Austrolebias ibicuiensis

Wilson J. E. M. Costa, 2006, The South American annual killifish genus Austrolebias (Teleostei: Cyprinodontiformes: Rivulidae): phylogenetic relationships, descriptive morphology and taxonomic revision., Zootaxa 1213, pp. 1-162 : 64-66

Austrolebias ibicuiensis (Costa)

(Fig. 26)

Cynolebias ibicuiensis Costa, 1999a: 93 ( type locality: rio Ibicui-Mirim , rio Ibicui drainage, rio Uruguay basin, road BR-287, between Sao Pedro do Sul and Santa Maria , Estado do Rio Grande do Sul, Brazil; holotype: MCP 10201 ).

Material examined

Brazil: Rio Grande do Sul: MCP 10201 , male holotype, 32.8 mm SL; MCP 21171 , 1 paratype; rio Ibicui-Mirim , rio Ibicui drainage, rio Uruguay basin, road BR-287, between Sao Pedro do Sul and Santa Maria ; Universidade Federal de Santa Maria party, 6 Aug. 1982. UFRJ 4966 , 12; UFRJ 5241 , 4 (c&s); road BR-287, 34 km W of Sao Pedro do Sul, rio Toropi floodplains, a tributary of rio Ibicui , rio Uruguay basin ; W. J. E. M. Costa & A. C. Bacellar, 1 Sep. 1999.

Diagnosis

Similar to A. alexandri and distinguished from remaining species of the A. alexandri group in having dark gray bars alternating with light zones on flank in males, and a black spot on the anterior portion of anal fin; differs from A. alexandri by the absence of bright dots on flank in males and a shorter anal-fin base in males (36.4-42.8 % SL, vs. 44.7-48.7 % SL). Other features useful for identifying A. ibicuiensis are: pelvic-fin membrane never medially coalesced; dorsal-fin origin anterior to anal-fin origin in males; dorsal-fin rays 22-23 in males, 16-19 in females, anal-fin rays 22-24 in males, 17-21 in females, and longitudinal series scales 26-28.

Description

Morphometric data appear in Table 4. Males larger than females, largest male examined 33.0 mm SL, largest female 28.8 mm SL. Dorsal profile nearly straight to slightly concave on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle; sometimes weak adipose ridge on frontal region of head in males. Ventral profile convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Greatest body depth at level of pelvic-fin base. Body moderately deep and compressed. Snout blunt and jaws short.

Tip of both dorsal and anal fins rounded. Anteromedian rays of anal fin of females not lengthened; distal portion of anal fin thickened in females. Caudal fin rounded. Pectoral fins elliptical, posterior margin on vertical between base of 4th and 6th anal-fin rays in males, between pelvic-fin base and anus in females. Tip of each pelvic fin reaching between base of 4th and 5th anal-fin rays. Pelvic-fin bases in close proximity. Urogenital papilla not attached to anal fin. Anal-fin origin on vertical between 1st and 3rd anal-fin ray; dorsal-fin origin between neural spines of 9th and 10th vertebrae in males, between neural spines of 10th and 12th vertebrae in females. Anal-fin origin between pleural ribs of 9th and 10th vertebrae in males, between pleural ribs of 10th and 12th vertebrae in females. Dorsal-fin rays 22-23 in males, 16-19 in females; anal-fin rays 22-24 in males, 17-21 in females; caudal-fin rays 25-27; pectoral-fin rays 11; pelvic-fin rays 5-6.

Scales large and cycloid. Trunk and head entirely scaled, except ventral surface of head. No scales on dorsal and anal-fin bases, and two rows of scales on caudal-fin base. Frontal squamation usually H-patterned, sometimes F or G-patterned; E-scales slightly overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 26-28, scales regularly arranged; transverse series of scales 12; scale rows around caudal peduncle 16. One contact organ on each scale of ventral portion of flank and opercular region in males. Rows of small contact organs on two uppermost pectoral-fin rays in males. No contact organ on anal, dorsal and caudal fins.

Cephalic neuromasts: supraorbital 13-19, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 2 + 22, preorbital 2, otic 1-2, post-otic 2-3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular 20-21, mandibular 11-12, lateral mandibular 3-4.

Basihyal subtriangular, width about 50 % of length; basihyal cartilage moderate, about 45 % of total basihyal length, without lateral projections. Six branchiostegal rays. Two or three teeth on second pharyngobranchial. Gill-rakers on first branchial arch 3 + 8.

Dermosphenotic ossification absent. Ventral process of posttemporal vestigial or absent. Total vertebrae 28-29.

Coloration

Males: side of body light bluish gray with 8-11 dark gray bars, often slightly widening dorsally; bars equal in width or narrower than interspaces. Urogenital papilla gray. Opercular and infraorbital regions bright blue; approximately rectangular dark gray infraorbital bar; subtriangular dark gray supraorbital blotch, not reaching neuromast parietal series. Iris yellow, with blue border and black bar through center of eye. Dorsal fin dark gray, with white dots over entire fin, except basal region, and narrow distal light blue stripe. Anal fin dark gray, with light blue dots over entire fin, except basal region, and distal bright blue stripe. Caudal fin dark gray, with light blue dots and distal bright blue zone. Pelvic and pectoral fins bright blue.

Females: sides of body light yellowish brown, with vertically elongated dark gray spots; spots on anterocentral portion of flank sometimes darker; never darker spots on caudal peduncle. Venter pale golden. Opercular region pale greenish golden. Iris light yellow, with gray bar through center of eye. Infraorbital and supraorbital bars dark gray. Unpaired fins hyaline with gray spots; paired fins hyaline.

Distribution

Upper rio Ibicuí drainage, floodplains of the rio Ibicuí-Mirim and rio Toropi, rio Uruguay basin, southern Brazil (Fig. 52).