Rivulus egens, 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 : 80-81

Rivulus egens , new species

Fig.11

Holotype. UFRJ 5973, male, 25.2 mm SL; Brazil: Estado de Mato Grosso do Sul: Município de Camapuã, road BR-060, rio São Domingos, upper rio Verde drainage, rio Paraná basin, 19 o 19’26.0”S 53 o 21’6.8”W, altitude 532 m; W. J. E. M. Costa, B. B. Costa and C. P. Bove, 12 Jan 2004.

Paratypes. UFRJ 5974, 4 males, 15.0-26.0 mm SL, 110 females, 14.1-22.8 mmSL; MCP 36126, 3 females,17.1-18.3 mmSL ; UFRJ 5975 , 1 male, 21.2 mm SL, 2 females, 19.1-19.4 mm SL (c&s); collected with the holotype .

Additional material (non type specimens). UFRJ 6009, 2; Brazil: Mato Grosso do Sul: Campo Grande, upper rio Inhanduí drainage, rio Paraná basin; A. Rosso, 13 Mar 2004 . UFRJ 6010, 1; UFRJ 6011, 5 (c&s); same locality and collector, 30 Mar 2004 .

Diagnosis. Differs from all other species of the R. punctatus group by the combination of the following features: frontal squamation E-patterned (vs. F-patterned), 9-10 dorsal fin rays (vs. 10-12), 30-31 scales on the longitudinal series (vs. 32-36), 13-14 pectoral fin rays (vs. 11-12), flank with striking iridescent colors in male, contrasting metallic blue to greenish blue on middle of flank with light purplish blue above anal fin and brownish golden on anterior dorsolateral portion of body (vs. never a similar color pattern), flank with narrow pale red chevron-like oblique bars with anteriorly directed vertex (vs. never a similar pattern), no distinctive dark stripe along midline of flank (vs. stripe present), caudal and anal fins without red marks in males (vs. red marks present), and caudal fin with vertical rows of dark gray spots in females (vs. dark gray bars).

Description. Morphometric data in Table 7. Largest specimen 26.0 mm SL, male. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight to weakly concave on caudal peduncle. Ventral profile convex on head, slightly convex to almost straight from anterior portion of venter to end of anal-fin base, nearly straight along caudal peduncle. Body slender, subcylindrical anteriorly, slightly deeper than wide, to compressed posteriorly. Greatest body depth at level of pelvic-fin base.

Dorsal and anal fins gently pointed in male, rounded in female. Caudal fin rounded, almost circular. Pectoral fin rounded, posterior margin on vertical through pelvic-base in male, just anterior to it in female. Tip of pelvic fin reaching base of 2nd anal-fin ray in male, and anus in female. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical through base of 9th anal-fin ray, and between neural spines of 19th and 20th vertebrae. Anal-fin origin between pleural ribs of 13th and 15th vertebrae. Dorsal-fin rays 9-10; anal-fin rays 13-14; caudal-fin rays 30-31; pectoral-fin rays 13-14; pelvicfin rays 7.

Scales large, cycloid. Trunk scaled; head scaled except on its anteroventral surface. Body scales slightly extending over caudal-fin base; no scales on dorsal and anal fins. Frontal squamation E-patterned; E-scales not overlapping medially; scales arranged in circular pattern around central A-scale without exposed margins. Longitudinal series of scales 30- 31; 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 29-30.

Coloration. Male: Side of body metallic blue to greenish blue, with red chevron-like oblique bars with anteriorly directed vertex; small dark red spots on humeral region. Anterior dorsolateral portion of flank pale brownish golden. Dorsum light yellowish brown, venter white. Opercular region silver with two faint oblique dark red to brown bars. Opercular and humeral marks becoming black when exposed to light. Infraorbital region and ventral surface of head white. Lower jaw dark gray. Iris light yellow. Dorsal fin yellow with three narrow orange bars. Anal fin yellow, base light blue; narrow black distal margin. Caudal fin yellow with dark orange line along margins. Pelvic fin pale yellow. Pectoral fin hyaline, distal portion gray.

Female: Side of body pale greenish golden, with narrow red chevron-like oblique bars with anteriorly directed vertex; dark reddish brown spots on anterior portion of midlateral region. Anterior dorsolateral portion of flank pale golden. Dorsum light brown with dark gray spots, venter white. Opercular region silver with two oblique brown bars. Brown marks on opercle and anterior portion of flank becoming black when exposed to light. Infraorbital region and ventral surface of head white. Lower jaw dark reddish gray. Iris light yellow. Dorsal fin light greenish yellow with three rows of small dark gray spots; narrow dark gray distal stripe. Anal fin pale yellow, base light blue; dark gray distal stripe. Caudal fin light yellow, dorsal and ventral portions pale pink, with vertically elongated spots; margins dark gray; black spot on subdorsal portion of caudal fin base. Pelvic fin pale blue, anterior margin dark gray. Pectoral fin hyaline.

Distribution. Rio São Domingos, upper rio Verde drainage, rio Paraná basin, central Brazil ( Fig. 2 ). Rio Verde here is a drainage situated between rio Pardo and rio Sucuruí drainages, Estado de Mato Grosso do Sul. Smaller specimens were collected in the upper rio Inhanduí drainage.

Etymology. From the Latin egens (poor), in reference to the color pattern in which dark marks are absent on the caudal fin of males.

Figures

Fig. 11. Rivulus egens, UFRJ 5973, male, holotype, 25.2 mm SL (one day after collection); Brazil: Mato Grosso do Sul: Camapuã. 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.