Austrolebias elongatus, Wilson J. E. M. Costa, 2006

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 : 57-59

Austrolebias elongatus (Steindachner), new combination

(Figs. 23-24)

Cynolebias elongatus Steindachner, 1881: 98 ( type locality: La Plata , Provincia de Buenos Aires, Argentina; holotype: NMW 76518 ).

Cynolebias porosus non C. porosus Steindachner; Perugia, 1891: 651 (misidentification of specimens from río de La Plata floodplains).

Cynolebias holmbergi Berg, 1897: 296 ( type locality: arroyo Vivorata , Mar Chiquita , Provincia de Buenos Aires, Argentina; lectotype: MACN 5169 , herein designated ).

Cynolebias spinifer Ahl, 1934: 310 ( La Plata, near Buenos Aires , Argentina; lectotype: ZMH H64 , designated by Paepke & Seegers, 1986 ).

Material examined

Argentina: Buenos Aires: NMW 76518 (photo), male holotype, about 50.0 mm SL; La Plata ; no data on collector and date. MACN 5169 , lectotype of C. holmbergi , male, 85.1 mm SL; MCNM 8154 , paralectotype, female, 83.6 mm SL; Argentina: Província de Buenos, arroyo Vivorata ; G. Gaglia, 13 Sep. 1895. MACN 3826 , 1; Argentina: Província de Buenos Aires, rio de la Plata ; G. Gaglia, 19 Sep. 1895. MNRJ 11400 , 2; carretera Villa Elisa-Punta Lara ; R. Vaz-Ferreira & B. Sierra, 2 Nov. 1962. MLP 1956 , 1; La Plata ; E. Mac Donagh, no date. MLP 8456 , 1; road La Plata-Magdalena ; C. Darrieu, no date. MLP 8287 , 2; laguna de Chascomus ; no data on collection. MLP 6408 , 1; rio de La Plata ; S. Coscarón, 23 Jul. 1958. MLP 7764 , 1; Flores ; A. Bachmann, 5 Mar. 1955. UFRJ 4737 , 1; ILPLA 1041 , 1; 13 from the Ruta 2, Vivorata ; W. J. E. M. Costa, R. Filiberto, A. Miquelarena & L. Protogino, 9 Sep. 1998. Uruguay: Soriano: UFRJ 6230 , 2 (c&s); CTL 1252 , 3; Ruta 96, km 8 , 33°26.30’S 58°16.59’W; P. Laurino et al., 12 Sep. 2004.

Diagnosis

Similar to A. monstrosus and A. prognathus , and distinguished from all other species of the A. elongatus group and most other cynolebiatines in possessing some transverse series of small scales on anal-fin base in males, contact organs on the outer surface of the pectoral fin and on caudal fin in males, long jaws (lower jaw 29.3-36.4 % of head length in males), and numerous gill-rakers on first branchial arch (5-6 + 14-16). Similar to A. monstrosus and other congeners in having minute scales on pectoral-fin and caudal-fin bases in older males. Differs from A. monstrosus in the absence of dark bars on flank in males and by having more dorsal-fin rays in males (18-20 vs. 16-18).

Description

Morphometric data appear in Table 3. Males larger than females, largest male examined 151.9 mm SL, largest female 110.7 mm SL. Dorsal profile slightly concave on head, convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle; no distinctive adipose ridge on frontal region. Ventral profile slightly 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 slender to deep in older specimens and slightly compressed. Snout profile slightly pointed and jaws elongated.

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 elliptical, posterior margin on vertical between pelvic-fin base and base of 2nd anal-fin ray in males, between anus and urogenital papilla in females. Tip of each pelvic fin reaching between base of 1st and 3rd anal-fin rays. Pelvic-fin bases medially united or not, the fin membrane not coalesced medially. Urogenital papilla not attached to anal fin. Dorsal-fin origin on vertical between base of 3rd and 7th anal-fin rays in males, between base of 2nd and 6th anal-fin rays in females; dorsal-fin origin between neural spines of 14th and 16th vertebrae; anal-fin origin between pleural ribs of 12th and 14th vertebrae. Dorsal-fin rays 18-20 in males, 16-19 in females; anal-fin rays 21-26 in males, 21-25 in females; caudal-fin rays 32-36; pectoral-fin rays 12-14; pelvic-fin rays 6.

Scales very small, cycloid, and irregularly arranged. Entire trunk scaled, except just above anal-fin base in females. Head scaled, except anterior third of frontal region and ventral surface. Small scales covering approximately one third of caudal fin, eight rows of minute scales on basal third of anal-fin, and minute scales on pectoral-fin base in males; no scales on dorsal fin. Frontal scales small, restricted to posterior frontal portion, without clear arrangement pattern; E-scales not overlapping medially. Longitudinal series of scales about 50-70; transverse series of scales about 30-50; series of scales around caudal peduncle about 30-40. One prominent contact organ on each scale of flank and opercle in males. Row of contact organs on inner surface of all pectoral-fin rays, outer surface of upper pectoral-fin rays, lateral surface of entire anal-fin rays, dorsal-fin rays, and distal lateral surface of caudal-fin rays in males.

Cephalic neuromasts: supraorbital 31-35, parietal 3-5, anterior rostral 3-4, posterior rostral 3-4, infraorbital 5-6 + 33-35, preorbital 3, otic plus post-otic 18-21, supratemporal 2-4, median opercular 1, ventral opercular 1-2, preopercular 32-45, mandibular 17-27, lateral mandibular 6-8.

Basihyal subtriangular, width about 85 % of length; basihyal cartilage short, about 35 % of total basihyal length, without lateral projections. Six branchiostegal rays. Four teeth on second pharyngobranchial. Gill-rakers on first branchial arch 5-6 + 15-16. Dermosphenotic ossification absent. Ventral process of posttemporal long. Total vertebrae 34-36.

Coloration

Males: side of body dark yellowish brown to dark gray, often with pale golden vermiculate marks. Urogenital papilla gray. Opercular and infraorbital regions dark brownish golden; approximately rectangular, elongate black infraorbital bar; dark gray supraorbital spot. Iris reddish brown, with dark brown bar through center of eye. Unpaired fins dark brown, with dark yellow rays. Pelvic fins dark gray. Pectoral fins hyaline.

Females: sides of body dark brown, with vermiculate pale golden marks; no dark spot on anterocentral portion of flanks and caudal peduncle. Opercular region pale golden. Iris reddish brown, with dark brown bar through center of eye. Dark gray infraorbital bar and faint gray supraorbital spot. Unpaired fins hyaline, with small dark brown spots; paired fins hyaline.

Distribution

Lower río de La Plata basin and adjacent coastal plains to south, and río Uruguay floodplains, Argentina and Uruguay (Fig. 18)

Remarks

Vaz-Ferreira & Sierra (1973) considered C. holmbergi to be a synonym of C. elongatus . Malumbres (1994) reported the occurrence of C. bellottii and C. nonoiuliensis Taberner, Fernández & Castelli at Arroyo Vivoratá, Província de Buenos Aires, the type locality of C. holmbergi . However, based on this record, Wildekamp (1995) considered C. holmbergi a valid species and senior synonym of C. nonoiuliensis , despite some highly conflicting characters presented in the original descriptions of both species (e.g., longitudinal series of scales more than 60, irregularly arranged in C. holmbergi , vs. 35-37, regularly arranged in C. nonoiuliensis ). Studies of recent collections from Arroyo Vivoratá revealed that specimens identified as C. nonoiuliensis by Malumbres (1994) and as C. holmbergi by Wildekamp (1995) were in fact A. robustus (see above; Costa, 2002a, 2003). Examination of type specimens of C. holmbergi and two topotypes (ILPLA 1041, a female, 63.1 mm SL, and UFRJ 4737, a male, 103.5 mm SL) revealed that C. holmbergi is a synonym of A. elongatus , as earlier suggested by Vaz-Ferreira and Sierra (1973). The original description of C. holmbergi was based on two specimens: MACN 5169, male, 85.1 mm SL, herein designated as lectotype, and MCNM 8154, female, 83.6 mm SL, now the paralectotype. Braga and Piacentino (1994: 101) listed a third syntype of C. holmbergi , MACN 3826. However, since Berg (1897: 297) cited this specimen (a male, 151.9 mm SL) in a footnote, without confirming its identity, it is not considered part of the type series.