Austrolebias nigripinnis

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 : 67-69

Austrolebias nigripinnis (Regan)

(Fig. 27)

Cynolebias nigripinnis Regan, 1912: 508 ( Type locality: La Plata , Argentina; holotype: BMNH 1909.4.2.29 ).

Material examined

Argentina: Buenos Aires: UFRJ 4752 , 11; road between Villa Elisa and Punta Lara; temporary pool, road between Villa Elisa and Punta Lara ; W. J. E. M. Costa, A. Miquelarena, L. Protogino & R. Filiberto, 10 Sep. 1998. UFRJ 4744 , 6; swamp on the road Ruta Nacional 11, coming from Magdalena ; W. J. E. M. Costa, A. Miquelarena, L. Protogino & R. Filiberto, 7 Sep. 1998. MLP 7889 , 6; Tigre ; A. Bachmann, 30 Nov. 1952. MLP 9391 , 10; Delta del Parana , Estacion Experimental INTA ; A. Bachmann, 1 Aug. 1968. Uruguay: Soriano: CTL 1253 , 30; Ruta 96, km 8 , 33°26.30’S 58º16.59’W; P. Laurino et al., 12 Sep. 2004. Colonia: CTL 1265 , 13; Carmelo , 34°0.31’S 58º17.00’W; P. Laurino et al., 12 Sep. 2004.

Diagnosis

Distinguished from all other congeners by possessing a bright blue distal stripe on dorsal fin in males, and a narrow, about rectangular basihyal, its width about 35 % basihyal length (vs. 45-100 %). Similar to A. paranaensis and distinguished from all other species of the genus in possessing a wide infraorbital bar, its dorsal portion approximately as wide as orbital diameter. Differs from A. paranaensis in having dorsal-fin origin anterior (vs. posterior) to anal-fin origin.

Description

Morphometric data appear in Table 4. Males larger than females, largest male examined 32.0 mm SL, largest female 28.7 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; often 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 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 4th and 7th anal-fin rays in males, between urogenital papilla and anal-fin origin in females. Tip of each pelvic fin reaching base of 3rd anal-fin ray in males, and base of 1st anal-fin ray in females. Pelvicfin bases united, sometimes medial margin about 20 % coalesced. Urogenital papilla not attached to anal fin. Anal-fin origin on vertical between base of 2nd and 4th dorsal-fin rays in males, between bases of 1st and 3rd dorsal-fin rays in females; dorsal-fin origin between neural spines of 7th and 8th vertebrae in males, between neural spines of 9th and 10th vertebrae in females. Anal-fin origin between pleural ribs of 7th and 9th vertebrae in males, between pleural ribs of 9th and 10th vertebrae in females. Dorsal-fin rays 20-25 in males, 15-19 in females; anal-fin rays 21-24 in males, 16-21 in females; caudal-fin rays 23-25; pectoral-fin rays 10-11; pelvic-fin rays 5-6.

Scales large and cycloid. Trunk and head entirely scaled, except for ventral surface of head. No scales on dorsal and anal-fin bases, and two rows of scales on caudal-fin base. Frontal squamation F, G or H-patterned; E-scales overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 25-27, scales regularly arranged; transverse series of scales 10-11; 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 two uppermost pectoral-fin rays in males, sometimes absent; no contact organs on unpaired fins.

Cephalic neuromasts: supraorbital 14-17, parietal 1-2, anterior rostral 1, posterior rostral 1, infraorbital 2 + 22-26, preorbital 2-3, otic 4-5, post-otic 3-4, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 18-22, mandibular 9-11, lateral mandibular 4-5.

Basihyal almost triangular, width about 35 % of length; basihyal cartilage short, about 30 % of total basihyal length, without lateral projections. Six branchiostegal rays. Two teeth on second pharyngobranchial. Gill-rakers on first branchial arch 2 + 8. Dermosphenotic ossification absent. Ventral process of posttemporal short. Total vertebrae 26-28.

Coloration

Males: sides of body dark bluish gray to black, with 7-12 vertical rows of bright blue dots arranged in zigzag pattern. Urogenital papilla dark gray. Opercular and infraorbital region bright blue; faint, wide and short, with a gray infraorbital bar and supraorbital blotch. Iris brown, with black bar through center of eye. Unpaired fins dark gray to black, with light blue dots over entire fins; light blue to golden subdistal stripe, bordered by a narrow black distal stripe on dorsal fin; distal row of bright blue spots on distal margin of caudal and anal fins. Pectoral fins bluish gray, darker on ventral portion, with light blue spots. Pelvic fins dark bluish gray, with a bright blue distal spot.

Females: sides of body light yellowish brown, with dark gray spots, usually coalesced, sometimes forming short bars above anal fin; no black spots on anterocentral portion of flank and caudal peduncle; venter pale golden. Opercular region pale greenish golden. Iris light yellow, with a gray bar through center of eye. Faint gray infraorbital and supraorbital bars. Unpaired fins hyaline with dark gray spots, darker and elongated on basal portion; paired fins hyaline.

Distribution

Río de La Plata and río Uruguay floodplains, Argentina and Uruguay (Fig. 20).