Triportheus signatus (Garman, 1890)

Triportheus signatus (Garman, 1890) View in CoL

( Fig. 12-13; Tab. 4)

Chalcinus angulatus signatus Garman, 1890:4 [original description; type-locality: rio Puty, Therezina, Brazil (rio Potí, tributary of the rio Parnaíba, Terezina municipality, Piauí State, Brazil)]. —Eigenmann, Eigenmann, 1891:58 [listed]. —Miranda Ribeiro, 1941:171 [keys to identification and comments regarding subspecies of C. angulatus ].

Triportheus angulatus signatus . —Fowler, 1941:194 [listed as synonym of Triportheus angulatus ]. —Fowler, 1950:357 [redescription, type-locality: “ Brazil, rio Itapicura”].

Triportheus signatus . — Portugal, 1990:159–65 [redescription, illustration, and distribution]. —Lima et al., 2003:158 [list]. —Malabarba, 2004:193–94 [redescription and distribution]. —Buckup et al., 2007:44 [listed from Brazil]. —Nakagawa, 2011:57–61 [comments regarding distribution and morphology]. —Ramos et al., 2014:4 [list from rio Parnaíba basin, Brazil]. —Mariguela et al., 2016:132 [phylogenetic relationships]. —Melo et al., 2016:376 [list from lower rio Parnaíba basin, with discussions regarding occurrence of the species in Northeastern Brazil]. —Reis et al., 2020:463 [list from Paraná State, Brazil, invasive within upper rio Paraná basin]. —Silva et al., 2020:9 [list from Bahia State, Brazil]. —Koerber et al., 2022:32 [list from Maranhão State, Brazil]. —Toledo-Piza et al., 2024:437 [list]. —Dagosta et al., 2024:81 [listed as introduced in the upper rio Paraná basin].

Diagnosis. Triportheus signatus differs from its congeners by the following combination of characters: two normal scales between the insertion of the pectoral fin and the ventral keel (vs. one elongated scale between the origin of the pectoral fin and the ventral keel in T. albus , T. auritus , T. brachipomus , T. culter , and T. magdalenae ); 35–44 gill rakers (mode = 39, n = 9) on the lower branch of the first branchial arch (vs. 24–32 gill rakers in T. rotundatus , 52–57 in T. guentheri , 22–24 in T. pictus , 23–28 in T. curtus , 26–33 in T. pantanensis , 24–28 in T. orinocensis , 27–33 in T. venezuelensis , and 24–29 in T. claudiae ); perforated scales on the lateral line: 34–38 (mode = 36, n = 12) (vs. 30–33 in T. guentheri , 30–32 in T. pictus and 28–32 in T. pantanensis ); scales distributed in a regular series on predorsal line (vs. predorsal scales disposed irregularly, not in series, in T. angulatus , T. rotundatus , T. nematurus , T. guentheri , T. curtus , T. pantanensis , T. orinocensis , and T. venezuelensis ); six scales above the lateral line (vs. 5 scales above the lateral line in T. trifurcatus ); 22–23 epipleural bones (vs. 21 in T. nematurus , 16–17 in T. pantanensis , and 20–21 in T. claudiae ), 5 ventral tubules in laterossensorial canal of the preopercule (vs. 7 in T. pantanensis and T. claudiae ).

Description. Morphometric and meristic data in Tab. 4. Other characters and color in alcohol in Malabarba (2004). Total vertebrae: 36(3) or 37(1); precaudal vertebrae: 17(4). Hemal arch and canal in the 15 th or 16 th caudal vertebrae. Caudal vertebrae, 19(3) or 20(1); 37(1) or 38(3) epineural bones; first to 22 nd epineural bones branched in ventral region; epipleural bones 22(3) or 23(1); first epipleural unbranched; second to nineth epipleural branched in dorsal portion; 10 th to 16 th, or 17 th epipleural unbranched. Number of supraneurals: nine (4). Upper procurrent rays: 9(1) or 10(3); lower procurrent rays: eight (4).

Coloration in life. Overall silvery coloration, darker dorsally. Dorsal-middle region of body with greenish or yellowish tones. Scattered melanophores on dorsal portion of head, as in premaxilla, frontal, supraorbital, infraorbitals 4, 5 and 6, parietal and opercle. Melanophores concentrated in proximal and central field of scales, forming four to seven longitudinal fainted black longitudinal stripes on dorsolateral portion of body, above lateral line. Lateral stripes converge on caudal peduncle as a single large stripe, which follow medial rays of caudal fin, black in all extension.

Sexual dimorphism and ontogenetic variations. No secondary sexual dimorphism characters were found in Triportheus signatus , including variation in size of females and males. Species present differences in caudal fin form in small and large specimens, similar to identified to all the other Triportheus species of rios Paraná-Paraguai basin. In small individuals (smaller than 50 mm), caudal fin bifurcated, without elongated medial rays; in large individuals, caudal fin truncated, with elongated medial rays.

Geographical distribution. Chalcinus angulatus signatus (= Triportheus signatus ) was described by Garman (1890) with the type-locality in “rio Puty, Therezina”, refering to the rio Potí, a tributary from the rio Parnaíba, in Teresina city, Piauí State, Brazil. The species occurs naturally within the rio Parnaíba basin and other coastal river basins from the Northeast region of Brazil. Triportheus signatus has also been identified within the upper rio Paraná basin tributaries, mainly in the rio Tietê basin ( Fig. 13) since 1990 and it is an invasive species in this river basin.

Ecological notes. Data about the natural history of Triportheus signatus are scarce. According to Höfling et al. (2000), the species is generalist, mainly found in environments associated to aquatic macrophytes, with high heterogeneity of habitats. In situations of hypoxia on their natural distribution, they develop lip extensions, called as barbels, which aid surface respiration (Barros-Neto et al., 2019). However, none of the examined specimens in the rio Paraná basin presented barbels. In the upper rio Paraná basin, it occurs mainly in reservoirs with the rios Tietê and Paranapanema basins (Höfling et al., 2000; Nakagawa, 2011; Mariguela et al., 2016). It has an omnivorous or insectivorous diet and feeds on larvae and pupae of aquatic insects, fragments of terrestrial insects, crustaceans, seeds, and fragments of superior terrestrial plants (Höfling et al., 2000; Mendes et al., 2011; Oliveira et al., 2019). According to Höfling et al. (2000), this species is most abundant in the hot and rainy season, between October and April, when they reproduce .

Remarks. Triportheus signatus occurs naturally in the rio Parnaíba basin and other coastal river basins of the Northeast region of Brazil. The occurrence of this species in the upper rio Paraná basin is probably a consequence of an introduction, which is supported by the sampling locations, which are always near to hydroelectric reservoirs,

and by the restocking program conducted by energy company of São Paulo State,

which begin in 1974 and includes the silver croaker Plagioscion squamosissimus (Heckel,

1840) as well other species considered as prey for the establishment of this predator (e.g.,

Triportheus signatus and two species of freshwater shrimp) (Queiroz-Sousa et al., 2018).

The first citations of this species in the Tietê and Paranapanema basins were made by

Portugal (1990) in their unpublished master’s thesis. Published records of T. signatus in the upper rio Paraná basin date from the early 2000ʼs (Silvano, Begossi, 2001; Buckup et al., 2007). However, specimens deposited at the DZSJRP and MZUSP indicate that the introduction of this species is even older and corroborates that this species was introduced in the region in 1970’s–1980’s (e.g., MZUSP 37221, collected in 1987; DZSJRP 625, collected in 1988, both in rio Tietê). Currently, T. signatus is known to inhabit the upper rio Paraná basin within the rios Tietê, Paranapanema and the “Canal de Pereira Barreto”, which connects the rios Tietê and São José dos Dourados. The lots of T. signatus which were collected in the 1980ʼs and 1990ʼs in the upper rio Paraná basin (e.g., DZSJRP 625, DZSJRP 3248, and MZUSP 37221) were mistakenly identified as T. angulatus , T. paranensis (= T. nematurus ), T. nematurus , or just Triportheus sp.

Material examined. Brazil: Ceará State: rio Salgado: MNRJ 44325, 2, 73.7– 90.7 mm SL. Paraíba State: UFRGS 20345, 2, 138.5–144.0 mm SL. Paraná State: rio Paranapanema basin: MZUEL 2485, 2, 144.1– 174.2 mm SL. MZUEL 2864, 1, 88.0 mm SL. Piauí State: rio Parnaíba basin: MNRJ 29130, 2, 58.2–60.8 mm SL. MNRJ 43204, 2, 61.6–66.4 mm SL. São Paulo State: rio Tietê basin: CITL 423, 13 (4 c&s), 49.2–57.8 mm SL. DZSJRP 625, 1, 122.7 mm SL. DZSJRP 3248, 1, 103.0 mm SL. DZSJRP 17731, 2, 100.8– 117.3 mm SL. MZUEL 5667, 1, 133.1 mm SL. MZUSP 37221, 9, 135.3– 157.8 mm SL. MZUSP 53890, 3, 84.4–148.5 mm SL. NUP 2678, 1, 195.3 mm SL. NUP 16530, 2, 175.0– 186.8 mm SL.