Moenkhausia venerei, Petrolli, Marina G., Azevedo-Santos, Valter M. & Benine, Ricardo C., 2016

Petrolli, Marina G., Azevedo-Santos, Valter M. & Benine, Ricardo C., 2016, Moenkhausia venerei (Characiformes: Characidae), a new species from the rio Araguaia, Central Brazil, Zootaxa 4105 (2), pp. 159-170 : 160-164

Moenkhausia venerei , new species

( Fig. 1 , Tab. 1 )

Moenkhausia collettii ( Steindachner 1882) : Venere & Garutti (2011): 105. Moenkhausia sp: Jarduli et al. (2014): 486 –500.

Holotype. MZUSP 119006, 35.8 mm SL, Brazil, Barra do Garças, Mato Grosso, rio Araguaia, Córrego Grande. 15°44” S, 52°5’W; P. C. Venere; 27 Ago 2013.

Paratypes. All from Brazil. LBP 13491, 21 (6 c&s), 15.3–37.3 mm SL, same data as holotype. ZUEC 12277, 5, 23.1–37.0 mm SL, same data as holotype. MZUSP 119007, 5, 21.1–34.3 mm SL, same data as holotype. MCP 49454, 5, 19.1–31.6 mm SL, same data as holotype. INPA 52430, 5, 20.0– 33.2 mm SL, same data as holotype. LBP 4931, 29, 19.7–35.7 mm SL, Mato Grosso, Barra do Garças, rio Araguaia, Córrego Correntes, 15º29’59”S, 52º12’12”W; P.C. Venere, V. Garutti; 22 Mar 2007. LBP 9028, 3, 26.7–28.2 mm SL, Mato Grosso, Barra do Garças, rio Araguaia, Córrego Taquaral; 15º41’S, 52º18”W; C. Oliveira, J.C. O. Santana, P.C Venere, M. Taylor, M. Alexandrou; 21 Jan 2008. LBP 1533, 5, 25.6–32.6 mm SL, Mato Grosso, Barra do Garça, rio das Mortes/Araguaia; Ribeirão Ínsula; 15º40’58”S, 52º13’24.8”W; C. Oliveira et al.; 0 9 Dec 2002. LBP 2425, 17, 18.8–36.1 mm SL, Mato Grosso, Barra do Garça, rio das Mortes/Araguaia; Ribeirão Ínsula; 15º40’58”S, 52º13’24.8”W; C. Oliveira, O.A Shibatta, M.A. Spadella, G.F. França, E.M.R. Martinez; 0 7 Oct 2004. MZUEL 7847, 1 of 2, 21.5 mm SL, Mato Grosso, Barra do Garça, rio Araguaia basin, rio Corrente; 15º29’57” S, 52º42’41” W; L. R. Jarduli, W. G. B. Ruiz, E. Santana; 31 Jul 2008. MZUEL 7850, 5 of 10, 22.5–26.9 mm SL, same data as MZUEL 7847. MZUEL 7845, 5 of 7, 25.7–32.6 mm SL, same data as MZUEL 7847. MZUEL 7846, 2 of 3, 19.7–23.2 mm SL, same data as MZUEL 7847. MZUEL 7852, 1 of 2, 34.0 mm SL, Mato Grosso, Barra do Garças, rio Araguaia basin, rio Corrente, 15º35’45”S, 52º22’36”W; L. R. Jarduli, W. G. B. Ruiz, E. Santana; 30 Jul 2008.

Diagnosis. Moenkhausia venerei differs from all congeners, except M. collettii and M. copei , by the presence of a conspicuous dark line along the base of the anal fin (vs. absence of dark line) and by the presence of a wellmarked longitudinal dark stripe extending from the tip of the snout to the base of caudal fin (vs. absence of dark stripe). The new species is promptly distinguished from M. copei by the higher number of branched anal-fin rays (19–24 vs. 15–17 in M. copei ). Moenkhausia venerei differs from M. collettii by presenting a more conspicuous and wider longitudinal lateral dark stripe, about a scale deep along the flank (vs. stripe narrow, more restricted to the posterior half of the horizontal septum). Out of the limits of the genus, M. venerei shares similarities with Hemigrammus ulrey , H. barrigonae , and H. ataktos . The diagnostic features for the similar species of the genus Hemigrammus are detailed in the Discussion.

Description. Morphometric data summarized in Table 1 . Largest specimen examined 38.8 mm SL. Body compressed and elongate. Greatest body depth at dorsal-fin origin. Dorsal profile of head straight to slightly convex, straight along the supraoccipital spine; slightly convex from tip of supraoccipital spine to dorsal-fin origin; straight and posteroventrally inclined along dorsal-fin base, straight to slightly convex from end of dorsal fin up to end of adipose fin; caudal peduncle slightly concave in dorsal and ventral margins; ventral profile slightly convex from tip of snout to end of anal fin.

Mouth terminal. Distal tip of maxilla at vertical passing through fourth quarter of second infraorbital. Premaxillary teeth in two rows. Inner row with four (9) or five* (88) pentacuspidate teeth ( Fig. 2 ) with median cusp pronounced; outer row with four* (65) or five (33) pentacuspidate teeth; maxilla with one (eight), two* (27), three (52) or four (8) tricuspidate teeth. Dentary bearing four* (89) or five (9) tricuspidate to pentacuspidate teeth with median cusp pronounced followed by nine to ten distinctly small conical or tricuspidate teeth.

Dorsal-fin rays ii,9. Pectoral-fin rays i, 9(5), 10(28), 11*(61), 12(4). Tip of pectoral fin extending slightly beyond anterior insertion of pelvic fin. Pelvic-fin rays i,7, tip of adpressed pelvic fin not reaching anal fin. Anal-fin rays iii, 18(3), 19(3), 20(20), 21*(46), 22(16), 23(7), 24(4), 25(1). Caudal fin forked with i,9,8,i.

Scales cycloid. Scales with radii not diverging; lateral line with 30(9), 31(12), 32(18), 33*(14), 34(29), 35(8), 36(2) perforated scales; Scale rows between lateral line and dorsal-fin origin five (50) or six* (46). Scale rows between lateral line and midventral scale series five* (43) or six (54). Circumpeduncular scale rows 10(2), 11(10), 12(14), 13(17), 14*(17). Small scales covering proximal two-third of caudal-fin lobes.

First gill arch with 10(34), 11*(56), 12(5) gill rakers on lower limb and 5(19), 6*(68), 7(7) 8(1) on upper limb. Total vertebrae 30. Supraneurals 4.

Sexual dimorphism. Mature males present small hooks on the median portion of the last (more developed) unbranched anal-fin ray and on the median portion of the posterior branch of the anterior three branched anal-fin rays. One or two hooks per segment on each side. Hooks are also observed on the median portion of the posterior (medial) branch of the two anterior (lateral) branched pelvic-fin rays of mature males. One hook per segment restricted to the ventral surface of the pelvic fin.

Color in alcohol. Overall coloration yellowish tan or slightly silvery. Field of few dark chromatophores on upper lip and maxilla. Infraorbital series, and gular and opercular regions silvery. Mid-dorsal line darker from tip of snout to base of caudal fin. A field of dark chromatophores at posterior half of the exposed portion of the flank scales above horizontal septum. A one scale deep longitudinal dark stripe along flank extending from the tip of the snout to the base of caudal fin, its anterior half dorsally delimited by the horizontal septum. Adipose fin with dark chromatophores; dorsal, pectoral, pelvic and anal fins hyaline; and caudal lobules hyaline. Humeral mark resembles an inverted triangle, three scales long (at its base) and three scales deep, extending downward toward the ventral limit of the longitudinal stripe and reaching the lateral line scale series. Myomere limit of posterior hypaxial musculature enhanced by dark chromatophores. A conspicuous dark line along the anal-fin base, somewhat wider at its anterior portion.

Habitat and ecological notes. The type locality has a well-preserved riparian vegetation extending from three to 30 meters wide ( Fig. 3 a). The vegetation is mainly formed by native vegetation, secondary trees, shrubs and grass. The margin structure is taut, covered by grass and shrubs with some areas with erosion ( Fig. 3 b). The overall environment varies from turbid and rapid waters to ponds and lentic waters over a substrate mostly composed by rocks, gravel and sand ( Fig. 3 c). The sample site is mostly shaded and with about 0.4 m depth and 3.5 m width. Large amounts of algae, mosses and macrophytes are present in the substrate, which also presents gravel, roots, sand and litter ( Fig. 3 d) (P. C. Venere and P. C. Lima, pers. comm.).

Observation of gonads of eight specimens (four from LBP 2425, two from LBP 1533, and two from LBP 13491) indicates that the reproductive season of M. venerei possibly starts in October, with high maturation of ovocytes in December. Two of the specimens from LBP 2425 were females (22.8 and 36.0 mm SL) with ovaries full of ovocytes at early stages of maturation; a third specimen (30.2 mm SL) was a mature male with developed testicles and with the small hooks on anal- and pelvic-fin rays; and the fourth specimen (23.0 mm SL) was a male, with developing testicles and hooks on anal- and pelvic-fin rays. From the two specimens collected in December (LBP 1533), one of them (27.7 mm SL) was a female, with ovaries full of ovocytes at final stages of maturation, and the other one (25.6 mm SL) appeared to be a mature male with developed testicles and anal- and pelvic-fin hooks. Two specimens collected in August (LBP 13491) presented undeveloped gonads not suitable for sex determination.

Distribution. Moenkhausia venerei sp. n. is known from streams around Barra do Garças, MT, Brazil, rio Araguaia basin, and from Araguaçu, rio Araguaia basin ( Fig. 4 ).

Etymology. The specific epithet venerei is in honor of Dr. Paulo César Venere, collector of this new species and for his contributions to our knowledge of the Rio Araguaia ichthyofauna.

Figures

FIGURE 2. Moenkhausia venerei, MZUSP 119007, paratype, 32.7 mm SL: (a) right premaxilla (medial view); (b) right dentary (medial view); (c) right maxilla (medial view).

FIGURE 3. Córrego Grande, type locality of Moenkhausia venerei sp n., rio Araguaia, Barra do Garças, Amazon basin, central Brazil.

FIGURE 4. Partial map of South America indicating the distribution of Moenkhausia venerei.

FIGURE 1. a) Moenkhausia venerei, MZUSP 119006, holotype, 35.8 mm SL. b) X-ray image of the holotype of M. venerei.

Tables

TABLE 1. Morphometic data for Moenkhausia venerei new species and Moenkhausia cf. venerei.

	Moenkhausia venerei (n= 96)		Moenkhausia cf. venerei (n=44)
	Holotype Range	Mean	Range Mean
Standard Length (mm)	35.8 15.3–38.8		21.1–30.0
Percentage of Standard Length
Greatest depth	32.7 27.1–36.8	32.1	30.6–38.6 35.7
Snout to dorsal-fin origin	50.5 46.5–54.9	50.6	49.8–53.5 51.5
Snout to pectoral-fin origin	27.3 22.7–31.7	28.6	27.3–31.6 29.5
Snout to pelvic-fin origin	46.4 43.0–53.4	46.9	43.9–51.2 48.5
Snout to anal-fin origin	64.0 59.1–66.6	62.2	58.2–66.0 63.1
Caudal-peduncle depth	9.3 6.7–10.3	8.5	8.0–10.5 9.3
Caudal-peduncle length	6.7 6.4–13.1	9.1	8.0–11.4 9.4
Pectoral-fin length	22.0 17.0–24.4	21.3	20.7–24.1 22.3
Pelvic-fin length	17.9 14.7–20.8	17.9	15.8–20.0 18.1
Dorsal-fin length	32.6 25.9–36.0	31.6	31.3–35.5 33.7
Dorsal-fin base	14.9 12.2–16.7	15.0	13.6–16.1 15.5
Anal-fin length	22.5 18.7–28.5	24.2	18.5–26.3 24.3
Anal-fin base	30.7 26.1–33.7	30.8	29.1–32.5 31.5
Eye to dorsal-fin origin	35.4 27.6–50.3	34.3	32.7–38.6 35.4
Dorsal-fin origin to caudal-fin origin	51.5 48.9–56.6	52.7	48.0–56.0 53.0
Head length	24.7 21.8–29.3	26.4	25.8–28.7 27.2
Head depth	27.7 24.0–33.4	27.9	20.9–34.8 31.7
Percentage of Head length
Snout length	27.9 21.4–32.0	27.0	23.4–27.8 26.4
Maxillary length	48.6 43.8–54.0	49.1	41.7–48.4 46.0
Horizontal orbital diameter	43.2 41.1–53.3	47.5	41.7–48.1 45.9
Least interorbital width	35.0 31.6–40.8	36.7	34.5–39.8 38.9