Moenkhausia parecis, Ohara & Marinho, 2016

Ohara, William M. & Marinho, Manoela M. F., 2016, A new species of Moenkhausia Eigenmann (Characiformes: Characidae) from the upper rio Machado at Chapada dos Parecis, rio Madeira basin, Brazil, Neotropical Ichthyology (Neotrop. Ichthyol.) 14 (1), No. e 150041, pp. 1-8 : 2-5

Moenkhausia parecis , new species

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Figs. 1-2

Holotype. MZUSP 116070 , 77.9 mm SL, Brazil, Rondônia, Vilhena, rio Madeira basin, upper rio Machado , tributary of igarapé Piracolina , near road BR 364 , 12°48’56.5”S 60°06’37.6”W, 14 Sep 2013, W. M. Ohara, D. B. Hungria & B. S. Barros.

Paratypes. All form Brazil, Rondônia State, Vilhena . ANSP 198235 , 5 , 27.8-48.7 mm SL ; INPA 46708 , 10 , 28.0- 52.8 mm SL ; MCP 48398, 10 , 25.3-51.8 mm SL ; MZUSP 116071 , 57 (4 c&s, 28.8-42.6 mm SL), 22.0- 65.5 mm SL ; UFRO-I 22721 , 84 , 16.2-67.3 mm SL (18 measured, 44.7- 77.9 mm SL); same data as holotype . MZUSP 115509 , 47 , 24.1-72.8 mm SL (12 measured, 44.0- 71.6 mm SL), same locality as holotype, 3 Sep 2014, W. M. Ohara & P. L. Cunha . MZUSP 116072 , 9 , 23.0- 59.6 mm SL ; UFRO-I 22906 , 7 , 20.1-30.4 mm SL, same locality as holotype, 19 Jul 2013, I. da Costa . MZUEL 11836 , 7 , 22.9-60.6 mm SL ; MZUSP 117066 , 8 , 26.5-71.2 mm SL, same locality as holotype, 12 Nov 2014, W. M. Ohara, F. C. P. Dagosta & V. Giovannetti.

Diagnosis. Moenkhausia parecis is distinguished from all congeners, except M. clorophthalma Sousa, Netto-Ferreira & Birindelli, 2010 , some populations of M. cotinho Eigenmann, 1908 (see Discussion), M. lineomaculata Dagosta, Marinho & Benine, 2015 , M. petymbuaba Lima & Birindelli, 2009 , and M. plumbea Sousa , Netto- Ferreira & Birindelli, 2010 by the presence of a dark blotch on the anterior portion of each scale of the second to seventh longitudinal series (vs. pigmentation absent or, when present, concentrated at the posterior margin of scales, forming a reticulate pattern). Moenkhausia parecis can be readily distinguished from all aforementioned species by having completely blue eyes in life (vs. green in M. clorophthalma , mostly green with some red in M. petymbuaba , lower portion blue and upper portion orange in M. lineomaculata , clear or red in M. cotinho , and clear, with a longitudinal dark stripe in M. plumbea ). Additionally, it is distinguished from M. clorophthalma , M. petymbuaba and M. plumbea by having 15-18 (rarely 18) branched anal-fin rays (vs. 18-24), from M. cotinho and M. lineomaculata by having a smaller caudal-peduncle spot, with only the base of the middle caudal-fin rays pigmented (vs. blotch larger, base of all caudal-fin rays pigmented in M. cotinho and M. lineomaculata , except the outermost unbranched rays in some specimens of M. lineomaculata ) and by the absence of a light area preceding caudalpeduncle spot (vs. presence of a light area preceding caudal-peduncle spot). It can be further distinguished from M. clorophthalma , M. petymbuaba and M. plumbea by having a well-defined, round caudal-peduncle spot, that does not extend to the tip of the middle caudal-fin rays (vs. caudal-peduncle spot absent or poorly defined in M. clorophthalma and M. plumbea or caudal-peduncle spot confluent with longitudinal stripe on body, reaching the tip of middle caudal-fin rays in M. petymbuaba ).

Description. Morphometric data of the holotype and paratypes presented in Table 1. Body compressed, moderately deep. Greatest body depth anterior to vertical through dorsal-fin origin. Dorsal profile of head convex from anterior tip of upper jaw to vertical through anterior nostril; straight or slightly concave from that point to tip of supraoccipital spine. Dorsal body profile convex from tip of supraoccipital spine to base of last dorsal-fin ray, approximately straight from that point to adipose-fin insertion and slightly concave along caudal peduncle. Ventral profile of body convex from anterior tip of dentary to anal-fin origin, straight along anal-fin base and slightly concave along caudal peduncle.

Mouth terminal, upper jaw slightly longer than lower jaw. Posterior terminus of maxilla reaching vertical through middle of pupil. Maxilla approximately at 45 degree angle relative to longitudinal axis of body. Nostrils close to each other, anterior opening circular, posterior opening crescent-shaped. Nostrils separated by narrow skin flap.

Premaxillary teeth in two rows; outer tooth row with 3(2), 4*(20), or 5(12) tricuspid teeth; inner tooth row with 5*(34) teeth bearing three to five cusps, symphyseal tooth of inner series narrow, asymmetric, with four cusps. Tooth cusps of the inner premaxillary row arranged in semicircular line, directed inward. Maxilla with 2(8), 3*(21), or 4(5) teeth along its anterodorsal margin, bearing three to five cusps ( Fig. 2 ); anterior tooth usually largest. Dentary with 4*(31) or 5(2) larger tri- to pentacuspid teeth, followed by a series of 9(1), 10(1), 11(1), or 12(1) diminutive teeth, conical or tricuspid, considerably smaller than the anterior larger teeth. Cusps of large dentary teeth arranged in semicircular line, directed outward. Central cusp of all teeth more developed than lateral cusps.

Scales cycloid, moderately large, circuli distributed over whole area of scales; six to twenty radii well-defined and slightly divergent posteriorly. Lateral line complete, slightly curved downward, with 32(10) or 33*(20) perforated scales. Longitudinal scale rows between dorsal-fin origin and lateral line 5*(30). Longitudinal scale rows between lateral line and pelvic-fin origin 4*(30). Median series of scales along dorsal line between tip of supraoccipital spine and dorsal-fin origin 9(22) or 10*(6). Horizontal scale rows around caudal peduncle 14*(30). Single row of 5(1), 6(7), 7*(7), 8(7), 9(4), or 10(1) scales covering base of anterior most anal-fin rays. Caudal-fin lobes with small scales on basal third, squamation slightly more extensive on ventral lobe than on dorsal.

Dorsal-fin rays ii,9*(29) or iii,8(2). Dorsal-fin origin approximately at midpoint of standard length, slightly posterior to vertical through pelvic-fin origin. First unbranched dorsal-fin ray half length of second or less. Distal profile of dorsal fin round. First dorsal-fin pterygiophore posterior to neural spine of 9 th (4) vertebrae. Adipose fin present.Pectoral-fin rays i,11*(17) or i,12(13). Tip of adpressed pectoral fin reaching vertical through pelvic-fin origin or falling just short of that point.Pelvic-fin rays i,7(30). Tip of adpressed pelvic fin not reaching anal-fin origin, except in specimens smaller than 42.0 mm SL. Unbranched anal-fin rays iv(4). Branched anal-fin rays 15*(5), 16(20), 17(6), or 18(3). Posterior unbranched and anterior branched anal-fin rays longest, subsequent rays gradually decreasing in size. Distal margin of anal fin slightly concave. Principal caudal-fin rays i,9,8,i*(28); caudal fin forked, lobes somewhat pointed and of similar size. Dorsal procurrent caudal-fin rays 12(1) or 13(3), ventral procurrent caudal-fin rays 11(4).

Total vertebrae 32(1) or 33(3): precaudal vertebrae 16(4) and caudal vertebrae 17 (1) or 16(3). Supraneurals 4(3) or 5(1), slightly wider dorsally. Branchiostegal rays 4. First gill arch with one (4) gill-raker on hypobranchial, 7(2) or 9(2) on ceratobranchial, one (4) on cartilage between ceratobranchial and epibranchial, and 6 (4) on epibranchial.

Color in alcohol. Overall ground color pale, with small dark chromatophores covering the entire head and body, densely concentrated on dorsal portion, gradually fading ventrally ( Fig. 1a ). Dorsal midline of head and body dark brown. Jaws, opercular and infraorbital areas densely pigmented with small dark chromatophores. Opercular areas with guanine. Humeral blotch vertically oriented, extending two scale rows above and one or two scale rows below lateral line. Dorsal portion of humeral blotch spanning three scales in width; ventral portion narrower, spanning just over one scale. Area posterior to humeral blotch followed by faint and wide horizontal dark stripe spanning two scale rows above lateral line that fades posteriorly on caudal peduncle; horizontal dark stripe not conspicuous in specimens smaller than 44.5 mm SL. Deeper and narrower longitudinal dark stripe at horizontal septum, formed by underlying chromatophores, extending from vertical through dorsal-fin origin to caudal peduncle. One dark blotch at the anterior portion of each scale of the second to seventh dorsalmost scale rows. Well-defined, black, round caudal-peduncle spot, extending from posterior portion of caudal peduncle to base of middle caudal-fin rays, not extending to tip of fin rays. Caudal-peduncle spot not reaching upper and lower margins of caudal peduncle and restricted to middle caudalfin rays. All fins with scattered dark chromatophores. Distal portion of interradial membranes of anal fin with increased concentration of dark chromatophores.

Color in life. Dorsal portion of head and body light brown; ventral half yellowish ( Fig. 1b ). Eyes bright blue. Longitudinal iridescent clear stripe at midline of body. Second to seventh dorsalmost scale rows with brown blotches on its anterior portion. Humeral blotch and caudalpeduncle spot conspicuous. All fins intense orange to yellow.

Sexual dimorphism. No sexually dimorphic characters were found among analyzed specimens.

Etymology. The specific name parecis refers to the Chapada dos Parecis (plateau including the type locality), an important watershed that separates tributaries of three basins: rio Madeira, rio Tapajós and rio Paraguai. A noun in apposition.

Distribution. Moenkhausia parecis is known only from its type locality, a headwater tributary of igarapé Piracolina, itself a tributary of the upper rio Machado at Chapada dos Parecis, rio Madeira basin, about 9 km south of Vilhena, near the border of Rondônia and Mato Grosso States, Brazil ( Fig. 3 ). Moenkhausia parecis is possibly an additional species endemic to the rivers draining the Chapada dos Parecis (see list in Ohara & Lima, 2015).

Ecological notes. The type locality of Moenkhausia parecis is located at 585 m above sea level on the Chapada dos Parecis. It is a small “terra-firme igarapé” (= highland creek) with little preserved riparian vegetation and surrounded by large plantation fields (mostly soy and corn), near Vilhena, Mato Grosso. It is a clear water stream 1.5-2.5 m wide and 0.3-0.8 m deep, with swift currents, and a bottom composed of sand and dead leaves ( Fig. 4 ). During snorkeling, Moenkhausia parecis was observed in small groups of 10-15 individuals swimming in midwater. Syntopic species included Ancistrus verecundus Fisch-Muller, Cardoso, da Silva & Bertaco, 2005, Bryconops piracolina Wingert & Malabarba, 2011 , Cetopsorhamdia sp. 3 (cf. Bockmann & Slobodian, 2013: 25), Corydoras sp. , Hyphessobrycon lucenorum Ohara & Lima, 2015 , Hyphessobrycon aff. melonostichos Carvalho & Bertaco, 2006 and Pyrrhulina sp. The stomach contents of the four (c&s) paratypes included ants, scales, unidentified insect fragments, seeds, unidentified vegetal fragments and sediments.

Conservation status. Despite intensive and broad collecting efforts in the rio Madeira basin during 2009 to 2013 (Queiroz et al., 2013) and recent surveys conducted in the southeastern portion of Rondônia State and northwest of Mato Grosso State undertaken in 2010-2011 and 2013-2014, Moenkhausia parecis was only collected at its type locality. Additionally, examination of several fish collections failed to reveal additional specimens. Thus, it is possible that the species is restricted to the upper rio Machado, at the Chapada dos Parecis. The type locality of M. parecis is a small forest fragment near Vilhena town that is surrounded by farms. According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014), Moenkhausia parecis might be considered as ‘Vulnerable (D2)’, based on its occupation area (AOO) apparently less than 20 km 2 and the plausible future threat (agricultural development and expansion of Vilhena town around its very restricted distribution) that could lead the species to become critically endangered or extinct.

Figures

Fig. 1. Moenkhausia parecis new species, (a) holotype, MZUSP 116070, 77.9 mm SL (b) paratype, MZUSP 115509, 41.7 mm SL, immediately after capture, upper rio Machado, rio Madeira basin, Rondônia, Brazil.

Fig. 2. Medial view of left side of premaxilla, maxilla and dentary of Moenkhausia parecis, MZUSP 116071, paratype, 26.2 mm SL. Scale bar = 1 mm.

Fig. 3. Type locality (blue square) of Moenkhausia parecis, a tributary of the igarapé Piracolina, upper rio Machado drainage, rio Madeira basin, Brazil.

Fig. 4. Tributary of igarapé Piracolina, upper rio Machado, Vilhena, Rondônia, Brazil, type locality of Moenkhausia parecis.