Tetragonopterus manaos, Urbanski & Melo & Silva & Benine, 2018

Urbanski, Bruna Q., Melo, Bruno F., Silva, Gabriel S. C. & Benine, Ricardo C., 2018, A new species of Tetragonopterus (Characiformes: Characidae) from Central Amazon lowlands, Brazil, Neotropical Ichthyology 16 (2), pp. 1-7 : 2-5

Tetragonopterus manaos , new species

u r n:l s i d:z o o b a n k.o rg:a c t: 6 4 2 0E C4 7-E4B 5-4 7 7 4-9 A3 2 - 68E104E1BF02

Figs. 1-3 , Tab. 1

Holotype. MZUSP 117250 , 64.1 mm SL, radiographed, Brazil, Amazonas, Manaus, Anavilhanas National Park, igapó of rio Negro , approximately 02°42’S 60°45’W, Mar-Apr 1980, M. Goulding.

Paratypes. All from Brazil. INPA 25533 , 1 , 80.4 mm SL, Amazonas, Presidente Figueiredo, Cachoeira Morena, rio Uatumã , 02°07’24.0”S 59°19’49.0”W, 24 Apr 2005, E. G. Ferreira & S. Amadio. INPA 44352 , 1 , 54.6 mm SL, Amazonas, Iranduba, Sítio Santa Marta, rio Negro , 03°06’23.0”S 60°19’07.0”W, 31 May 2014, D. A. Bastos. INPA 18708 , 2 , 60.2-63.6 mm SL, Amazonas, Tefé, Toco Preto, rio Tefé , 03°47.31’S 64°59.91’W, 21 Oct 1999, W. G. R. Crampton. LBP 24888, 2, 62.8-69.1 mm SL, Amazonas, Manaus, Anavilhanas, igapó, rio Negro , 02°42’0.0”S 60°45’0.0”W, Aug 1980, M. Goulding. MZUSP 56523 , 1 , 55.3 mm SL, Pará, Oriximiná, rio Trombetas , 01°49’42.0”S 55°48’41.0”W, 24 Oct 1994, O. T. Oyakawa et al. MZUSP 121680 , 12 , 1 c&s, 56.1-78.2 mm SL, Amazonas, Manaus, Anavilhanas National Park, igapó, rio Negro , approximately 02°42’S 60°45’W, Aug 1980, M. Goulding. MZUSP 123507 , 7 , radiographed, 62.8-81.6 mm SL, same data as holotype .

Diagnosis. Tetragonopterus manaos is distinguished from all congeners, except Tetragonopterus ommatus Silva, Melo, Oliveira, Benine (2016) by having a vertically-oriented patch of dark pigmentation limited to the posterior portion of the caudal peduncle (vs. mark centered on the caudal peduncle). Tetragonopterus manaos differs from T. ommatus by the number of maxillary teeth 4-6 (vs. 7-8), by having thinner and sharper dentary teeth (vs. more robust dentary teeth), and by the greatest body depth 47.5-54.9% of SL (vs. 42.1- 44.7% of SL). Tetragonopterus manaos further differs from all congeners, except T. anostomus Silva, Benine (2011) , T. denticulatus Silva, Melo, Oliveira, Benine (2013) , T. juruena Silva, Melo, Oliveira, Benine (2016) , T. kuluene Silva, Melo, Oliveira, Benine (2016) , and T. rarus ( Zarske, Géry, Isbrücker, 2004) , by the presence of five principal, sharper teeth on dentary (vs. three to four robust teeth). Moreover, the new species differs from T. anostomus by having a terminal mouth (vs. subsuperior mouth) (sensu Silva et al., 2016). In addition, T. manaos differs from T. anostomus and T. araguaiensis Silva, Melo, Oliveira, Benine (2013) by the number of gill rakers on the lower (13-15) and upper (8-10) limbs of the first gill arch (vs. 17-20 and 10-13, respectively); it differs from T. kuluene by having two humeral dark marks (vs. one humeral dark mark); it differs from T. argenteus Cuvier (1816) by having 7-9 predorsal scales (vs. 11-18); it differs from T. chalceus by bearing five thinner and sharper dentary teeth (vs. four robust teeth); it differs from T. carvalhoi Melo, Benine, Mariguela, Oliveira (2011) by the presence of a vertically-oriented dark mark on the caudal peduncle (vs. a lozenge-shaped dark mark); it differs from T. rarus and T. georgiae by the presence of 3.5 scale rows between lateral line and pelvic-fin origin (vs. 4.5-5); it differs from T. juruena by having 13-15 rakers on the lower limb of the first gill arch (vs. 10-12); it differs from T. rarus by the absence of dark longitudinal stripes on the lateral surface of the body (vs. presence).

Description. Morphometric data summarized in Tab. 1 . Compressed body, proportionally deep. Greatest depth at dorsal-fin origin. Dorsal profile slightly convex from snout tip to vertical through middle of orbit and slightly concave from this point to end of occipital process. Convex from end of occipital process to dorsal-fin origin and slightly convex along dorsal-fin base. Slightly convex from rear of dorsal-fin base to rear of adipose fin. Caudal peduncle with slightly concave dorsal and ventral profiles. Ventral profile convex from lower lip to pelvicfin origin; straight from this point to anal-fin origin and straight along anal-fin base.

Snout shorter than orbital diameter. Mouth terminal with premaxillary teeth in two rows. Outer row with 5(2), 6(13), 7*(12) or 8(1) teeth with three cusps. Inner row with 4(1), 5*(24) or 6(3) teeth with three or five cusps. Maxilla with 4(3), 5*(16) or 6(9) teeth with three cusps. Dentary bearing 5(28) anterior most principal teeth with five cusps, followed by a series of small tricuspidate or conic teeth ( Fig. 3 ).

Dorsal-fin rays ii,9(28). First unbranched dorsal-fin ray shorter than second one. Dorsal-fin origin at middle of the body in SL. Anal-fin rays ii,27(1); iii,25(1); iii,27(5); iii,28(2); iii,29(2); iv,26*(3); iv,27(4); iv,28(1); v,26(2); v,27(5); v,28(1) or v,29(1). Posterior unbranched analfin rays and anterior branched rays slightly longer than following rays. Anal-fin origin at vertical through two scales posterior to last branched dorsal-fin ray. Pectoralfin rays i,12(4); i,13*(23) or i,15(1). Tip of adpressed pectoral fin reaching two scales posterior to pelvic-fin origin. Pelvic-fin rays i,7*(23); ii,6(1) or ii,7(4). Pelvic-fin origin located at vertical through dorsal-fin origin. Distal margin of pelvic fin angled, anterior rays longest. Tip of adpressed pelvic fin not reaching the anal-fin origin.

Scales large and cycloid. Lateral line complete 28(3), 29(10), 30(6), 31*(6) or 32(3) pored scales; anterior portion distinctly bent downward. Predorsal scales 7*(2), 8(21) or 9(5). Scale rows between dorsal-fin origin and lateral line 6(28). Scale rows between lateral line and pelvic-fin origin 3.5(28). Scale rows around caudal peduncle 10(4), 11(4), 12*(11) or 13(6). Anal-fin base covered by up to four rows of small scales. Few scales covering the base of caudal-fin lobes.

First gill arch with 13(6), 14(12) or 15*(8) rakers on lower limb and 8*(9), 9(12) or 10(5) rakers on upper limb. Total vertebrae 30(1) or 31*(7). Supraneurals 2(1) or 3*(7) ( Fig. 1b ).

Color in alcohol. Overall ground coloration yellowish tan. Dorsolateral portions of head and body darkly pigmented. Dorsolateral portion of body with few chromatophores along distal margins of scales. Ventrolateral portion of body unpigmented. Two pale brown humeral spots vertically elongate and separated by one and half scales from each other. Each humeral mark covering two to three scales vertically and two or three scales horizontally. Anterior humeral mark more evident than the posterior humeral mark; anterior mark separated by one and half or two scales from posteriormost margin of opercular bone. Caudal peduncle with a ventrally-oriented patch of dark pigmentation limited to posterior portion of caudal peduncle; dark mark often quite faint. Midlateral silver stripe broad, extending from supracleithrum to caudal peduncle. Distal portions of anal, dorsal, adipose and caudal, and more lateral rays of pectoral and pelvic fins densely scattered by dark chromatophores. Unbranched rays of all fins outlined by dark chromatophores ( Figs. 1a , 2 ).

Sexual dimorphism. Secondary sexual characters were not found in any analyzed specimen of Tetragonopterus manaos .

Geographic distribution. Tetragonopterus manaos is known from the Central Amazon in the lower sections of Tefé, Negro, Uatumã and Trombetas rivers, near the mainstream of rio Amazonas ( Fig. 4 ).

Etymology. The specific name manaos is in reference to the Manaós, indigenous tribe that inhabited the lower rio Negro, which includes the type-locality of the new species. A noun in apposition.

Conservation status. Given the wide-ranging occurrence area throughout Central Amazon, the good environmental conditions and the lack of significant threats along most of the sampled localities, Tetragonopterus manaos should be categorized as Least Concern (LC) under the categories and criteria of the International Union for Conservation Nature (IUCN Standards and Petitions Subcommittee, 2017). Furthermore, sampled localities are proximate to several governmental protection zones, such as the Tefé National Forest, Anavilhanas National Park, Uatumã Biological Reserve, and Saracá-Taquera National Forest, northern Brazil.

Figures

Fig. 1. a. Tetragonopterus manaos, holotype, MZUSP 117250, 64.1 mm SL, Brazil, Manaus, Anavilhanas National Park, rio Negro, Amazon basin; b. radiograph of the holotype.

Fig. 2. Tetragonopterus manaos, paratype, MZUSP 123507, 62.8 mm SL, Brazil, Manaus, Anavilhanas National Park, rio Negro, Amazon basin.

Fig. 3. Left side dentition of Tetragonopterus manaos, MZUSP 121680, paratype, 56.1 mm SL. Medial view of a. maxilla, b. premaxilla, c. dentary, and d. lateral view of premaxilla. Scale bars = 1 mm.

Fig. 4. Map of northern South America showing the distribution of Tetragonopterus manaos; yellow circle represents the holotype and black circles represent paratypes.