Moenkhausia forestii, Benine & Mariguela & Oliveira, 2009

Benine, Ricardo C., Mariguela, Tatiane C. & Oliveira, Claudio, 2009, New species of Moenkhausia Eigenmann, 1903 (Characiformes: Characidae) with comments on the Moenkhausia oligolepis species complex, Neotropical Ichthyology 7 (2), pp. 161-168 : 162-165

Moenkhausia forestii , new species

Figs. 1-2

Holotype. MZUSP 97827 , 34.0 mm SL, undetermined sex, Brazil, Mato Grosso State, Cáceres, rio Sepotuba , rio Paraguay basin, 15º46’07”S 57º38’54”W, 3-4 Mar 2002, H. A. Britski, O. Fröehlich, A. Catella & F. Marques.

Paratypes. MZUSP 90270 , 14 , 24.0- 36.4 mm SL, (2 c&s, 25.6- 33.1 mm SL), same data as the holotype . MZUSP 19111 , 10 , 30.7 - 35.0 mm SL, Brazil, Mato Grosso State, Descalvados , rio Paraguay, 16º46’S 57º44’W, 9 Aug 1980 , R. M. C. Castro & H. Ortega . LBP 3793 , 10 , 28.3-33.4 mm SL, Brazil, Mato Grosso do Sul State, Aquidauana, rio Negro , rio Paraguay basin, 19º34’02.3”S 56º14’09.1”W, 2 Aug 2006, C. Oliveira & L. H. G. Pereira .

Non-types. LBP 5074 , 10 , 25.7-32.1 mm SL, Brazil, Mato Grosso State, Cáceres, Baía do Caiçara , 16º03’11.3”S 57º48’32.0”W . LBP 3739 , 10 , 22.4 - 32.5 mm SL, Brazil, Mato Grosso do Sul State, Aquidauana, rio Negro , rio Paraguay basin, 19º34’54.6”S 56º15’16.5”W . LBP 4655 , 65 , 21.9-32.9 mm SL, Brazil, Mato Grosso do Sul State, Batayporã , rio Baía, rio Paraná basin, 22º43’46.2”S 53º19’04.2”W . LBP 2630 , 18 , 23.0- 37.9 mm SL, Brazil, Paraná State, Porto Rico, rio Paraná , 22º43’03.2”S 53º17’27.6”W . LBP 5225 , 10 , 25.0- 32.8 mm SL, Brazil, Paraná State, Porto Rico, rio Paraná , 22º47’29”S 53º20’58”W .

Diagnosis. Moenkhausia forestii is readly distinguished from all congeners, except M. oligolepis , M. sanctaefilomenae , M. pyrophthalma , and M. diktyota , by the presence of a reticulated body pigmentation pattern, and a conspicuous dark blotch on the caudal peduncle extending to the base of caudal-fin rays preceded by a lighter area (vs. absence of a reticulated body pigmentation pattern, and a conspicuous dark blotch on the caudal peduncle extending to the base of caudal-fin rays preceded by a lighter area). Moenkhausia forestii is readily distinguished from M. oligolepis in the degree of poring of the lateral line (incomplete, vs. complete, respectively), and the total number of lateral line scales (23- 26, vs. 28-31 scales, respectively). Moenkhausia forestii can be distinguished from M. sanctaefilomenae in the number of transverse series of scales above the lateral line (5, vs. 4 scales, respectively), by the number of transverse series of scales below the lateral line (4, vs. 3 scales, respectively). Moenkhausia forestii is distinguished from M. pyrophthalma by its higher body depth (38.3-45.2% in SL vs. 31.2-33.0% in SL, respectively), by its shorter lateral line (23-26 vs. 27-31 scales, respectively), and by the form of the humeral spot (an inconspicuous dark inverse triangular humeral blotch located on second and third lateral line scales vs. a conspicuous black inverse drop-shaped humeral blotch located on second to fourth lateral line scales, respectively). Moenkhausia forestii is distinguished from M. diktyota by the color pattern of the caudal peduncle (caudal peduncle with very widely scattered dark pigment resulting in conspicuous lighter area preceding a conspicuous caudal-fin blotch which extends between the dorsal to ventral margins of the proximal one-third of caudalfin base vs. caudal peduncle with elongate black stripe extending from the vertical through the last anal-fin ray to the tips of middle caudal fin rays, respectively).

Description. Morphometric data summarized in Table 1. Overall size small (maximum of 36.4 mm SL). Greatest body depth at origin of dorsal fin. Dorsal profile of head straight or slightly convex. Dorsal profile of body sligthly convex from posterior tip of supraocciptal to end of dorsal-fin base; slightly convex from rear of dorsal-fin base to end of adipose-fin base. Caudal peduncle profile slightly concave both dorsally and ventrally. Ventral profile of body convex from tip of lower jaw to caudal peduncle origin. Prepelvic region transversely flattened, flattening more pronounced proximate to pelvic-fin insertion. Postpelvic median keel extending from pelvic-fin insertion to anal-fin origin.

Mouth terminal, with lower jaw as long as, to somewhat longer than, upper jaw. Premaxillary teeth in two rows; outer row teeth 3-5* (mode = 5, n = 35), with 3-5 cusps, central cusp longer than other cusps; inner row teeth 5, with 4-5 cusps and rarely with lateral-most tooth with 3 cusps. Maxillary teeth 1-2* (mode = 2, n = 35), each with 5 cusps. Dentary with 4 larger teeth anteriorly, each with 4-5 cusps with central cusp longest (n =35). Larger anterior teeth followed by 5-7 small teeth with 1-3 cusps in two c&s paratypes ( Fig. 2 ).

Dorsal-fin rays ii,9. Dorsal-fin origin at middle body length, slightly posterior to vertical through pelvic-fin origin. Posterior margin of dorsal fin slightly concave. Anal-fin rays iv,17-23, iv,22* (mode = iv,22, n = 35). Distal margin of anal fin straight to somewhat concave with 4 th unbranched and anterior 1 st- 3 rd branched fin ray longer. Remaining anal-fin rays decreasing gradually in length rearward. Pectoral-fin rays i,11-12* (mode = i,12, n = 35). Pectoral fin pointed, 1 st- 2 nd branched rays longer, lateral and medial margins straight, posterior margin oblique and straight. Tip of adpressed pectoral fin extends posterior of mid-length of adpressed pelvic fin. Pelvic-fin rays i,7*. Pelvic fin pointed, lateral and medial margins straight, posterior margin oblique and straight.Tip of pelvic fin reaches anal-fin origin. Adipose fin origin at vertical through insertion point of antepenultimate branched anal fin. Principal caudal-fin rays i,9,8,i. Caudal-fin lobes equal.

Scales cycloids. Lateral line with 7-11 (10*; mode = 9, n = 34) pored scales and 23-26 (25*; mode = 25, n = 34) total scales. Lateral line slightly ventrally curved anteriorly; with 5 (n = 35) series of scales above and 4 (n = 35) series of scales below. Scales around caudal peduncle 7-9* (mode = 9, n = 35). Single row of scales overlaying basal portion of anterior rays of anal fin. Sheet of scales covering proximal one-third of upper caudal-fin lobe and proximal one-half of lower caudalfin lobe.

First gill arch with 6-7* (mode = 7, n = 35) gill-rakers on upper limb and 10-11* (mode = 11, n = 28) gill-rakers on lower limb. Precaudal vertebrae 13, caudal vertebrae 17 (n = 2). Supraneurals 4 (n = 2).

Color in alcohol. Overall ground coloration dark silver or yellowish tan (depending on degree of retention of guanine). Dark chromatophores concentrated on distal margin of scales resulting in conspicuous reticulated pattern. Mid-dorsal region darker than flanks. Humeral region with dark inverse triangle-shaped blotch located on second to third lateral line scales, extending 3-4 scales vertically, including lateral line. Few dark chromatophores scattered on infraorbitals and opercle. Dark thin stripe extending along horizontal septum on posterior half of body. Caudal fin with conspicuous dark blotch extending from its anterior portion onto proximal onethird of caudal-fin rays. Caudal peduncle with very widely scattered dark pigment resulting in conspicuous lighter area preceding caudal-fin blotch. Dorsal fin with scattered dark pigmentation, more concentrated on anterior half. Anal fin with scattered dark pigmentation. Paired fins hyaline with scattered dark pigmentation, more so on unbranched rays.

Sexual dimorphism. One paratype (30.9 mm SL, MZUSP 90270 ) has small hooks on the segments of each anal-fin ray (up to four hooks per segment in each side of the anal fin). Additional non-type material from the upper rio Paraná system ( LBP 5225 ) collected during the reproductive season included males with the same pattern of hooks. No further dimorphic characters were observed .

Distribution. Moenkhausia forestii is known from tributaries from rio Paraguay drainage (Mato Grosso and Mato Grosso do Sul States), from rio Baía (upper rio Paraná system at Batayporã, Mato Grosso do Sul State) and from rio Paraná (at Porto Rico, Paraná State) ( Fig. 3 ).

Etymology. The specific epithet, forestii , is in honour of Fausto Foresti for his contributions to our knowledge of fish genetics.

Molecular Analyses. DNA sequences were obtained from: Moenkhausia forestii LBP 3739, LBP 4655 and LBP 5074; Moenkhausia oligolepis LBP 4098; LBP 1498 and LBP 5073; Moenkhausia sanctaefilomenae LBP 4695.

The sequences obtained in this study have been deposited in GenBank ( Table 2). Genetic distances ( Kimura, 1980) range from zero among specimens of Moenkhausia forestii from Paraná basin to 0.200 ± 0.021 between M. oligolepis from the rio Araguaia Basin and M. sanctaefilomenae from the upper rio Paraná system ( Table 2). The combined sequence data of the 35 specimens resulted in a matrix with 611 base pairs (bp), from which 419 were conserved sites and 181 were phylogenetically informative. The MP consensus tree obtained from the analysis of 1000 bootstrap replicates is presented in Fig. 4 .

The MP analyses showed that there are six monophyletic groups supported by values of equal or higher than 99% ( Fig. 4 ). Three monophyletic groups corresponding to the species Moenkhausia sanctaefilomenae , M. oligolepis and M. forestii and three monophyletic groups correspond to the different samples of M. oligolepis . The relationship between M. oligolepis from the Amazon and Paraguay river basins was weakly supported but they are apparently different from the sample from the rio Araguaia basin.

Figures

Fig. 1. Moenkhausia forestii, holotype, MZUSP 97827, undetermined sex, 34.0 mm SL, Cáceres, rio Sepotuba, Mato Grosso State, Brazil.

Fig. 2. Moenkhausia forestii, new species, paratype, MZUSP 90270, 33.1 mm SL, premaxillary, maxillary and dentary; right side, lateral view (maxillary and dentary) or frontal view (premaxillary).Scale bar = 1 mm.

Fig. 3. Map of the rio La Plata basin showing the localities of collection of Moenkhausia forestii, new species. Star represents the type locality.

Fig. 4. Maximum Parsimony consensus tree for the mitochondrial gene Cytochrome Oxidase I. Numbers represent values of 1000 bootstrap replicates.