Serrapinnus aster Malabarba & Jerep, 2014

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 : 58-63

Serrapinnus aster Malabarba & Jerep , new species

Figs. 1 , 2a–b , 3 , 4a , 5a

Holotype. MZUSP 115011 , 22.9 mm SL, male, Brazil, Tocantins State, Município de Arraias, periodic lake at confluence of rio Paraná and rio Bezerra , rio Tocantins drainage, 11 Jan 1989, J. C. Oliveira & W. Costa.

Paratypes. All from Brazil, rio Tocantins-Araguaia basin. Goiás State: MCP 41862, (3, 31.6–33.2 mm SL), córrego Volta Grande, tributary of left margin of PCH Piranhas reservoir, Município de Piranhas , 16°35’59’’S 51°48’33’’W, 18 Jul 2007, Equipe CPA ltda. MCP 42033, (3, 28.4–32.7 mm SL), córrego Salobrinha, tributary of rio Claro, Município de Montes Claros de Goiás , 15°58’35’’S 51°24’09’’W, 27 Feb 2007, G. A. Pereira. UFRGS 12015 , 22 , 23.0– 31.1 mm SL, Município de Piranhas, tributary of rio Piranhas , between Piranhas and Bom Jardim de Goiás , 16°21’43.3”S 51°55’10.2”W, 7 Feb 2010, V. A. Bertaco, F. R. Carvalho & F. C. Jerep. UFRGS 12023 , 54 , 32.3 – 10.6 mm SL, 2 c&s, 25.3–26.1 mm SL, Município de Montes Claros de Goiás, tributary of rio Claro, 100 km from road intersection to Betânia , between Jussara and Montes Claros de Goiás , 15°55’32.0”S 51°19’25.8”W, 6 Feb 2010, V. A. Bertaco, F. R. Carvalho & F. C. Jerep. UFRGS 12034 , 5 , 28.5 –31.0 mm SL, Município de Jussara, tributary of rio Claro , 15°58’0.0”S 50°48’59.7”W, 6 Feb 2010, V. A. Bertaco, F. R. Carvalho & F. C. Jerep. Tocantins State: MZUSP 115012 , 10 , 21.3–26.3 mm SL, 2 c&s, 23.9–25.0 mm SL, same data as holotype .

Diagnosis. Serrapinnus aster is distinguished from all congeners except S. potiguar , by the scimitar-shaped ventral procurrent caudal-fin rays of mature males, almost all of which form a semicircle, resulting in a portion of the ventral procurrent caudal-fin rays having a multi-pointed partial star-shaped margin ( Fig. 2a ) vs. ventral procurrent caudal-fin rays rod-shaped or spatulate, usually parallel to each other, except for the anteriormost procurrent rays being inclined forward in some species. Furthermore S. aster can be diagnosed from S. potiguar and other species of the genus by the presence of 7–9 cusps on the premaxillary teeth (vs. 5 cusps in S. microdon and S. potiguar , 9 to 11 in S. lucindai , S. sterbai and S. tocantinensis and 10 to 12 in S. gracilis and S. littoris ), the incomplete lateral line (vs. complete in S. heterodon ), the hyaline dorsal fin (vs. with a proximal black blotch in S. notomelas ), and the absence of a black spot on the posteroventral region of the abdomen (vs. the presence of a black spot in that region in S. kriegi ).

Description. Morphometric data in Table 1 . Body short and compressed. Greatest body depth at dorsal-fin origin. Snout slightly pointed in profile. Dorsal profile of head gently convex from snout to anterior portion of supraoccipital bone. Posterior portion of supraoccipital slightly concave. Predorsal profile slightly convex from posterior end of supraoccipital to dorsal-fin origin. Dorsal-fin origin located at midbody. Dorsal profile from base of last dorsal-fin ray to caudal-fin origin straight to slightly convex in females and ventrally arched in preserved mature males. Ventral profile of caudal peduncle straight in females, distinctly convex due to hypertrophy of ventral procurrent caudal-fin rays in males. Caudal peduncle slightly longer than deep. Ventral profile of head and body from tip of mouth to pelvic-fin origin convex, then straight until anal-fin origin on females but slightly concave in mature males. Anal-fin base straight to slightly concave in females, anteriorly convex and distinctively concave posteriorly in mature males.

Head relatively small. Posterior margin of opercle sinusoidal with upper portion concave and lower portion convex. Mouth terminal, mouth slit situated immediately below horizontal through middle of pupil. Maxilla angled posteroventrally; posterior tip reaching vertical close to anterior border of eye and horizontal through ventral border of eye. All teeth pedunculated, distally expanded. Premaxilla with 4(1) or 5(1) teeth in single row and bearing 7–9 cusps. Midcentral cusp higher and wider than lateral cusps. Maxilla with 2(2) teeth bearing 5–7 cusps. Dentary with 7(2) large teeth bearing 5 or 7 cusps, followed by one smaller tooth with 3 cusps and one conical tooth. Smaller lateral cusps of dentary teeth sometimes overlapping adjacent tooth cusps; overlap usually absent between posteriormost teeth. All dentary tooth cusps upwardly pointed or slightly directed towards interior of mouth ( Fig. 3 ).

Dorsal-fin rays ii,8(1), 9*(16). Dorsal-fin origin at midlength of body. First unbranched dorsal-fin ray about one-half length of second unbranched ray; following branched rays progressively decreasing in size. Adipose-fin origin slightly posterior to vertical through end of anal-fin base. Anal-fin rays iii,16(2), 17*(6), 18(7) or 19(2). First unbranched anal-fin ray only observable in cleared and stained specimens. Distal profile of anal-fin slightly concave in females, deeply concave in males. Last unbranched and first 5–6 branched anal-fin rays longer, remaining rays progressively decreasing in size. Tip of longest anal-fin rays of mature males laterally overlapping last anal-fin rays, and sometimes reaching ventral procurrent caudal-fin rays when caudal peduncle arched. Analfin origin posterior to vertical through base of last dorsal-fin ray. Males with acute, elongate, retrorse hooks, posterolaterally arranged on last unbranched to 8 th, 9 th or 10 th branched anal-fin rays ( Fig. 4a ). Two unpaired hooks present per lepidotrichia ray segment of on each lateral half of ray. Hooks situated along posterior margin and posterior branches of rays; extending from distal half of proximal lepidotrichia segment to distal end of ray. Hookbearing rays with segments and branches progressively fused with increasing maturation of males. Mature males with hypertrophied soft tissue associated with hook-bearing anal-fin rays. Pectoral-fin rays i,9*(6), 10(9), 11(2). Pectoral-fin ray falling short of pelvic-fin origin in females, but extending beyond that point in males. Pelvic-fin rays i,7*. Pelvic-fin origin anterior to vertical through dorsal-fin origin. Pelvic-fin rays of males with 1 or 2 acute, elongate hooks per lepidotrichia segment. Hooks ventromedially placed on all rays, and associated with hypertrophied soft tissue. Principal caudal-fin rays 18(1), 19*(14). Procurrent caudal-fin rays 11(2) dorsal, 13(2) ventral. Ventral procurrent caudal-fin rays hypertrophied in mature males, extending beyond ventral muscles and skin of caudal-peduncle resulting in multi-pointed semicircular star-shaped structure. Hypertrophied ventral procurrent ray scimitar-shaped: anteriorly bent, proximally acute, expanding distally and ending abruptly in pointed distal tip ( Fig. 2a ).

Scales cycloid, similar in size over all of body. Lateral line partially pored with 6*(2), 8(5), 9(8), 11(1), 13(1) pored scales; scales in lateral line scale row 31(3), 32*(6), 33(4), 34(3), 35(1). Predorsal scales 9(7), 10(6), 11(2), 12(1). Scale rows between lateral line and dorsal-fin origin 5(1) or 6*(16). Scale rows between lateral line row and pelvic-fin origin 4*(16) or 5(1). Scale rows around caudal peduncle 12(1), 13*(8), 14(8). Scales along anal-fin base 6(1), 8*(2), 9(3), 10(6), 11(3), 12(1), 13(1).

Supraneurals 4 or 5; abdominal vertebrae 15; caudal vertebrae 19 in two clear and stained specimens.

Color in alcohol. Overall background body color yellow ( Fig. 1 ). Head with numerous and large melanophores on dorsal and opercular regions. Small, dark melanophores surrounding mouth opening and over maxilla. Scales on dorsum and on rows above lateral line with subtle reticulated color pattern due to concentration of melanophores along distal border of scales. Body with faint dark midlateral stripe, usually in form of narrow black line along middle longitudinal body axis, beginning anterior to dorsal-fin origin and ending in caudal spot. Body with scattered pigmentation ventral of lateral line. Melanophores aligned along myosepta on posteroventral region of body. Black to brown, rounded spot on caudal-fin base; spot not reaching upper or lower margin of caudal peduncle and extending posteriorly over one-half to two-thirds of middle caudal-fin rays. Dorsal, anal, pectoral and pelvic fins scattered with few melanophores between rays. Adipose fin unpigmented. Caudal fin covered with diffuse dark chromatophores along fin rays, except for clear areas on base of caudal-fin lobes just posterior of caudal-fin spot. No humeral spot; triangular, darkened area in humeral region due to presence of pseudotympanum within musculature.

Sexual dimorphism. Sexually mature males with hooks on pelvic- and anal-fin rays, ventrally arched caudal peduncle in preserved specimens; hypertrophied hook bearing anal-fin rays, expanded in sagittal plane usually with fused ray segments; and hypertrophied ventral procurrent caudal-fin rays ( Figs. 1 , 2a–b , 4a ).

Distribution. Serrapinnus aster is distributed on the upper portions of the rio Tocantins basin, mainly in the tributaries of the rio Paraná and rio Tocantins ( Fig. 5a ).

Etymology. The species name, aster , refers to the star-shaped ventral profile of the set of hypertrophied procurrent caudal-fin rays present in the mature males of the species.

Figures

FIGURE 1. Serrapinnus aster, (a) holotype, male, MZUSP 115011, 22.9 mm SL; Município de Arraias, periodic lake at confluence of rio Paraná and rio Bezerra, Tocantins drainage, Tocantins State, Brazil; (b) paratype, female, MZUSP 115012, 23.6 mm SL, same data as holotype.

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 3. Serrapinnus aster, MZUSP 115012, 25.2 mm SL; Scanning Electron Microscopy images showing (a) left side premaxilla; (b) maxilla; (c) dentary, and (d) detail of dentary teeth.

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.