Knodus cupariensis, Dos Anjos De Sousa & Silva-Oliveira & Canto & Ribeiro, 2020

Dos Anjos De Sousa, Deise J., Silva-Oliveira, Cárlison, Canto, André Luiz C. & Ribeiro, Frank Raynner V., 2020, A new species of Knodus (Characiformes: Characidae) from the Rio Cupari drainage, lower Rio Tapajós basin, Brazil, Zootaxa 4747 (3), pp. 575-584 : 576-581

Knodus cupariensis , new species

( Figs. 1-4 , Table 1 )

Knodus sp.: Silva-Oliveira et al., 2016: 7 ( Brazil, Pará state, Rio Cupari drainage: abundance and distribution).

Holotype. INPA 59396 , 40.5 mm SL, Brazil, Pará State, Rurópolis, unnamed stream tributary of rio Tinga, rio Cupari drainage, rio Tapajós basin, 4°05’10.80”S, 54° 51’10.60”W, 07 May 2015, F. R. V. Ribeiro, C. Silva-Oliveira, J. S. Sousa & D. J. A. de Sousa.

Paratypes. All from Brazil, Pará State, Rurópolis, rio Cupari drainage, rio Tapajós basin: INPA 59397 , 11 , 31.6-45.5 mm SL (2 c&s, 34.8–39.5 mm SL), igarapé Cachoeirinha , tributary of rio Braço Oeste , 4º14’49.9”S, 55º28’08.54”W, 09 Dec 2014, F. R. V. Ribeiro, C. Silva-Oliveira, J. S. Sousa & D. J. A. de Sousa . MCP 54280, 14 , 26.4–41.8 mm SL, unnamed stream tributary of rio Tinga , rio Lux drainage, Floresta Nacional do Tapajós , 3º59’04.3”S, 54º54’49.4”W, 01 Sep 2013, A. L. C. Canto, F. R. V. Ribeiro & C. Silva-Oliveira . UFOPA-I 297 (3 c&s, 37.2–40.1 mm SL), collected with holotype . UFOPA-I 298 , 9 , 31.7–43.2 mm SL (1 c&s, 33.1 mm SL), same data of the holotype, 18 May 2016. UFOPA-I 299 , 13 , 22.3–46.3 mm SL (2 c&s, 29.1–46.3 mm SL), unnamed stream tributary of rio Braço Leste , Floresta Nacional do Tapajós , 3º57’21.5”S, 55º05’01.2”W, 29 Sep 2013, A. L. C. Canto, F. R. V. Ribeiro & C. Silva-Oliveira . UFOPA-I 300 , 1 , 31.7 mm SL, rio Peixotinho , tributary of rio Braço Oeste , 4°10’24.7’’ S, 55°26’40.6’’ W, 09 Dec 2014, F. R. V. Ribeiro, C. Silva-Oliveira, J. S. Sousa & D. J. A. de Sousa . UNT 20996, 3 , 33.3–35.2 mm SL, unnamed stream tributary of rio Peixotinho , 4°11’37.5”S, 55°29’32.8”W, 31 Oct 2015, F. R. V. Ribeiro, A. L. C. Canto, C. Silva-Oliveira, J. S. Sousa & D. J. A. de Sousa . ZUEC 17146 , 4 , 31.8–37.6 mm SL, unnamed stream tributary of rio Tinga , rio Lux drainage, Floresta Nacional do Tapajós , 3º59’04.3”S, 54º54’49.4”W, 01 Sep 2013, A. L. C. Canto, F. R. V. Ribeiro & C. Silva-Oliveira

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Diagnosis. Knodus cupariensis differs from all its congeners, except from K. geryi , by having a dark basal blotch on each caudal fin lobe (vs. caudal fin lobe with sparse chromatophores, lacking a basal blotch) and, with exception from K. borki , K. heteresthes , and K. pasco , by having 10–12 scales around the caudal peduncle (vs. 13–15). Additionally, Knodus cupariensis differs from K. geryi and K. pasco by the lower number of longitudinal series of scales between dorsal-fin origin and lateral line (4 or 5 vs. 6 or 7). It differs from K. heteresthes by presenting a higher body depth (29.1–35.7 vs. 24.3–27.8 % SL) and by having dark chromatophores concentrated in conspicuous humeral blotch (vs. humeral blotch inconspicuous, with scattered chromatophores). Knodus cupariensis differs from K. borki and K. delta by having lateral line complete (vs. incomplete lateral line) and from K. smithi , K. delta , K. meridae , K. gamma , and K. nuptialis by having 17–21 branched rays in the anal-fin (vs. 12–15 in K. meridae and K. nuptialis and 23–30 in K. gamma , K. delta , and K. smithi ). Additionally, it can be distinguished from K. geryi by lower number of perforated lateral line scales (35–38, vs. 39–41).

Description. Morphometric data presented in Table 1 . Largest specimen examined 46.3 mm SL. Body compressed, greatest body depth slightly anterior to dorsal-fin origin. Dorsal profile of head convex from upper lip to vertical through middle portion of eye; slightly concave from this point to tip of supraoccipital spine; straight to slightly convex from posterior tip of supraoccipital spine to dorsal-fin origin; dorsal-fin base straight; slightly convex to straight from end of dorsal-fin base to adipose fin. Ventral profile of body convex from lower lip to anal-fin origin; straight, posterodorsally inclined along anal-fin base. Dorsal and ventral profile of caudal peduncle slightly concave.

Mouth terminal; jaws isognathous. Posterior terminus of maxilla extending well beyond anterior margin of orbit. Premaxillary teeth in two rows; outer row with 4 (7), 5* (50), 6 (1), or 7 (1) tricuspid teeth, central cusp longest; inner row with 4* (59) pentacuspid teeth, central cusp longest. Maxilla with 2 (5), 3 (30), 4* (15), 5 (8) or 6 (1) tri- to pentacuspid teeth. Dentary with 9–13, four anteriormost teeth large, pentacuspid teeth, followed by 5–9 smaller, uni- or tricuspid teeth. ( Fig. 2 ). Scales cycloid, moderately large, with 1–6 well-marked radii; circuli only present proximally. Caudal fin scaled, smaller than caudal peduncle scales, covering proximal third of lower lobe, and reaching ventral procurrent rays. Upper lobe with scale covering only proximal fourth, reaching dorsal procurrent rays. Lateral line complete, slightly curved ventrally along its anterior third, with 35 (4), 36* (22), 37 (18), or 38 (7) perforated scales. Longitudinal series of scales between dorsal-fin origin and lateral line 4* (41) or 5 (15). Longitudinal series of scales between lateral line and pelvic-fin origin 3* (51), 31/2 (3) or 4 (2). Predorsal scales 10 (1), 11* (12), or 12 (42). Scales around caudal peduncle 10* (3), 11 (31), or 12 (4). Single series with 15 (5), 16* (8), 17 (8), 18 (5), 19 (2) or 20 (1) scales on anal-fin base.

Dorsal fin rays ii,8* (59). Dorsal-fin origin slightly posterior to middle of body, and slightly posterior to vertical through pelvic-fin origin. First unbranched ray approximately half length of second unbranched ray. Adipose-fin origin approximately at vertical through base of 18 th to 20 th branched anal-fin rays. Pectoral-fin rays i,10 (5), or 11* (54); tip of pectoral fin reaching pelvic-fin origin when adpressed. Pelvic-fin rays i,6,i* (56); tip of pelvic fin usually reaching first anal-fin rays when adpressed. Anal-fin origin located anterior to vertical through posterior terminus of dorsal-fin base. Anal-fin rays v (8), 17 (1), 18 (13), 19* (23), 20 (19), or 21 (3); last unbranched ray and first three or four branched anal-fin rays longest, subsequent rays decreasing gradually in length. Caudal fin forked; lobes equal in size. Principal caudal-fin rays i,9,8,i*(59); dorsal procurrent caudal-fin rays 10 (2), 12 (1), 15 (2) or 16 (1); ventral procurrent caudal-fin rays 10 (1), 11 (1), 12 (2) or 13 (2).

Gill rakers on first gill arch 15 (2), 16 (4) or 17 (2): hypobranchial 2 (4) or 3 (4), ceratobranchial 7 (8), cartilage between epibranchial and ceratobranchial 1 (8), epibranchial 5 (4) or 6 (4). Gill rakers setiform. Branchiostegal rays 4 (8): 3 (8) on anterior ceratohyal and 1 (8) on posterior ceratohyal. Precaudal vertebrae 16 (8); caudal vertebrae 20 (3) or 21 (5); total vertebrae 36 (3) or 37 (5); ribs 10 (3) or 11 (5). First dorsal-fin pterygiophore inserted between 10 th and 12 th vertebrae. First anal-fin pterygiophore inserted between 16 th to 17 th vertebrae. Supraneurals 4 (1), 5 (6) or 6 (1).

Color in alcohol. Overall body coloration light brown. Third infraorbital and opercular regions silvery. Snout, dorsal region of head, anterior portion of maxilla, and mid-dorsal region of the body darker than the ventral region. Gular region light yellow. Dark chromatophores more concentrated at the scales edge of dorsal and dorsolateral scales of body, forming slightly reticulated pattern; ventral and ventrolateral scales of body with few scattered dark chromatophores or completely pale. Rectangular conspicuous humeral blotch, vertically elongated, extending vertically through two longitudinal scales series above lateral line and one below it, and horizontally encompassing second to fourth lateral line scales. Dark chromatophores concentrated over scales series immediately above and below lateral line, forming a diffuse longitudinal stripe extending from humeral blotch to basis of middle caudal-fin rays.

Fins hyaline, dorsal fin with chromatophores more concentrated along interradial membranes. Pectoral and pelvic fins with few scattered chromatophores along anterior and posterior borders of rays. Anal fin slightly darkened, with chromatophores present along interradial membranes, more concentrated in distal portion. Caudal fin with chromatophores at interradial membranes and over rays, more concentrated along the proximal region of rays forming two symmetric, inconspicuous dark blotches basally on caudal fin lobes. Distal margin of caudal fin with scattered chromatophores ( Fig. 3 ).

Color in life. Based on specimens recently collected ( Fig. 4 ). General color of body gray to light brown. Lips, snout, and upper portion of head dark gray to light yellow. Dorsolateral region of orbit light yellow. Ventrolateral region of orbit, maxilla, and opercular regions silvery. Dorsal portion of body, dorsal, anal, and caudal fins with reddish pigmentation. Dorsal and caudal fins reddish in basal portion. Anal fin reddish in middle portion of the rays. Adipose, pectoral and pelvic fins similar to preserved specimens.

Sexual dimorphism. Observed in two mature males (INPA 57160, 34.8–39.5 mm SL). The pelvic-fin rays of these specimens possess 6–12 small hooks per branched ray and the anal-fin rays possess 8–9 hooks per ray, on last unbranched and anteriormost seven branched rays.

Geographical distribution. Knodus cupariensis is only known from the rio Cupari drainage, a tributary of the right margin of the lower rio Tapajós, Pará State, Brazil ( Fig. 5 ).

Ecological notes. Specimens of Knodus cupariensis were captured in first to fourth order streams, about 1–5 m wide and 0.2–2.0 m deep, with moderate to fast-flowing waters, substrate composed mainly of rocks, gravel, and sand, and with the following physico-chemical parameters: pH 4.3–6.7; dissolved oxygen 4.2–8.3 mg l-1; conductivity 14.6–32.1 μS cm-1; and temperature 24.1–28.1 ° C ( Fig. 6 ). Knodus cupariensis occurs syntopically with several other characids: Astyanax cf. bimaculatus (Linnaeus) , Brachychalcinus copei (Steindachner) , Bryconops sp., B. aff. caudomaculatus (Günther) , B. cf. colaroja Chernoff & Machado-Allison , Hemibrycon surinamensis Géry , Hemi- grammus bellottii (Steindachner), H. ocellifer (Steindachner) , Hyphessobrycon pulchripinnis Ahl , Jupiaba apenima Zanata , Moenkhausia comma Eigenmann , M. hasemani Eigenmann , M. oligolepis (Günther) , and another unidentified species of Knodus .

Etymology. The specific epithet, cupariensis , is an adjective referring to the rio Cupari, from where the species is currently exclusively known to occur.

Conservation status. Knodus cupariensis is currently known to has a restricted distribution, with an Extent of Occurrence (EOO) of approximately 2,000 km 2. Anthropic pressures have caused intense deforestation in the drainage basin of the rio Cupari, mainly due to the removal of native forest to create pastureland. In addition, the Brazilian Regulatory Electricity Agency (ANEEL) plans to build 13 small hydropower plants, distributed along the rio Cupari and its main tributaries, which may result in substantial spatiotemporal changes to the natural hydrological characteristics of the river. However, part of the known population occurs within a protected biological reserve (Floresta Nacional do Tapajós). We consider that K. cupariensis should be categorized as Least Concern (LC) according to International Union for Conservation of Nature (IUCN) categories and criteria (IUCN 2017).

Figures

FIGURE 1. Knodus cupariensis, new species, INPA 57159, holotype, 40.5 mm SL, male, rio Cupari, rio Tapajós basin, Rurópolis, Pará State, Brazil.

FIGURE 2. Knodus cupariensis, UFOPA-I 297, paratype, 40.1 mm SL, upper and lower jaws, lateral view, left side. Scale bar = 1 mm.

FIGURE 3. Knodus cupariensis, UFOPA-I 298, paratype, 39.6 mm SL, lateral view of posterior portion of the body, showing dark blotches on caudal-fin lobes.

FIGURE 4. Knodus cupariensis, coloration in life, rio Cupari, rio Tapajós basin, Rurópolis, Pará State, Brazil (specimen not cataloged).

FIGURE 5. Map of lower rio Tapajós basin and adjoining areas showing the distribution of Knodus cupariensis (dark dots; yellow star indicates type-locality). Some symbols represent more than one lot.

FIGURE 6. Type locality of Knodus cupariensis, stream tributary of rio Tinga, rio Cupari drainage, rio Tapajós basin, Rurópolis, Pará State, Brazil.