Rivulus cyanopterus, Costa, 2005

Costa, Wilson J. E. M., 2005, Seven new species of the killifish genus Rivulus (Cyprinodontiformes: Rivulidae) from the Paraná, Paraguay and upper Araguaia river basins, central Brazil, Neotropical Ichthyology 3 (1), pp. 69-82 : 73-74

Rivulus cyanopterus , new species

Figs. 3-4

Holotype. UFRJ 5911, male, 27.6 mm SL; Brazil: Estado de Mato Grosso: Jaciara, swamp close to rio Tenente Amaral, a tributary to upper rio São Lourenço , rio Paraguay basin, 15 o 58’48.9”S 54 o 57’20.0”W, altitude 246 m; W. J. E. M. Costa, C. P. Bove & B. B. Costa, 21 Jul 2003.

Paratypes. UFRJ 5912, 1 male, 25.5 mm SL, 2 females, 20.9- 21.4 mm SL; UFRJ 5913 , 22 males, 15.3-26.4 mm SL, 12 females, 16.7-24.2 mm SL, 2 juveniles, 9.6-12.1 mm SL ; MCP 36121, 5 males, 17.6-22.9 mm SL, 3 females, 17.2-19.9 mm SL ; UFRJ 5914 , 3 males, 21.7-24.9 mm SL, 2 females, 20.9-21.1 mm SL (c&s); collected with the holotype .

Diagnosis. Distinguished from all other species of the R. punctatus group in possessing an entirely anal fin blue with oblique red bars in both sexes (vs. anal fin yellow with blue base, red dots or bars restricted to the basal portion) and caudal-fin base with two large, round black spots vertically arranged in females (vs. a single spot in all other species, except sometimes in R. punctatus with two smaller spots). Differs from all congeners from the rio Paraná-Paraguay basin by the following combination of features: flank

with oblique rows of red dots (vs. oblique red bars), flank with dark gray stripe along midline (vs. no distinctive dark stripe), and entire caudal fin yellow, without distinctive colors on margins in males (vs. caudal-fin margins with distinctive color stripe in all other species of the rio Paraguay basin).

Description. Morphometric data in Table 2. Largest specimen 27.6 mm SL, male. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight to gently concave on caudal peduncle. Ventral profile convex on head, almost straight from anterior portion of venter to end of analfin base, nearly straight to slightly concave along caudal peduncle. Body slender, subcylindrical anteriorly, slightly deeper than wide, to compressed posteriorly. Greatest body depth at level of pelvic-fin base.

Dorsal fin rounded. Anal fin slightly pointed in male, rounded to slightly pointed in female. Caudal fin oval. Pectoral fin rounded, posterior margin on vertical through pelvic-fin base in male, just anterior to it in female. Tip of pelvic fin reaching between base of first and third anal-fin ray in male, and urogenital opening in female. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical through base of 9th or 10th anal-fin ray, and between neural spines of 18th and 20th vertebrae. Anal-fin origin between pleural ribs of 13th and 15th vertebrae. Dorsal-fin rays 8-9; anal-fin rays 13-14; caudal-fin rays 29-31; pectoral-fin rays 13-14; pelvicfin rays 7.

Scales large, cycloid. Trunk scaled; head scaled except on anteroventral surface. Body scales slightly extending over caudal-fin base; no scales on dorsal and anal fins. Frontal squamation F-patterned; E-scales not overlapping medially; scales arranged in circular pattern around central A-scale without exposed margins. Longitudinal series of scales 30-32; transverse series of scales 8; scale rows around caudal peduncle 16. Contact organs absent. Supraorbital neuromasts 3 + 3. Six branchiostegal rays. Gill rakers of first branchial arch 1 + 7. Two vomerine teeth. Total vertebrae 31-32.

Coloration. Male: Side of body metallic green with oblique chevron-like rows of red dots, with vertex anteriorly directed; faint laterodorsal brown spots on anterior portion of body; dark gray stripe between eye and caudal-fin base, darker when exposed to light. Dorsum light brown, venter white. Postorbital region metallic green with red dots. Infraorbital region and ventral surface of head white. Lower jaw dark gray. Iris light yellow. Dorsal fin light greenish yellow with 5-7 oblique dark red bars. Anal fin light blue with 6-8 oblique dark red bars. Caudal fin light greenish yellow. Pelvic fin pale yellow. Pectoral fin hyaline.

Female: Side of body light gray with oblique chevronlike rows of dark red dots, with vertex anteriorly directed; laterodorsal gray spots on anterior portion of body; dark gray stripe between eye and caudal-fin base, darker when fish is exposed to light. Dorsum light brown, venter white. Postorbital region gray with red reticulation. Infraorbital re- gion and ventral surface of head white. Lower jaw dark gray. Iris light yellow. Dorsal fin pale yellow with 5-7 oblique dark gray bars, and dark gray distal stripe. Anal fin light blue with 6-8 oblique dark red bars, and dark gray distal stripe. Caudal fin white with 3-5 dark gray bars or vertical rows of spots; dark gray zone along fin margin; two round black spots vertically arranged on basal portion, not contacting fin margin. Paired fins hyaline; anterior margin of pelvic fin dark gray.

Distribution. Known only from the type locality, floodplains of rio Tenente Amaral, upper rio São Lourenço drainage, rio Paraguay basin, central Brazil ( Fig. 2 ).

Etymology. From the Greek kyanos (blue) and pteron (fin) referring to the blue anal fin occurring in both sexes of the new species.

Figures

Fig. 3. Rivulus cyanopterus, UFRJ 5911, male, holotype, 27.6 mm SL (one day after collection); Brazil:Mato Grosso: Jaciara. Photo by W. J. E. M. Costa.

Fig. 4. Rivulus cyanopterus, UFRJ 5912, female, paratype, 21.4 mm SL (one day after collection); Brazil: Mato Grosso: Jaciara. Photo by W. J. E. M. Costa.

Fig. 2. Geographic distribution of species of the genus Rivulus in the Paraná, Paraguay, and upper Araguaia river basins, central Brazil.