Austrolebias robustus

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 : 37-40

Austrolebias robustus ( Günther)

(Figs. 14-15)

Cynolebias robustus Günther, 1883: 140 ( type locality: “ten miles of San Antonio”, Buenos Ayres [provincia de Buenos Aires], Argentina; holotype: BMNH 1879.6.28:12 ).

Cynolebias nonoiuliensis (non Taberner, Fernandez & Castelli); Malumbres, 1994: 78 ( misidentification of specimens collected in arroyo Vivorata , Argentina ).

Cynolebias holmbergi (non Berg), Wildekamp, 1995: 217 ( misidentification of specimens collected in arroyo Vivorata , Argentina ).

Material examined

Argentina: Buenos Aires: BMNH 1879.6.28:12 (photo), male holotype, about 72.5 mm SL; within ten miles of San Antonio ; E. Gibson, 1879. UFRJ 4740 , 30; UFRJ 4739 , 8 (c&s); small road 13 km from Ruta Nacional 2, near arroyo Vivorata ; W. J. E. M. Costa, A. Miquelarena, L. Protogino & R. Filiberto, 9 Sep. 1998. UFRJ 4748 , 8; Ruta Nacional 2, km 276, near arroyo Vivorata ; W. J. E. M. Costa, A. Miquelarena, L. Protogino & R. Filiberto, 9 Sep. 1998.

Diagnosis

Distinguished from all other species of the A. robustus group by the following combination of features: dorsal-fin origin on vertical through base of 2nd or 3rd anal-fin ray in males, anterior to anal-fin origin in females; longitudinal series scales 31-35; vertebrae 30-34; flank gray in males; spots and bars on flank and one or two large, round dark gray to black spot on caudal peduncle end in females.

Description

Morphometric data appear in Table 2. Males larger than females, largest male examined 72.0 mm SL, largest female 53.1 mm SL. Dorsal profile of head concave, convex from nape to end of dorsal-fin base, and approximately straight on caudal peduncle; no distinctive 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 deep, slightly compressed. Snout blunt and 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 elliptical. Pectoral fins elliptical, posterior margin on vertical between base of 3rd and 5th anal-fin ray in males, between anus and urogenital papilla in females. Tip of each pelvic fin reaching between base of 4th and 5th anal-fin rays. Pelvic-fin bases medially united, sometimes medial pelvic-fin margins not united, often 30-80% united. Urogenital papilla not attached to anal fin. Dorsal-fin origin on vertical through base of 2nd or 3rd anal-fin ray in male, slightly anterior to anal-fin origin in female, anal-fin origin through base of 3rd dorsal-fin ray in female; dorsal-fin origin between neural spines of 10th and 12th vertebrae in male, between neural spines of 11th and 13th vertebrae in female. Anal-fin origin between pleural ribs of 8th and 10th vertebrae in male, between pleural ribs of 10th and 12th vertebrae in females. Dorsal-fin rays 20-25 in males, 19-22 in females; anal-fin rays 23-28 in males, 21-25 in females; caudal-fin rays 26-31; pectoral-fin rays 11-12; pelvicfin rays 5-6.

Scales large and cycloid. Trunk and head entirely scaled, except anterior ventral surface of head. Often one or two rows of scales on anal-fin base; no scales on dorsal-fin base; three rows of scales on caudal-fin base. Frontal squamation F-patterned; E-scales not overlapping medially; scales arranged in transverse pattern. Longitudinal series of scales 31-35, scales regularly arranged; transverse series of scales 15-18; scale rows around caudal peduncle 15-18. One prominent contact organ on each scale of ventral portion of flank and opercle in males. Rows of prominent contact organs on anal-fin rays, sometimes minute contact organs on distal portion of dorsal fin, and row of contact organs on four uppermost pectoral-fin rays in males. No contact organ on caudal fin.

Cephalic neuromasts: supraorbital 17-20, parietal 1-3, anterior rostral 1, posterior rostral 1, infraorbital 2 + 25-27, preorbital 2, otic 4-7, post-otic 7-9, supratemporal 1, median opercular 1, ventral opercular 2, preopercular plus mandibular 39-42, lateral mandibular 4-5.

Basihyal subtriangular, width about 70-80 % of length; basihyal cartilage moderate, about 50-60 % of total basihyal length, with pronounced lateral projection. Six branchiostegal rays. Four to six teeth on second pharyngobranchial. Gill-rakers on first branchial arch 4 + 11. Dermosphenotic ossification absent. Ventral process of posttemporal long. Total vertebrae 30-34.

Coloration

Males: sides of body bluish to greenish gray, sometimes with faint light brown vertical lines, sometimes dark gray round spot on dorsoposterior portion of caudal peduncle; juvenile with vertically elongated dark gray spots on flank and dark gray to black spot at end of caudal peduncle. Urogenital papilla dark gray. Opercular and infraorbital regions pale green; approximately rectangular gray infraorbital bar, faint gray supraorbital bar. Iris yellow, with brown bar through center of eye. Unpaired and pelvic fins dark bluish gray. Pectoral fins hyaline.

Females: sides of body light yellowish brown, with vertically elongated dark gray spots, sometimes forming short bars above anal fin; no distinctively darker spot on anterocentral portion of flank; often one, sometimes two dark gray to black spots on posterior portion of caudal peduncle. Opercular region pale greenish golden. Iris yellow, with gray bar through center of eye. Faint infraorbital and supraorbital gray bars. Unpaired fins hyaline with small dark gray spots; paired fins hyaline.

Distribution

Small isolated coastal basins of northeastern Argentina, between mouth of río de la Plata and Mar del Plata (Fig. 8).

Remarks

Austrolebias robustus has been confused in the ichthyological literature. It was equivocally considered a synonym of either Austrolebias bellottii or Megalebias elongatus over the last three decades. Günther (1883), in a brief note, described the species (as Cynolebias robustus ) on the basis of a single specimen collected in Buenos Aires Province. In that paper, C. robustus was compared with C. porosus , but no mention was made of the three species described by Steindachner (1881) from the same area (Buenos Aires Province). No reference was made to C. robustus in Garman’s (1895) monograph on the Cyprinodontiformes, but it was considered, without justification, to be a synonym of C. bellottii Steindachner by Berg (1897). Subsequently, however, C. robustus was treated as a valid species in most important revisionary studies (Regan, 1912; Ahl, 1922, 1934; Myers, 1952).

Again, without justification, Ringuelet et. al. (1967) followed Berg (1897) in considering C. robustus a synonym of C. bellottii . Vaz-Ferreira and Sierra (1973) claimed that C. robustus was usually regarded as a synonym of C. elongatus , although they provided no supporting evidence, and I could find no previous record of this in the literature (probably the name C. elongatus was mistaken for C. bellottii ). Subsequent authors have uncritically accepted Vaz-Ferreira and Sierra’s (1973) statement (Lazara, 1981; Huber, 1996). In recent years, C. robustus has appeared in checklists as a synonym of either C. bellottii (Radda, 1980) or C. elongatus (Lazara, 1984; Costa, 1995; Wildekamp, 1995), but synonymies and conflicting opinions were based only on suppositions or equivocal interpretations about characters of C. robustus presented in its original description, never on examination of type specimens. Material collected in recent years was misidentified as either C. nonoiuliensis (Malumbres, 1994) or C. holmbergi (Wildekamp, 1995). Following examination of the holotype and recent collections from the vicinity of the type locality, I concluded that C. robustus is a valid species (Costa, 2002a), and transferred it to Austrolebias .