Triportheus trifurcatus ( Castelnau, 1855 )

Malabarba, Maria Claudia S. L., 2004, Revision of the Neotropical genus Triportheus Cope, 1872 (Characiformes: Characidae), Neotropical Ichthyology 2 (4), pp. 167-204 : 180-182

Triportheus trifurcatus ( Castelnau, 1855)

Fig. 9

Chalcinus trifurcatus Castelnau, 1855: 70 , Pl. 37, fig. 1, rio Araguaia, Brazil. Günther, 1864:340-341 (synonym of Chalcinus brachypomus ). Garman, 1890:3 (synonym of Chalcinus angulatus ). Eigenmann & Eigenmann, 1891:56 (synonym of Chalcinus angulatus ). Ulrey, 1895:294 (synonym of Chalcinus angulatus ). Eigenmann, 1910:440 (synonym of Chalcinus angulatus ). Fowler, 1950:359 (synonym of T. rotundatus ).

Triportheus trifurcatus . Portugal, 1990:129-135 (redescription, illustration, map).

Diagnosis. A deep bodied Triportheus species reaching 165 mm of SL (depth at dorsal-fin origin, 27.0-36.2 % SL; depth at pectoral-fin insertion, 31.6-39.1 % SL). The presence of 2 longitudinal scale rows between the pectoral-fin insertion and ventral keel distinguish this species from all elongate bodied Triportheus species that have 1 longitudinal scale row between the pectoral-fin insertion and the ventral keel. Triportheus trifurcatus differs from other deep-bodied Triportheus species by the combination of the number of gill rakers on the lower limb of the first gill arch (40-47, mean = 42.1, n = 24); the number of lateral line scales (32-35, mean = 32.8, n = 20); and the 5 scale series dorsal to the lateral line.

Description. Morphometric data for Triportheus trifurcatus presented in Table 7. 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; slightly curved along caudal peduncle.

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

PROOFS

Head blunt in profile; posterior margin of opercle reaching pectoral-fin insertion. Mouth terminal; lower jaw as long as upper jaw. Nostrils of each side close together; anterior opening circular; posterior elongate.

Gill rakers thin and close together, almost so long as branchial filament length; gill rakers on lower limb of first arch 40-47.

Teeth on premaxilla in 3 rows; teeth of inner row largest. Five tricuspidate teeth on outer row; outer row teeth arranged along margin of mouth and can be seen externally in closed mouth. Medial row with 3 tricuspidate teeth; inner row with 6 multicuspidate teeth. Maxilla with 2 flattened teeth, smaller than those on premaxilla. Teeth on lower jaw in 2 rows, outer row with 4 smaller teeth posteriorly and 4 larger teeth anteriorly. Inner row consisting of one conical symphyseal tooth.

Scales cycloid, thin, large. Lateral line distinctly decurved ventrally, completely pored from supracleithrum to base of caudal-fin rays. Thirty-two to 35 (mean = 33.8, n = 20) scales in lateral line; 5 scale series above lateral line; 2-3 scale rows below lateral line. Two scale rows between pectoral-fin insertion and midventral keel; 4-5 scale series on caudal peduncle. Nine to12 scales (mean = 10.2, n = 20) along mid-dorsal line from supraoccipital process to dorsal-fin origin.

Dorsal-fin rays ii,9; anal-fin rays iii-iv, 26-29 (mean = 27.3, n = 24); pectoral-fin rays i,10-12; pelvic-fin rays i,6. Dorsal-fin base located on posterior one-half of body with last dorsal-fin ray located at vertical line through base of third or fourth anal-fin ray; first branched ray longest; following rays decreasing slightly in length. Pectoral fin pointed, tip reaching posteriorly to area middle and tip of pelvic fin. Anal-fin margin straight, first branched anal-fin ray longest; following rays gradually decreasing in length. Margin of caudal fin truncate; median rays extend about one-half their length beyond margin of remainder of fin. Scales covering basal one-third of fin.

Total vertebrae 37.

Coloration in alcohol. Overall ground color yellowish silvery. Snout and dorsal portion of head dark. Scattered dark chromatophores present on opercle and infraorbitals 5 and 6. Body darker dorsally and dorsal to anal-fin base and on caudal peduncle. Five or 6 sinuous, brown, longitudinal stripes present on dorsolateral portion of body. Dark chromatophores distributed over all fins. Dorsal-fin rays outlined by dark chromatophores. Chromatophores distributed over pectoral-fin between the rays; more intense pigmentation present on first unbranched ray. Anal-fin margin darker. Middle caudal-fin rays very dark.

Distribution. Rio Tocantins and rio Araguaia drainages ( Fig. 4 ).

Type-material remarks. The type material of Chalcinus trifurcatus consists of a dry specimen ( MNHN A 9837 ). Measurements of the holotype presented in Table 7 are fairly accurate. They were obtained from a radiograph of that specimen .

Type-material examined. Chalcinus trifurcatus : holotype, MNHN A 9837 , 136.29 mm SL, (dry specimen, only radiograph examined), Brazil, Pará, Araguaya, collected by Castelnau.

Non-type material. Brazil: Goiás: MZUSP 4832 (21 of 36), rio Araguaia, Aruanã (14°53’S, 51°4’W) . Tocantins: MZUSP 52122 (3), Araguaçu, rio Água Fria in the road between Araguaçu and Barreira do Piqui , 27 km North to Araguaçu (12°43’S, 49°55’W) . Mato Grosso: MZUSP 19633 (3), rio Araguaia, Santa Terezinha (10°35’S, 50°34’W) . Pará: MZUSP 20640 (5), Tucuruí, rio Tocantins , below Tucuruí lake in the margin of igarapé Espírito Santo (3°46’S, 49°41’W) .

Figures

Fig. 9. Triportheus trifurcatus, MZUSP 19633, 165 mm SL, Brazil, Mato Grosso, rioAraguaia, Santa Terezinha.

Fig. 4. Map of central and northern South America showing geographic distribution of Triportheus rotundatus (circles; asterisk = neotype locality), T. trifurcatus (black squares), T. pictus (triangle; diamond = type-locality) and T. signatus (stars, white square = type-locality) (some symbols represent more than one locality or lot of specimens).