Moenkhausia rubra, Pastana & Dagosta, 2014

Pastana, Murilo N. L. & Dagosta, Fernando C. P., 2014, Moenkhausia rubra, a new species from rio Juruena, upper rio Tapajós basin, Brazil (Characiformes: Characidae), Neotropical Ichthyology 12 (2), pp. 389-396 : 390-393

Moenkhausia rubra , new species

Figs. 1-3

Holotype. LIRP 8183 , 41.3 mm SL, Brazil, Mato Grosso, município de Sapezal, Pequena Central Hidroelétrica ( PCH) Sapezal, rio Juruena, rio Tapajós basin, 13º16’10"S 59º01’26"W, 01 May 2010, R. Ilário.

Paratypes. LIRP 7657 , 1 , 31.1 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, 13º22’39"S 59º00’58"W, 23 May 2008 , R. Ilário . LIRP 8164 , 8 , 36.5-54.3 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, PCH Parecis, 13º04’43"S 58º58’06"W, 24 May 2010 , R. Ilário . LIRP 8177 , 6 , 37.1-47.2 mm SL, 1 c&s, 45.8 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, PCH Cidezal, 13º22’39"S 59º00’57"W, 3 Jun 2010 , R. Ilário . LIRP 8178 , 8 , 32.7-47.91 mm SL; 1 c&s, 40.7 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, collected with holotype, 13º16’10"S 59º01’26"W, 01 May 2010 , R. Ilário . LIRP 8180 , 19 , 18.9-28.8 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, PCH Cidezal , small beach on the side of a rapid, 13º22’20"S 59º00’51"W, 05 Jan 2008 , R. Ilário . MZUSP 109218 , 3 , 36.5-39 mm SL, Brazil, Mato Grosso, município de Sapezal, rio Juruena, rio Tapajós basin, PCH Cidezal, 13º22’39"S 59º00’57"W, 3 Jun 2010 , R. Ilário . MZUSP 114032 , 1 , 39.8 mm SL, Brasil, Mato Grosso, Campos de Júlio, rio Juína, tributary of rio Juruena , rio Tapajós basin, 13°47’41’’S 59°27’20’’W, 8 Set 2013, O. T. Oyakawa, F. C. P. Dagosta, M. M. F. Marinho & P. Camelier .

Diagnosis. Moenkhausia rubra is distinguished from all congeners, except M. hemigrammoides Géry and M. nigromarginata Costa , by the presence of dark pigmentation on the anteriormost rays of dorsal and anal fins. It can be distinguished from M. hemigrammoides and M. nigromarginata by the number of branched anal-fin rays 17- 20 (vs. 20-22 in M. nigromarginata and 22-25 in M. hemigrammoides ). It can be further distinguished from M. hemigrammoides by the presence of a dark blotch on the caudal peduncle extending to middle caudal-fin rays (vs. absence) and from M. nigromarginata by the absence of dark pigmentation on the anteriormost pelvic fin rays (vs. dark pigmentation present), absence of dark pigmentation along the distal margin of anal fin (vs. presence) and absence of longitudinal black zigzag stripes between longitudinal rows of scales on body (vs. presence). Moenkhausia rubra can also be distinguished from its congeners by the combination of the following characters: 5 or 6 scale rows above and 4 or 5 scale rows below the lateral line, 17-20 branched anal-fin rays, 33-34 lateral line scales, 3-6 maxillary teeth, one round humeral spot, absence of reticulated color pattern on body, absence of a dark broad stripe extending from the opercle to the caudal peduncle, distal portion of caudal-fin lobes hyaline, and dark caudal-peduncle spot extending posterior to the middle caudal-fin rays.

Description. Morphometric data of M. rubra in Table 1 . Smallsized species, largest examined specimen 54.3 mm SL (LIRP 8164). Body compressed and moderately deep ( Fig. 1 ). Greatest body depth slightly anterior to dorsal-fin insertion. Dorsal profile of head strongly convex from snout tip to vertical through nostrils, straight to slightly concave from that point to tip of supraocciptal spine; convex from tip of supraoccipital spine to dorsal-fin origin. Dorsal-fin straight along its base, straight to slightly convex from dorsal-fin terminus to adiposefin origin, concave between latter and origin of anteriormost dorsal caudal-fin procurrent ray. Ventral profile of head convex from tip of snout to pelvic-fin origin, slightly straight from pelvic-fin origin to anal-fin origin, straight along anal-fin base, posterodorsally inclined, concave between last anal-fin ray to anteriormost ventral caudal-fin procurrent ray.

Mouth terminal. Posterior margin of maxilla approximately at vertical through middle of orbit. Premaxillary teeth in two rows. Outer premaxillary tooth row with 4(13) or 5*(15) tricuspid teeth with median cusp more developed than others ( Fig. 2); inner tooth row with 5*(28) pentacuspid teeth. Premaxillary teeth gradually decreasing in size laterally. Maxilla with 3(1), 4(3), 5*(18), or 6(6) uni- to tricuspid teeth. Dentary with 4*(27) or 6(1), pentacuspid teeth followed by a series of 10-15 small conical teeth ( Fig. 2). First gill arch with 17(2) gill rakers, 6 (2) rakers on epibranchial, 1 (2) between epibranchial and ceratobranchial, 8 (2) on ceratobranchial, 1 (2) between ceratobranchial and hypobranchial, and 1 (2) on hypobranchial. Four branchiostegal rays (2): three branchiostegal rays articulating with anterior ceratohyal and one with posterior ceratohyal.

Scales cycloid, without circuli on exposed portion of scales, usually up to 6 divergent radii extending to posterior margin of scale. Lateral line complete, slightly curved ventrally, with 33*(11) or 34(15) pored scales on longitudinal series. Scale rows between dorsal-fin origin and lateral line 6 (26) or 5*(2); scale rows between lateral line and pelvic-fin origin 5*(27) or 4(1). Predorsal scales 8(1), 9*(13), 10(11), or 11(1). Circumpeduncular scale rows 14*(21) or 15(1).

Pectoral-fin rays i,10(2), i,11*(24) or i,12(2) rays reaching pelvic-fin origin. Pelvic-fin rays i,7*(28), reaching origin of anal fin in some specimens. Supraneurals 4(2). Dorsal-fin rays ii,9*(28), first unbranched anal-fin ray about one-half the length of second unbranched ray. Dorsal-fin origin at midbody, slightly posterior to vertical through pelvic-fin origin, base of posteriormost dorsal-fin ray slightly anterior to vertical through anal-fin origin. First dorsal-fin pterygiophore inserting posterior to neural spine of 9 th (2) vertebrae. Adipose fin present.Anal-fin rays iii,17(3), iii,18(8)*, iii,19(14) or iii,20(2). Distal border of anal fin concave. Caudal fin forked, with scales covering proximal half of caudal-fin lobes. Principal caudalfin rays i,9/8,i* (28). Dorsal caudal-fin procurrent rays 13(2) and ventral caudal-fin procurrent rays 10(1) or 11(1). Precaudal vertebrae 14 (2), caudal vertebrae 18 (2), total vertebrae 32 (2).

Color in alcohol. Background body coloration pale yellow ( Fig. 1 ). Dorsal and dorsolateral portion of head grey with dark chromatophores scattered on dorsal surface of head, opercle and infraorbital bones. High concentration of dark chromatophores on dorsal midline of body, from tip of supraoccipital spine to anteriormost dorsal procurrent ray. Diffuse, dark and round humeral spot with borders not well delimited, extending horizontally along two to three scales, and vertically by three scale rows. Diffuse longitudinally stripe extending along flanks from humeral spot to median caudal-fin rays, more diffuse anteriorly, gradually wider posteriorly. Stripe wider at caudal peduncle and extending onto middle caudal-fin rays. Unbranched and first to third anteriormost branched dorsal-fin rays with dark chromatophores along its length, densely concentrated on its distal portion; remaining rays with few scattered dark chromatophores along their length. Unbranched and first to fifth anteriormost branched anal-fin rays with dark chromatophores along their length, densely concentrated on distal portion; remaining rays with few scattered dark chromatophores along its length. Caudal, pectoral, and pelvic fins with few scattered dark chromatophores mainly on interradial membranes.

Color in life. Overall background color ranging from yellowish to reddish, mainly on mid-dorsal area ( Fig. 3 ). Midventral area silvery. Snout and gular area orange. Eye mostly orange, dorsal portion blue to green. Opercular region and circumbital bones silvery. Dark longitudinal stripe at mid-body. Humeral spot round and diffuse. Pectoral and pelvic fins hyaline. Anal and dorsal fins with unbranched and first to third branched anteriormost rays with dark marks. Dorsal, adipose, and caudal fins intense orange to reddish, except for distal hyaline portion on dorsal and caudal fins.

Sexual dimorphism. Males and females/immature specimens were sexed based on the pelvic-fin elongation ( Fig. 4). Sex was confirmed by dissection in 10 specimens (male n=5; female n=5). Adult males with pelvic-fin rays slightly longer than females or juvenile specimens, with pelvic-fin length ranging from 17.4-19.5% of SL in mature males (vs. 14.7-17.6% SL in mature females/immature specimens). Bony hooks were not observed on fins of any analyzed specimen.

Distribution. Moenkhausia rubra is known from rio Juína and rio Juruena, rio Juruena basin, upper rio Tapajós drainage, Mato Grosso State, Brazil ( Fig. 5 ).

Etymology. From the latin ruber (red), in allusion to the reddish coloration of the body, and the dorsal, adipose, and caudal fins in live specimens. An adjective.

Figures

Fig. 1. Moenkhausia rubra, Brazil, Mato Grosso, Sapezal, Pequena Central Hidrelétrica (PCH) Sapezal, rio Juruena, rio Tapajós basin:(a) LIRP 8183, holotype, female, 41.3 mm SL, (b) LIRP 8164, paratype, male, 47.4 mm SL.

Fig. 3. Moenkhausia rubra, paratypes: (a) LIRP 8180, 29.1 mm SL, Brazil, Mato Grosso, Sapezal, rio Juruena, immediately after capture; (b) MZUSP 114032, 39.8 mm SL, Brazil, Mato Grosso, Campos de Júlio, rio Juína, immediately after capture.

Fig. 5. Distribution of Moenkhausia rubra. Black star represents type locality. Symbols may represent more than one lot.