IUCN threat status:

Vulnerable (VU)

Comprehensive Description

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Austrolebias affinis (Amato)

(Fig. 29)

Cynolebias affinis ZBK Amato, 1986: 6 ( type locality: floodplains of arroyo Tres Cruces, Ruta 5, km 399.5 , Tacuarembó , Uruguay [ 31°39.11’S55°54.01’W ]; holotype : MUNHINA 2468 )

Material examined

Uruguay : Tacuarembó , ríoTacuarembó drainage, río Uruguay basin: MZUSP 36448 , 1 paratype ; MZUSP 36449 , 1 paratype ; floodplains of the arroyo Tres Cruces, road 5, km 399.5 ; L. H. Amato , 3 Nov. 1985 . UFRJ 6158 , 5; CTL 158 , 12; same locality ; P. Laurino et al. , 17 Aug. 2004 . UFRJ 6159 , 10; UFRJ 6160 , 8 (c&s); same locality ; P. Laurino et al. , 22 Aug. 2004 . UFRJ 5058 , 2 (c&s); Tranqueras ; C. Grosse-Schware & T. Litz , 21 Oct. 1999 . UFRJ 6197 , 2; CTL 080 , 11; Paso Lambare , 31°31.89’S55°57.64’W ; P. Laurino et al. , 15 Aug . 2002 . UFRJ 6198 , 2; CTL 1213 , 20; Ansina , 31°53.08’S55°29.52’W ; P. Laurino et al. , 25 Aug. 2004 . CTL 176 , 18; Ansina , 31°53.08’S55°29.52’W ; P. Laurino et al. , 17 Aug. 2002 . Rivera : UFRJ 6195 , 5; UFRJ 6196 , 5 (c&s); CTL 1126 , 86; 31°14.03’S55°50.69’W ; P. Laurino et al. , 24 Aug. 2004 [[ Rivera ]]. - CTL 1173 , 15; 31°11.60’S55°47.35’W ; P. Laurino et al. , 24 Aug. 2004 [[ Rivera ]]. CTL 1178 , 6; 31°11.20’S55°46.83’W ; P. Laurino et al. , 24 Aug. 2004 [[ Rivera ]]. CTL 1132 , 30; 31°13.42’S55°50.60’W ; P. Laurino et al. , 24 Aug. 2004 [[ Rivera ]].

Diagnosis

Usually differs from the remaining species of the A. alexandri group by female possessing anterodorsal profile of trunk strongly convex. Similar to A. duraznensis and A. juanlangi and distinguished from all other species of the A. alexandri group by the posterior margin of each pectoral fin in males reaching a vertical between urogenital papilla and base of second anal-fin ray (vs. reaching between base of 2nd and 6th anal-fin rays). Differs from A. duraznensis and A. juanlangi by having more neuromasts in the infra-orbital series (2 + 25-27 vs. 2 + 19-23) and light dots on unpaired fins in males covering the entire fins (vs. restricted to the basal portion of fins).

Description

Morphometric data appear in Table 4. Males larger than females, largest male examined 32.3 mm SL, largest female 29.2 mm SL. Dorsal profile convex from snout 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 pelvic-fin base and base of 2nd anal-fin ray in males, on vertical through pelvic-fin base in females. Tip of each pelvic fin reaching between base of 2nd and 3rd anal-fin rays in males, through urogenital papilla in females. Pelvic-fin bases united or in close proximity, medial membrane never coalesced. Urogenital papilla not attached to anal fin. Anal-fin origin on vertical between bases of 1st and 4th dorsal-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 8th and 10th vertebrae in males, between pleural ribs of 10th and 12th vertebrae in females. Dorsal-fin rays 21-27 in males, 16-20 in females; anal-fin rays 22-25 in males, 17-21 in females; caudal-fin rays 25-28; pectoral-fin rays 10-12; pelvicfin 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 H-patterned; E-scales overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 28-29, scales regularly arranged; transverse series of scales 10; scale rows around caudal peduncle 16. One contact organ on each scale of ventral portion of flank 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 15-20, parietal 1-2, anterior rostral 1, posterior rostral 1, infraorbital 2-3 + 25-27, preorbital 2-3, otic 2-3, post-otic 2-5, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 20-26, mandibular 11-13, lateral mandibular 4-5.

Basihyal subtriangular, width about 60 % of length; basihyal cartilage long, about 60 % of total basihyal length, without lateral projections. Six branchiostegal rays. Two teeth on second pharyngobranchial. Gill-rakers on first branchial arch 3 + 9. Dermosphenotic ossification absent. Ventral process of posttemporal vestigial or absent. Total vertebrae 28-29.

FIGURE 29. Austrolebias affinis , UFRJ 6158, male, 26.1 mm SL, above, UFRJ 6158, female, 26.6 mm SL, below; Uruguay: Tacuarembó : arroyo Tres Cruces floodplains.

Coloration

Males: sides of body dark bluish gray to dark brown, with 9-14 rows of bright blue dots, sometimes dots of anteriormost rows united and forming narrow vertical lines in larger males. Urogenital papilla gray. Opercular and infraorbital regions bright blue; approximately rectangular, wide 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 to white dots over entire fins, usually forming subdistal transverse series 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, often with small bright blue spots.

Females: sides of body light yellowish brown, with dark gray spots, usually as large as eye, vertically elongated, sometimes forming short bars above anal fin; 1-7 black spots on anterocentral portion of flank and 1-3 on caudal peduncle, sometimes absent; 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

RíoTacuarembó drainage, río Negro basin, northern Uruguay (Fig. 20).

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