Moenkhausia sthenosthoma, Petrolli, Marina G. & Benine, Ricardo C., 2015

Petrolli, Marina G. & Benine, Ricardo C., 2015, Description of three new species of Moenkhausia (Teleostei, Characiformes, Characidae) with the definition of the Moenkhausia jamesi species complex, Zootaxa 3986 (4), pp. 401-420 : 408-411

Moenkhausia sthenosthoma , new species

( Figs. 6 a–c, 9e–f, Table 1 )

Moenkhausia jamesi: Queiroz et al. (2013) : 312–313. Mariguela et al. (2013): 4–5.

Holotype. MCP 48789, 56.0 mm SL, Rondônia, Madeira, Rio Jaci-Paraná between Porto Velho and Jaci-Paraná; 9º15’23”S, 64º23’13”W, R. E. Reis, P. A. Buckup, F. Langeani, V. Bertaco, P. Lehmann., 18 Jul 2004.

Paratypes. All from Brazil. Rondônia. MCP 39421, 20, 40.5–56.0 mm SL, Rio Jaci-Paraná, between Porto Velho and Jaci-Paraná, rio Madeira, 9º15’23”S, 64º23’13”W, R. E. Reis et al., 18-Jul-2004. MCP 39417, 30, 29.6– 41.4 mm SL, Rio Madeira, Rio Mamoré, in front of Cristo Rei neighborhood, Gujará-Mirim, 10°47’03”S 65°20’58”W, R. E. Reis et al., 25-Jul-2004. ANSP 200003, 10, 32.3–45.6mm SL, same data as MCP 39417. MNRJ 43441, 10, 33.7–46.7, same data as MCP 39417. UFRO 300, 1, 40.3 mm SL, Igarapé Arara, Porto Velho; 10º0’45”S, 65º19’7”W; L. Queiroz; 08-Apr-2004. UFRO 317, 1, 52.7 mm SL, Fortaleza do Abuña, Rio Abuña waterfall, rio Madeira; 09º47’S, 65º31’W; M.A.L, Lima; 09-Jun-2004. UFRO 3785, 2, 41.5–46.1 mm SL, Jaci- Paraná, mouth of Rio Jaci-Paraná, rio Madeira; 09º13’01,5”S, 64º22’58,4”W; T. Fernandes; 07-Nov-2009. INPA 48440, 2, 22.3–31.4, Fortaleza do Abuña, Rio Abuña waterfall, Rio Madeira; 09º04’S, 65º31’W; G. Vilara; 07-Apr- 2004. INPA 48441, 1, 40.8 mm SL, Guajará-Mirim, rio Pacaás Novos, near to the confluence with rio Mamoré; 10º51’31,6”S, 65º16’39,1”W; A. Ribeiro, 30-Sep-2009. INPA 48442, 3, 44.1–56.6 mm SL, Pimenteiras do Oeste, Rio Guaporé, mouth of Rio Cautário; 12º12’4989”S, 64º35’09,41”W; D. Hungria; 10-Jan-2012. MZUSP 117143,1, 49.7 mm SL, Jaci-Paraná, Lago Madalena, rio Jaci-Paraná; 9º13’00” S, 64º00’70’’W; L.C.R Melo; 10-Jul-2009. MZUSP 117144, 1, 35.4 mm SL, mouth of Igarapé Belmont, Rio Madeira; 8º37’56,56”S, 63º50’20,51”W; G. Vilara; Feb-2006. MZUSP 117145, 2, 57.5–61.4 mm SL, Jaci-Paraná, upstream of rio Jaci- Paraná, left margin shore; 09º27’16,5”S, 64º24’51,9”W; T. Fernandes; 03-Aug-2011. MZUSP 117142,1, 39.0 mm SL, Guajará-Mirim, rio Soterio, shore at mouth of Rio Negro; 11º35’51,9”S, 65º 13’ 49,1”W; LIP/ UNIR team, 04-Jul-2011. MZUSP 117141, 3, 49.3–54.6 mm SL, Pimenteiras do Oeste, rio Guaporé, mouth of rio Cautário; 12º12’49,89”S, 64º35’09,41”W; D. Hungria; 10-Jan-2012. LBP 19956, 1 (c&s), 46.0 mm SL, Jaci-Paraná, mouth of Igarapé Karipuna, rio Madeira; 09º11’27,7”S, 64º37’04”W; Talles Fernandes; 04-Sep-2009. LBP 19957, 1, 57.2 mm SL, Jaci-Paraná, mouth of Rio Jaci-Paraná, rio Madeira; 09º17’29”S, 64º23’56,67”W; G. Vilara; 01-Apr-2006. LBP 19958, 2, 1 (c&s), 61.9–63.4 mm SL, Jaci-Paraná, Três Praias, rio Jaci-Paraná, rio Madeira. 9º27’9.9”S, 64º24’56,7”W; C. Röpke; 11-Dec-2009. LBP 19959, 3, 54.9–63.0 mm SL, Guajará-Mirim, Surpresa, rio Guaporé; 11º53’S; 65º01’W; LIP/ UNIR team; 11-Jan-2012. 08-Apr-2004. Mato Grosso. LBP 19960, 3, 52.1–53.4 mm SL, Vila Bela da Santíssima Trindade, rio Guaporé, ponte para Vila Bela da Santíssima Trindade; 15ºS, 59,95ºW; W. M. Ohara; 13-Dec-2011.

Diagnosis. Moenkhausia sthenosthoma is readly distinguished from M. jamesi by the number of scale rows between lateral line and the midventral scale series (seven vs six in M. jamesi ). It differs from M. ischyognatha by its greater head depth (33.9–37.8% in SL vs 29.3–32.6 in SL in M. ischyognatha ). It is distinguished from M. alesis by the number of scale rows between lateral line and dorsal-fin origin (seven vs eight to nine in M. alesis ). Moenkhausia sthenosthoma is distinguished from M. justae by the number of teeth in maxilla (edentulous vs one tooth with 5 cusps in M. justae ), and by the number of cusps on the fourth dentary tooth (three to five vs six in M. justae ) ( Fig. 9 b, 9e–f).

Description. Morphometric data summarized in Table 1 . Largest specimen examined 63.4 mm SL. Body compressed and deep. Greatest body depth slightly anterior to or at dorsal-fin origin. Dorsal profile of head slightly convex; straight to slightly concave along the occipital spine; slightly convex to convex from tip of supraoccipital spine to end of dorsal-fin base; straight to slightly convex from end of dorsal fin up to end of adipose fin; caudal peduncle concave in dorsal and ventral margins; ventral profile slightly convex from tip of snout to end of anal fin.

Mouth terminal. Maxilla only reaching the vertical through anterior margin, and not trespassing anterior third of second infraorbital. Premaxillary teeth in two rows. Inner row with five tetracuspidate (symphyseal) or pentacuspidate teeth with median cusp pronounced, the first two or three teeth from the symphysis with cusps arranged in a pronounced arch when examined from a ventral view; outer row with four to five pentacuspid teeth; edentulous maxilla. Dentary bearing four to five pentacuspidate teeth with central cusp longest followed by three to four distinctly small conical or tricuspidate teeth. First two or three dentary teeth from the symphysis with cusps arranged in a pronounced arch when examined from a dorsal view.

Dorsal-fin rays ii,9. Pectoral-fin rays i,11(4), 12*(68), 13(25). Tip of pectoral fin extends slightly beyond anterior insertion of pelvic fin. Pelvic-fin rays i,7, tip of adpressed pelvic fin not reaching anal fin. Anal-fin rays iv,28(3), 29(14), 30(27), 31*(34), 32(15), 33(3). Caudal fin forked with i,9,8,i.

Scales cycloid. Lateral line with 34(2), 35(10), 36(43), 37*(36), 38(6) perforated scales; scale rows between lateral line and dorsal-fin origin 7*. Scale rows between lateral line and midventral scale series 7*. Circumpeduncular scale rows 13(4), 14(61), 15*(28), 16(3). Scale sheath along anal-fin base 7–15*, in 1–3* series, covering base of anteriormost rays. Small scales covering proximal two-third of caudal-fin lobes.

First gill arch with 11(3), 12(35), 13*(45), 14(2) gill rakers on lower limb and 8*(25), 9(57), 10(3) on upper limb. Total vertebrae 31–32. Supraneurals 4.

Color in alcohol. Overall coloration slightly silvery or yellow tan. Field of few dark chromatophores on upper lip and maxilla. Infraorbital and opercular series silvery due to the presence of guanine pigmentation. Dark chromatophores more densely concentrated along entire dorsal midline. Sparsely spread dark chromatophores dorsal of horizontal skeletogenous septum. Dark line over horizontal skeletogenous septum. Conspicuous silver midlateral stripe extending from posterior margin of opercle to base of median caudal fin-rays. In some individuals, silver stripe is not preserved. Irregularly shaped humeral mark located over fourth to eight lateral line scales and extending vertically over four-five horizontal scale rows above and over one-two horizontal scale rows below lateral line. Paired fins and anal fin hyaline. Round dark spot at the base of the caudal-fin rays formed by few chromatophores. Adipose with very few dark chromatophores ( Fig. 5 ).

Distribution. Moenkhausia sthenosthoma occurs in the Rio Madeira basin ( Fig. 4 ).

Etymology. The species name sthenosthoma is from the Greek sthenos meaning strong, and sthoma meaning mouth, in reference to the strong musculature associated to the dentary, and robust teeth of the premaxilla and dentary, a characteristic feature of the Moenkhausia jamesi species complex.

Figures

FIGURE 4. Partial map of South America indicating the distribuition of Moenkhausia jamesi species complex and M. justae. Red circle = M. jamesi; Blue circle = M. ischyognatha; Orange circle = M. alesis; Light blue circle = M. sthenosthoma; Yellow circle = M. justae.

FIGURE 5. Moenkhausia alesis, MZUSP 117139, holotype, 52.6 mm SL.

FIGURE 6. Moenkhausia sthenosthoma. (a) MCP 48789, holotype, 56.0 mm SL. (b) UFRO 311, 57.21 mm SL. (c) UFRO 13621, 50.31 mm SL.

FIGURE 9. Dentary of Moenkhausia jamesi species complex. (a) M. jamesi, MZUSP 49507, 54.0 mm SL; (b) M. justae, INPA 21489, 47.0 mm SL; (c) M. ischyognatha, LBP 15948, 48.2 mm SL; (d) M. alesis, INPA 48444, 50.4 mm SL; (e) M. sthenosthoma, LBP 19956, 46.0 mm SL; and (f) M. sthenosthoma, LBP 19958, 63.4 mm SL. Scale bars = 1 mm.