Tetragonopterus carvalhoi, Melo & Benine & Mariguela & Oliveira, 2011

Melo, Bruno F., Benine, Ricardo C., Mariguela, Tatiane C. & Oliveira, Claudio, 2011, A new species of Tetragonopterus Cuvier, 1816 (Characiformes: Characidae: Tetragonopterinae) from the rio Jari, Amapá, northern Brazil, Neotropical Ichthyology 9 (1), pp. 49-56 : 50-52

Tetragonopterus carvalhoi , new species

Fig. 1

Holotype. MZUSP 102268 , 36.5 mm SL, undetermined sex, Brazil, Amapá, Laranjal do Jari, Igarapé Iratapuru, rio Jari , Amazon basin, 00º33’30’’S 52º34’45’’W, 14 Oct 2007, M. R. Carvalho, A. Akama, C. Oliveira & F. Marques.

Paratypes. LBP 5306, 7, 33.5-45.8 mm SL, Brazil, Amapá, Laranjal do Jari, Igarapé Iratapuru, rio Jari , Amazon basin, 00º34’03’’S 52º34’41’’W, 11 Oct 2007, M. R. Carvalho, A. Akama, C. Oliveira & F. Marques (Genbank numbers HM 070389 to HM 070393 ). LBP 5376, 34 (4 c&s), 29.7-45.8 mm SL, Brazil, Amapá, Laranjal do Jari , Igarapé Iratapuru, rio Jari , Amazon basin, 00º33’51’’S 52º34’45’’W, 10 Oct 2007, M. R. Carvalho, A. Akama, C. Oliveira & F. Marques. MZUSP 106813 , 15 , 34.2-41.9 mm SL, same data as the holotype .

Diagnosis. Tetragonopterus carvalhoi can be diagnosed from its congeners by the lozenge-shaped spot on the caudal peduncle, extending from the vertical through the beginning of adpressed adipose fin to the median caudal-fin rays vs. rounded to square-shaped spot confined to the posterior half of caudal peduncle ( Fig. 2 ). Tetragonopterus carvalhoi further differs from T. argenteus by the number of predorsal scales (6-10 vs. 12-16, respectively) and from T. rarus by the absence of dark longitudinal stripes on the lateral surface of the body (vs. present).

Description. Morphometric data given in Table 1 . Largest specimen 45.8 mm SL. Compressed body, proportionally deep. Greatest depth at vertical through origin of dorsal fin. Dorsal profile of head straight to slightly concave above orbit. Each nostril closer to anterior margin of orbit than to each other. Supraoccipital spine elongate, but tip of spine not extending beyond vertical through posterior of opercle. Dorsal profile of body convex from tip of supraoccipital spine to posterior terminus of base of dorsal fin; straight to slightly convex from that point to end of base of adipose fin; caudal peduncle profile slightly concave both dorsally and ventrally. Ventral profile of body convex from tip of lower jaw to origin of caudal peduncle. Prepelvic region of body transversely flattened, with flattening more pronounced proximate to pelvic-fin insertion. Scales along lateral margins of flattened region immediately anterior to insertion of pelvic fin with distinct angle.

Mouth terminal. Premaxillary teeth in two rows; outer row with 4 (8), 5* (45), 6 (3), or 7 (1) tricuspid teeth; inner row with 4 (2), 5* (51) or 6 (4) relatively compressed, pentacuspid teeth, except from the central pair which presents tetracuspidated. Maxilla with 2 (1), 3* (29), 4 (22), 5 (4), or 7(1) tri- to pentacuspid teeth. Dentary with 4* (55) or 5 (2) pentacuspid large teeth gradually decreasing in size. Remaining dentary teeth considerably smaller, conical to tricuspid.

Dorsal-fin rays ii,9* (57). Anal-fin rays iv,29 (3), 30 (9), 31 (18), 32* (23), 33 (2), or 34 (2); last unbranched and first branched anal-fin rays more elongated; posterior remaining anal-fin rays decreasing gradually in length. Pectoral-fin rays i,12 (8), 13* (48), or 15 (1); tip of pectoral fin extending beyond vertical through insertion of pelvic fin. All specimens with i,7* rays in pelvic fin.

Scales cycloids. Lateral line with 29 (2), 30* (23), 31 (25), or 32 (7) pored scales with its anterior portion distinctly curved. Median scales between tip of supraoccipital spine and base of first ray of dorsal fin 6 (2), 7 (10), 8 (37), 9* (7), or 10 (1). Scale rows between dorsal-fin origin and lateral line 7* (55) or 8 (2). Scale rows between lateral line and pelvic-fin insertion 3.5 (26) or 4* (31). Single or double row of small scales covering base of anal fin. Scales around caudal peduncle 11 (2), 12 (1), 13* (34) or 14 (20). First gill arch with 9,1,12 (12); 9,1,13* (36); 9,1,14 (3); 10,1,13 (4); or 10,1,14 (2) gill rakers. Vertebrae 28 (4).

Coloration in alcohol. Overall ground coloration yellowish tan. Dorsal portion of head, nape, and portion of middorsal region of body anterior and posterior to base of dorsal fin darker. A scattered field of dark chromatophores below orbit mainly on second and third infraorbital bones. Two conspicuous vertical dark marks on humeral region. Anterior humeral mark more evident than posterior humeral mark. Anterior humeral mark, located over second to fourth lateral line scales and vertically extending over 4 horizontal scale rows above lateral line, lateral line, and 2 horizontal scale rows below lateral line. Posterior humeral mark located over fifth and sixth lateral line scales and vertically extending over 4 horizontal scale rows above lateral line and lateral line; dorsal half of both humeral marks wider and more densely pigmented. Limits of posterior epaxial and hipoaxial miomeres enhanced by dark pigments, more evident at area of horizontal septum from just posterior second humeral mark to origin of caudal peduncle, resulting in a chevron-like pattern along lateral of body. A sparse field of dark chromatophores surrounding horizontal septum and resulting in an unconspicuous lateral band. Distal margin of unpaired rayed-fins scattered with small dark chromatophores throughout extension. Pectoral and pelvic fins with scattered dark chromatophores, more concentrated on lateral unbranched rays. Adipose fin with very few dark chromatophores. Caudal peduncle with a large, lozenge-shaped dark spot extending from vertical through end of adpressed adipose fin to median caudal-fin rays.

Distribution. Tetragonopterus carvalhoi is known from the rio Jari, upstream from the Cachoeira de Santo Antônio, rio Amazonas drainage, Amapá, northern Brazil ( Fig. 3 ).

Etymology. The specific epithet is in honor of Marcelo Rodrigues de Carvalho (USP), the leader of the expedition to rio Jari which resulted in the collection of this new species and in recognition of his contributions to our knowledge of the Neotropical ichthyology.

Molecular analysis. DNA sequences were obtained from tissues of following samples: Tetragonopterus argenteus LBP 3758 (5), LBP 3058 (2), LBP 3059 (1), LBP 5535 (1); Tetragonopterus carvalhoi LBP 5306 (5 paratypes); Tetragonopterus chalceus LBP 264 (4), and Tetragonopterus rarus LBP 5375 (1). The sequences from 19 specimens resulted in a matrix with 779 base pairs (bp) from which 617 positions were conserved, and 161 were variable. 118 positions were parsimony informative. The nucleotide frequencies were 30.9% thymine/uracil, 24.7% cytosine, 24.6% adenine and 19.8% guanine. Graphical analyses does not show any saturation in transitions or transversions. The overall transition/transversion rate was 3.9. Genetic distances ( Kimura, 1980) range from zero among specimens of Tetragonopterus chalceus from São Francisco basin to 0.125 ± 0.019 between T. carvalhoi and T. rarus , both from rio Jari ( Table 2 ). Figure 4 presents the neighbor-joining majorityrule consensus tree with bootstrap values for 1,000 pseudoreplicates which has the same topology observed in MP analyses. Three monophyletic groups ( T. carvalhoi , T. chalceus , and T. argenteus ) presented well-supported by values equal or higher than 97% in both methods of phylogenetic analysis.

Figures

Fig. 1. Tetragonopterus carvalhoi, holotype, MZUSP 102268, undeterminated sex, 36.5 mm SL: Brazil, Amapá State, Laranjal do Jari, Igarapé Iratapuru, rio Jari, Amazon basin.

Fig. 2. Caudal peduncle evidencing dark spots of (a) Tetragonopterus carvalhoi, paratype, MZUSP 102268, 39.9 mm SL (rio Jari); (b) T. argenteus, LBP 3758, 60.8 mm SL (rio Negro); (c) T. chalceus, MZUSP 35008, 67.9 mm SL (rio Araguari); (d) T. rarus, LBP 5375, 38.0 mm SL (rio Jari).

Fig. 3. Lower rio Amazonas indicating the position of the type locality of Tetragonopterus carvalhoi in rio Jari.

Fig. 4. Unrooted neighbor-joining majority-rule consensus tree for the mitochondrial gene Cytochrome Oxidase C subunit I evidencing a high genetic distance (Kimura-2-parameter) among species. First number on branches represents indexes of bootstrap by 1,000 pseudoreplicates for neighbor-joining method and second number represents indexes of bootstrap by 1,000 pseudoreplicates for maximum-parsimony. Values <50% are not shown.