Moenkhausia conspicua, Soares, Isabel Matos & Bührnheim, Cristina Motta, 2016

Soares, Isabel Matos & Bührnheim, Cristina Motta, 2016, A new species of Moenkhausia Eigenmann, 1903 (Characiformes: Characidae) from Amazon basin, Brazil, Zootaxa 4208 (4), pp. 392-400 : 393-396

Moenkhausia conspicua , new species

Figs. 1–4

Holotype. INPA 38782 , male, 33.9 mm SL, Brazil, Pará, Mojuí dos Campos, rio Curuá-Una, igarapé near Tabocal community, 2°37’35.9”S 54°42’36.3”W, 3 Aug 2010, R. P. Leitão & C. G. Leal.

Paratypes. All from Brazil, Pará State, rio Curuá-Una drainage: Belterra : INPA 42360, 10 (23.8–41.2 mm SL, 1 c& s 35.5 mm SL), igarapé Onça tributary of rio Moju , 3°33’31.5”S 54°52’13.5”W, 18 Oct 2012, A. C. Canto, C. S. Oliveira & F. R. V. Ribeiro; INPA 42371, 133 (12.4–36.1 mm SL); ANSP 200304, 5 (28.8–36.4 mm SL); MCP 48356, 10 (23.8–37.0 mm SL); MPEG 30615, 20 (22.3–36.0 mm SL); MZUSP 120821, 10 (22.1–37.6 mm SL); UFAM 674, 5 (25.5–35.7 mm SL); ZUEC 13429, 5 (30.7–36.3 mm SL), igarapé São Jorge, 3°11’15”S 54°59’02”W, 24 Jul 2010, R. Leitão & C. Leal. Mojuí dos Campos: INPA 38781, 49 (15.5–40.1 mm SL, 3 c& s 32.6 –36.0 mm SL), collected with the holotype; UFOPA- I 0 0 0 0 6, 6 (31.4–41.7 mm SL), igarapé tributary of rio Moju, at road Cuiabá-Santarém (BR-163), village of Santo Antônio , 3°21’43.2”S 54°42’37.5”W, 6 Jan 2012, Equipe Projeto Moju I e II; UFOPA-I 0 0 0 42, 10 (33.8–39.5 mm SL), igarapé tributary of rio Moju , at road Cuiabá- Santarém (BR-163), village of Santo Antônio , 3°22’53.8”S 54°42’58.9”W, 6 Jan 2012, Equipe Projeto Moju I e II; UFOPA- I 0 0 0 35, 5 (31.6–38.8 mm SL), igarapé tributary of rio Moju , at road Cuiabá-Santarém (BR-163), village of Estrela da Bica , 3°19’56.3”S 54°37’4.9”W, 6 Jan 2012, Equipe Projeto Moju I e II.

Non-types. All from Brazil. Pará State, rio Curuá-Una drainage: Belterra: INPA 42372, 18 (16.4–38.7 mm SL), igarapé tributary of rio Moju , at road Cuiabá-Santarém (BR-163), 3°09’41”S 54°50’18”W, 14 Jul 2010, R. Leitão & C. Leal ; INPA 42374, 14 (13.3–33.9 mm SL), igarapé at km 85, FLONA do Tapajós , 3°02’31”S 55°01’13”W, 8 Jul 2010, R. Leitão & C. Leal ; INPA 42375, 3 (16.1–33.8 mm SL), igarapé near São Jorge community, 3°08’33”S 54°49’47”W, 14 Jul 2010, R. Leitão & C. Leal. Mojuí dos Campos: INPA 42373, 27 (13.5– 39.6 mm SL), igarapé at the headwaters of rio Moju , 2°47’03”S 54°41’22”W, 26 Jul 2010, R. Leitão & C. Leal.

Diagnosis. Moenkhausia conspicua is distinguished from all congeners, except M. collettii , M. copei and M. venerei Petrolli, Azevedo-Santos & Benine, 2016 by the presence of a rounded and horizontally elongated humeral blotch; a broad dark horizontal stripe across the middle portion of the eye; a longitudinal dark midlateral stripe, from immediately after opercle to caudal-fin basis; and a well defined dark stripe along the base of the anal-fin. It differs from M. collettii , M. copei and M. venerei by having up to seven cusps on inner premaxillary, maxillary and dentary teeth (vs. up to five cusps). Moenkhausia conspicua also can be distinguished from M. collettii , M. copei and M. venerei by having four, rarely five, longitudinal rows of scales below lateral line (vs. three rows in M. collettii and M. copei , and five to six in M. venerei ). The new species can be distinguished from M. colletti and M. copei by having six, rarely five, longitudinal rows of scales above lateral line (vs. five longitudinal rows of scales, except in M. venerei ). M. conspicua is distinguished from M. collettii by presence of a well-defined longitudinal midlateral dark stripe (vs. absent). Additionally, M. conspicua differs from M. copei by greater number of branched anal-fin rays (18-26 vs. 15-17). Finally, M. conspicua is promptly distinguished from M. venerei by having a welldefined large dark stripe along the entire anal-fin base, extending into the anal-fin interradial membrane (vs. narrow, well-defined dark stripe along the anal-fin base restricted to anterior portion of the fin).

Description. Morphometrics of Moenkhausia conspicua are summarized in Table 1. Body compressed, greatest body depth anterior to dorsal-fin origin. Dorsal profile of head straight or slightly concave. Dorsal profile of body slightly convex from tip of supraoccipital spine to dorsal-fin origin, moderately convex and posteroventrally slanted along dorsal-fin base, moderately convex from posterior end of dorsal-fin base to adiposefin origin, and gently concave along caudal peduncle. Ventral profile of body convex from anterior tip of lower jaw to pelvic fin; straight from pelvic-fin origin to anal-fin origin; straight and posterodorsally slanted along anal-fin base and slightly concave along caudal peduncle.

Mouth terminal. Two rows of premaxillary teeth ( Fig. 2 ); outer row with 0(1), 1(1), 2(5), 3(33) or 4*(40) teeth with three cusps, median cusps longer; inner row with 4(7), 5*(66), 6(7) or 7(1) teeth with five to seven cusps. Maxillary with 1(1), 2*(56), 3(23) or 4(1) teeth three to five cusps. Dentary with 4*(49) or 5(32) teeth with five to seven cups, followed by 0(3), 2(1), 3(4), 4(9), 5(17), 6*(19), 7(19), 8(6) or 9(3) smaller teeth with one to five cusps.

Dorsal-fin rays ii(81), 8(3) or 9*(78). Dorsal-fin origin slightly posterior to middle of body. First unbranched ray smaller than half of length of second unbranched ray. Adipose fin relatively well developed. Pectoral-fin rays i*(81), 9(8), 10(28), 11(36) or 12*(9); tip of adpressed longest rays reaching pelvic-fin origin. Pelvic-fin rays i*(81), 6(4), 7*(76) or 8(1); tip of adpressed longest rays reaching anal-fin origin. Anal-fin rays iii*(53) or iv(28), 18(1), 21(1), 22(8), 23(21), 24*(35), 25(11) or 26(4); last unbranched ray and first four or five branched anal-fin rays longer than remaining. Principal caudal-fin rays i*(80) or ii(1), 8(6) or 9*(75) + 7(5) or 8*(76), i*(81). Dorsal procurrent caudal-fin rays 10(1), 11(2) or 12(1) and ventral procurrent caudal-fin rays 8(2) or 9(2). Caudal-fin forked, lobes similar in size.

Scales cycloid. Lateral line completely pored, slightly curved anteriorly, with 31(1), 32(4), 33(20), 34*(35), 35(17) or 36(2) perforated scales. Longitudinal scale rows between dorsal-fin origin and lateral line 5(7) or 6*(74); longitudinal scale rows between lateral line and pelvic-fin origin 4*(78) or 5(3). Predorsal scales row with 7(1), 8(4), 9*(42), 10(31) or 11(2) scales. Circumpeduncular scales 12(17), 13 (5) or 14*(57). Single row of small scales overlying basal portion of anteriormost anal-fin rays. Scales covering two proximal thirds of caudal-fin lobes.

Supraneurals 4(4). Precaudal vertebrae 15(4); caudal vertebrae 19(2) or 20(2); total vertebrae 34(2) or 35(2). First gill-arch with 5*(41), 6(34) or 7(6) gill-rakers on upper limb and 9(8), 10*(55), 11(16) or 12(2) gill-rakers on lower limb.

Color in alcohol. Overall ground color pale beige, with few dark chromatophores scattered on body surface. Top of head, snout, premaxilla, maxilla and dentary with small dark chromatophores. Five to six dorsalmost longitudinal scale rows with small chromatophores concentrated on posterior half of scales; ventralmost longitudinal scale rows with fewer chromatophores concentrated on posterior half of scales. Dark horizontal stripe crossing middle portion of eye. A conspicuous, rounded humeral blotch, horizontally extending from 2nd to 4th lateral line scales and vertically extending two scale rows above lateral line. Midlateral longitudinal dark stripe, two scale rows wide, extending from immediately posterior from eye to caudal peduncle terminus, reaching middle caudal-fin rays. Longitudinal dark stripe along anal-fin base broad, covering base of anal-fin rays and proximal portion of interradial membranes. Base of median caudal-fin rays with chromatophores. Distal margin of dorsal, adipose, caudal and anal-fins with scattered dark chromatophores, generally more densely concentrated in males than females ( Fig. 3 ).

Male Males Females

Holotype N Range N Range Standard length (mm) 33.9 45 24.0–39.5 36 15.5–41.7 Head length (mm) 8.7 45 6.9–9.8 36 4.9–10.5 Percentages of head length

Snout length 21.3 45 17.1–23.7 36 17.5–23.1 Upper jaw length 41.9 45 36.6–45.6 36 37.1–45.8 Orbital diameter 49.6 45 44.9–56.0 36 44.0–52.5 Interorbital width 37.6 45 29.3–37.9 36 25.9–38.8 Sexual dimorphism. Mature males of Moenkhausia conspicua have slightly curved bony hooks on the pelvic- and anal-fin rays. At the pelvic fin, one or two hooks are present per ray segment, along the mid-length to the distal tip of the unbranched pelvic-fin ray, and on the 1st to 5th branched pelvic-fin rays. At the anal fin, one, two and sometimes three pair of hooks are present per ray segment, arranged along the distal portion of the last unbranched ray and from the 1st to the 4th branched anal-fin rays.

Distribution. Moenkhausia conspicua is known from the rio Curuá-Una and rio Moju, lower Amazon basin, Pará State, Brazil ( Fig. 4 ).

Etymology. The specific epithet conspicua comes from the Latin, meaning visible, in allusion to the presence of two dark stripes, one extended along midbody and the other along the anal-fin basis.

Conservation status. The catchment areas of rio Moju and rio Curuá-Una have been suffering an intense anthropic pressure, mainly due to deforestation to create pastureland. Although some of these areas are now deeply modified, this impact does not seem to have caused harm to the populations of the new species. In addition, the igarapé Onça has its headwater area within the Floresta Nacional do Tapajós, and therefore, is currently not subject to man-induced disturbances. Hence, as no significant threats that may put their populations at risk were identified, Moenkhausia conspicua was categorized as Least Concern (LC), according to International Union for Conservation of Nature criteria (IUCN).

Figures

FIGURE 1. Moenkhausia conspicua, holotype, INPA 38782, male, 33.9 mm SL (top), and paratype, INPA 38781, female 34.1 mm SL (bottom), Brazil, Pará, Mojuí dos Campos, rio Curuá-Una basin.

FIGURE 2. Dentition of Moenkhausia conspicua, INPA 42360, male 35.5 mm SL: right premaxilla (top), maxilla (middle), and dentary (bottom), inner view.

FIGURE 3. Moenkhausia conspicua, unsexed, just after fixation, Brazil, Pará, rio Moju, rio Curuá-Una basin (specimen not cataloged).

FIGURE 4. Map of lower Amazon basin in Brazil showing the distribution of Moenkhausia conspicua (dots); star indicates the type locality.