IUCN threat status:

Not evaluated

Comprehensive Description

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Austrolebias cyaneus (Amato)

(Fig. 31)

Cynolebias cyaneus ZBK Amato, 1986: 2 ( type locality: arroyo Dom Marcos floodplains, close to the road BR-290, Municipio de Rio Pardo , Rio Grande do Sul , Brazil ; holotype : MCP 10441 ).

Material examined

Brazil : Rio Grande do Sul : MCP 10441 , male holotype , 37.8 mm SL; MCP 10442 , 1 paratype ; MCP 10443 , 16 paratypes ; MCP 10444 , 20 paratypes ; MZUSP 36446 , 1 paratype ; MZUSP 36447 , 1 paratype ; arroio Dom Marcos floodplains, road BR-290, rio Jacui basin, laguna dos Patos system ; L. R. Malabarba, C. A. Lucena & R. E. Reis , 12 Sep. 1983 . UFRJ 270 , 8; UFRJ 271 , 1 (c&s); UFRJ 5242 , 3 (c&s); same locality ; G. C. Brasil, M. T. Lacerda & D. Nielsen , 16 Aug. 1988 . UFRJ 4492 , 118 ex.; UMMZ 234765 , 15 ex.; same locality ; W. J. E. M. Costa, D. Belote & R. D’Arrigo , 13 Sep. 1997 .

Diagnosis

Distinguished from the remaining species of the A. alexandri group in having the flanks nearly black, with numerous (12-22) bars and vertical rows of bright blue dots in males (vs. never more than 14 vertical marks), and basihyal ossification very reduced, the cartilage occupying about 75 % of basihyal length (vs. about 45-60 %, except A. nigripinnis with about 30 %).

Description

Morphometric data appear in Table 5. Males larger than females, largest male examined 37.8 mm SL, largest female 28.4 mm SL. Dorsal profile convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle; sometimes a 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 in females not lengthened; distal portion of anal fin thickened in females. Caudal fin rounded. Pectoral fins elliptical, posterior margin on vertical between base of 2nd and 5th anal-fin rays in males, on vertical through anus in females. Tip of each pelvic fin reaching between base of 2nd and 3rd anal-fin rays in males, between urogenital papilla and base of 2nd anal-fin ray in females. Pelvic-fin bases in close proximity or united. Urogenital papilla not attached to anal fin. Anal-fin origin on vertical between bases of 1st or 3rd dorsal-fin rays; dorsal-fin origin between neural spines of 8th and 10th vertebrae in males, between neural spines of 10th and 11th vertebrae in females. Anal-fin origin between pleural ribs of 8th and 9th vertebrae in males, between pleural ribs of 10th and 11th vertebrae in females. Dorsal-fin rays 22-25 in males, 15-19 in females; anal-fin rays 21-24 in males, 17-21 in females; caudal-fin rays 24-25; pectoral-fin rays 11-12; pelvic-fin rays 5.

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, rarely G-patterned; E-scales overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 26-27, scales regularly arranged; transverse series of scales 11; scale rows around caudal peduncle 16. One contact organ on each scale of ventral portion of flank in males. Rows of small contact organs on one or two uppermost pectoral-fin rays in males. No contact organ on anal, dorsal and caudal fins.

Cephalic neuromasts: supraorbital 14-18, parietal 1-3, anterior rostral 1, posterior rostral 1, infraorbital 1-2 + 20-24, preorbital 2, otic 2-3, post-otic 4, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 15-17, mandibular 10, lateral mandibular 3-5.

Basihyal subtriangular, width about 60 % of length; basihyal cartilage long, about 75 % of total basihyal length, without lateral projections. Six branchiostegal rays. Urohyal deep. Two or three teeth on second pharyngobranchial. Gill-rakers on first branchial arch 2 + 9. Dermosphenotic ossification absent. Ventral process of posttemporal short. Total vertebrae 27-29.

Coloration

Males: sides of body dark bluish gray to dark brown, with 12-22 rows of bright blue dots, anterior dots united and forming narrow vertical lines. 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, with small bright blue dots over entire fins, irregularly arranged, except often forming subdistal transverse series on dorsal fin; pink or 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 base. Pectoral fins dark gray, with bright blue iridescence.

Females: sides of body light yellowish brown, with dark gray small spots always smaller than pupil; spots on anterocentral portion of flanks and posterior portion of caudal peduncle usually darker, sometimes black; 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 on basal portion; paired fins hyaline.

Distribution

Lower rio Jacuí drainage, laguna dos Patos system, Rio Grande do Sul, southern Brazil (Fig. 20).

FIGURE 31. Austrolebias cyaneus , UFRJ 270, male, 32.5 mm SL, above, UFRJ 270, female, 25.9 mm SL, below; Brazil: Rio Grande do Sul: arroio Dom Marcos floodplains.

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