Pseudanos varii, Birindelli, José L. O., Lima, Flávio C. T. & Britski, Heraldo A., 2012

Pseudanos varii View in CoL , new species

Figure 1 View FIGURE 1

Pseudanos gracilis View in CoL (not Kner).— Winterbottom, 1980: 24–27, 64 (in part, Río Atabapo, Río Casiquiare, and Rio Negro; description).— Goulding et al., 1988: 122, 138, 141, 167, 168 (Rio Negro basin; habitat preferences, diet).— Sidlauskas and Santos, 2005: 116–119, 121, 122 (Río Atabapo, Rio Negro; comparisons with P. winterbottomi View in CoL ).— Sidlauskas and Vari, 2008: 136, 138, 143, 153, 155, 164, 165, 179 (Río Atabapo, Rio Negro; phylogenetic relationships, morphology).

Holotype. MZUSP 109800 (126.0 mm SL), Brazil, Amazonas, Manaus, Igarapé Sirinau, tributary of Rio Cuieiras (tributary of Rio Negro), c. 2°42’S 60°20’W, 30 Jan 1977, Alpha Helix Expedition [= H. A. Britski and N. A. Menezes].

Paratypes. All from Brazil, Amazonas. MZUSP 74286 (10, 62.3–137.9 mm SL); same data as holotype.

INPA 15247 (3, 112.5– 121.5 mm SL), Manaus, Rio Tarumã-Açu, Igarapé Tarumãzinho, BR-174, km 28, at Sítio do Sr. Bonatti, 2°43’51”S 60°4’88”W, 27 Nov 1996, A. L. Kirowsky. MZUSP 29163 (7, 63.1–72.1 mm SL), Rio Negro, Lago Central, Ilha do Buiu-Açu, c. 0°31’S 64°50’W, 6 Feb 1980, M. Goulding. MZUSP 29164 (4, 60.5–92.7 mm SL), Rio Negro, immediately downstream of Rio Daraá, c. 0°28’S 64°45’W, 16 Feb 1980, M. Goulding. MZUSP 29168 (18, 45.5–137.9 mm SL; 3 CS, 56.5–77.3 mm SL), ANSP 192819 (2, 56.3–105.4 mm SL); ZUEC 6862 (2, 69.9–70.3 mm SL), Barcelos, Rio Negro, c. 0°58’S 62°57’W, 29 Feb 1980, M. Goulding. MZUSP 31252 (1, 210.0 mm SL), São Gabriel da Cachoeira, Rio Negro, c. 0°7’S 67°5’W, May/ Jun 1980, M. Goulding. MZUSP 92336 (1, 181.5 mm SL), Rio Tiquié, Pirarara-Poço, 0°8’N 69°12’W, Sep 2006, F. C. T. Lima et al. MZUSP 93430 (2, 142.4– 157.2 mm SL), Rio Tiquié, near Serra do Mucura, 0°10’N 69°7’W, Nov 2006, F. C. T. Lima et al. MZUSP 93461 (1, 136.8 mm SL), Rio Tiquié, at São José, 0°8’S 69°36’W, Sep to Nov 2006, Antenor.

Non-type specimens. Brazil. MZUSP 29165 (1, 65.4 mm SL); MZUSP 31059 (1, 59.4 mm SL), Amazonas, Rio Negro, immediately downstream mouth of Rio Daraá, c. 0°28’S 64°45’W, 12–16 Feb 1980, M. Goulding. MZUSP 35765 (1, 95.5 mm SL), Amazonas, Rio Cuieiras and tributaries, c. 2°49’S 60°29’W, Jan 1977, Alpha Helix Expedition. MZUSP 56304 (1, 49.8 mm SL), Roraima, Rorainópolis, Rio Negro, 1°30’49’’S 61°32’17’’W, 7 Dec 1993, M. Garcia et al. MZUSP 74276 (2, 50.6–64.5 mm SL), Amazonas, Manaus, Igarapé Jaradá, tributary of Rio Cuieiras, c. 2°49’S 60°29’W, 31 Jan 1977, Alpha Helix Expedition. MZUSP 91563 (1, 100.8 mm SL), Amazonas, Rio Uaupés (no precise locality), J. Chernela. MZUSP 92987 (1, 124.2 mm SL), Amazonas, Rio Tiquié, at São José, c. 0°13’N 69°36’W, Nov 2006, F. C. T. Lima et al. Venezuela. FMNH 103454 (30 alc, 55.7–102.8 mm SL), Amazonas, San Fernando de Atabapo, rocks in Río Atabapo, at approximately 1.2 hour above San Fernando de Atabapo, 28 Jan 1991, B. Chernoff et al. FMNH 104021 (1 alc, 156.5 mm SL), Amazonas, San Fernando de Atabapo, Caño Guasuriapana at Guasuriapana, tributary of Río Atabapo, 4°0'N 67°42'W, 28 Jan 1991, A. Machado et al. MCNG 25960 (1 alc, not measured), Amazonas, Río Siapa, 60 km from mouth of Río Casiquiare, c. 2°4’N 66°’12’W, 4 Sep 1991. MCNG 53510 (1 alc, not measured), Amazonas, San Fernando de Atabapo, Caño 22.7 km N of San Fernando de Atabapo, at Boca de Guapa Sucia, c. 4°1’N 67°40’W, 4 Apr 2005, N. Lujan et al.

Diagnosis. Pseudanos varii is distinguished from its congeners by having three branchiostegal rays (vs. four in P. gracilis and most specimens of P. winterbottomi ), dark transversal bars on dorsum absent (vs. present in P. trimaculatus ), dark spots present on the center of each body scale, forming conspicuous, straight dark lines (vs. dark spots absent in P. gracilis and in some specimens of P. trimaculatus ), four midlateral dark blotches on body (vs. usually two, sometimes three or four in P. trimaculatus , or body lacking midlateral blotches and presenting instead a broad midlateral stripe in P. winterbottomi ), angle of the dorsal and ventralmost radii of body scales between 40° and 90° (vs. angle between 110° and 180° in P. gracilis and P. trimaculatus ), and cranial fontanel opened along its entire length (vs. cranial fontanel partially closed in P. trimaculatus ).

Description. Morphometric and meristic data in Table 1. Moderately sized, largest examined specimen 210.0 mm SL. Body fusiform, moderately compressed. Dorsal profile straight to slightly concave from tip of upper jaw to terminus of supraoccipital process; slightly convex from latter point to dorsal-fin origin; slightly concave to straight from latter point to adipose-fin and slightly concave to caudal-fin origin. Ventral profile rounded or distinctly angled from tip of lower jaw to vertical through mouth opening, gently convex from latter point to analfin base, and distinctly concave on caudal peduncle. Greatest body depth at dorsal-fin origin.

Mouth small, strongly upturned and opening on dorsal surface of head. Lips plicated. Premaxilla approximately parallel to body axis, bearing four compressed teeth, directed anteriorly, with two to four cusps, forming a continuous serrated edge ( Fig. 2 View FIGURE 2 ); cusps more numerous and better developed in lateral teeth and smaller specimens; two median teeth with four cusps and two lateral teeth with four cusps in specimens up to 150 mm SL, and with two and three cusps, respectively, in larger specimens. Maxilla edentulous, oriented at approximately 45° relative to body axis, with ventral tip distinctly anterior to dorsal tip. Dentary with four compressed teeth, posteriorly directed, with two to four cusps ( Fig. 2 View FIGURE 2 ); cusps more numerous and better developed in lateral teeth and smaller specimens; two median teeth with two cusps and two lateral teeth with three cusps in specimens up to 150 mm SL, and with almost truncate edge and two to three cusps, respectively, in larger specimens.

Anterior and posterior nares conjoined, anterior naris tubular, posterior naris lying in groove. Six independent infraorbital bones, third one largest, sixth smallest. Infraorbital 1 with three or four externally visible pores (n=3, four pores only on one side of a single specimen). Nasal with two externally visible pores. Supraorbital positioned on anterodorsal border of eye, elongate. Antorbital curved, joined to infraorbital one. Three branchiostegal rays.

Dorsal fin located approximately at middle of body, its origin slightly anterior to half of SL, with rounded distal margin. Adipose fin teardrop shaped. Pectoral fin extending through 5 to 7 scales posterior to pectoral-fin origin, with rounded distal margin. Pelvic fin with rounded distal margin, its origin posterior to vertical through dorsal-fin origin. Anal fin subtriangular, with concave distal margin and rounded edge. Caudal fin distinctly forked with rounded to slightly acute lobe tips, dorsal lobe slightly larger than lower lobe. Vertebrae 41 to 43 (n=3), with ribs on vertebrae 5 to 29, 30 or 32 (n=3). Eight supraneurals (n=3).

Body completely covered with scales, fins not scaled, except for anteriormost portion of caudal-fin rays. Lateral line relatively straight, running along midbody. Scale immediately dorsal to pelvic-fin origin elongate with acute posterior tip. Scale immediately above lateral line and at vertical through dorsal-fin origin with three main radii in small specimens (up to 100 mm SL), or with several radii forming network in larger specimens; dorsal and ventralmost radii forming an angle between 40° and 90° ( Fig. 3 View FIGURE 3 ).

Coloration. Head and body tan, brownish, distinctly countershaded; fins pale, except caudal fin with upper and lower portion darkened in large specimens (> 180 mm SL). Four midlateral dark blotches on body: first on fourth to sixth lateral-line scale and adjacent ventral scales; second, largest, on middle of body, ventral to dorsal fin, and encompassing approximately four scale rows of length and two of depth; third dorsal to anal-fin origin, encompassing two or three lateral-line scales and adjacent ventral scales; fourth on posterior portion of caudal peduncle, encompassing approximately two scale rows of length and depth. First, and last two dark blotches faded in large specimens (from 180 mm SL). Dark spots on center of each body scale forming lines in small and medium sized species (up to 180 mm SL; Fig. 1 View FIGURE 1 b–c); in large specimens, dark spots somewhat rounded on anterior portion of body and forming interrupted, rather than continuous longitudinal stripes ( Fig. 1 View FIGURE 1 a).

Color in life. Based on a picture of a recently collected specimen, MZUSP 92336, from Rio Tiquié (upper Rio Negro basin). Overall color grey, lighter on lower portion of body. Second (largest) midlateral blotch and dark spots on scales very conspicuous. All fins (including adipose fin) slightly red.

Ecological notes. Pseudanos varii is only known from blackwater rivers, i.e., the Rio Negro and tributaries in Brazil, and the Río Casiquiare and Río Atabapo in Venezuela. The Río Síapa (a tributary of the Río Casiquiare) and the middle Rio Tiquié (a tributary of Rio Uaupés, upper Rio Negro basin) cannot be considered, however, strictly as blackwater rivers because both have some influence of clear to “semi-muddy” waters (for the Río Síapa, see Winemiller and Willis, 2011: 237, 238). The Rio Tiquié is a typical blackwater river until receiving a large tributary, the Igarapé Castanha (mouth at 0°13’0’’N, 69°35’38’’W), which is a “semi-muddy” river (see Lima and Ribeiro, 2011: 156 and references therein for comments on other “semi-muddy” rivers at the Rio Negro basin). Specimens of Pseudanos varii from the Rio Tiquié were collected in areas of seasonally flooded forest (“igapós”) on shores of river or oxbow lakes. Goulding et al. (1988) reported the species (as Pseudanos gracilis ) as occurring in “island lakes” (i.e., lakes inside islands within predominantly “igapó” settings) and rocky pools in the Rio Negro basin in Brazil. The diet of the specimens examined by Goulding et al. (1988) consisted solely of detritus.

Distribution. Pseudanos varii is recorded from the entire stretch of Rio Negro basin in Brazil, and Río Síapa (a tributary of Río Casiquiare, which connects the upper Rio Negro with the upper Río Orinoco) and Río Atabapo (a tributary of the upper Río Orinoco) in Venezuela ( Fig. 4 View FIGURE 4 ).

Etymology. The specific name honors Richard P. Vari, ichthyologist from the National Museum of Natural History, Washington D.C., in recognition of his vast, invaluable contribution to the knowledge of systematics of characiform fishes, particularly the anostomoid fishes (e.g., Vari, 1983).