Anostomoides atrianalis Pelegrin, 1909

Assega, Fernando Massayuki & Birindelli, José Luís Olivan, 2019, Taxonomic revision of the genus Anostomoides (Characiformes: Anostomidae), Zootaxa 4646 (1), pp. 124-144 : 129-132

Anostomoides atrianalis Pelegrin, 1909

( Figs. 1 , 2A , 3A , 4 A , 5 , 6 ; Tables 1 and 2 )

Anostomoides atrianalis Pellegrin, 1909: 346 (type locality: “Orénoque” [Río Orinoco, Venezuela]).— Bertin, 1948: 32 (type catalog).— Myers, 1950: 198 (taxonomic comments on the validity of the genus).— Garavello & Britski, 2003: 72 (list- ed).— Lasso et al., 2004: 105 (literature compilation; Colombia: Río Orinoco basin).— Santos & Zuanon, 2006: 60 , 66-67 (diagnosis in key; Venezuela, Río Orinoco).— Sidlauskas & Birindelli, 2017: 85 (Río Orinoco basin).

Schizodontopsis laticeps Eigenmann, 1912: 299 , pl. 41, fig. 4 (type locality: Crab Falls, Essequibo river, Guyana). [New synonym].

Anostomus (Schizodontopsis) laticeps . — Borodin, 1931: 45 (cited).

Laemolyta laticeps .— Myers, 1950: 197 (new generic combination).

Anostomoides laticeps .— Géry, 1974: 149 (comments in footnote; new generic combination).— Santos et al., 1984: 33, fig. 4, unnumbered fig. on p.71 (brief description, diagnosis in key; photo; lower Rio Tocantins, Brazil).— Santos & Jégu, 1989: 164, fig.; pl.IV, figs. 2-4 and 18 (brief description, diagnosis in key; photo, dentition; lower Rio Tocantins, Brazil).— Santos & Jégu, 1996: 160, fig. 9, tab.1 (brief description, diagnosis in key; Rio Uatumã, Brazil).— Ferreira et al., 1998: 63, unnumbered fig. on p. 63 (brief description, diagnosis in key, photo; Santarém, Pará, Brazil).— Garavello & Britski, 2003: 72 (listed).— Lasso et al., 2004: 105 (literature compilation; Colombia, Río Orinoco basin).— Santos et al., 2004: 47, unnumbered fig. on p. 47 (brief description, diagnosis in key, photo; lower Rio Tocantins, Brazil).— Santos & Zuanon, 2006: 60 , 67 (diagnosis in key; several localities in the Amazon basin, Brazil).—Santos et al., 2006: 29, unnumbered fig. on p. 29 (brief description, diagnosis in key, photo; Manaus, Amazonas, Brazil).— Sidlauskas & Vari, 2008: 78, figs. 19, 32 and 47. (phylogenetic relationships, illustration of neurocranium, dentition of dentary and basibranchial).— Sidlauskas & Vari, 2012: 75, 78, fig. 77 (comments; Essequibo River, Guyana).— Jegú et al., 2012: 119 (listed, Río Iténez basin, Bolivia and Brazil).— Feitosa & Santos, 2013: 149, unnumbered fig. on p. 148 (brief description, diagnosis in key; Rio Madeira basin, Brazil). — Sarmiento et al., 2014: 183 (literature compilation; Bolivia).— Ohara et al., 2017: 34, 86, fig. (brief description, photo, diagnosis in key; Rio Teles Pires, Brazil).— Sidlauskas & Birindelli, 2017: 85 (cited).

Anostomoides sp.— Santos et al., 2004: 48, fig (brief description, diagnosis in key, photo; lower Rio Tocantins basin, Brazil).

Diagnosis. Anostomoides atrianalis differs from A. nattereri by having three branchiostegal rays (vs. four), four pores in the infraorbital 1 (vs. three); symphyseal tooth of premaxillary bicuspid (vs. with blunt border); higher lateral-line scale counts (41–44 vs. 37–39); lower jaw lip dermal papillae forming ridges (vs. lower jaw lip with rounded dermal papillae) ( Fig. 4 ); three or four vertically elongated blotches and/or a faded dark longitudinal stripe (vs. three dark rounded midlateral blotches), dark lines between scale series on posterior half of body absent in specimens of all sizes (vs. dark lines between scale series on posterior half of body in specimens smaller than 150 mm SL).

Description. Body moderately slender, slightly compressed lateraly, greatest body depth at dorsal-fin origin. Dorsal profile slightly sloped and convex from snout tip to vertical through nostril; slightly concave from vertical through nostril to tip of supraoccipital spine and gently sloped and convex from this point to beginning of dorsalfin origin; slightly slanted and convex along dorsal-fin base; approximately straight or slightly convex from end of dorsal fin to adipose-fin origin, and concave from that point to origin of dorsal procurrent caudal-fin rays ( Fig. 5 ). Ventral profile slanted convex from tip of lower jaw to vertical through pectoral-fin origin; slightly convex from vertical through pectoral-fin origin to anal-fin origin; approximately straight along anal-fin base, and concave from anal-fin end to origin of ventral procurrent caudal-fin rays; caudal peduncle sligthly compressed, almost rectangular and slightly longer than deep.

Head pointed in profile; snout moderately long. Mouth slightly upturned; lips thick and fleshy, covered internally with numerous papillae. Four premaxillary teeth, symphyseal teeth bicuspid, remaining teeth with medial cusp often sided by diminutive cups. Four dentary teeth, two medial teeth with blunt cutting edge, two lateral teeth with medial cusp often sided by one to four diminutive cups. Upper jaw lip thick and covered by rounded dermal papillae or by ridges of dermal papillae. Lower jaw lip thick and covered by dermal papillae forming ridges (lip fringed) ( Fig. 4 ). Three branchiostegal rays.

Scales relatively small and cycloid; lateral line complete, with 41(3), 42(158)*, 43(49) or 44(1) perforated scales, extending from supracleithrum to base of middle caudal-fin rays. Horizontal scale rows between dorsal-fin origin and lateral line 5(8), 6(177), 7(21)* or 8(6). Horizontal scale rows between lateral line and pelvic-fin origin 4(2), 5(193)*, 6(15) or 7(2). Horizontal scale rows between lateral line and anal-fin origin 4(4), 5(193)* or 6(15). Horizontal scale rows around caudal peduncle 16(212)*. Predorsal scales from dorsal-fin origin to tip of supraoccipital spine 10(1), 11(1), 12(13), 13(44), 14(70)*, 15(52), 16(15), 17(8), 18(3), 19(3) or 20(2).

Dorsal-fin rays ii, 9(3) or 10(209)*. Dorsal-fin origin slightly anterior to middle of standard length and slightly anterior to vertical through pelvic-fin origin; distal margin of dorsal fin straight or gently concave. Adipose fin small, approximately rectangular shaped, its origin approximately at vertical through half anal-fin base length, its distal margin slightly convex. Pectoral-fin rays i, 13(3), 14(54)*, 15(154) or 16 (1); its tip extending approximately 3/4 distance between origins of pectoral and pelvic fins; its distal margin slightly convex. Anal-fin rays ii, 7(1), ii, 8(3), iii, 7(1) or iii, 8(207)*; fin origin approximately at vertical through fourth scale anterior to adipose-fin origin; when adpressed anal fin not reaching base of caudal-fin rays; distal margin slightly concave. Principal caudal-fin rays i, 9+8, i (212)*. Caudal fin forked, lobes rounded, upper lobe slightly longer than lower lobe.

Coloration in alcohol. Body with background color light brown. Body sides with three or four vertically elongated blotches: first blotch between opercular opening and vertical through dorsal-fin origin; second blotch below dorsal-fin base; third blotch above anal-fin origin; and the fourth blotch at caudal peduncle terminus. Faded dark longitudinal stripe present in some specimens. Dorsal fin slightly dark at base, interradial membranes pale on proximal region, and light dark on distal area. Caudal, pectoral and pelvic fins uniformly tan. Anal fin with rays and interradial membranes dark. Adipose fin light brown, except median portion, which is pale.

Distribution. Anostomoides atrianalis is distributed in the Río Orinoco basin in Venezuela, in the Essequibo River basin in Guyana, and in the Amazon basin, including Madeira, Negro, Tocantins and Xingu rivers, in Bolivia, Brazil, Colombia, and Peru ( Fig. 6 ).

Common names. “Aracu cabeça gorda” ( Santos et al., 1984; Santos et al., 2006); “piau de cabeça gorda” ( Santos et al., 1984; Ferreira et al., 1998; Santos et al., 2006).

Remarks. The three syntypes of Anostomoides atrianalis were examined through photographs. Two of the syntypes are relatively small and poorly preserved ( MNHN 1887-1897 and MNHN 1887-1799), whereas the third specimen is larger and better preserved ( MNHN 1887-0761) and, for these reasons, it is herein selected as the lectotype, the remaining syntypes becaming, thus, paralectotypes.

The types of Anostomoides laticeps were originally deposited at the Indiana University fish collection. Howev- er, in 1952, the Field Museum in Chicago acquired part of the fish collection of Indiana University. In this exchange, two paratypes of A. laticeps ( IU 12116) were lost, as reported in Henn (1928) and Ibarra & Stewart (1987).

Specimens of Anostomoides atrianalis are often misidentified as Laemolyta in fish collections ( Mautari & Menezes, 2006; pers. obs.). Mautari & Menezes (2006) noted that Anostomoides atrianalis and Laemolyta fernandezi share a similar color pattern and an upturned mouth, and co-occur in the Amazon basin. However, these species differ in the number of lateral-line scales (41 to 44 vs. 49 to 58, respectively) and in the morphology of the premaxillary teeth (symphyseal tooth bicuspid, and remaining teeth with medial cusp often sided by diminutive cups vs. all teeth multicupid and gradually decreasing in size, respectively), and dentary teeth (symphyseal tooth with truncate cutting edge, and remaining teeth with medial cusp often sided by diminutive cups, vs. all teeth of the dentary spatulated with the upper edge straight, respectively).

Figures

FIGURE 1. Scatter diagram of scores of specimens on second and third axes of Principal Components Analysis (PCA) of Anostomoides atrianalis from the Amazon basin (blue square), Essequibo River, Guyana (fill blue square), and Orinoco basin (black dot), A. nattereri from the Rio Xingu (yellow triangle), and A. nattereri from the Orinoco and remaining Amazon basin (filled pink square).

FIGURE 2. Lateral view of head showing the position of the mouth, upturned (A and C), slightly upturned (B) and terminal (D). (A) Anostomoides atrianalis, ANSP 182467, 128.3 mm SL, Peru, Loreto, Río Nanay; (B) A. nattereri, LIA 1229, 175.5 mm SL, Brazil, Pará, Rio Xingu; (C) Laemolyta proxima, MZUEL 17132, 215.5 mm SL, Brazil, Amazonas, Manaus; (D) Leporinus fasciatus, MZUEL 14698, 136.3 mm SL, Brazil, Amazonas, Rio Negro. Scale bar = 10 mm.

FIGURE 3. Scanning electron microscope image of left upper and lower jaws of Anostomoides: (A) A. atrianalis, INPA 15193, 137.2 mm SL; (B) A. nattereri, MZUSP 5429, 89.0 mm SL.

FIGURE 4. Lateral view of the head showing thickened, fringed lips with numerous dermal papillae in: (A) Anostomoides atrianalis, ANSP 159599, 132.8 mm SL, (B) Leporinus fasciatus, ANSP 161713, 189.9 mm SL, (C) Anostomoides nattereri, FMNH 103451, 141.8 mm SL, (D) Synaptolaemus latofasciatus, ANSP 190764, 80.2 mm SL. Scale bar = 5 mm.

FIGURE 5. Anostomoides atrianalis: (A) lectotype, MNHN-IC 1887-0761, 161.7 mm SL, Venezuela, Río Orinoco; (B) holotype of A. laticeps, FMNH 53359, 232.5 mm SL, Guyana, Crab Falls, Essequibo River; (C)AUM 43096, 140.4 mm SL, Venezuela, Río Orinoco; (D) ANSP 182467, 126.3 mm SL, Peru, Río Nanay. Scale bars = 10 mm.

FIGURE 6. Geographic distribution of species of Anostomoides atrianalis: yellow star: type-locality of A. atrianalis; black star: type-locality of A. laticeps; and yellow triangle: records of A. atrianalis. Some symbols may correspond to more than one locality.