Rivulus kirovskyi, Costa, 2004

Costa, Wilson J. E. M., 2004, Rivulus kirovskyi, a new killifish from the central Amazon, Brazil (Cyprinodontiformes: Rivulidae), Neotropical Ichthyology 2 (1), pp. 9-12 : 10-11

Rivulus kirovskyi , new species

Fig. 1

Holotype. UFRJ 5935, male, 20.3 mm SL; Brazil: Estado do Amazonas: Manaus: Reserva Ducke, temporary pools near igarapé Acará , lower rio Negro drainage, rio Amazonas basin (about 3 o 0’S 60 o 30’W; altitude 90 m); A. Kirovsky, 22 February 1996.

Paratypes. UFRJ 5936, male, 22.7 mm SL (c&s); collected with holotype . - UFRJ 5937 , 1 female, 16.1 mm SL (c&s); UFRJ 5938 , 1 female, 14.8 mm SL; same locality and collector, 25 January 1996 . - UFRJ 5939 , 2 females, 14.7-17.2 mm SL; same locality and collector, 1 February 1996 . - INPA 1850 , 2 females, 14.8-16.8 mm SL; same locality; J. Zuanon, 22 November 1986 .

Diagnosis. Similar to R. amanapira , R. atratus , R. ornatus , R. rectocaudatus , R. romeri , R. tecminae , and R. uakti Costa , and distinguished from all other species of the genus by possessing a frontal squamation pattern consisting of one scale with all margins exposed just posterior to snout (vs. scale with all margins exposed near the center of median portion of frontal region) and an oblique infraorbital dark gray bar through chin (vs. never a similar color pattern). Similar to R. atratus , R. ornatus and R. romeri and distinguished from the remaining congeners by having fewer anal-fin rays (8-10, vs. 11-19). Distinguished from R. romeri , R. ornatus and R. atratus by having a marginal dark reddish brown stripe on the caudal fin in males (vs. dark marginal stripes absent). Differs from R. atratus and R. ornatus by the absence of dermosphenotic (vs. presence), absence of preopercular canal absent (vs. conspicuous short canal), and frontal scales arranged transversally (vs. circularly). Differs from R. romeri by having short anal fin, its tip reaching vertical through caudal peduncle (vs. long anal fin in males, tip teaching vertical through caudal-fin base), 32 scales on the longitudinal series (vs. 29-30), 16 scale rows around caudal peduncle (vs. 12), and six branchiostegal rays (vs. five).

Description. Morphometric data given in Table 1. Male larger than female, largest male 22.7 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile convex on head, almost straight from anterior portion of venter to end of analfin base, nearly straight on caudal peduncle. Body slender, subcylindrical anteriorly, slightly wider than deep, to compressed posteriorly. Greatest body depth at level of pelvicfin base.

Tip of dorsal fin rounded. Tip of anal fin slightly pointed in male, rounded in female. Caudal fin oval. Pectoral fin rounded, posterior margin on vertical anterior to pelvic-fin base. Tip of pelvic fin reaching between base of 1st and 3rd anal-fin ray in male, and urogenital opening in female. Pelvicfin bases in close proximity. Dorsal-fin origin on vertical through base of 8th or 9th anal-fin ray, and between neural spines of 19th and 20th vertebra. Anal-fin origin between pleural ribs of 14th and 15th vertebra. Dorsal-fin rays 6-7; anal-fin rays 9-10; caudal-fin rays 23; pectoral-fin rays 15; pelvic-fin rays 6.

Scales large, cycloid. Trunk entirely scaled; head scaled, except in anterior ventral surface. Few scales on caudal-fin base; no scales on dorsal and anal fins. Frontal squamation comprising scales arranged in transverse pattern, each scale with exposed posterior margin, except scale just posterior to snout with all borders free; E-scales not overlapping medially. Longitudinal series of scales 32; transverse series of scales 7; scale rows around caudal peduncle 16. Cteniilike contact organ in each scale of ventral portion of male flank. Supraorbital neuromasts 3+3.

Basihyal subtriangular, greatest width about 40 % of length; basihyal cartilage about 25 % of basihyal length. Interhyal vestigial, not ossified. Six branchiostegal rays. Second pharyngobranchial teeth absent. Gill-rakers of first Etymology. Named in honor of the biologist Alexandre Kirovsky, collector of most specimens of the type series.

branchial arch 1 + 7. Vomerine teeth absent. Preopercular canal absent. Dermosphenotic absent. Ventral process of posttemporal absent. Neural prezygapophyses long, about 25 % of neural spine length in fifth caudal vertebra. Epipleural ribs rod-like. Total vertebrae 29-30.

Coloration. Unknown in live specimens, but faint dark marks weakly observable in preserved specimens. Flank of male with brown stripes and oblique brown bars on anterodorsal portion; female with irregular brown marks. Postorbital dark brown blotch and transverse preorbital bar through chin in both sexes. Dorsal fin with subbasal stripe, darker in female. No dark marks on anal fin. Caudal fin with brown bars on basal portion, darker in female; reddish brown marginal stripe around fin in male.

Distribution. Known only from the floodplains of igarapé Acará, lower rio Negro drainage, rio Amazonas basin, northern Brazil.

Figures

Fig. 1. Rivulus kirovskyi, holotype, UFRJ 5935, male, 20.3 mm SL; Brazil: Amazonas: Manaus.