Austrolebias melanoorus

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 : 97-101

Austrolebias melanoorus (Amato)

(Fig. 38)

Cynolebias melanoorus Amato, 1986: 4 ( type locality: swamp at the arroyo Tres Cruces, Ruta 5, km 399.5 , Tacuarembó, Uruguay [31°39.11’S 55°54.01’W]; holotype: MUNHINA 2545 ).

Material examined

Uruguay: Tacuarembó: CTL 158b , 1; temporary pool at floodplains of arroyo Tres Cruces, rio Tacuarembo drainage, rio Uruguay basin, Ruta 5, km 399.5 ; P. Laurino et al., 17 Aug. 2002. UFRJ 6161 , 2; UFRJ 6162 , 4 (c&s); CTL 1035b , 10; same locality ; P. Laurino et al., 22 Aug. 2004. UFRJ 6223 , 3; UFRJ 6224 , 5 (c&s); CTL 1213b , 150; Ansina , 31°53.08’S 55°29.52’W; P. Laurino et al., 25 Aug. 2004. Artigas: UFRJ 6225 , 11; Tranqueras ; C. Gorsse-Schware & T. Litz, 21 Oct. 1999. UFRJ 6221 , 10; UFRJ 6222 , 8 (c&s); CTL 1040 , 150; CTL 1734 , 15; Tranqueras, Ruta 30, temporary swamp near rio Tacuarembo , 31°10.60’S 55°45.88’W; P. Laurino et al., 23 Aug. 2004. Rivera: UFRJ 6219 , 8; UFRJ 6220 , 8 (c&s); CTL 1192 , 110; FYMNSA , 31°6.45’S 55°44.79’W; P. Laurino et al., 24 Aug. 2004. CTL 1196 , 31; 31°5.71’S 55°41.21’W; P. Laurino et al., 25 Aug. 2004 [[ Paso Ataques ]]. CTL 1198 , 78; temporary swamp near rio Tacuarembo , 31°5.22’S 55°41.87’W; P. Laurino et al., 25 Aug. 2004.

Diagnosis

Differs from remaining species of the A. bellottii group in possessing short dorsal and anal fins in males, anal fin with short filaments extending along distal border in males, two anterior rostral neuromasts, and numerous (5-16) black spots on anterocentral portion of flanks in females. Also distinguished from all other species of the A. bellottii group by the following combination of features: no contact organ on anal fin in males, urogenital papilla attached to anal fin in males, dorsal-fin origin slightly anterior or on vertical through anal-fin origin in males, flank light bluish gray with narrow dark gray bars in males, anal-fin rays 25-28 in males, 21-25 in females, longitudinal series scales 26-29, frontal squamation H or G-patterned, and vertebrae 27-31.

Description

Morphometric data appear in Table 7. Males larger than females, largest male examined 50.0 mm SL, largest female 30.3 mm SL. Dorsal profile convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle; dorsal profile on head and anterior portion of trunk often strongly convex in females; often adipose ridge on posterior portion of frontal region in males. Ventral profile gently 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 deep and compressed. Snout blunt and jaws short.

Tip of both dorsal and anal fins rounded. Dorsal and anal fins shortened in males. Fin membranes between rays on distal margin of dorsal and anal fins, and posterior margin of pectoral fins distinctively concave, ray tips forming fringe-like margin. Anteromedian rays of anal fin of females lengthened, anal fin shape nearly triangular; distal portion of anal fin thickened in females. Caudal fin rounded. Pectoral fins elliptical, posterior margin on vertical between base of 3rd and 5th anal-fin rays in males, on vertical through urogenital papilla in females. Tip of both pelvic fins reaching between base of 1st and 3rd anal-fin ray. Medial pelvic-fin membranes about 10-25 % coalesced. Entire urogenital papilla of males attached to anal fin. Dorsal-fin origin on vertical through anal-fin origin or slightly anterior to it in both sexes; dorsal-fin origin between neural spines of 7th and 9th vertebrae in males, between neural spines of 9th and 11th 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 22-27 in males, 17-21 in females; anal-fin rays 25-28 in males, 21-25 in females; caudal-fin rays 25-29; pectoral-fin rays 12-13; pelvicfin rays 5.

Scales large and cycloid. Trunk and head entirely scaled, except ventral surface of head. One row of scales on anal-fin base, no scales on dorsal-fin base, and three rows of scales on caudal-fin base. Frontal squamation usually H-patterned, rarely G-patterned; E- scales slightly overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 26-29; transverse series of scales 12-15; scale rows around caudal peduncle 16-18. No contact organs on flanks and opercle. Row of minute contact organs on two uppermost pectoral-fin rays in males. No contact organ on dorsal, anal, and caudal fins.

Cephalic neuromasts: supraorbital 18-23, parietal 3-7, anterior rostral 2, posterior rostral 1, infraorbital 2 + 22-26, preorbital 3, otic 2- 5, post-otic 3-6, supratemporal 1, median opercular 1, ventral opercular 2-3, preopercular 21-27, mandibular 14-18, lateral mandibular 5-10.

Basihyal nearly triangular, width about 65-90 % of length; basihyal cartilage long, about 55-65% of total basihyal length, with pronounced lateral projection. Six branchiostegal rays. Three or four teeth on second pharyngobranchial. Gill-rakers on first branchial arch 4 + 12. Sometimes two or one minute dermosphenotic ossifications. Ventral process of posttemporal long. Total vertebrae 27-31.

Coloration

Males: sides of body light bluish gray, with 10-18 dark gray bars; bars usually narrower, sometimes wider than interspace; rarely black spot on center of flank. Venter yellowish white. Sides of head dark gray to pale blue on opercular and infraorbital region; nearly rectangular dark gray infraorbital bar; subtriangular dark gray supraorbital bar, not extending to parietal neuromast series. Iris dark yellow, with dark gray bar through center of eye. Unpaired fins dark gray, with light gray small spots on half basal portion; white spots longitudinally elongated on dorsal-fin base and caudal-fin base, and transversely elongated on middle of dorsal fin; distal portion of anal fin black. Pelvic fins dark gray. Pectoral fins hyaline, with black ventral margin.

Females: sides of body light yellowish brown, with vertically elongate dark gray spots, often arranged in vertical series; 5-16 black spots on anterocentral portion of flank; venter pale yellow. Opercular region pale greenish blue. Iris light yellow, with gray bar through center of eye. Pale gray supraorbital and infraorbital bars. Fins hyaline; dorsal and anal fins with dark gray small spots on basal region.

Distribution

Río Tacuarembó drainage, río Uruguay basin, northern Uruguay (Fig. 11).