Potamorhina laticeps (Valenciennes 1850)

Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.

Feeds on detritus.

Forms big schools (Ref. 26543). Feeds on detritus (Ref. 26543).

fisheries: commercial

Potamorhina laticeps (Valenciennes)

Curimatus laticeps Valenciennes, 1849:21, pl. 634 [type-locality: Venezuela, Lake Maracaibo drainage basin].—Günther, 1864:293 [after Valenciennes].—Eigenmann and Eigenmann, 1889:432 [reference in part, Venezuela; not listed specimens from Brazil; Curimatus altamazonicus Cope (1878) incorrectly placed as a synonym]; 1891:48 [reference in part]. [Not Steindachner, 1882:137.]

Semitapicis laticeps.—Eigenmann, 1910:422 [citation in part, Lake Maracaibo]. [Not Bertoni, 1914:10; Fowler, 1906:305, 1939:256, 1945:119.]

Anodus laticeps.—Schultz, 1944:251 [Venezuela, Lago Maracaibo basin: Río Negro, Río Palmar. Río San Ignacio, Río Apón].—Mago-Leccia, 1970:75 [Venezuela]. [Not Pearson, 1937:109; Eigenmann and Allen, 1942:300; Fowler, 1950:275; Marlier, 1968:25, 40; Ringuelet, 1975:72; Dorn and Schaller, 1972:169; Schaller, 1974:249.]

Suprasinelepichthys laticeps.—Fernandez-Yepez, 1948:35 [assignment to Suprasinelepichythys; not illustrated figure].—Fowler, 1975:375 [reference].

Gasterotomus latior.—Roberts, 1974:433 [erroneous citation of Anodus laticeps (Valenciennes)].

Curimata (Semitapicis) laticeps.—Géry, 1977:230 [reference in part, not Amazon].

Semitapiscis laticeps.—Braga and Azpelicueta, 1983:148 [in part, Lago Maracaibo citation; not Amazonian references].

DIAGNOSIS.—A large Potamorhina species that reaches 260 mm SL. Potamorhina laticeps is readily distinguishable in having 31 vertebrae contrary to the 33 to 37 in its congeners. Externally the moderately developed, longitudinal prepelvic median keel not continuous with the distinct, nonserrate postpelvic keel distinguishes P. laticeps within the genus. Potamorhina pristigaster, in contrast, has a flattened or transversely concave, laterally keeled prepelvic region and a serrate median postpelvic keel. In P. latior and P. squamoralevis the midventral keel anterior to the pelvic fin insertion is more highly developed and continuous posteriorly with the comparable postpelvic median ridge. Potamorhina altamazonica, in turn, has the ventral body surface anterior to the pelvic fin smoothly rounded transversely.

DESCRIPTION.—Body moderately elongate, compressed, more so in specimens over 150 mm SL. Dorsal profile of head straight or very slightly concave. Dorsal profile of body smoothly curved from rear of head to origin of rayed dorsal fin; straight and posteroventrally slanted at base of dorsal fin, gently convex from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with an indistinct median keel anterior to rayed dorsal fin, smoothly rounded transversely posterior to fin. Ventral profile of body gently curved from tip of lower jaw to caudal peduncle. Prepelvic region with an obtuse median keel that extends from anteroventral margin of pectoral girdle to area between insertion of pelvic fins. A well-developed median keel posterior to pelvic fin insertion. Pre- and post-pelvic median keels not continuous, interrupted in region of pelvic fin insertion.

Greatest body depth at origin of rayed dorsal fin, depth 0.34–0.44 [0.34]; snout tip to origin of rayed dorsal fin 0.47–0.54 [0.47]; snout tip to origin of anal fin 0.71–0.79 [0.74]; snout tip to insertion of pelvic fin 0.47–0.53 [0.49]; snout tip to anus 0.68–0.73 [0.72]; origin of rayed dorsal fin to hypural joint 0.55–0.59 [0.58]. Rayed dorsal fin pointed, less so with increasing age; anteriormost fin rays 2.5–3.0 times length of ultimate ray. Pectoral fin pointed; length of pectoral fin 0.17–0.23 [0.20]; fin extends distinctly beyond vertical through insertion of pelvic fin in smaller adults, barely beyond in largest specimens examined. Pelvic fin pointed, length of pelvic fin 0.20–0.26 [0.20]; fin reaches to origin of anal fin in young adults, only three-quarters of distance in larger specimens. Caudal fin forked. Adipose fin well developed. Anal fin emarginate, anteriormost branched rays twice length of ultimate ray. Caudal peduncle depth 0.11–0.12 [0.11].

Head distinctly pointed in profile, head length 0.29–0.35 [0.32]; jaws equal, mouth terminal; snout length 0.24–0.31 [0.26]; nostrils of each side very close, anterior circular, posterior cresent-shaped with aperture closed by thin flap of skin that separates nares; orbital diameter 0.20–0.27 [0.21]; adipose eyelid present, most highly developed anteriorly, with a vertically ovoid opening over middle of eye; postorbital portion of head elongate, length 0.53–0.58 [0.55]; gape width 0.27–0.31 [0.27]; interorbital width 0.39–0.45 [0.39].

Pored lateral line scales from supracleithrum to hypural joint 92 to 106 [105]; all scales of lateral line pored, sensory canals in lateral line scales diverge dorsally and ventrally; 5 to 10 series of scales extend beyond hypural joint onto caudal fin base; 24 to 29 [25] scales in a transverse series from origin of rayed dorsal fin to lateral line, 25 to 31 [27] scales in a transverse series from the lateral line to origin of anal fin. Scales weakly ctenoid, ctenii most highly developed on region anterior to insertion of pelvic fin.

Rayed dorsal-fin rays ii,9–10 [ii,9]; anal-fin rays ii, 12–15 or iii, 12–14 [ii, 15]; pectoral-fin rays 15 to 17 [16]; pelvic-fin rays i,8–9 [i,9].

Total vertebrae 31 (12).

Color in Alcohol: Overall coloration silvery-yellow to silvery-brown, head and body pigmentation more intense dorsally. A distinct, dark, round or slightly vertically elongate spot located on midlateral posterior portion of caudal peduncle at base of middle caudal fin rays. All fins with scattered small chromatophores.

DISTRIBUTION.—Lago Maracaibo drainage basin of Venezuela (Figure 13).

COMMON NAME.—Venezuela: Manamana (Mago-Leccia, 1970).

DISTRIBUTION.—Río Paraguay and Paraná drainage basins (Figure 15).

MATERIAL EXAMINED.—91 specimens (60, 70.0–234.1).

BRAZIL. Paraná: Rio Paraná below Sete Quedras, MZUSP 21092, 6 (4, 205.0–234.1). Mato Grosso do Sul: Rodovia between Miranda and Rio Miranda, Corumbá, MZUSP 21683, 2 (103.4–114.3). Port of Corumbá, Rio Paraguai, MZUSP 21684, 2 (192.1–217.5). Rio Paraguai, Cáceres, MZUSP 21532, 2 (139.0–163.4). Baia Bela ou Albuquerque, Rio Paraguai, MZUSP 21533, 4 (2, 142.4–165.3). Mato Grosso: Ranchão da logoa, Sto. Antonio do Leverger, MZUSP 21576, 4 (2, 187.5–209.7). Rio Cuiabá, Sto. Antonio de Leverger, MZUSP 4384, 1. Campo do Jofre, Poconé, MZUSP 21585, 3 (143.2–157.0). Rio Pixaim, Poconé, MZUSP 21587, 1 (145.0). Baiazinha, Rio Pixaim, MZUSP 21544, 2 (1, 183.1). Ilha de Taiamã, Rio Paraguai, MZUSP 21736, 8 (4, 111.3–113.4); MZUSP 21737, 1 (179.4). Sangraduoro Grande, Rio Cuiabá, MZUSP 21600, 1 (179.1). Baia Caranda Grande, MZUSP 21546, 2 (165.0–168.5). Baia do Buritizal, MZUSP 21686, 11 (5, 87.5–113.3); USNM 243228, 2 (1 specimen cleared and counterstained for cartilage and bone). Cuiabá, NMW 68834, 2 (175.1–181.9). Descalvado, GC, 1 (164.0).

PARAGUAY. No specific locality, USNM 2106, 2. Central: Río Paraguay near Asunción, USNM 181711, 7 (95.0–122.5, 1 specimen cleared and counterstained for cartilage and bone). Asunción Bay, USNM 181715, 1 (115.5); USNM 181707, 1, (146.6); USNM 181708, 1 (109.5); USNM 181705, 3 (104.5–129.2). Asunción, BMNH 1935.6.4.330–333, 3 (70.1–92.0); BMNH 1895.5.17.140, 1 (216.5); CAS 12056 (formerly IU 9934), 1; CAS-IU 9935, 1 (213.0). Río Paraguay, Zeballos Que, USNM 181803, 3. Hatipapunta, NMW 68835, 1; NMW 68836, 1. Alto Paraná: Puerto Bertoni, MHNG uncat., 1. Presidente Hayes: Km 180 along TransChaco Highway, MHNG uncat., 1.

ARGENTINA. No specific locality, USNM 229610, 1. Buenos Aires: Buenos Aires, NMW 68846, 2 (95.4–107.2). La Plata, NMW 68845, 1. Santa Fe: Rosario NMW 68831, 3 (1, 184.4).

URUGUAY. No specific locality, NMW 68847, 1.

Lago Maracaibo