Austrolebias quirogai, Loureiro & Duarte & Zarucki, 2011

Loureiro, Marcelo, Duarte, Alejandro & Zarucki, Matías, 2011, A new species of Austrolebias Costa (Cyprinodontiformes: Rivulidae) from northeastern Uruguay, with comments on distribution patterns, Neotropical Ichthyology 9 (2), pp. 335-342 : 336-338

Austrolebias quirogai , new species

Fig. 1

Holotype. ZCV-P 9758 , male, 36.8 mm SL, Uruguay, Departamento de Cerro Largo, río Negro basin, pond near arroyo Cordobés , 32º36’59’’S 55º19’24’W, Sep 2009, M. Loureiro, M. Zarucki & A. Duarte.

Paratypes. Uruguay, Departamento de Cerro Largo. ZVC-P 8725 , 33 males, 24.7-38.2 mm SL (5 c&s), 36 females, 21.0- 29.9 mm SL (5 c&s), río Negro basin , pond near arroyo Cordobés, 32º36’59’’S 55º19’24’W, Sep 2009, M. Loureiro, M. Zarucki & A. Duarte. ZVC-P 8742 , 25 males, 23.3-34.0 mm SL (2 c&s), 20 females, 20.1-26.0 mm SL, río Negro basin , pond near arroyo Quebracho , 32º35’29’’S 54º41’6.44’’W, Sep 2009, M. Loureiro, M. Zarucki & A. Duarte. ZVC-P 8699 , 10 males, 37.3-48.2 mm SL (2 c&s), 28 females, 29.4-36.4 mm SL (6 c&s), río Negro basin , pond near arroyo Quebracho , 32º35’29’’S 54º41’6.44’’W, Sep 2007, M. Loureiro, S. Clavijo-Baquet, M. Zarucki & F. Teixeira de Mello. ZVC-P 7743 , 2 females, 28.2-30.2 mm SL, río Negro basin , pond near río Negro at Paso Mazangano, route 44, 32º06’37’’S 54º38’20’’W, 23 Sep 2003, M. Loureiro. ZVC-P 7758 , 3 females, 28.6-29.0 mm SL, Laguna Merín basin , pond near río Yaguarón at Paso San Diego, 31º58’37’’S 53º55’20’’W, Sep 2007, M. Loureiro, S. Clavijo-Baquet, M. Zarucki & F. Teixeira de Mello. ZVC-P 8731 , 36 males, 24.7-30.6 mm SL (5 c&s), 34 females, 16.0- 22.7 mm SL (5 c&s), Laguna Merín basin , pond near Río Yaguarón at Paso San Diego, 31º58’37’’S 53º55’20’’W, Sep 2009, M. Loureiro, M. Zarucki & A. Duarte . Departamento de Rivera. ZVC-P 7807, 2 males, 31.4-31.5 mm SL, río Negro basin , pond near río Negro North of Paso Mazangano, route 44, 31º59’14’’S 54º32’59’’W, 8 Aug 2004, M. Loureiro, F. Teixeira de Mello, A. D’Anatro & E. Charbonier .

Diagnosis. The new species is distinguished from all other species of Austrolebias by the unique pigmentation pattern of body and fins in males. This consists of a uniform bluish gray background color on the body that lacks vertical bands, and uniform pigmentation of unpaired fins. Most individuals of the new species can also be recognized by the combination of characters associated with reduced squamation in the abdominal, preopercular, and opercular regions. Reduction in the number of scales in the abdomen occurs in three alternative states: a completely naked abdomen, only a ventral row of small scales, or just area below pectoral fin without scales (vs. scales always absent in anterior part of the abdomen as in A. gymnoventris ). The preopercular region is either completely naked or only has a few scales present in its center (vs. preopercular region always naked as in A. gymnoventris ). The opercular region is from completely naked to only distal edge naked (vs. only opercular distal edge naked as in A. gymnoventris ). In extremely large males (SL> 40 mm) and females (SL> 34 mm), which represent less than 7% of individuals analyzed ( Fig. 2 ), scales almost completely cover the preopercular, opercular, and abdominal regions.

Description. Morphometric data in Table 1 . Body elongate, laterally compressed. Dorsal profile from dorsal tip of mouth to back of head straight, slightly convex to origin of dorsal fin, straight below dorsal fin, and straight on caudal peduncle. Ventral profile arched from tip of lower jaw to origin of anal fin, straight over anal fin, and straight on caudal peduncle. Mouth slightly prognathous.

Dorsal-fin rays in males 19-27 (mode 23); in females 15-19 (mode 17). Dorsal and posterior tip of dorsal fin of males rounded. Origin of dorsal fin in males at vertical through vertebrae 6 and 8 in males, in females through vertebrae 10 and 12.Anal-fin rays in males 17-24 (mode 21); in females 14- 19 (mode 17). Anal-fin tip rounded in males.Anal-fin contour rounded in females. Anal-fin origin at vertical through 3 rd and 7 th (mode 5 th) dorsal-fin rays in males and through 2 nd and 5 th (mode 4 th) in females. Caudal fin distal margin rounded, 16-23 (mode 20) rays in males and 16-23 (mode 21) fin rays in females. Caudal-fin rays supported by last 4 or 5 (mode 4) vertebrae. Pectoral fin rays 9-14 (mode 11) in males, 10-12 (mode 11) in females; pectoral-fin margin rounded in males, slightly pointed in females. Pectoral-fin posterior tip reaching from urogenital papilla to 5 th anal-fin ray in males, from origin of pelvic fin to 3 rd anal-fin ray in females. Three pectoral-fin radials. Pelvicfin rays 4 or 5 (mode 5). Pelvic-fin posterior tip from origin of anal fin to 4 th anal-fin ray in males, from urogenital papilla to 3 rd fin ray in females. Pelvic fins separated from each other. Total number of vertebrae 28-31 (mode 30), 11-13 (mode 13) precaudal; 2-4 (mode 3) flattened anterior neural spines.

Scales cycloid, 27-34 (mode 29) in lateral series; transverse scales 11-19 (mode 14) in males, 10-18 (mode 16) in females; scales around caudal peduncle 10-21 (mode 17). Preopercular and opercular region of adults of less than 40 mm of SL (males) and less than 34 mm of SL (females) with naked areas lacking scales, from completely naked to edges without scales ( Fig. 3a ). Abdominal region same pattern of scale reduction: completely naked, only one ventral row of small scales, or area below pectoral fin without scales ( Fig. 3d ).

Contact organs on scales throughout most of body, more conspicuous on abdominal and opercular regions. Contact organs on inner surface of pectoral rays with bony support from first to sixth ray. Contact organs on 2 nd to 8 th anal-fin rays, in some males with bony support from 2 nd to 6 th.

Cephalic neuromast series: Anterior rostral 2; posterior rostral 2; supraorbital 11-19; parietal 1-2; infraorbital 15-25; orbital 1-3; preorbital 2; preopercular 13-21; lateral mandibular 3-5; mandibular 8-14; lateral supratemporal 1-2; posttemporal 1-2; postotic 2-5; median opercular 1; ventral opercular 1.

Ventral gill rakers 7-10 (mode 8), dorsal gill rakers 2-3 (mode 2). Anterior cartilaginous basihyal approximately 1/3 of total length; 1-3 (mode 3) teeth on second pharyngobranchial. Unicuspid rakers on ceratobranchials. Urohyal deep. Ventral process of anguloarticular reduced. Dermosphenotic absent.

Color in life ( Fig. 1b ): Males bluish gray body, darker on dorsal half; abdominal region light pale blue; dorsal portion of head bluish gray with some green hues laterally; isthmus and opercular region bright light blue. Dorsal-fin base bluish gray, distal portion ochre; anal-fin base bluish gray, distal 2/ 3 portion bright light blue; caudal fin same tonalities as body, bluish in ventral half; pectoral fin base light blue, distal half gray; pelvic fin bright light blue. Suborbital band dark gray, supraorbital dark gray but less conspicuous. Female’s body brownish with scattered and sometimes faint dark gray or dark brown vertically elongate spots; abdominal region lighter and yellowish. Fins hyaline. Supra and suborbital band light gray inconspicuous. Faint dark gray vertical bands from origin of dorsal fin to caudal peduncle in 5% of males collected (all from same population) ( Fig. 1c ).

Color in alcohol ( Fig. 1a, d ): Males with brown body, darker in anterior third. Head dark brown, preopercular region lighter. Dark brown supra and suborbital band. Supraorbital band reaching supraorbital neuromast series. Dorsal and anal fins dark brown with basal margin light brown. Caudal, pectoral, and pelvic fins dark brown.

Females light brown body background with scattered darker rounded or slightly elongate spots on whole body. Fins hyaline.

Distribution. The new species lives in temporary ponds from the middle to the upper and eastern río Negro tributaries (río Uruguay basin), and río Yaguarón (Laguna Merín basin) ( Figs. 4-5 ).

Etymology. We name this species to honor Horacio Quiroga, an Uruguayan writer from the early 20 th century, whose tales and fables based on his life in the Misiones rainforest inspired the authors to explore nature and its mysteries. Specific epithet is used as a patronym.

Figures

Fig. 1. a. Holotype of Austrolebias quirogai (ZVC-P 9758, 36.8 mm SL); b. Live male, paratype, from type locality (ZVC-P 8725, 39.8mm SL); c.male,paratype(ZVC-P8742, 31.2mmSL)showing rare pigmentation pattern. d. Female, paratype, from type locality (ZVC-P 8725, 27.8 mm SL).Scale bars = 10 mm.

Fig. 2. Size distribution of individuals analyzed of Austrolebias quirogai. Arrows indicate size above which there is little or no reduction in squamation patterns; F. females, M. males.

Fig. 3. Squamation pattern in head and abdomen of males. a and d, Austrolebias quirogai (ZVC-P 8725, 38.2 mm SL); b and e, A. gymnoventris (ZVC-P 8708, 33.4 mm SL); c and f, A. luteoflammulatus (ZVC-P 4105, 39.4 mm SL).Arrows indicate scales rows.

Fig. 4. Distribution of Austrolebias quirogai (stars); empty star indicates type locality. Distribution data of A. arachan (light gray circles), A. vazferreirai (dark gray circles), A. melanoorus (white triangles), and the A. affinis species group (gray shaded area) were obtained from ZVC-P catalogue database, Costa (2006), and Volcan et al. (2010); each point may represent more than one locality.

Fig. 5. a. Map of hypothesized areas of drainage rearrangements (empty squares) between río Negro and Laguna Merín tributaries, based on distribution patterns of Austrolebias and rivers morphology (elbows of capture); b. Detailed map of localities of Austrolebias and rivers configurations in río Negro and río Yaguarón; c. Detailed map of localities of Austrolebias and rivers configurations in río Negro and río Tacuarí. Scale bars = 10 km; Black arrows indicate proposed elbow of capture. Austrolebias quirogai (stars), A. arachan (light gray circles), A. vazferreirai (dark gray circles), A. melanoorus (white triangles), and A. affinis species group (white circles).