Austrolebias arachan Loureiro & Azpelicueta & Garcia 2004, sp. n.
Creators: name: Loureiro, Marcelo
name: Azpelicueta, María de las Mercedes
name: Garcia, Graciela
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Cyprinodontiformes
Rivulidae
Austrolebias
Austrolebias arachan

description: Austrolebias arachan sp. n.
Figs 1, 2, Tables I, II
Cynolebias uruguayensis Nion et al., 1994, nomen nudum.
Holotype. ZVC-P 4336, male, 38.6 mm SL, Departamento de Cerro Largo, pond close to Route 7 and Arroyo Chuy, Laguna Merín basin, Uruguay, col. M. Loureiro, F. Teixeira, A. D'Anatro, L. Bocardi, September 2000.
Paratypes. ZVC-P 4574, 6 males (1 C&S), 31.9-43.7 mm SL, 8 females (1 C & S), 24.8- 31.3 mm SL, collected with the holotype. ZVC-P 4314, 2 males, 22.9-24.9 mm SL, 1 female 21.6 mm SL, Departamento cle Cerro Largo, pond close to Melo city, road to the airport, Uruguay, coll. M. Loureiro, F. Teixeira, A. D’Anatro, L. Bocardi, September 2000. ZVC-P 4317, 4 males (2 C &S), 26.0- 29.5 mm SL, 4 females (2 C&S), 23.2-28.3 mm SL, Departamento Cerro Largo, pond at Parque Municipal, Melo city, Uruguay, coll. M. Loureiro, F. Teixeira, A. D'Anatro, L. Bocardi, September 2000. ZVC-P 4329, 4 ınales (all C&S), Departamento de Cerro Largo, pond close to Route 26 and Negro River, Uruguay, coll. M. Loureiro, G. Yemini, C. Hernández, October 1999. ZVC-P 4331, 14 males (3 C&S), 26.9 -33.8 mm SL, 7 females, 24.7- 33.0 mm SL, Departamento de Cerro Largo, pond close to Route 26 and Río Negro, Uruguay, coll. M. Loureiro, F. Teixeira, A. D'Anatro, L. Bacardi, September 2000. ZVC-P 4332, 10 males, 23.6-28.2 mm SL, 5 females, 16.4-22.7 mm SL, Departamento de Cerro Largo pond close to Melo city, road to the airport, Uruguay, coll. M. Loureiro, F. Teixeira, A. D’Anatro, L. Bocardi, September 2000. ZVC-P 4333, 5 males (3 C& S) 28.5-35.6 mm SL, 14 females (5 C&S), 24.5- 35.6 mm SL, Departamento de Cerro Largo pond close to Melo city, road to the airport, Uruguay, coll. M. Loureiro, G. Yemini, C. Hernández, October 1999. ZVC-P 4335, 2 males, 30.95-32.45 mm SL, 4 females, 26.3 -31.9 mm SL, Departamento de Tacuarembó, Route 26, km 331 pond next to the road, Uruguay, coll. M. Loureiro, F. Teixeira, A. D’Anatro, L. Bacardi, September 2000. ZVC-P 4528, 3 males (l C& S), 25.0- 29.4 mm SL, 3 females (1 C &S), 23.6-25.9 mm SL, Departamento de Cerro Largo, a pond at Parque Municipal, Melo city, Uru guay, coll. G. Garcia, July 2000. MHNG 2641.88, 3 males, 30.58-33.89 mm SL, 3 females, 24.53-29.38 mm SL, Departamento de Cerro Largo, pond close to Route 26 and Río Negro, Uruguay, coll. M. Loureiro, F. Teixeira, A. D'Anatro, L. Bocardi, September 2000.
Diagnosis. Austrolebias arachan is distinguished by the following combination of characters: medium size body (no more than 45.8 mm SL); dorsal-ﬁn insertion anterior to anal-ﬁn origin; long dorsal- and anal-ﬁn bases; male body dark brown to black with light yellow narrow vertical bands, dorsal ﬁn dark brown with vertically elongated light yellow dots on basal half, yellowish brown without dots on distal half; proximal half of anal ﬁn dark brown with vertically elongated light blue dots, distal half light blue without dots; caudal ﬁn light blue with light yellow dots proximally, hyaline on distal fourth; pectoral ﬁn light grey with the ventral margin black. Males with contact organs on scales of ﬂanks, specially distributed over anal ﬁn and around pectoral-, pelvic-, and caudal-ﬁn bases; contact organs on distal third of second to ﬁfth anal ﬁn rays and on three or four uppermost pectoral ﬁn rays distally. Anal ﬁn of females with anterior rays elongated, forming a triangular-shaped ﬁn. Pelvic ﬁns joined to each other at their bases or by an epithelial membrane covering completely or partially (one third) of inner edge in both ﬁns. Two to four laarietal neuromasts, sometimes continuous with supra-orbital series. Three pectoral radiais in 92 % of individuals examined, four radiais in the remaining 8 %.
Description. Meristic and morphometric values are presented in tables I and II respectively. Dorsal proﬁle of head straight or slightly concave; dorsal proﬁle strongly convex from rear of head to dorsal-fin origin, less convex in "females; straight below dorsal ﬁn, and straight or scarcely concave on caudal peduncle. Ventral proﬁle arched from tip of lower jaw to end of anal-ﬁn. Maximum body depth at pelvic-ﬁn origin (Fig. 1); females with lower body.
Dorsal ﬁn with 21 -26 rays in males; in females, 16-20. Dorsal-ﬁn tip of males founded, acute in females. Second proximal pterygophore of dorsal ﬁn through a vertical between vertebrae 7 and 8 in males; through vertebrae 9 and 11 in females. Anal ﬁn with 22-27 rays in males, 17 - 22 in females. Anal-ﬁn tip rounded in males; anterior rays elongated, forming a triangular ﬁn in females, ratio between longest anal-ﬁn ray/anal-ﬁn base 0.76- 1.21 (mean 0.94). Anal-ﬁn origin through a vertical between 211d to 51h dorsal-ﬁn rays in males and females. Caudal ﬁn with distal margin slightly rounded in males, with 20-29 rays; caudal ﬁn rounded with 20-26 rays in females. Caudal-ﬁn skeleton supported by last three or four vertebrae. Pectoral ﬁn with 11 - 13 rays in males, 10- 14 in females; pectoral-ﬁn margin rounded, with middle rays longer; tip of pectoral ﬁn reaching bases of 2nd to 6*" anal-ﬁn rays in males, and half or two thirds of pelvic-ﬁn length of females. Pelvic ﬁn with 4-7 rays, covering urogenital papilla and surpassing 3 to 5 anal-ﬁn ray bases in males, scarcely surpassing anal-ﬁn origin in females; distal ﬁn margin rounded. Pelvic ﬁns joined to each other at their bases or joined by an epithelial membrane covering completely or partially (one third) of inner edge in both ﬁns.
Total number of vertebrae 27 -30, number of precaudal vertebrae 11- 13; second vertebrae pre-zygapophysis poorly developed; post-temporal ventral process variably developed, process reduced or absent in 47 % of the individuals, in rest process moderate or well developed.
Scales cycloid, 27 - 34 on lateral series; transverse scales 11 - 18; scales around caudal peduncle 14-20; 1 -3 series over caudal ﬁn. Suborbital and postorbital regions scaled.
Contact organs on scales placed over anal-ﬁn base, many contact organs distributed around pectoral and pelvic ﬁn bases, peduncular area completely covered by contact organs. Contact organs on distal half of uppermost pectoral ﬁn rays 1 -3 and on distal third of anal ﬁn rays 2-6.
Supraorbital neuromasts 13 -22, parietal neuromasts 2-4. Ventral gill rakers 7 - 11, dorsal gill rakers 2-4. Basihyal slightly widened, basihyal cartilage 50-60 % of total basihyal length. Two to 4 teeth in second pharyngobranchial. Fourth ceratobranchial with l or 2 series of teeth mono-, bi- or multicuspidate. Dermosphenotic absent.
Coloration in life: Male: Body dark brown with transverse well deﬁned narrow light yellow bands, between those bands may appear some poorly deﬁned bands with the same coloration. Opercular region bluish. Suborbital and supraorbital bands black. Dorsal ﬁn dark brown with vertically elongated light yellow dots in the proximal half, yellowish brown without dots in the distal half; proximal half of anal ﬁn dark brown with vertically elongated light blue dots, distal half light blue without dots; caudal ﬁn light blue with light yellow dots proximally, hyaline in distal fourth; pectoral ﬁn grey with lower margin black; pelvic ﬁn bluish.
Female: Pale brown body, with darker brown iiregular dots or stripes on ﬂanks. Dorsum darker than rest of body. Opercular region yellowish green iridescent. Suborbital band faint, supraorbital absent. Dorsal and anal ﬁns proximally covered by irregular black to brown dots or diffuse vertical bands or completely hyaline; most specimens with dots on basal one third of caudal ﬁn; a few specimens, more or less one third of them, Without dots 0n caudal ﬁn. Pectoral ﬁn hyaline; pelvic ﬁn light grey.
Cytogenetic analysis. The mitotic metaphase studies from 15 individuals (ten males and ﬁve females) showed 2n=48, NF= 60 and gonial meiotic cells from testis N=24. A 11 individuals with following chromosome formula: three pairs of biarmed chromosomes of submetacentric (SM) type, and 23 pairs of ST-A chromosomes (Fig. 2); three pairs of large acrocentric chromosomes; two Ag-NORs placed at terminal position in small aims of ﬁrst SM chromosome pair (see arrows, Fig. 2). C-bands located at centromeric and telomeríc positions in some chromosome pairs. Large heterochromatic blocks of C-bands occuring at interstitial regions of extra large ST-A type.
Etymology. The name arachan, Originally refers te native inhabitants from the vicinity of Porto Alegre city and Laguna de los Patos system (Brazil). At present, it refers to people from Departamento de Cerro Largo (Uruguay), where several populations of the new species of Austrolebias occur.
Distribution. The new species is known from localities of the upper Río Tacuan’ drainage (Laguna Merín basin), and upper Río Negro drainage (Rio Uruguay basin); all localities are between 50 and 100 meters above sea level (Fig. 3).
description: Published as part of Loureiro, Marcelo, Azpelicueta, María de las Mercedes & Garcia, Graciela, 2004, Austrolebias arachan (Cyprinodontiformes, Rivulidae), a new species of annual fish from northeastern Uruguay, pp. 21-30 in Revue Suisse de Zoologie (21 - 30) (21 - 30) 111 on pages 23-26, DOI: 10.5962/bhl.part.80223, http://zenodo.org/record/10019166