Lebiasina marilynae, Netto-Ferreira, 2012

Netto-Ferreira, André L., 2012, Three new species of Lebiasina (Characiformes: Lebiasinidae) from the Brazilian Shield border at Serra do Cachimbo, Pará, Brazil, Neotropical Ichthyology 10 (3), pp. 487-498 : 488-491

Lebiasina marilynae , new species

Fig. 1

Holotype. MZUSP 101375 , 88.8 mm SL, Brazil, Pará, Altamira, rio Xingu drainage, unnamed tributary of rio Curuá , rio Iriri basin, near BR-163 road, 08°49’12”S 54°58’11”W, 11 Jan 2009, A. L. Netto-Ferreira, J. L. O. Birindelli, L. M. Sousa & P. Hollanda-Carvalho.

Paratypes. Brazil, Pará, Altamira , MZUSP 99607 , 3 , 31.6-33.7 mm SL, rio Xingu drainage, unnamed tributary of rio Curuá, rio Iriri basin, near BR-163 road, 08°49’12”S 54°58’11”W, 29 Oct 2007, J. L. O. Birindelli, L. M. Sousa, A. L. Netto-Ferreira, M. H. Sabaj Pérez & N. K. Lujan ; MZUSP 99608 , 1 , 31.8 mm SL cs, rio Xingu drainage, unnamed tributary of rio Curuá, rio Iriri basin, near BR-163 road, 08°49’12”S 54°58’11”W, 29 Oct 2007 J. L. O. Birindelli, L. M. Sousa, A. L. Netto-Ferreira, M. H. Sabaj Pérez & N. K. Lujan .

Diagnosis. Lebiasina marilynae is distinguished from all lebiasinins by its color pattern consisting of a slightly concave primary stripe, extending from the tip of the snout to the distal border of the caudal peduncle, a series of approximately 14 small blotches running nearly parallel to the primary stripe along the ventrally adjacent longitudinal series of scales and converging towards the stripe near the anal fin origin, and the lack of a secondary stripe. The new species further differs from its congeners by the presence of a pair of foramina on the ventral surface of the vomer through which the ramus palatinus of the facial nerve passes ( Fig. 2a ), the round dorsal surface of the mesethmoid ( Fig. 3a ), and the absence of an adipose fin (vs. vomer lacking a pair of foramina, ramus palatinus of the facial nerve passing lateral to the vomer - Fig. 2b ; and a T-shaped dorsal surface of the mesethmoid - Fig. 3b ).

Description. Morphometric data of the holotype and paratypes is presented in Table 1. Lateral view of holotype (preserved and live), and a fresh juvenile paratype in Fig. 1 (a, b, and c, respectively). Body cylindrical, elongate. Greatest body depth located anterior to dorsal-fin origin between pectoral and pelvic fins. Dorsal profile of head convex from tip of upper lip to dorsal-fin origin, straight from latter point to base of dorsal fin, and concave from that point to anteriormost dorsal caudal-fin procurrent ray. Ventral profile of head and trunk distinctly convex from tip of lower lip to pelvic-fin origin, concave between origins of pelvic and anal fins. Anal-fin base profile slightly concave to nearly straight, from anal-fin terminus to origin of anteriormost ventral caudal-fin procurrent ray.

Mouth sub-superior. Premaxillary with single row of 9(1) tricuspid teeth. Maxillary with 5(1) tricuspid or conic teeth. Anteriormost tooth usually largest. Posterior terminus of maxilla reaching slightly beyond anterior margin of orbit. Dentary with two series of teeth; outer series with 12(1) pedunculate tricuspid teeth with central cusp distinctly longer than ones along margins, decreasing gradually in size posteriorly; inner series with several minute conical teeth extending from symphysis to coronoid process. Branchiostegal rays 4(5); three rays articulating with anterior ceratohyal and one with posterior ceratohyal.

Scales cycloid, circuli restricted to border of scales, several radii converging to center of scale and strongly anastomosed in center and forming several cells. Lateral line series with 25(2) or 26*(3) scales, of which only 6*(5) are perforated. Longitudinal rows of scales between dorsal and pelvic fins 7*(5). Predorsal scales 11*(3) or 12(2). First longitudinal row of scales usually reaching vertical through dorsal-fin terminus, but sometimes extending beyond that point by one or two scales. Circumpeduncular scales 12(5).

Pectoral-fin rays i,11(1) or 12*(4). Tip of longest pectoral-fin ray falling far short of vertical through pelvic-fin insertion. Pelvic-fin rays i,7*(5). Supraneurals 8(1), anterior to neural spine of centra 6 to 13(1). Dorsal-fin rays iii,8(1) or ii,8*(4). First dorsal-fin pterygiophore inserting behind neural spine of centrum 13*(4). Distal margin of extended dorsal fin rounded. Dorsal-fin origin located distinctly closer to caudal-fin origin than to tip of snout. Base of last dorsal-fin ray situated distinctly anterior to vertical through anal-fin origin.Anal-fin rays iii,8*(5), with last ray adnate. Distal margin of extended anal fin rounded. First anal-fin pterygiophore inserted posterior to haemal arch of centrum 22(4). Adipose fin absent. Caudal fin furcate with upper lobe slightly longer than lower lobe; both lobes rounded. Principal caudal-fin rays ii,8/i,8(1) or i,9/i,8*(4). Dorsal caudal-fin procurrent rays 8(1), 9(1) or 10(2); ventral caudal-fin procurrent rays 7(2) or 8(2). Precaudal vertebrae 21(3) or 22(1); caudal vertebrae 14(1) or 15*(3).

Color in alcohol. Ground coloration light yellowish. Head densely darkly pigmented from upper lip to origin of scales on the mid-posterior portion of parietals. Dark brown pigmentation extending from that point to caudal-fin insertion, over mid-dorsal series of scales and immediately bordering scale rows. Infraorbitals and opercular series largely covered with small chromatophores, with densely pigmented areas covered by primary stripe. Lower lip densely darkly pigmented. Ventral portion of head largely unpigmented except for patch of chromatophores posterior to dentary symphisis. Opercular membrane with small scattered chromatophores.

Body dark dorsally, becoming lighter ventrally from third longitudinal series of scales. Abdominal area yellowish and lacking distinct pigmentation between isthmus and anal-fin origin. Primary stripe extending from tips of upper and lower lips, passing through maxilla, antorbital, infraorbitals one, two, four, and five, eyes and opercle, interrupted from that point to humeral area and then extending over scales of longitudinal series 4 and 5. Primary stripe becomes irregular with zigzag aspect at vertical through terminus of dorsal fin, and terminates at the caudal blotch. Dark spots present at base of scales of sixth longitudinal series, forming longitudinal series of around 14 dark spots converging towards primary stripe at vertical through first anal-fin branched ray. Abdominal region light yellow, with minute dark chromatophores. Conspicuous humeral blotch present. Dark pigmentation present along rays and intervening membranes of all fins.

Color in life. Same as in alcohol, except for dorsal portion of eyes red; fins orange; ventral portion of head yellowish; posterior border of scales on third to sixth longitudinal series greenish; scales 4 to 6 of lateral line system with intense guanine deposition giving metallic coloration. When specimens are submitted to stress primary stripe chromatophores seem to contract ( Fig. 1b ).

Sexual dimorphism. All known specimens of Lebiasina marilynae are juveniles and an adult female, lacking secondary sexual characters.

Distribution. Lebiasina marilynae is known, until now, from a single collection site in the rio Curuá, rio Xingu basin ( Fig. 4 ).

Etymology. The specific epithet is in honor to Marilyn J. Weitzman, who devoted her career to the study of fishes of the families Lebiasinidae and Characidae . A noun.

Figures

Fig. 1. Lebiasina marilynae: a) preserved, b) fresh holotype, MZUSP 101375, 88.8 mm SL, Altamira, Pará, Brazil; c) fresh juvenile paratype, MZUSP 99607, 32.6 mm SL,Altamira, Pará, Brazil.

Fig. 2. Ventral view of medioanterior portion of the neurocranium of: a) Lebiasina melanoguttata, MZUSP 99610, paratype, 89.4 mm SL,Altamira, Pará, Brazil; b) Lebiasina ortegai CAR145, 94.5 mm SL,Alcalá, Valle del Cauca, Colombia.FRO - frontal; LAT - lateral ethmoid; MES - mesethmoid; NAS - nasal; ORB - orbitoshpenoid; PAR - parasphenoid; PTE - pterosphenoid; SPH - sphenotic; VOM - vomer.

Fig. 3. Dorsal view of the mesethmoid of: a) Lebiasina marilynae, MZUSP 99608, paratype, 31.8 mm SL,Altamira, Pará, Brazil; b) Lebiasina elongata, MUSM 21356, 73.1 mm SL, Cenepa, Amazonas, Peru. FRO - frontal; LAT - lateral ethmoid; MES - mesethmoid; NAS - nasal.

Fig. 4. Map of rio Tapajós basin and adjoining areas, showing the distribution of Lebiasina marilynae n. sp. (star); Lebiasina melanoguttata n. sp. (circle); Lebiasina minuta n. sp. (triangle). Symbols may represent more than one collection event.