Triportheus pantanensis, Malabarba, 2004

Malabarba, Maria Claudia S. L., 2004, Revision of the Neotropical genus Triportheus Cope, 1872 (Characiformes: Characidae), Neotropical Ichthyology 2 (4), pp. 167-204 : 197-198

Triportheus pantanensis , new species

Fig. 24

Triportheus nematurus . Portugal, 1990:166. Britski et al., 1999:29.

Holotype. Triportheus pantanensis, MCP 35006, 99.5 mm SL, rio Paraguay, pond under bridge along Transpantaneira road, 70 km S of Poconé, L. R. Malabarba & R. E. Reis, 9 Feb 1986 (16°51’S, 56°50’W).

Paratypes. Brazil: Mato Grosso: MCP 10751 (6, 77- 84.7 mm SL), rio Paraguay, pond under bridge along Transpantaneira road, 70 km S of Poconé, L. R. Malabarba & R. E. Reis, 9 Feb 1986 (16°51’S, 56°50’W) ; MCP 10733 (3, 92.7-94.5 mm SL), rio Pixaim on Porto de Pixaim, 60 km from Poconé , L. R. Malabarba & R. E. Reis, 9 Feb 1986 (16°45’S, 56°51’W) ; MCP 15741 (1, 88.6 mm SL), stream in Porto Estrada, on road to Barra do Bugres- Cáceres 35 km S from Barra do Bugres , R. E.Reis,L. R. Malabarba & N. A. Menezes, 11 Aug 1991 (15º24’S, 57º15’W) ; MCP 35824 (4, 68.3-81.5 mm SL), rio Paraguay in Cáceres and vicinity, R. E. Reis, L. R. Malabarba & N. A. Menezes, 11 Aug 1991 (16°4’S, 57°41’W) ; MZUSP 27187 (2, 89,5- 111.8 mm S) L, Taiamã, río Paraguay, A. S. Soares, 01-07 Dec 1980 (18°28’S, 55°40’W) . Paraguay: Presidente Hayes: NRM 31456 (11, 77.9-125.8 mm SL), Estancia La Rural, río Confuso , S. O. Kullander et al., 15 Oct 1994 (24º50’S, 57º46’W) ; USNM 181682 (2, 107- 117.5 mm SL) , Asuncion Bay , río Paraguay, near Asuncion, C. J. D. Brown, 10 Jan 1957 (25°15’S, 57°40’W) ; USNM 181689 (2, 137.2- 158 mm SL), lago Ypacaray near San Bernardino, C. J. D. Brown, 11 Oct 1956 (25°28’S, 57°33’W) .

Diagnosis. A deep-bodied Triportheus species reaching 158 mm SL (depth at dorsal-fin origin, 34.6-42.5, mean = 38.6% SL, n = 32; depth at pectoral-fin insertion, 30.7-42.8, mean = 38.4% SL, n = 32). The presence of 2 longitudinal scale rows between the pectoral-fin insertion and the ventral keel distinguishes 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. pantanensis differs from its congeners by the combination of few gill rakers on the lower limb of the first gill arch (26-33, mean = 29.1, n = 29); the lateral-line scales counts (28-33, mean = 31.1, n = 32), the bony head length (22.5-27.3 of SL, mean = 25.1), the snout to anal-fin origin distance (66.4-74.1, mean = 70.2), the length of anal-fin base (25.5-31.0, mean = 28.1), and the possession of median caudal-fin rays that extend well beyond the caudal-fin margin.

Description. Morphometric data for Triportheus pantanensis presented in Table 16. Body deep and compressed laterally. Greatest body depth located slightly posterior to vertical through pectoral-fin insertion. Dorsal profile of head straight from margin of snout to rear of head. Dorsal profile of body gently convex from rear of head to dorsal-fin origin; posteroventrally slanted from dorsal-fin origin to caudal peduncle; and slightly concave along caudal peduncle.

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

Head blunt in profile; posterior margin of opercle falling short of vertical through 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, length equivalent to one-half length of branchial filament; gill rakers on lower limb of first gill arch 26-33 [30] (mean = 29.1, n = 29).

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

Scales cycloid, thin, and large. Lateral line distinctly decurved ventrally, completely pored from supracleithrum to base of caudal-fin rays. Scales in lateral line 28-33 [30] (mean = 31.1, n = 32); 6 scale series above lateral line; 2-3 scale rows below lateral line. Two scale rows between pectoralfin insertion and midventral keel; 5-6 scale series on caudal peduncle. Scales along mid-dorsal line very irregular, 6-13 (mean = 10.2, n = 29) scales from supraoccipital process to dorsal-fin origin.

Dorsal-fin rays ii,9; anal-fin rays iii,25-30 [29] (mean = 27.9, n = 31); pectoral-fin rays i,10-12 [12]; pelvic-fin rays i,6. Dorsal-fin distal margin straight. Dorsal fin situated on posterior one-half of body. Last dorsal-fin ray located at vertical through base of third or fourth anal-fin ray; first branched ray longest; following rays gradually decreasing in length. Pectoral fin pointed, with tip reaching vertical through distal one-third 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 extending one-half of their length beyond margin of remainder of fin. Scales cover basal onethird of caudal fin.

Total vertebrae 36-37.

Coloration in alcohol. Overall ground color yellowish and overlain in areas by guanine. Snout and dorsal portions of head dark. Scattered dark chromatophores present on opercle and infraorbitals 5 and 6. Body darker dorsally and above anal-fin base and on caudal peduncle. Five or 6 longitudinal brown stripes present on dorsolateral portion of body. Dorsal-fin rays outlined by dark chromatophores. Chromatophores distributed over pectoral-fin membranes, with more intense pigmentation on first unbranched ray. Anal-fin margin darkened. Middle caudalfin rays very dark.

Remarks. This species was previously erroneously referred to as Chalcinus nematurus or Triportheus nematurus by Ribeiro (1941), Fowler (1975), Portugal (1990), and Britski et al. (1999). Triportheus nematurus , however, is a distinct species. See remarks under Triportheus nematurus .

Distribution. Río Paraguay and lower rio Paraná basins ( Fig. 23 ).

Etymology. The species name, pantanensis , refers to the Pantanal de Mato Grosso, region where the new species commonly occurs and should be considered in apposition to the genus name.

Figures

Fig. 24. Triportheus pantanensis, holotype, MCP 35006, 99.5 mm SL, Brazil, Mato Grosso, pond under bridge along Transpantaneira road, 70 km S of Poconé.

Fig. 23. Map of central and northern South America showing geographic distribution of Triportheus magdalenae (circles; asterisk = type locality), T. pantanensis (black squares; white square = type locality) and T. orinocensis n. sp. (triangles; white diamond = type locality) (some symbols represent more than one locality or lot of specimens).