Astyanax endy, J. M. Mirande, G. Aguilera & M. D. L. M. Azpelicueta, 2006

J. M. Mirande, G. Aguilera & M. D. L. M. Azpelicueta, 2006, Astyanax endy (Characiformes: Characidae), a new fish species from the upper Río Bermejo basin, northwestern Argentina., Zootaxa 1286, pp. 57-68 : 59-66

Astyanax endy , new species

(Figs. 1-3, table 1)

Holotype. CI-FML 3834 male, 55.8 mm SL, Argentina: Salta, Orán, Río Bermejo basin, tributary of Río Bermejo in its intersection with Ruta Provincial 19, near Estancia Santa Rosa (64º24’13’’W - 22º43’18’’S; approximately 440 meters above sea level). Coll: M. Mirande, G. Aguilera and G. Padilla, August 2003.

Paratypes: CI-FML 3835, 14 ex., 48.6-56.3 mm SL, collected with the holotype. CI-FML 3836, 13 ex., 39.3-62.0 mm SL, Argentina: Salta, Orán, El Oculto, Río Bermejo basin, Río Anta Muerta, tributary of Río Blanco. Coll: M. Mirande & G. Aguilera, May 2002.

Additional Material (not designated as paratypes): CI-FML 3262, 23 ex., 29.4-50.7 mm, Argentina, Salta, La Bambú, Río Bermejo basin, Río Anta Muerta. CI-FML 3838, 4 ex., 24.2-44.6 mm, Argentina, Salta, Orán, Estancia Anta Muerta, Río Bermejo basin, Río Pescado. CI-FML 3839, 2 ex., 52.8-63.2 mm, Argentina, Salta, Orán, Río Bermejo basin, Río Santa María. CI-FML (uncatalogued) 2 ex. (C&S), 48.6-49.6 mm, same data as holotype. CI-FML (uncatalogued) 2 ex. (C&S), 46.3-54.7 mm, Argentina, Salta, Orán, El Oculto, Río Anta Muerta. CI-FML 3848, 1 ex (C&S), 43.6 mm, Argentina, Salta, Orán, El Oculto, Arroyo El Oculto.

Diagnosis: Astyanax endy is distinguished by the combination of the following characters: a markedly convex snout profile; deep body (36.6-42.2 % SL); relatively large orbital diameter (36.0-40.9 % HL); relatively short interorbital distance (31.9-37.6 % HL); deep caudal peduncle (11.7-14.1 % SL); long caudal peduncle (12.6-15.9 % SL), short upper-jaw length (34.4-40.2 % HL); maxilla scarcely reaching anterior margin of eye; maxilla meeting mouth commissure at an oblique angle; 35-37 perforated scales in lateral line; 7/6 transverse scales above and below lateral line on body; 17-24 branched anal-fin rays; tricuspidate or pentacuspidate teeth on outer premaxillary row; 1-2 tricuspidate or pentacuspidate maxillary teeth; 4 gradually decreasing dentary teeth, followed by 1 intermediate and 3-6 small tricuspidate or conical teeth; and 19-21 gill-rakers in first branchial arch.

A detailed comparison of Astyanax endy with the other species of Astyanax appears in the “Discussion” section later in this paper.

Description: Morphometric data for the holotype and 27 paratypes are presented in Table 1. Body rather deep, the maximum depth anterior to dorsal-fin origin. Dorsal profile of body moderate to strongly convex in snout region, straight to supraoccipital tip, convex from this point to dorsal-fin origin; slanted ventrally from dorsal-fin origin to caudal peduncle; gently concave along caudal peduncle to caudal-fin base. Ventral profile of body convex from tip of lower jaw to pelvic-fin origin, straight between pelvic and analfin origins, posterodorsally slanted from anal-fin origin to caudal peduncle, and slightly convex along caudal peduncle. Ventral portion of body between bases of pectoral and pelvic fins transversally rounded; ventral portion of body between origins of pelvic and anal fins more compressed. Dorsal-fin origin usually situated nearer base of caudal-fin rays than snout tip. Pelvic-fin origin located anteriorly to vertical through dorsal-fin origin. Anal-fin origin located posteriorly to vertical through base of last dorsal-fin ray. Tip of pectoral fin reaching pelvic-fin origin, and pelvic fin reaching anal-fin origin in larger mature males.

Mouth terminal, placed at level of lower third of eye. Premaxilla bearing two series of teeth; a developed ascending process, with rather broad base and acute tip. Outer premaxillary tooth row with 3(9) or 4(19*) tricuspidate or pentacuspidate teeth. Inner premaxillary row with 5 teeth gently concave anteriorly; slender symphysial tooth, with 4 cusps, the second and third with 5-7 cusps; and the remaining teeth with 3-5 cusps (Fig. 2). Ascending maxillary process well developed; laminar portion of maxilla meeting mouth commissure at an oblique angle, bearing 1(23*), or 2(5) tricuspidate or pentacuspidate teeth. Dentary with 9-12 teeth: four anterior teeth decreasing gradually in size, followed by one tooth of intermediate size, and a series of 4-7 smaller conical or tricuspidate teeth (Fig. 2); two anterior teeth hexacuspidate or heptacuspidate, the third and fourth pentacuspidate to heptacuspidate, the fifth tricuspidate to pentacuspidate.

Eye of medium size. Third infraorbital reaching close to horizontal arm of preopercle latero-sensory canal, although not contacting it.

Dorsal fin rays iii, 9; first one readily visible in C&S specimens; last unbranched and first branched rays longest. Anal fin rays iv -v, 17(1), 19(1), 20(1), 21(6*), 22(6), 23(12), or 24(1); females with last unbranched and first 5-6 branched rays forming a small lobe. Anal fin in males with straight distal margin. Males with hooks on last unbranched analfin ray and posterior branch of anterior 6-12 branched anal-fin rays. Principal caudal-fin rays i,17,i; caudal lobes of approximately same size. Pectoral fin rays i,11(2), 12(15), or 13(11*). Each pelvic fin with splint and i,7 rays; males with medially directed hooks well developed in medial branches of first to fifth or sixth branched pelvic-fin rays.

Scales cycloid, with radii only on posterior field and not meeting each other anteriorly; no circuli on posterior field. Lateral-line with 35(11*), 36(13) or 37(4) perforated scales; 6(2) or 7(26*) transverse scales from dorsal-fin origin to lateral line, and 5(2), 6(24), or 7(2*) scales from lateral line to pelvic-fin origin; 15(3), 16(17*) or 17(8) scales around caudal peduncle; one row with 9-14 scales covering base of anterior seventh to fourteenth anal-fin ray; scales covering only base of caudal-fin rays.

Lateral edge of first branchial arch with 19-21 gill rakers, placed as follows: 7-8 on epibranchial, 1 on cartilage, 10 on ceratobranchial, and 2 on hypobranchial; medial-posterior edge of epibranchial with a second row of 4-5 gill rakers. One row of 3-7 hooks on anterior edge of first ceratobranchial gill rakers; occasionally also a 1-3 hooks on posterior edge. Total vertebrae 33-35 (16-17 precaudal vertebrae and 17-18 caudal vertebrae). Pairs of ribs 11-12. Caudal fin with 9-10 dorsal and 7-9 ventral procurrent rays.

Color in life: Body silvery, especially over lateral stripe and abdominal area; darker on dorsal part of body. Dark humeral spot vertically elongated. Caudal spot hardly visible, becoming evident over caudal fin to end of its medial rays. Orange to intense red on dorsal and anal fins; caudal lobes yellowish proximally and distally, with an intense red area in middle of its length. Pupil with a reddish area on upper margin and often on lower one.

Color in alcohol-preserved specimens: Uniformly yellowish, darker dorsally.

First black humeral spot vertically elongated; second one faint although always evident. Lateral stripe very faint anteriorly, becoming more evident posteriorly. Caudal spot well developed, black, triangular or irregular in shape, extending to tip of middle caudal-fin rays. Dorsal, anal, pelvic and adipose fins hyaline; caudal-fin lobes hyaline. Sometimes, pupil bearing a vertical brownish stripe.

Distribution: Upper Río Bermejo basin, Provincia de Salta, Argentina (Fig. 3).

Habitat notes: In a series of collections made by the authors during different seasons over a three-year period, this species was very abundant in a broad range of environments, from rather fast-flowing streams to deep pools.

Etymology: The specific epithet endy is a Chiriguano word meaning flame, in allusion to the color of the caudal-fin in life. A noun in apposition.

Discussion

Astyanax endy resembles A. eigenmanniorum in number of lateral line scales and fin-rays, but is distinguished from that species by having a higher number of transverse scales (7/6 vs. 6/5) on the body, the maxilla scarcely reaching (vs. surpassing) the anterior margin of the eye, a lower number of gill-rakers in the first branchial arch (19-21 vs. 23-26), lesser upper-jaw length (34.4-40.2 vs. 41.0-46.3% HL), deeper body (36.6-42.2 vs. 32.1-37.9% SL), and greater postorbital distance (41.0-48.5 vs. 33.0-41.7 % HL).

The new species is distinguished from Astyanax leonidas Azpelicueta, Casciotta & Almiron ; A. ojiara Azpelicueta & Garcia ; A. troya Azpelicueta, Casciotta & Almiron ; A. pynandi Casciotta, Almiron & Azpelicueta ; A. chico Casciotta & Almiron ; A. hermosus Miquelarena, Protogino & Lopez ; and A. tumbayaensis Miquelarena & Menni by the absence of hooks on the dorsal, caudal and/or pectoral fins of males. Astyanax endy differs from A. ojiara , A. troya , A. pynandi , A. chico , and A. ita Almiron, Azpelicueta & Casciotta in having 4 gradually decreasing dentary teeth, 1 intermediate, and 4-7 posterior conical teeth of approximately equal size (vs. 7-10 gradually decreasing dentary teeth).

Astyanax endy shares a similar shape of the 5 anterior dentary teeth with A. leonidas , A. hermosus , and A. pampa Casciotta, Almiron & Azpelicueta . It is further distinguished from A. leonidas by the dorsal profile of the body (nearly straight vs. very convex), greater number of small posterior dentary teeth (4-7 vs. 3-4), greater number of anal-fin rays (usually 21-23 vs. 17-21), deeper body (36.6-42.2 vs. 30.2-35.3 % SL), greater interorbital distance (31.9-37.6 vs. 26.9-30.4 % HL), and greater number of gill rakers on first branchial arch (19-21 vs. 17-19). Astyanax endy is also distinguished from A. hermosus by shape of the humeral spot (vertically elongated vs. Y-shaped), longer caudal peduncle (12.6-15.9 vs. 6.8-10.4 % SL), greater eye diameter (36.0-40.9 vs. 29.7-34.7 % HL), and shorter maxillary length (22.7-28.0 vs. 30.8-34.0 % HL). The new species is also distinguished from A. pampa by the greater number of branched anal-fin rays (usually 21-23 vs. 17-20), greater number of transverse scales (7/6 vs. 6/5), and longer caudal peduncle (12.6-15.9 vs. 10.5-12.7 % SL).

Astyanax endy is distinguished from A. latens , A. tupi Azpelicueta, Mirande, Almiron & Casciotta ; and A. saguazu Casciotta, Almiron & Azpelicueta by a lower number of branched anal-fin rays (17-24 vs. 24-29 in A. latens , 24-27 in A. tupi , and 25-29 in A. saguazu ). In addition, it is distinguished from A. latens and A. tupi by a lower number of gill rakers on the first branchial arch (19-21 in A. endy vs. 26-27 in A. latens and 24-25 in A. tupi ). The new species is distinguished from A. paris Azpelicueta, Almiron & Casciotta by the lower number of maxillary teeth (1-2 vs. 3-4). Astyanax endy lacks longitudinal stripes between the scale rows, which are found in A. lineatus ; and also lacks the horizontally oval first humeral spot found in both A. asuncionensis and A. abramis . Astyanax endy can be further distinguished from A. chico by a convex (vs. straight) snout profile; an oblique (vs. nearly right) angle between maxilla and mouth commissure; cusp bases from inner premaxillary row teeth following an arch (vs. nearly aligned) in lingual view; and a longer caudal peduncle (12.6-15.9 vs. 10.1-12.0 % SL). The new species can be further distinguished from A. tumbayaensis by the absence of a reticulated pigmentation pattern; the absence of densely concentrated superficial chromatophores on the third infraorbital, opercle, premaxilla, maxilla and dentary; a greater orbital diameter (36.0-40.9 vs. 28.9- 35.0 % HL); a shorter interorbital distance (31.9-37.6 vs. 38.8-44.1 % HL); and a different distribution of anal-fin hooks (on anterior 7-12 rays vs. on anterior 16-19 rays).

In the upper Río Bermejo basin, the following species occur together with Astyanax endy : A. latens , A. chico , A. lineatus , A. asuncionensis , A. abramis , and A. tumbayaensis , with the last species limited to a restricted area in the highlands of Jujuy Province, Argentina.