Austrolebias alexandri

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 : 60-64

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Austrolebias alexandri


Austrolebias alexandri (Castello & Lopez)

(Fig. 25)

Cynolebias alexandri   ZBK Castello & Lopez, 1974: 35 ( type locality: Parque Unzue , Gualeguaychu , Provincia de Entre Rios, Argentina; holotype: MACN 6438 ).

Material examined

Argentina: Entre Rios: MACN 6438 , holotype; MACN 6439 , paratype; MACN 6425 , 7 paratypes; Parque Unzue , Gualeguaychu ; R. Barbetti, 13 Oct. 1972. MACN 6437 , 4 paratypes; Gualeguaychu ; J. O. Fernandez-Santo & J. Castelli, 20 Jul. 1972. Uruguay: Río Negro: UFRJ 6157 , 6; CTL 1249 , 26; San Javier, rio Uruguay basin , 32°39.34’S 58°7.73’W; P. Laurino, F. I. Prieto, H. Salvia & J. Salvia, 12 Sep. 2004. GoogleMaps CTL 1251 , 20; San Javier, rio Uruguay basin , 32°39.84’S 58°7.64’W; P. Laurino, T. Litz, E. Perujo, F. I. Prieto & H. Salvia, 19 Mar. 2003. GoogleMaps Brazil: Rio Grande do Sul: MNRJ 11720 , 4; MZUSP 37205 , 2; MZUSP 38473 , 2 (c&s); Uruguaiana ; U. Caramaschi, M. Soma & J. Jim, 19 Jul. 1980. UFRJ 4924 , 177; UFRJ 4925 , 8 (c&s); MCP 28040 , 8; Uruguaiana, road BR-472, close to arroio Salso I, a small tributary of rio Uruguay ; W. J. E. M. Costa & A. C. Bacellar, 2 Sep. 1999.


Distinguished from all other species of the A. alexandri group by having dark gray bars, the three anterior bars dark, alternating with light zones with vertical rows of bright blue dots on flank in male. Also distinguished from all other congeners by the combination of the following features: no prominent contact organs on male anal fin, pelvic-fin membrane never medially coalesced; anal fin short in females; urogenital papilla not attached to anal fin; dorsal-fin origin usually anterior to anal-fin origin in males, dorsal-fin rays 21-26 in males, 16-22 in females, anal-fin rays 23-27 in males, 19-23 in females, and longitudinal series scales 26-27. Similar to A. ibicuiensis and distinguished from remaining species of the A. alexandri group in having a black spot on the anterior portion of anal fin; differs from A. ibicuiensis by possessing longer anal-fin base in males (44.7-48.7 % SL, vs. 39.8-42.8 % SL).


Morphometric data appear in Table 4. Males larger than females, largest male examined 43.0 mm SL, largest female 29.8 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 male. 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 5th and 6th anal-fin rays in males, between pelvic-fin base and anus in females. Tip of each pelvic fin reaching base of 3rd anal-fin ray. Pelvic-fin bases in close proximity. Urogenital papilla not attached to anal fin. Dorsal-fin origin usually slightly anterior to anal-fin origin, sometimes slightly posterior to it; dorsal-fin origin between neural spines of 7th and 9th vertebrae in males, between neural spines of 10th and 12th vertebrae in females. Anal-fin origin between pleural ribs of 7th and 9th vertebrae in males, between pleural ribs of 10th and 12th vertebrae in females. Dorsal-fin rays 21-26 in males, 16-22 in females; anal-fin rays 23-27 in males, 19-23 in females; caudal-fin rays 24-27; pectoral-fin rays 11-12; pelvicfin rays 5-6.

Scales large and cycloid. Trunk and head entirely scaled, except on 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 26-27, scales regularly arranged; transverse series of scales 10-12; 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 three uppermost pectoral-fin rays in males. No contact organ on anal, dorsal and caudal fins.

Cephalic neuromasts: supraorbital 15-18, parietal 1-3, anterior rostral 1, posterior rostral 1, infraorbital 1-2 + 22, preorbital 2, otic 2, post-otic 4, supratemporal 1, median opercular 1, ventral opercular 1-2, preopercular 18-19, mandibular 11-14, lateral mandibular 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 + 9. Dermosphenotic ossification absent. Ventral process of posttemporal vestigial or absent. Total vertebrae 27-29.


Males: side of body light bluish gray with 5-11 dark gray bars, two or three anteriormost bars darker, often black; usually all bars narrower than interspace, sometimes bars wider than interspace on caudal peduncle; often ventral portion of anterior bars oblique, slightly anteriorly directed; bars rarely interrupted or branched; small bright blue spot on center of each scale of interspace between bars. 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. Unpaired fins dark gray; golden dots on entire dorsal, usually more concentrated on subdistal zone, and light blue dots over entire anal and caudal fins; anterior margin of dorsal fin and anterior portion of dorsal margin of caudal fin black; pink iridescence on distal portion of dorsal fin; intense bright blue iridescence on distal portion of anal fin, forming distinctive stripe; bright blue iridescence on distal portion of caudal fin. Pelvic and pectoral fins bright blue.

Females: sides of body light yellowish brown, with dark gray spots, usually small and rounded, sometimes vertically elongated, sometimes forming short bars; spots on anterocentral portion of flank usually darker, often black; spots on and posterior portion of caudal peduncle rarely darker; rarely spots on flank inconspicuous. 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 dark gray spots over entire fins, often absent on caudal fin; anterior margin of dorsal fin and anterior portion of dorsal margin of caudal fin black; paired fins hyaline.


Floodplains of rio Uruguay, in southern Brazil, western Uruguay and northeastern Argentina (Fig. 52).