Serrapinnus sterbai Zarske, 2012

Malabarba, Luiz R. & Jerep, Fernando C., 2014, Review of the species of the genus Serrapinnus Malabarba, 1998 (Teleostei: Characidae: Cheirodontinae) from the rio Tocantins-Araguaia basin, with description of three new species, Zootaxa 3847 (1), pp. 57-79 : 67-70

Serrapinnus sterbai Zarske, 2012

Figs. 2e–f , 4c , 5c , 8 , 9

Serrapinnus sterbai Zarske, 2012: 4 (original description; type locality: Araguaya [misspelled locality name Araguaia] - Gebiet, Ostbrasilien(?), Import Firma Glaser, Holotype: UFRJ 8516, 34.1 mm SL [fig. 1 of an alcohol preserved specimen labeled as the holotype is actually one paratype, male, from MTD F 32658-32664 ; figs. 3 and 4 of a radiographed specimen and a live specimen in aquarium correspond to the holotype UFRJ 8516. See Remarks below]).

Diagnosis. Serrapinnus sterbai is distinguished from all congeners by the presence of a wide, black, lateral stripe extending from the region of the supracleithrum to the dark spot on the caudal peduncle ( Fig. 8 ).

Description. Morphometric data in Table 3 . Body short and compressed. Greatest body depth at dorsal-fin origin. Snout slightly rounded to pointed. Dorsal profile of head gently convex from tip of snout to vertical through anterior nares, slightly convex from that point to anterior portion of supraoccipital bone, with posterior region of supraoccipital spine slightly concave. Predorsal profile slightly convex between tip of supraoccipital spine and dorsal-fin origin, slightly convex to straight along dorsal-fin base, straight to slightly convex from last dorsal-fin ray insertion to caudal-fin origin, but ventrally arched in mature males. Ventral profile convex from mouth opening to isthmus, convex from that point to pelvic-fin origin, then straight until vertical through anal-fin origin in immatures and females and slightly concave in mature males. Anal-fin base straight to slightly concave in immatures and females, but distinctively convex along anterior portion and ventrally arched along posterior portion in mature males. Caudal peduncle slightly longer than deep. Dorsal and ventral profiles of caudal-peduncle straight to lightly concave in immatures and females, but dorsal profile ventrally arched and ventral profile distinctly convex due to ventral procurrent caudal-fin rays hypertrophy in mature males ( Fig. 2e , 8 ). Head relatively small. Posterior margin of opercle sinusoidal with upper portion concave and lower portion convex. Mouth terminal, mouth slit just above horizontal through middle of pupil. Maxilla angled posteroventrally, posterior tip reaching vertical close to anterior border of orbit and horizontal through ventral border of orbit. All teeth pedunculated, distally expanded and similar in shape ( Fig. 9 ). Premaxillary teeth 4(2) or 5(2) with 9 or 11 cusps, lateralmost tooth rarely with 5 cusps; central cusp longer and wider than other cusps. Two (4) maxillary teeth with 7 cusps; a third conical tooth in one specimen. Large anterior dentary teeth 5(3) or 6(1) with 7 cusps; these followed by 1(2) or 2(2) teeth with 3 or 5 cusps. Smaller cusps of dentary teeth overlapping adjacent tooth cusps. All dentary tooth cusps pointed dorsally or slightly curved towards interior of mouth.

Dorsal-fin rays ii,9(30). Dorsal-fin origin at midlength of SL. First unbranched dorsal-fin ray about one-half length of second unbranched dorsal-fin ray; following branched rays decreasing in size posteriorly. Adipose-fin origin slightly posterior to or along vertical through base of last anal-fin ray. Anal-fin rays iii–iv,16(1), 17(3), 18(8), 19(17) or 21(1). First unbranched anal-fin ray only observable in cleared and stained specimens. Distal border of anal-fin concave; last unbranched and 5–6 anterior branched rays longest; remaining rays decreasing in size posteriorly. Tip of depressed anterior anal-fin rays of mature males laterally overlapping last anal-fin rays; sometimes reaching ventral procurrent caudal-fin rays in arched caudal peduncle. Anal-fin origin posterior to vertical through insertion of last dorsal-fin ray. Males with acute, elongate, retrorse hooks on anal-fin rays; hooks posterolaterally arranged on last unbranched to 7 th or 8 th branched rays ( Fig. 4c ). Two or three unpaired hooks per lepidotrichia segment on each contralateral half of ray. Hooks distributed along distal half of anal-fin rays on posterior and rarely anterior margins of rays. Rays segments and branches bearing hooks progressively fused during maturation. Mature males with hypertrophied soft tissue on interradial membrane anterior to hook bearing anal-fin rays. Pectoral-fin rays i,9(18), 10(11) or 11(1). Tip of pectoral fin reaching pelvic-fin origin in immature and females; extending beyond that point in mature males. Pelvic-fin rays i,7(30). Pelvic-fin origin anterior to vertical through dorsal-fin origin. Longest pelvic-fin ray not reaching anal-fin origin in immature and females, but extending beyond that point in mature males. Males with one or two acute elongate hooks per lepidotrichia segment of all pelvic-fin rays; hooks ventral-medially aligned. Mature males with hypertrophied soft tissue on interradial membrane anterior to hooks and ventral surface of pelvic fin. Principal caudal-fin rays 19(29) or 20(1). Procurrent caudal-fin rays: dorsal 12(3) or 13(1); ventral 15(3) or 17(1). Mature males with ventral procurrent caudal-fin rays hypertrophied and contralateral elements fused; rays extending beyond ventral caudal-peduncle muscles and skin. Hypertrophied ventral procurrent rays rod-shaped, sometimes fused, anteriorly bent along their axes, proximally acute, slight expanded distally and ending in rounded to flat distal tip ( Fig. 2e ).

Scales cycloid, similar in size over all body. Lateral line partially pored with 7(3), 8(9), 9(15), 10(3) pored scales, or rarely completely pored (MZUSP 83894, 83971). Scales in lateral-line series 31(4), 32(8), 33(10), 34(7) or 35(1). Predorsal scales in regular row 9(17), 10(10) or 11(3). Scale rows between lateral line and dorsal-fin origin 5(21) or 6(9). Scale rows between lateral line and pelvic-fin origin 4(30). Scale rows around caudal peduncle 12(1), 13(10) or 14(19). Axillary scale on pelvic fin base extends posteriorly over 1–2 scales. Scales along anal-fin base 9(1), 10(10), 11(8), 12(7), 13(3) or 15(1).

Counts based on four clear and stained specimens: Supraneurals 3(1) or 4(3); abdominal vertebrae 15(2) or 16(2); caudal vertebrae 17(2), 18(1) or 19(1).

Color in alcohol. Overall ground coloration of body pale yellow. Dorsal region of head and body with higher concentration of melanophores. Body with longitudinal, midlateral dark stripe extending from posterior margin of opercle to caudal spot. Longitudinal black stripe one or one and half scale wide. Black, horizontally elongated spot at base of caudal fin extending posteriorly until midlength of central caudal-fin rays. Scales above longitudinal line with melanophores primarily along posterior border, resulting in faint reticulated pattern. Abdominal region lightly colored, almost without pigmentation. Dorsal, pectoral and pelvic fins mostly hyaline, with scattered melanophores along fin rays. Adipose fin not pigmented. Caudal fin covered with diffuse melanophores along fin rays, except for clear areas at base of each caudal-fin lobe just posterior of caudal-fin spot. Humeral region with triangular, dark area due to pseudotympanum within muscular hiatus ( Fig. 8 ).

Sexual dimorphism. Sexually mature males have the following dimorphic characters: the presence of hooks on the pelvic and anal-fin rays; the ventrally arched caudal peduncle; the hypertrophied hook bearing anal-fin rays, expanded in the sagittal plane, and sometimes with a fusion of ray segments; the slightly elongate dorsal- and pelvic-fin rays; and the hypertrophied ventral procurrent caudal-fin rays extending ventrally through the musculature and skin ( Figs. 2e–f , 4c , 8 ).

Distribution. Serrapinnus sterbai was described based on aquarium specimens. Zarske (2012) states that the imprecise type locality was the “region of Araguaia, eastern Brazil? (our translation). Our new records extend the distribution of S. sterbai to several tributaries and the main course of the rio Tocantins drainage ( Fig. 5c ).

Remarks. Zarske (2012) figured the holotype, a male specimen, three times in his paper: as a preserved specimen ( Zarske, 2012: fig. 1), as a radiograph ( Zarske, 2012: fig. 3) and as a live specimen in an aquarium ( Zarske, 2012: fig. 4). The three images belong, however, to at least two different specimens, since the shape and profile of the procurrent fin rays in the alcohol preserved specimen is clearly different from that in the radiographed and live specimens. The same seems to occur with the female paratype shown as a preserved specimen in Zarske´s fig. 2 and as a radiograph in his fig. 3, since the body shape and body proportions differ between the figured specimens. The holotype catalogued as UFRJ 8516 was examined and photographed by Fernando R. Carvalho at the Museum für Tierkunde, Dresden. The shape and number of anal fin hooks allowed him to recognize it as the specimen showed in radiograph ( Zarske, 2012: 7, fig. 3), but not as the specimen labeled as holotype in Zarske (2012: 6, fig. 1). Examining the radiograph in Zarske (2012: fig. 3) we observe that the second and longest unbranched ray of dorsal fin is anomalous at its midlength and near the tip of the first unbranched ray of dorsal fin. The same anomaly can be seen in the specimen photographed alive in Zarske (2012: 8, fig. 4). Accordingly, specimens labeled as the holotype in Zarke´s figs. 3 and 4 are actually images of the holotype. The specimen erroneously listed as the holotype in Zarske (2012: fig. 1) is a paratype male of MTD F 32658-32664. The female labeled as the allotypus of fig. 2 in Zarske (2012) also does not correspond to the specimen catalogued as allotype under MTD F 32657, but rather to one of the paratypes at MTD F 32658-32664.

Material examined. All from Brazil, rio Tocantins-Araguaia basin. Goiás State: MZUSP 40375 , 12 , 14.5–20.9 mm SL, rio Macacos, tributary of left margin of rio Paraná, Fazenda Fortaleza, Município de Flores de Goiás. MZUSP 40470 , 4 , 14.2–21.8 mm SL, Poço da Gandaia , marginal pond of rio Paraná, Fazenda Olho d’água, Município de Flores de Goiás. MZUSP 40511 , 13 , 11.4–24.9 mm SL (2 males 24.5–24.9 mm SL, 1 female 22.4 mm SL), pond close to highway GO 236, Município de Flores de Goiás. MZUSP 40518 , 33 , 12.5–22.9 mm SL, tributary of rio Corrente , on highway GO 236, 15 km from Alvorada de Goiás. MZUSP 40701 , 2 , 23.9–26.5 mm SL, rio Bezerra , tributary on left margin of rio Paraná, Município de Flores de Goiás. Tocantins State: MZUSP 40359 , 69 , 22.2–26.7 mm SL, 4c&s, 23.6–25.8 mm SL (13, 22.8–25.7 mm SL), Brazil, Tocantins, Município de Arraias , temporary pond on rio Paraná and rio Bezerra confluence, Tocantins drainage. MZUSP 83894 , 19 of 52, 23.7–34.5 mm SL, Brazil, Tocantins, Porto Alegre do Tocantins, rio Manuel Alves da Natividade , 11°36’41’’S 47°02’39’’W. MZUSP 83971 , 40 of 444, 18.7–35.2 mm SL, Brazil, Tocantins, Porto Alegre do Tocantins, rio Manuel Alves da Natividade , 11°36’41’’S 47°02’39’’W. UFRGS 16447 , 24 , 28.3–31.7 mm SL (10, 27.8–31.7 mm SL, 2c&s males 28.7–29.7 mm SL, 2c&s females 28.6–28.7 mm SL), Município de Paraná, Maranhão pond, Fazenda Traçadal. UNT 6621 , 1 , 20.6 mm SL, Município de Peixe , rio Tocantins, near confluence with rio Santa Tereza. UNT 7227 , 28 , 27.3–32.5 mm SL, Município de Paraná, Maranhão pond, Fazenda Traçadal. UNT 7322 , 1 , 18.0 mm SL, Município de Porto Nacional , rio Tocantins. UNT 7324 , 1 , 16.4 mm SL, Município de Ipueiras , rio Tocantins, near confluence with rio Manoel Alves. UNT 7386 , 3 , 15.5–21.2 mm SL, Município de Paraná, Maranhão pond, Fazenda Traçadal. UNT 7402 , 1 , 18.2 mm SL, Município de Paraná, Maranhão pond, Fazenda Traçadal. UNT 7403 , 4 , 19.6–25.2 mm SL, Município de Paraná, Maranhão pond, Fazenda Traçadal. UNT 7412 , 1 , 29.5 mm SL, Paraná, Maranhão pond, Fazenda Traçadal .

Figures

FIGURE 2. Ventral procurrent caudal-fin rays of species of Serrapinnus from the rio Tocantins-Araguaia basin. (a) Serrapinnus aster, male, UFRGS 12023, 26.9 mm SL; (b) S. aster, female, UFRGS 12023, 35.7 mm SL; (c) S. lucindai, male, UFRJ 1260, 24.9 mm SL; (d) S. lucindai, female, UFRJ 1260, 25.9 mm SL; (e) S. sterbai, male, UFRGS 16447, 28.7 mm SL; (f) S. sterbai, female, UFRGS 16447, 29.6 mm SL; (g) S. tocantinensis, male, MCP 40417, 31.6 mm SL; (h) S. tocantinensis, female, MCP 40417, 33.4 mm SL. Lateral view, anterior to left. Scale bar = 1 mm.

FIGURE 4. Anal fin of mature males of the species of Serrapinnus from rio Tocantins-Araguaia basin showing hypertrophied anal-fin rays and hooks shape and distribution. (a) Serrapinnus aster, male, UFRGS 12023, 26.9 mm SL; (b) S. lucindai, male, UFRJ 1260, 24.9 mm SL; (c) S. sterbai, male, UFRGS 16447, 29.7 mm SL; (d) S. tocantinensis, male, MCP 40417, 31.6 mm SL. Lateral view, anterior to left. Arrow head pointing to ligaments connecting approximately midlength of posterior face of proximal segment of lepidotrichia to proximal anterior face of lepidotrichia of the subsequent ray. Scale bar = 1 mm.

FIGURE 5. Geographic distribution of the species (a) Serrapinnus aster (black stars; white star in black dot = type locality), (b) S. lucindai (black triangles; white triangle in black dot = type locality), (c) S. sterbai (black dots) and (d) S. tocantinensis (black lozenges; white lozenge in black dot = type locality) in rio Tocantins-Araguaia basins. Some symbols represent more than one locality.

FIGURE 8. Serrapinnus sterbai (a) male, MZUSP 40359, 22.8 mm SL, Município de Arraias, periodic lake in the confluence of rio Paraná and rio Bezerra, Tocantins drainage, Tocantins State, Brazil; (b) male, MZUSP uncat., not measured, and (c) female, MZUSP uncat., not measured.

FIGURE 9. Serrapinnus sterbai, UFRGS 16447, 28.7 mm SL; Scanning Electron Microscopy images showing (a) left side premaxilla; (b) maxilla; (c) dentary, and (d) detail of dentary teeth.