Triportheus nematurus ( Kner, 1858 )

Malabarba, Maria Claudia S. L., 2004, Revision of the Neotropical genus Triportheus Cope, 1872 (Characiformes: Characidae), Neotropical Ichthyology 2 (4), pp. 167-204 : 182-184

Triportheus nematurus ( Kner, 1858)

Figs. 10 and 11

Chalcinus nematurus Kner, 1858:163 . Kner, 1860:13-15 (more detailed description). Garman, 1890:3 (synonym of C. angulatus ). Eigenmann & Eigenmann, 1891:56 (synonym of Chalcinus angulatus ). Ulrey, 1895:294 (synonym of Chalcinus angulatus ). Ribeiro, 1941:162 (table with morphometrics).

Chalcinus paranensis Günther, 1874:454 (description, type locality: rio Paraná).

Triportheus paranensis . Fowler, 1950:358 (listed; rio Paraguay, rio Paraná). Portugal, 1990: 136-142. Britski et al., 1999:27. Reis et al., 2003:158.

Diagnosis. A deep bodied Triportheus species reaching 159 mm of SL (depth at dorsal-fin origin, 31.9-36.9, mean = 33.6% SL, n = 36; depth at pectoral-fin insertion, 31.3-38.4, mean = 34.9% SL, n = 36). The presence of 2 longitudinal scale rows between the pectoral-fin insertion and ventral keel distinguish this species from elongate bodied Triportheus species that have 1 longitudinal scale row between the pectoral-fin insertion and the ventral keel. Among deep bodied Triportheus species, T. nematurus differs by the combination of the number of gill rakers on the lower limb of the first gill arch (38-48, mean = 42.7, n = 34); the number of lateral-line scales (33-37, mean = 34.2, n = 32); the number of branched anal-fin rays (25-31, mean = 28.5, n = 35); and the presence of longitudinal dark stripes on the lateral surface of the body.

Description. Morphometric data for Triportheus nematurus presented in Table 8. Body deep and compressed laterally. Greatest body depth located slightly posterior to vertical through pectoral-fin insertion. Dorsal profile of head straight from snout to rear of head. Dorsal profile of body gently curved from rear of head to dorsal-fin origin; posteroventrally slanted from dorsal-fin origin to caudal peduncle; nearly straight along caudal peduncle.

Ventral profile of head straight from tip of lower lip to anteroventral margin of dentary; arched from that point to pelvic-fin insertion; nearly straight from pelvic-fin insertion to anal-fin origin; posterodorsally slanted along anal-fin base; straight along caudal peduncle. Prepelvic region very expanded ventrally and flattened, with well developed keel.

Head pointed in profile; posterior opercle margin almost reaching vertical through pectoral-fin insertion. Snout somewhat rounded anteriorly. Mouth terminal; lower jaw usually as long as upper jaw, but slightly longer in some specimens. Most specimens with very small barbel at each side of the mouth. Nostrils of each side close together; anterior opening circular; posterior elongate.

Gill rakers thin and close together, length equivalent to one-half of branchial filament length; gill rakers on lower portion of first gill arch 38-48 [47] (mean = 42.7, n = 34).

Teeth on premaxilla in 3 rows; teeth of inner row largest. Four to 5 tricuspidate teeth on outer row; outer row teeth arranged along margin of mouth and visible externally in closed mouth. Medial row with 3 tricuspidate teeth. Inner row with 6, rarely 7, multicuspidate teeth. Maxilla with 0-2 flattened teeth smaller than those on premaxilla. Teeth on lower jaw in 2 rows; outer row with 4-5 larger anterior teeth, and 4-6 smaller posterior teeth. Inner row consisting of conical symphyseal tooth.

PROOFS

Scales cycloid, thin, large. Lateral line distinctly decurved ventrally, completely pored from supracleithrum to base of caudal-fin rays. Thirty-three to 37 [35] (mean = 34.2, n = 32) scales in lateral line; 6 scale series above lateral line; 1-2 scale rows below lateral line. Two scale rows between pectoral-fin insertion and midventral keel; 5-6 scale series on caudal peduncle. Scales along mid-dorsal line very irregular; scales 7- 13 [9] (mean = 9.5, n = 29) from tip of supraoccipital process to dorsal-fin origin.

Dorsal-fin rays ii,9; anal-fin rays iii,25-31 [28] (mean = 28.5, n = 35); pectoral-fin rays i,10-12; pelvic-fin rays i,6. Dorsal-fin margin straight; dorsal-fin base situated on posterior one-half of the body; base of last dorsal-fin ray located at vertical through base of third or fourth anal-fin ray; first branched ray longest with following rays gradually decreasing in length. Pectoral fin pointed, tip reaching vertical through distal one-third of pelvic fin. Anal fin margin straight, first branched anal-fin ray longest; following rays gently decreasing in length. Margin of caudal fin truncate; median rays extend to varying degrees beyond margin of remainder of fin. Scales present over basal one-third of fin.

Total vertebrae 36-37 [37].

Coloration in alcohol. Overall ground color yellowish silvery. Snout and dorsal portion of head dark. Scattered dark chromatophores on opercle and infraorbitals 4-6. Body darker dorsally and on caudal peduncle. Five or 6 sinuous, brown, longitudinal stripes present along scale rows on dorsolateral portion of body. Dark chromatophores distributed over and between rays of all fins. Dorsal-fin rays outlined by dark chromatophores. Middle caudal-fin rays very dark.

Distribution. Río Paraguay and lower rio Paraná basins ( Fig. 12 ).

Remarks. Two Triportheus species occur in the río La Plata drainage, including the rio Paraná and río Paraguay basins. These can be easily distinguished based on the number of lateral line scales and gill rakers. Two nominal species of Triportheus have been described for this drainage: T. nematurus ( Kner, 1858) and T. paranensis ( Günther, 1874) . These names have been recently applied ( Portugal, 1990; Britski et al., 1999; Reis et al., 2003) to the two Triportheus species recognized in the rio Paraná and rio Paraguay. Triportheus nematurus has been assigned to the form with lower counts of lateral line scales (28-32) and gill rakers (26- 33); while T. paranensis has been used for the form with higher counts (34-37 lateral line scales, 38-48 gill rakers).

The examination of the type-specimens of Chalcinus nematurus and C. paranensis , however, revealed that both nominal species are based on the form with higher lateral line and gill rakers counts. Since Chalcinus nematurus Kner, 1858 is the oldest available name, Chalcinus paranensis Fowler, 1950 becomes a junior synonym.

As a result, the species with higher lateral line and gill rakers counts referred to as T. paranensis by Portugal (1990), Britski et al. (1999) and Reis et al. (2003) is rather T. nematurus . This necessitates a new name for the species with lower lateral line and gill rakers counts erroneously referred by those authors as T. nematurus (see account of T. pantanensis ).

Remarks about type-specimens. Syntypes of Chalcinus nematurus include 3 lots: NMW 69034(1), NMW 62694 (2) and NMW 62689 (2). The specimens of NMW 69034 and NMW 62694, have 35-36 lateral line scales, account that agrees with the 34-36 scales reported in the original description of C. nematurus ( Kner, 1860) . Lot NMW 69034 (1) is herein designated as the lectotype of C. nematurus and the specimens in the lot NMW 62694(2) become paralectotypes.

Type-material examined: Chalcinus nematurus : lectotype by present designation, NMW 69034 (1), 148.22 mm SL, Cujaba, Natterer . Paralectotypes: NMW 62694 (2, 143.91- 168.67 mm SL), Cujaba, Natterer ; NMW 16171 (1), dry specimen ; NMW 62689 (2), 181-190 mm SL, Cujaba, Suaguragua, Caicara, J. Natterer .

Chalcinus paranensis , holotype, BMNH 1872.5.6:32 (1), 97.25 mm SL, rio Paraná.

Non-type material. Brazil: Mato Grosso: MZUSP 85808 (28), Ilha de Taiamã , rio Paraguay (10 o 16’S, 55 o 40’W) . USNM 326324 (1), río Paraguay and tributaries around Cáceres (16 o 4’S, 57 o 41’W) . Paraguay: Presidente Hayes: NRM 50734 (2), río Paraguay , (24°50’4”S, 57°46’0”W) ; USNM 181691 (3 of 4) ; USNM 181682 (3) ; USNM 181687 (1), Baía Asuncion, río Paraguay , near Asuncion (25°15’N, 57°40’W) .

Figures

Fig. 10. Chalceus nematurus, lectotype, NMW 69034, 148.2 mm SL, Brazil, Mato Grosso, Cuiabá.

Fig. 11. Triportheus nematurus, NRM 50734, 135.81 mm SL, Paraguay, Presidente Hayes, río Paraguay.

Fig. 12. Map of central and northern South America showing geographic distribution of T. culter (circles; asterisk = type-locality), T. albus (squares; asterisk = type-locality), T. nematurus (triangles; diamond = type-locality) and T. venezuelensis (lozenges; white square = type-locality) (some symbols represent more than one locality or lot of specimens).