Austrolebias gymnoventris

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 : 21-23

Austrolebias gymnoventris (Amato)

(Fig. 7)

Cynolebias gymnoventris Amato, 1986: 2 ( type locality: arroyo India Muerta floodplains, 150 m from bridge on Ruta 13 and 50 m from the road to Southeast, near Velazquez , Rocha, Uruguay [34°3.36’S 54°14.59’W]; holotype: MUNHINA 2460 ).

Material examined

Uruguay: Rocha: MZUSP 36450 , 1 paratype; MZUSP 36451 , 1 paratype; arroyo India Muerta floodplains, 150 m from bridge on Ruta 13 ; L. H. Amato, G. Dittricht & C. Pérez, 10 Sept. 1984. UFRJ 5254 , 6; UFRJ 5253 , 6 (c&s); CIMC 3502 , 13; same locality ; M. Cheffe, 7 Jul. 2000. UFRJ 6163 , 4; UFRJ 6164 , 2 (c&s); CTL 1454 , 20; temporary pool near arroyo India Muerta, Ruta 13, km 251 ; P. Laurino et al., 28 Aug. 2004. CTL 1385 , 7; Ruta 9, km 254.8 , 34°13.23’S 53°57.26’W; P. Laurino et al., 27 Aug. 2004. Maldonado: CTL 1399 , 2; Salamanca , 34°6.32’S 54°36.05’W; P. Laurino et al., 28 Aug. 2004.

Diagnosis

Similar to A. jaegari , from which it is distinguished by having shorter pectoral fins (23.9-26.0 % SL in males, 24.9-26.6 % SL in females, vs. 26.3-29.2 % SL in males, 27.8-29.9 % SL in females), anal-fin origin between pleural ribs of 8th and 10th vertebrae in males (vs. between pleural ribs of 6th and 8th vertebrae), dorsal-fin origin on vertical through pelvic-fin base or anterior to it in males (vs. on vertical between pectoral-fin base and anus), and anterior light bars of flank in male narrower (widest bar 2.5-3.2 % SL, vs. 1.7-2.2 % SL).

Distinguished from remaining congeners by the combination of absence of scales on venter (vs. entire venter covered with scales), absence of suborbital and supraorbital dark marks in live specimens (vs. conspicuous dark grey to black supraorbital and suborbital bars), and flank side dark brownish gray to black with light grey bars on anterior portion, without brilliant colors in male (vs. never a similar color pattern).

Description

Morphometric data appear in Table 1. Males larger than females, the largest male examined 30.8 mm SL, largest female 25.5 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; no adipose ridge on frontal region. 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; jaws short.

Tip of both dorsal and anal fin rounded. Anteromedian rays of anal fin of females not lengthened; distal portion of anal fin thickened in females. Caudal fin rounded. Pectoral fins elliptical, posterior margin on vertical between base of 1st and 4th anal-fin rays in males, between pelvic-fin base and anus in females. Tip of each pelvic fin reaching base of 3rd anal-fin ray in males, between urogenital papilla and base of 1st anal-fin ray in females. Pelvic-fin bases in close proximity or united, medial membrane never united. Urogenital papilla not attached to anal fin. Anal-fin origin on vertical through base of 3rd or 4th dorsal-fin ray. Dorsal-fin origin between neural spines of 5th and 7th vertebrae in males, between neural spines of 9th and 10th vertebrae in females. Anal-fin origin between pleural ribs of 8th and 10th vertebrae in males, between pleural ribs of 11th and 12th vertebrae in females. Dorsal-fin rays 22-26 in males, 17-19 in females; anal-fin rays 21 -23 in males, 16-18 in females; caudal-fin rays 21-23; pectoral-fin rays 12; pelvic-fin rays 5.

Scales large and cycloid. Trunk and head scaled, except venter, ventral surface of head, and preopercular region; squamation reduced on opercle. No scales on dorsal and anal-fin bases, and two rows of scales on caudal-fin base. Frontal squamation E- or F- patterned; E-scales slightly overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 26-27, the scales regularly arranged; transverse series of scales 11-13; scale rows around caudal peduncle 16. One prominent contact organ on each scale of anteroventral portion of flank and opercular region in male. Row of small contact organs on uppermost pectoral-fin ray, sometimes on distal portion of first two anal-fin rays in males. No contact organs on dorsal and caudal fins.

Cephalic neuromasts: supraorbital 12-14, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 1-2 + 16-18, preorbital 2, otic 2, post-otic 3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular 12-15, mandibular 8-9, lateral mandibular 4.

Basihyal subtriangular, width about 85 % of length; basihyal cartilage short, about 35 % of total basihyal length, with slight lateral projections. Six branchiostegal rays. Five teeth on second pharyngobranchial. Gill-rakers on first branchial arch 2 + 9. Dermosphenotic ossification absent. Ventral process of posttemporal short, sometimes vestigial. Total vertebrae 28-30.

Coloration

Males: sides of body dark bluish gray to dark brown, with 5-9 light gray bars; anterior bars lighter and wider than posterior ones, 2.5-3.2 % SL; anterior bars approximately half interspace width. Urogenital papilla dark gray. Opercular and infraorbital regions bright blue; infraorbital and supraorbital absent, sometimes scarcely visible. Iris yellowish brown with gray bar through center of eye. Unpaired fins dark gray, with white to light blue dots over entire fin; pink iridescence on distal portion of dorsal fin; intense bright blue iridescence on distal portion of anal fin, forming distinctive stripe. Pelvic fins bright blue. Pectoral fins hyaline.