Cynolebias ibicuiensis, Costa, 1999

Costa, Wilson J. E. M., 1999, Cynolebias ibicuiensis, a new annual fish from the rio Ibicui basin, southern Brazil (Cyprinodontiformes: Rivulidae), RevueFrAquariol 25 (3), No. 4, pp. 92-94 : 93

Cynolebias ibicuiensis sp. n.

(Figs l-2)

Holotype. MCP 10201, male, 32.8 mm SL; Brazil: Estado do rio Grande do Sul, rio Ibicui-Mirim , rio Ibicui drainage , rio Uruguai basin , road BR-287, between São Pedro do Sul and Santa Maria ; collected by Universidade Federal de Santa Maria party, 6 Aug. 1982.

Paratype. MCP 21 171, female, 27.0 mm SL; collected with holotype.

Diagnosis

Distinguished from all other species of the genus by the combination of the following features: short predorsal distance (46.5 % SL in male), dorsal-fin rays 23 in male and 19 in female, anal-fin rays 23 in male and 21 in female, anterior portion of head concave, body sides of males with dark stripes dorsally widened, reduced light spots on unpaired fins of male, and darkly pigmented pectoral fin of male.

Description

Morphometric data of holotype and paratype, respectively, are: body depth 34.1 and 3 1.5 % SL, caudal peduncle depth 15.6 and 14.6 % SL, predorsal length 46.5 and 61.8 % SL, prepelvic length 45.7 and 54.0 % SL, length of dorsal-fin base 44.2 and 29.7% SL, length of anal-fin base 36.4 and 26.2 %SL, head length (HL) 26.8 and 28.3 % SL, head depth 112.4 and 101.4% HL, head width 70.9 and 74.0 % HL, snout length 15.4 and 13.9% HL, and eye diameter 34.4 and 34.9 % HL.

Dorsal profile concave on anterior portion of head, approximately convex from eye to base of last dorsal-fin ray, nearly straight on caudal peduncle. Ventral profile convex from lower jaw to end of anal-fin base, about straight on caudal peduncle. Body moderately deep, laterally compressed, body depth 1.8 times body width in holotype.

Tip of dorsal and anal fins rounded. Caudal fin rounded. Pectoral fin elliptical. Posterior margin of the pectoral fin reaches a vertical through the base of 2nd anal-fin ray in male (damaged in female). Tip of pelvic fin reaches base of the 1st anal-fin ray. Pelvic fins in close proximity but not medially coalesced. Anal-fin origin in a vertical through base of the 4th dorsal-fin ray. Dorsal-fin rays 23 in male, 19 in female; anal-fin rays 23 in male. 2 I in female. Small, papilliform contact organs on the medial surface of the first pectoral-fin ray of male.

Scales cycloid, but with ctenii-like contact organs on scales of the anteroventral portion of body side of male. Frontal squamation G-patterned. Supraorbital neuromasts 17. Longitudinal series of scales 27-28; transverse series of scales 10; scale rows around caudal peduncle 16.

Colouration. Male. Color in life unkown. Sides of body light brown with I I vertical dark brown stripes, the two posterior ones lighter; anterior stripes becoming wider in their dorsal tips, forming a series of inverted triangles on dorsal portion of body sides. Sides of head light brown; a vertical, suborbital dark brown bar and a triangular, supraorbital dark brown blotch. All fins dark brown; a series of sparse spots along dorsal-fin base.

Female. Color in life unkown. Sides of body light brown with rounded brown blotches irregularly arranged. No dark spot on center of body sides. Sides of head light brown; a faint vertical, suborbital dark brown bar and a triangular, supraorbital dark brown blotch. Dorsal and anal fins hyaline with faint brown spots. Caudal and paired fins hyaline.

Distribution

Known only from the type locality. Recent attempts to find this species (September 1997 and July 1998) were unsuccessful. The type locality and many visited points of the floodplains of the rio Ibicui basin, including the Ibicui-Mirim drainage, are highly modified by the rice culture. No typical annual fish biotope was found. It is possible that the new species is presently extinct.

Etymology

The name ibicuiensis refers to the occurrence of the new species in the rio Ibicui basin. An adjective.