Triportheus pantanensis Malabarba, 2004

Triportheus pantanensis Malabarba, 2004 View in CoL

( Figs. 9–10; Tab. 3)

Triportheus pantanensis Malabarba, 2004:197 [original description; type-locality: Transpantaneira road, pond below bridge, 70 km South of Poconé, Mato Grosso, Brazil]. —Buckup et al., 2007:44 [listed from Brazil]. —Mirande, 2010:485 [phylogenetic relationships]. —Nakagawa, 2011:49 [comments about distribution, taxonomy, and study of cephalic musculature]. —Mariguela et al., 2016:134 [phylogenetic relationships]. —Koerber et al., 2017:27 [list from Paraguay]. —Lopes et al., 2022:247 [illustrated guide and key to identification]. —Toledo-Piza et al., 2024:437 [list].

Triportheus nematurus (non Kner 1858). — Portugal, 1990:166 [misidentification, redescription]. —Malabarba, 1998:76 [phylogenetic relationships within Triportheus and Lignobrycon ]. —Britski et al., 1999:29 [listed and key to identification]. —Lima et al., 2003:158 [listed]. —Britski et al., 2007:44 [listed and key to identification].

Diagnosis. Triportheus pantanensis differs from its congeners by the following combination of characters: two non-elongated scales between the insertion of the pectoral fin and ventral keel (vs. one elongated scale between the origin of the pectoral fin and ventral keel in T. albus , T. auritus , T. brachipomus , T. culter , and T. magdalenae ); 26–33 (mode = 28, n = 19) gill rakers on the lower branch of first branchial arch (vs. 40–47 in T. trifurcatus , 38–48 in T. nematurus , 52–57 in T. guentheri , 22–24 in T. pictus , 35–44 in T. signatus ); perforated scales on the lateral line: 28–32 (mode = 31, n = 29) (vs. 34–37 in T. angulatus , 33–37 in T. nematurus , 34–37 in T. signatus , 34–39 in T. orinocensis , and 33–36 in T. venezuelensis ); three rows of cuspid teeth on the premaxilla (vs. two rows of cuspid teeth in T. curtus and T. pictus ); scales of the predorsal series irregularly disposed (vs. scales of the predorsal series regularly disposed in T. trifurcatus , T. signatus , T. pictus , and T. claudiae ); six scale series on the lateral of caudal peduncle (vs. five in T. angulatus , T. curtus , and T. orinocensis , four or five in T. guentheri , T. rotundatus , T. trifurcatus , and T. venezuelensis ); epineural bones, 34–35 (vs. 36–37 in T. nematurus ); epipleural bones: 16–17 (vs. 21 in T. nematurus , 22–23 in T. signatus , and 20–21 in T. claudiae ); number of supraneurals: 10 (vs. nine in T. nematurus and T. signatus ); seven ventral tubules in the laterossensorial canal of the preopercule (vs. 4–5 in T. nematurus and 5 in T. signatus ).

Description. Morphometric and meristic data in Tab. 3. Other characters and color in alcohol in Malabarba (2004). Total vertebrae: 36(1) or 37(3); precaudal vertebrae: 17(4). Caudal vertebrae: 18(1) or 19(3); 34(2) or 35(2) epineural bones; first to 25 th or 26 th epineural bones branched in ventral region; 27 th to 34 th or 35 th epineural bone unbranched; epipleural bones 18(3) or 19(1); first epipleural unbranched; second to nineth epipleural branched in dorsal portion; 10 th to 16 th or 17 th epipleural unbranched. Supraneurals: 10(4). Upper procurrent rays: 8(1) or 9(3); lower procurrent rays: six (4).

Coloration in life. Overall coloration silvery, darker dorsally. Dorsal-middle region of body with greenish or yellowish tones. Scattered or concentrated melanophores on proximal field of scales, forming five or six longitudinal black fainted stripes on dorsolateral portion of body, above lateral line. Fins mostly hyaline, with scattered melanophores. First five pectoral-fin rays darker, with concentrated melanophores. Medial rays of caudal fin, black in all extension. Some individuals with conspicuous melanophores in first dorsal and anal fin rays ( Fig. 10). Small individuals with high concentration of melanophores in dorsal and pectoral fins and a black stripe on base of anal fin; in adults, fins hyaline, with scattered chromatophores and black stripe on base of anal-fin inconspicuous or absent.

Sexual dimorphism and ontogenetic variations. No characteristics of secondary sexual dimorphism were found in Triportheus pantanensis , including variations in size. This species presents differences in caudal fin form and coloration pattern between large and small individuals. In small individuals (smaller than 50 mm SL) the caudal fin is bifurcated, without elongated medial rays; in adults’ caudal fin is emarginated, with elongated medial rays.

Geographical distribution. Triportheus pantanensis presents a wide distribution within the floodplain of the rio Paraguai basin ( Fig. 11) and in the lower rio Paraná basin, including rivers from Argentina (Mirande, Koerber, 2015) and Paraguay (Koerber et al., 2017).

Ecological notes. Triportheus pantanensis occurs in lentic and lotic environments (Súarez et al., 2013; Polaz et al., 2014; Severo-Neto et al., 2015), including reservoirs (Corrêa et al., 2009). Omnivorous, with tendencies to insectivory or herbivory, depending on the dynamics of the hydrological periods (Corrêa et al., 2009). Despite the issue that its effectiveness as a seed disperser has not been tested, it is a known fact that this species consumes small fruits (Costa-Pereira et al., 2011), therefore we can assume that it possibly plays an interactive biological role in the dispersion of seeds. There is no information on the reproductive biology to this species.

Material examined. Brazil: Mato Grosso State: rio Paraguai basin: MCP 35006 View Materials , 1 View Materials , 97.1 mm SL, holotype. MCP 10733 View Materials , 3 View Materials , 88.3–88.7 mm SL, paratypes. MCP 10751 View Materials , 3 View Materials , 77.5–78.3 mm SL, paratypes. MCP 15741 View Materials , 1 View Materials , 88.5 mm SL, paratype. MCP 35824 View Materials , 4 View Materials , 65.9–78.5 mm SL, paratypes. MCP 11119 View Materials , 1 View Materials , 99.1 mm SL. MCP 38829 View Materials , 1 View Materials , 58.8 mm SL .

MZUSP 38106, 2, 40.4–59.1 mm SL. NUP 888, 2, 112.4– 116.7 mm SL. NUP 3136, 3, 87.8–105.1 mm SL. NUP 6945, 1, 84.7 mm SL. NUP 7053, 1, 76.3 mm SL. Mato Grosso do Sul State: rio Paraguai basin: CITL 1136, 4 (c&s) of 17, 52.5–69.1 mm SL. CPUEMS not catalogued p.24, 1, 41.8 mm SL. CPUEMS not catalogued p.84, 2, 42.5– 44.0 mm SL. CPUEMS not catalogued p.89, 1, 64.1 mm SL. CPUEMS not catalogued p.90, 2, 63.1–70.2 mm SL. MZUEL 12268, 2, 68.3–74.7 mm SL. MZUSP 49968, 1, 50.2 mm SL. MZUSP 59827, 2, 46.7–56.6 mm SL. NUP 12552, 2, 18.9–31.0 mm SL. ZUFMS 857, 1, 51.2 mm SL. ZUFMS 858, 1, 58.9 mm SL. ZUFMS 859, 1, 75.2 mm SL. ZUFMS 880, 2, 45.1–51.0 mm SL. ZUFMS 1055, 8, 68.2–94.3 mm SL. ZUFMS 1525, 3, 65.5–65.8 mm SL. ZUFMS 3723, 3, 84.9–95.5 mm SL. ZUFMS 3886, 7, 67.7– 86.9 mm SL. ZUFMS 5716, 5, 65.6–103.4 mm SL. ZUFMS 5729, 2, 62.3–64.2 mm SL. Paraguay: Alto Paraguay Department: Río Paraguay basin: MZUSP 54144, 1, 58.6 mm SL. MZUSP 54146, 2, 52.9–55.0 mm SL. MZUSP 54147, 2, 60.4–66.9 mm SL. MZUSP 54148, 2, 64.2–70.8 mm SL.