d´água, a tributary of rio Braço Norte, 9°21’59.9”S 54°54’55.4”W, O. Oyakawa, W. Ohara and M. Pastana, 3 August 2015. MZUSP 119869 (1, 77.1 mm SL), small tributary of rio Braço Norte, 9°18’16”S 54°56’43”W, F. Dagosta, M. M. F. Marinho, P. Camelier & V. Giovanetti, 3 August 2015. MZUSP 119922 (2, 72.8– 78.9 mm SL), tributary of rio Braço Norte, 9°16’31.7”S 54°49’13.4”W, F. Dagosta, M. M. F. Marinho, P. Camelier & V. Giovanetti, 4 August 2015. Diagnosis. Moenkhausia guaruba is distinguished from its congeners, except Moenkhausia moisae Géry, Planquette & Le Bail 1995 and Moenkhausia pirauba Zanata, Birindelli & Moreira 2010 by having a higher number of scales in the longitudinal series (43–46 vs. 23–41 in other Moenkhausia species). The new species differs from M. moisae by having fewer branched anal-fin rays (21–25, modal 23 vs. 25–29, modal 27 in M. moisae; Fig. 2), a complete and regularly arranged series of predorsal scales (vs. irregular arranged of scales at predorsal region), and by having a single, vertically elongated and relatively wide humeral blotch (vs. two humeral blotches in M. moisae; see Discussion for further details). Moenkhausia guaruba differs from M. pirauba by having a conspicuous, rounded, and symmetrical dark blotch located at the posterior limit of the caudal peduncle and base of caudal-fin rays (vs. caudal blotch horizontally elongated, asymmetrical, continuous anteriorly with midlateral stripe and extending posteriorly to margins of four or five middle caudal-fin rays in M. pirauba), and a thin longitudinal line formed by dark pigmentation running along horizontal septum of body (vs. dark longitudinal line wide, forming an elongated blotch at caudal peduncle in M. pirauba). Description. Morphometric data of Moenkhausia guaruba in Table 1. Largest examined specimen 96.9 mm SL (holotype). Body compressed and moderately deep (Fig. 1). Greatest body depth at dorsal-fin origin. Dorsal profile of head convex from snout tip to vertical through nostrils, and straight from that point to tip of supraoccipital spine. Dorsal profile of body convex from tip of supraoccipital spine to dorsal-fin origin, straight along dorsal-fin base, straight to slightly convex from dorsal-fin terminus to adipose fin origin, and concave from that point to anteriormost dorsal caudal-fin ray. Ventral profile of body convex from tip of lower jaw to pelvic-fin origin, approximately straight from pelvic-fin origin to urogenital papilla, straight along anal-fin base, and concave between last anal-fin ray to anteriormost ventral caudal-fin procurrent ray. Mouth terminal, posterior end of maxilla not reaching vertical through the middle of the orbit. Premaxillary teeth arranged into two rows (Fig. 3), outer row with 3(1), 4*(25) or 5(4) tricuspid* (29) or pentacuspid (1) teeth. Inner row with 4(1), 5* (27), 6(1) or 7(1) pentacuspid (21) or heptacuspid teeth* (9). Maxilla with 1(2), 2* (23), 3(4) or 4(1) tricuspid (20) or pentacuspid* (10) teeth. Dentary teeth with 4*(25) large pentacuspid (23) or heptacuspid (2) teeth followed by 12(2) conical to tricuspid teeth. Hypobranchial with 1(1), or 3(1) rakers, ceratobranchials with 10(2) rakers, epibranchials with 8(1), or 9(1) rakers, and one raker between those last two elements. Branchiostegals 4(2), three articulating with the anterior ceratohyal, and one with the posterior ceratohyal. Scales cycloid, without circuli on exposed portion of scales and with seven divergent radii reaching the posterior margin of the scale. Longitudinal line with 43*(7), 44(10), 45(2), or 46(2) perforated scales. Scale rows above lateral line 8(7) or 9*(23). Scale rows below lateral line 7*(27) or 8(2). Predorsal scales 12(7), 13(8), or 14*(1). Circumpeduncular scales 16*(18) or 17(1). Scales on caudal fin rays restricted to base of upper and lower lobes. Axillary scale present. Pectoral-fin rays i,11(1), i,12(19), or i,13*(10), longest ray reaching vertical through pelvic-fin insertion. Pelvic-fin rays i,7(26) or i,8*(4), distal tip of pelvic fin nearly straight, not reaching anal-fin origin. Dorsal-fin rays ii,8(5), ii,9*(24), or ii,10(1). First dorsal-fin pterygiophore inserted posteriorly to ninth neural spine (2). Anal-fin rays iv,21(1), iv,22(7), iv,23(10), iii,24*(9), or iv, 25(3), first unbranched ray covered by skin and last unbranched and first branched anal-fin ray the longest. First anal-fin pterygiophore inserted posteriorly to 18 th haemal spine (2). Caudal fin forked, with lobes equal in size, slightly pointed. Caudal-fin rays i,17,i*(29). Dorsal caudal-fin procurrent rays 11(1), or 12(1). Ventral caudal-fin procurrent rays 9(1), or 13(1). Adipose fin present. Supraneurals 4(2). Precaudal vertebrae 18(2). Caudal vertebrae 18(2). Laterosensory system fully developed, tubules opening in individual pores (i.e. never forming subpores). Supraorbital canal associated with nasal, frontal, and parietal bones. Epiphyseal and parietal branches of supraorbital canal present. Supraorbital connecting to infraorbital and otic canal near posterolateral margin of frontal bone. Infraorbital canal fully developed. Otic canal present, associated with anterior portion of pterotic. Postotic canal running along pterotic, extrascapular, post-temporal and supracleithrum. Supratemporal canal associated with extrascapula and posterior margin of parietal bone, running dorsomedially and opening in a pore near cranial fontanel. Preopercular canal extending along entire extension of pre-opercular bone, continuous with mandibular canal. Mandibular canal associated with the anguloarticular and dentary bones. Color in alcohol. Ground body coloration pale brown to tan (Fig. 1). Dorsal portion of head dark brown, with high concentration of chromatophores. Lateral and ventral portion of head pale brown. Guanine pigmentation and few large chromatophores present on infraorbitals, preopercle and opercle. Body tan on dorsal and dorsolateral portion, becoming cream ventrally, usually with few and sparse chromatophores. Humeral region with a single vertically elongated and relatively narrow dark blotch with diffuse margins, bordered anteriorly and posteriorly by unpigmented areas. Humeral blotch encompassing eight to 10 scales vertically and two to three scales horizontally. Humeral blotch wider and darker above lateral-line series of scales, becoming narrower, and fainter towards its ventral limit. Thin longitudinal line formed by dark pigmentation running along horizontal septum of body. Longitudinal line starting on vertical through first to third branched dorsal-fin rays, and extending to caudal peduncle. Broad brown to black blotch with diffuse margins located on posterior limit of caudal peduncle and base of middle caudal-fin rays. Caudal blotch pigmentation restricted to base of principal caudal-fin rays, usually not continuing onto middle caudal-fin rays to posterior margin of the fin. Caudal fin mostly dusky due to presence of scattered chromatophores along ray margins, and on inter-radial membranes. Dorsal, pectoral, and anal fins uniformly dusky, with dark chromatophores more concentrated along leading margin of rays and at interradial membrane. Pelvic fin pale to translucid, with few dark chromatophores distributed along ray margin, unbranched rays more pigmented than remaining ones. Adipose fin pale brown, with scattered chromatophores. Color in life. Ground coloration silvery, with golden to olive-green hue (Fig. 4). Body darker on dorsal and dorsolateral regions and lighter on abdominal region. Head dark dorsally. Snout, jaws, first and second infraorbitals and gular area yellow to light orange. Infraorbitals three to six and opercular series silvery, with guanine pigmentation. Eyes golden yellow dorsally and silvery ventrally. Body mostly silvery on flanks, with olive-green hue dorsally and yellow to golden hues on lateral and ventral regions. Bright silvery to greenish stripe present, starting immediately posterior to humeral region and extending onto caudal blotch. Fins mostly yellow, coloration more pronounced on dorsal, adipose and caudal fins; paler on paired and anal fins. Anal fin more pigmented along first to sixth rays and inter-radial membrane; seventh to last anal-fin rays with faint yellow pigmentation restricted to basal portion of rays, inter-radial membranes dusky. Tip of unbranched and first branched dorsal and anal-fin rays lacking pigmentation. Black round blotch visible at base of caudal fin. Sexual dimorphism. The examined specimens of Moenkhausia guaruba did not exhibit any secondary sexual dimorphism. Bony hooks on fins were not observed. Geographical distribution. Moenkhausia guaruba is known from rio Braço Norte, a tributary of rio Teles Pires draining from the Serra do Cachimbo, rio Tapajós basin, Pará state, Brazil (Fig. 5). Ecological notes. The type locality of Moenkhausia guaruba is at an altitude of 445 m above sea level at the Serra do Cachimbo, within the Campo de Provas Brigadeiro Velloso (CPBV), an area under the management of the Brazilian Air Force. The sampled stretch was immediately downstream to a 3-meter waterfall (Fig. 6a), where the river is 50 wide and up to 4 m deep (Fig. 6b). The substrate was composed mainly by sand and rocks and the river is bordered by Cerrado (Brazilian savannah) vegetation. Etymology. The specific name guaruba refers to the Brazilian popular name for Guaruba guarouba Gmelin 1788, also known as the Golden Parakeet, a medium-sized golden-yellow Neotropical parrot native to the Brazilian Amazon domain. The name alludes to the intense yellow present on all fins of the new species. A noun in apposition.Published as part of Lima, Arthur De, Vita, George, Dutra, Guilherme M., Ohara, William M. & Pastana, Murilo N. L., 2023, A new Moenkhausia (Characiformes: Characidae) from rio Braço Norte, rio Tapajós basin, with comments on the fish endemism of Serra do Cachimbo plateau, pp. 586-596 in Zootaxa 5330 (4) on pages 587-592, DOI: 10.11646/zootaxa.5330.4.6, http://zenodo.org/record/825537