Austrolebias periodicus

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 : 83-86

Austrolebias periodicus (Costa)

(Fig. 33)

Cynolebias periodicus Costa, 1999b: 299 ( type locality: temporary floodplains of the rio Santa Maria, rio Ibicui drainage, rio Uruguay basin, road BR-293, 4 km W from Dom Pedrito , Estado do Rio Grande do Sul, Brazil; holotype: MCP 20819 ).

Austrolebias luzardoi Perujo, Calviño, Salvia & Prieto, 2005: 3 ( type locality: temporary swamp, 30°25.00’S 55°27.03’W, near rio Cuareim, tributary of the rio Uruguay, near Artigas , Uruguay; holotype: MUNHINA 3200 ).

Material examined

Brazil: Estado do Rio Grande do Sul, in rio Ibicuí drainage, rio Uruguay basin: MCP 20819 , holotype, male, 29.1 mm SL; MCP 20820 , 5 paratypes; UFRJ 4671 , 12 paratypes; UFRJ 4672 , 6 paratypes (c&s); UFRJ 4246 , 36; UMMZ 234761 , 4 paratypes; MZUSP 52925 , 2 paratypes; temporary floodplains of the rio Santa Maria, road BR-293, 4 km W from Dom Pedrito ; W. J. E. M. Costa, M. I. Landim & C. Moreira, 18 Jul. 1997. UFRJ 4986 , 80; same locality ; W. J. E. M. Costa & A. C. Bacellar, 4 Sep. 1999. UFRJ 4949 , 40; temporary pool, 6 km W of Rosario do Sul, rio Ibicui de Armada drainage, road BR-290 ; W. J. E. M. Costa & A. C. Bacellar, 4 Sep. 1999. UFRJ 5040 , 11; temporary pool, arroio Santo Antonio floodplains, a tributary of rio Ibicui de Armada, road BR-158 ; W. J. E. M. Costa & A. C. Bacellar, 4 Sep. 1999. UFRJ 5030 , 162; UFRJ 5031 , 8 (c&s); temporary swamp at rio Ibicui de Armada floodplains, road BR-293 ; W. J. E. M. Costa & A. C. Bacellar, 4 Sep. 1999. Uruguay: Artigas: UFRJ 6190 , 2; UFRJ 6191 , 4 (c&s); CTL 1063 , 31; Las Cavas, rio Cuareim drainage, rio Uruguay basin , 30°25.00’S 55°27.03’W; P. Laurino, T. Litz, E. Perujo, R. Recuero, H. Salvia & J. Salvia, 23 Aug. 2004.

Diagnosis

Distinguished from remaining species of the A. alexandri group by the following combination of characters: posterior margin of each pectoral fin in male reaching a vertical between base of second and fifth anal-fin rays (vs. between urogenital papilla and base of second anal-fin ray), dorsal-fin origin either on vertical through anal-fin origin or posterior to it (vs. anterior), and larger males with vertical rows of light blue dots on entire flank (vs. light blue bars).

Description

Morphometric data appear in Table 5. Males larger than females, largest male examined 33.1 mm SL, largest female 28.3 mm SL. Dorsal profile nearly straight to convex on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle; often 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 slender 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 rounded, posterior margin on vertical between base of 3rd and 5th anal-fin rays in males, on vertical between pelvic-fin base and anus in females. Tip of each pelvic fin reaching between base of 2nd and 3rd anal-fin rays in males, between base of 1st and 2nd anal-fin rays in females. Pelvic-fins bases united or in close proximity, medial membrane never coalesced. Urogenital papilla not attached to anal fin. Dorsal-fin origin on vertical between bases of 1st and 2nd anal-fin rays; 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 9th and 11th vertebrae in females. Dorsal-fin rays 22-26 in males, 16-18 in females; anal-fin rays 21-25 in males, 17-23 in females; caudal-fin rays 24-27; pectoral-fin rays 10-11; 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 H-patterned; E-scales overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 26-28, 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 opercle in males. Row of minute contact organs on three uppermost pectoral-fin rays in males; no contact organs on unpaired fins.

Cephalic neuromasts: supraorbital 14-17, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 2 + 21-22, preorbital 2, otic 1-3, post-otic 3-4, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 17-18, mandibular 9, lateral mandibular 3-5.

Basihyal subtriangular, width about 60 % of length; basihyal cartilage moderate in length, about 50 % of total basihyal length, without lateral projections. Six branchiostegal rays. Two to five teeth on second pharyngobranchial. Gill-rakers on first branchial arch 3 + 8. Dermosphenotic ossification absent. Ventral process of posttemporal vestigial. Total vertebrae 27-29.

Coloration

Males: side of body dark bluish gray to dark brown, with 7-15 rows of bright blue dots, sometimes dots of anteriormost rows united forming narrow vertical lines. Urogenital papilla gray. Opercular and infraorbital regions bright blue; approximately rectangular, dark gray to black infraorbital bar; subtriangular dark gray to black supraorbital blotch, not reaching neuromast parietal series. Iris brown with black bar through center of eye. Unpaired fins dark gray, with light blue on whole fins or concentrated on basal two thirds of fins, usually irregularly arranged, sometimes forming subdistal row on dorsal fin; blue iridescence on distal portion of dorsal fin; intense bright blue iridescence on distal portion of anal fin, often forming distinctive stripe; bright blue iridescence on distal portion of caudal fin. Pelvic fins dark bluish gray, with light blue basal spot. Pectoral fins dark bluish gray, with bright blue iridescence.

Females: side of body light yellowish brown, with dark gray spots, usually as large as eye, vertically elongated, sometimes forming short bars above anal fin; often 1-4 black spots on anterocentral portion of flanks, sometimes 1 or 2 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 dark gray spots, darker and elongated on basal portion; paired fins hyaline.

Distribution

Ibicuí and Quaraí (= Cuareim) river drainages, rio Uruguay basin, southern Brazil and northwestern Uruguay (Fig. 20).

Remarks

Perujo et al. (2005) described A. luzardoi from the río Cuareim drainage, which is a eastern tributary of the rio Uruguay, just adjacent to rio Ibicuí drainage, where the type locality of A. periodicus is located. Examination of topotypes of A. luzardoi reveals that it is indistinguishable from A. periodicus .