Steindachnerina conspersa (Holmberg 1891)

Steindachnerina conspersa (Holmberg, 1891)

Curimatus conspersus Holmberg, 1891:185 [type locality: Argentina: Formosa, Río Paraguay].—Eigenmann, 1910:421 [reference].—Bertoni, 1914:9 [Paraguay, ? based on Holmberg, 1891].—Vari, 1989a, tables 2, 3 [assignment to Steindachnerina].

Curimatus bimaculalus.—Boulenger, 1900:2 [Mato Grosso].—Eigenmann and Kennedy, 1903:511 [Paraguay: Estancia La Armonia, Arroyo Tremintina, Asuncion].—Eigenmann, McAtee and Ward, 1907:124 [Paraguay: Columba].—Eigenmann and Ogle, 1907:3 [Paraguay].—Eigenmann, 1910:421 [reference in part; Paraguay basin citations].—Bertoni, 1914:9 [? based on Eigenmann, McAtee, and Ward, 1907].

Curimata conspersa.—Pearson, 1937:109 [Río Paraguay basin, based on Holmberg, 1891].—Bertoni, 1939:54 [Paraguay, ? based on Holmberg, 1891].—Fowler, 1950:281 [literature compilation].—Ringuelet and Aramburu, 1961:36 [Argentina, based on Holmberg, 1891].—Fowler, 1975:368 [reference].—Ringuelet, 1975:72 [Río Paraguay, based on Holmberg, 1891].—[not Géry et al, 1987:427].

Curimata bimaculatus.—Pearson, 1937:109 [in part, Paraguay basin citations].

Curimata bimaculata.—Bertoni, 1939:54 [Paraguay, based on Eigenmann and Kennedy, 1903].—Géry et al., 1987:424, fig. 40 [Paraguay, Río Paraguay and Río Paraná systems; Brazil, Río Cuiaba].

Cruxentina bimaculata.—Fernández-Yépez, 1948:53 [in part. Alto Rio Paraná citations].

Curimata bimaculata bimaculata.—Fowler, 1950:278 [references in part, Río de La Plata basin citations; not Amazon basin references].—Ringuelet and Aramburu, 1961:36 [Argentina].—Lopez et al., 1987:19 [Argentina].

Pseudocurimata bimaculata.—Aramburu, Aramburu, and Ringuelet, 1962:227 [Argentina].—Ringuelet, 1975:61 [in part, Río de La Plata system references; not Amazon basin citations].—Bonetto et al., 1978:17 [Argentina: Río Riachulo basin. Lagunas Totoras and Gonzalez].— Pignalberi de Hassan and Cordiviola de Yuan, 1985:21 [Argentina: middle Río Paraná, Corrientes and Santa Fe areas].—Cordiviola de Yuan and Pignalberi de Hassan, 1985:215 [Argentina: lower Río Paraná, Diamante and San Pedro areas].

Pseudocurimata bimaculata bimaculata.—Ringuelet, Aramburu, and Aramburu, 1967:198 [Argentina].—Bonetto et al., 1978:57 [Argentina: Río Riachulo basin, Laguna La Brava].—Azpelicueta, 1980:85 [osteological observations].

Rivasella conspersa.—Ringuelet, Aramburu, and Aramburu, 1967:202 [Argentina, based on Holmberg, 1891].—Lopez et al., 1987:20 [possible assignment to Rivasella; Argentina].

Steindachnerina conspersa, Venere and Galetti, 1989:19, 21, fig. 1 [Brazil: Mato Grosso do Sul, Columbá, Rio Paraguai; karyotype information].

DIAGNOSIS.—The presence of three weakly developed longitudinal folds on the roof of the oral cavity rather than three very fleshy flaps and/or one or more series of tabulate fleshy processes in that region discriminates Steindachnerina conspersa from its congeners with the exception of S. binotata, S. leucisca, S. argentea, and S. bimaculata. The 38 to 43 scales along the lateral line from the supracleithrum to the hypural joint separate S. conspersa from S. bimaculata, S. binotata, and S. leucisca, which have 43 or more scales along the lateral line, and from S. argentea, which has 36 or fewer scales in that series. Steindachnerina conspersa is most similar to its allopatric congener S. bimaculata of the Amazon and Orinoco basins. In addition to differing in the number of scales in a series along the lateral line, the species differ in details of pigmentation. Steindachnerina bimaculata typically has a series of small dark spots on the dorsal and dorsolateral surfaces of the body, with the pigmentation around the base of the dorsal fin of the same overall intensity as in proximate portions of the body. Specimens of S. conspersa, in contrast, lack the small dark spots on the body and typically have the region proximate to the base of the dorsal fin much lighter than neighboring regions of the body.

DESCRIPTION.—Body moderately elongate, somewhat compressed, less so in large specimens. Dorsal profile of head straight or very slightly concave. Dorsal profile of body smoothly curved from rear of head to origin of dorsal fin, somewhat more convex with increasing size; straight and posteroventrally slanted at base of dorsal fin, straight or very slightly convex from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with discrete median keel anterior to dorsal fin, keel more distinct posteriorly; surface of body smoothly rounded transversely posterior to fin. Ventral profile of body straight from tip of lower jaw to vertical line through origin of pectoral fin, gently curved from that point to origin of anal fin, sigmoid from origin of anal fin to caudal peduncle. Prepelvic region obtusely flattened, with rounded lateral keels; keels more distinct proximate to origin of pelvic fin. Obtuse median keel posterior to pelvic-fin origin. Secondary obtuse keel on each side of postpelvic portion of body, about two scales dorsal of ventral midline.

Greatest depth of body 0.35–0.41; snout tip to origin of dorsal fin 0.46–0.52; snout tip to origin of anal fin 0.80–0.87; snout tip to origin of pelvic fin 0.51–0.55; snout tip to anus 0.75–0.81; origin of dorsal fin to hypural joint 0.58–0.61. Border of dorsal fin pointed, less so with increasing age; anteriormost rays approximately three times length of ultimate ray. Pectoral-fin profile acute; length of pectoral fin 0.18–0.23, extends about three-quarters of distance to origin of pelvic fin. Pelvic-fin profile acute, length of pelvic fin 0.24–0.28, reaches about three-quarters of distance to origin of anal fin. Caudal fin forked. Adipose dorsal fin well developed, unsealed. Border of anal fin distinctly emarginate, anteriormost branched rays over three times length of ultimate ray; tips of depressed anterior rays contacting lower lobe of caudal fin. Caudal peduncle depth 0.14–0.15.

Head distinctly pointed in profile, head length 0.27–0.32; upper jaw slightly longer; mouth subterminal; portion of buccopharyngeal complex on roof or oral cavity consisting of three weakly developed folds without fleshy lobulate bodies; snout length 0.28–0.33; nostrils very close, anterior circular, posterior crescent-shaped, with aperture closed by thin flap of skin separating nares; orbital diameter 0.30–0.36; adipose eyelid present, with broad vertically ovoid opening over center of eye; length of postorbital portion of head 0.38–0.44; gape width 0.30–0.35; interorbital width 0.44–0.49.

Pored lateral-line scales to hypural joint 38 to 43; all scales of lateral line pored, canals in scales straight; 3 to 5 series of scales extend beyond hypural joint onto caudal-fin base; 7½ to 8½ scales in transverse series from origin of dorsal fin to lateral line; 5½ to 6½ scales in transverse series from lateral line to origin of anal fin.

Dorsal-fin rays ii,9 or iii,9 (when three unbranched rays present, first very small); anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very small); pectoral-fin rays 13 to 16; pelvic-fin rays i,8 or i,9.

Total vertebrae 33 (18), 34 (27).

COLOR IN ALCOHOL.—Specimens retaining guanine on scales silvery, darker on dorsal portions of head and body. Overall ground coloration of specimens fixed in formalin and lacking guanine on scales yellowish tan to brown, darker on dorsal portions of head and body. Dorsal portion of body proximate to base of dorsal fin typically slightly (Figure 21) to markedly (Figure 22) less pigmented than adjoining areas or body. Faint, narrow, deep-lying, dusky band extends along mid-lateral surface of body from supracleithrum to caudal peduncle. Distinct, transversely elongate spot of dark pigmentation situated along dorsal midline immediately anterior of dorsal fin. Second, less distinct, longitudinally elongate mid-dorsal spot of pigmentation immediately posterior of tip of supraoccipital spine. Dorsal fin typically with spot of dark pigmentation near base of middle fin-rays and their membranes (Figure 21); spot more pronounced in smaller individuals; sometimes very faint (Figure 22). Anterior and distal portions of dorsal fin dusky. Distinct spot of dark pigmentation at base of middle rays of caudal fin. Lower lobe of caudal fin dusky. Ventral and distal portions of anal fin dusky.

DISTRIBUTION.—Río Paraguay and lower Río Paraná systems (Figure 23).

KARYOTYPE.—Venere and Galetti (1989:19) report that Steindachnerina conspersa has 2n = 54 chromosome consisting exclusively of metacentric and submetacentric chromosomes.

MATERIAL EXAMINED.—132 specimens (53, 45.3–128.1).

BRAZIL. Mato Grosso: Fazenda Jofre, Rodovia Transpantaneira, MZUSP 26915, 1. Santo Antônio de Leverger, MZUSP 21578, 1. Rio Pixaim, Municipio de Poconè, MZUSP 21589, 1. Munícipio de Barăo de Malgaço, MZUSP 21661, 1; MZUSP 21687, 1. Rio Cuiabá, Sangradouro Grande, Municipio de Barăo de Melgaço, MZUSP 21599, 2 (53.9–66.5). Rio Jaurú, Porto Esperidião, MZUSP 28103, 6 (5, 99.5–103.2). Mato Grosso do Sul: Rio Miranda, Munícipio de Corumbá, MZUSP 21676, 12 (6, 83.7–104.2). Rio Miranda, Salobra, MNRJ 8898, 2 (1, 100.1). Corumbá, MZUSP 21676, 12. Carandasinho (= Carandazinho), BMNH 1900.4.14:40–41, 2 (45.3–58.2).

PARAGUAY. No specific locality, USNM 2107, 2; USNM 55648, 2. Paraguayan Chaco, BMNH 1898.7.4:7, 1 (112.4). Central: Asuncion Bay, USNM 181639, 1 (118.0); USNM 181636, 22 (8, 77.4–102.4); USNM 181638, 8 (5, 66.0–92.3); USNM 181637, 9 (5, 76.5–128.1); USNM 220164, 1 (48.2); USNM 181644, 3 (71.3-102.8); USNM 181641, 1; BMNH 1935.6.4:319–322, 7. Rio Paraguay at Asuncion, AMNH 1297, 2 (99.0–99.4). Vicinity of Asuncion, BMNH 1935.6.4:326–329, 10 (3, 79.0–83.7); BMNH 1935.6.4:319–322, 7. Hatipapunta, NMW 67032, 1. Cordillera: Lago Ypacarai, 17.6 km west of San Bernardino, USNM 232222, 1 (92.6). Presidente Hayes: Trans Chaco Highway, 194 km north of Asuncion, USNM 229442, 1 (62.7); USNM 232223, 2 (54.5–57.4). Trans Chaco Highway, 50 km north of Asuncion, USNM 232224, 4 (69.5–82.3).

ARGENTINA. Río Paraná, USNM 196671, 1.

Uruguay. No specific locality, NMW 67033, 5.