Moenkhausia alesis, 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 : 407-408

Moenkhausia alesis , new species

( Figs. 5 , 9 d, Table 1 )

Holotype. MZUSP 117139, 52.6 mm SL, Tocantins, Conceição de Tocantins; rio Palmas at TO 0 50, near to Chuva de Manga locality, 12°25’7”S, 47°11’52”W, J.L. Birindelli; F.C. Dagosta; M.V. Loeb; C. Santos; 0 1 Dec 2012.

Paratypes. MZUSP 113845, 2, 45.1–55.6 mm SL, same data as holotype. INPA 48444, 6 (1 c&s), 44.7–55.1 mm SL, Caseara, Parque Estadual do Cantão, E.G. Ferreira, J. A. Zuanon & G. M. Santos, May 2000. MZUSP 52354, 10 of 20, 53.9–57.7 mm SL, Goiás; Rio Araguaia, at beach between Bandeirantes and Luis Alves; 13°40’00”S, 50°48’00”W, Coleção Rio Araguaia, Jul/ Aug 1997. LBP 18905, 1, 58.4 mm SL, Goiás, Aragarças, beach of rio Araguaia; 15°53'30.09"S, 52°14'59.70" W, P.C. Vênere, no date. MZUSP 52347, 12, 52.0– 57.4 mm SL, Mato Grosso; Rio Araguaia, Fio Velasco, 12°52’58”S, 50°30’07”W, R. S.A. Matias, Jul 1997.

Diagnosis. Moenkhausia alesis is distinguished from M. jamesi , M. ischyognatha , and M. sthenosthoma by the number of scale rows between lateral line and dorsal-fin origin (eight to nine vs seven in the last three). Differs from M. ischyognatha by its greater body depth (43.5–54.6% in SL vs 37.0–43.0% in SL in M. ischyognatha ), by its greater head depth (35.9–43.2% in SL vs 29.3–32.6% in SL in M. ischyognatha ), and by its lower caudal peduncle length (3.8–7.5% in SL vs 8.3–11.2% in SL in M. ischyognatha ). Moenkhausia alesis is additionaly distinguished from M. jamesi by the number of scale rows between lateral line and midventral scale series (seven to eight vs six in M. jamesi ) and by the number of principal dentary teeth (four vs five in M. jamesi ) ( Fig. 9 a, d). It is distinguished from M. justae by the number of teeth in the maxilla (edentulous vs one tooth with five cusps in M. justae ), and by the number of cusps on the fourth dentary tooth (three to five vs six in M. justae ) ( Figs. 9 b, d).

Description. Morphometric data summarized in Table 1 . Largest specimen examined 57.7 mm SL. Body compressed and deep. Greatest body depth slightly anterior to 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 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 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(2), 12*(23), 13(7). 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(5), 29*(11), 30(8), 31(6), 32(2) rays; caudal fin forked with i,9,8,i.

Scales cycloid. Lateral line with 36(11), 37*(13), 38(6), 39(1) perforated scales; Scale rows between lateral line and dorsal-fin origin 8*(30), 9(2). Scale rows between lateral line and midventral scale series 7*(23) to 8*(9). Circumpeduncular scale rows 13(1), 14*(22), 15(2), 16(2), 17(1), 18(4). 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 13(9), 14(9)*,15(1) gill rakers on lower limb and 9(5), 10(11)*, 11(3) on upper limb. Total vertebrae 32. Supraneurals 4.

Color in alcohol. Overall coloration slightly silvery or pale yellow. 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. Irregularly shaped, humeral mark located over fourth to seventh lateral-line scales and extending vertically over four-five horizontal scale rows above and up to one horizontal scale row 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 alesis occurs in the upper and middle portions of Rio Araguaia and Rio Tocantins ( Fig. 4 ).

Etymology. The species name alesis is from the Greek meaning grinder, in reference to the robust teeth of the premaxilla and dentary, a diagnostic 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 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.