Zootaxa, Redescription of Astyanax stenohalinus

Zootaxa 2434: 60–68 (2010) www.mapress.com / zootaxa/

ISSN 1175-5326 (print edition)

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Copyright © 2010 · Magnolia Press

ZOOTAXA ISSN 1175-5334 (online edition)

Redescription of Astyanax stenohalinus Messner, 1962 (Characiformes: Characidae), a poorly known species from Argentina and Uruguay ADRIANA E. ALMIRÓN1, JORGE R. CASCIOTTA1, MARÍA DE LAS M. AZPELICUETA1 & MARCELO LOUREIRO2,3 1

División Zoología Vertebrados, Museo de La Plata, UNLP, Paseo del Bosque, 1900 La Plata, Argentina. E-mail: [email protected] 2 Sección Vertebrados, Departamento de Biología Animal. Facultad de Ciencias, Iguá 4225 3 Departamento de Ictiología Museo Nacional de Historia Natural y Antropología. Montevideo, Uruguay

Abstract Astyanax stenohalinus Messner, 1962 is redescribed based on type material and new specimens collected in many localities of Argentina and Uruguay. This species is distinguished by a combination of the following characters: possession of hooks in all fins of males, teeth not expanded distally, two or three maxillary teeth, 37–39 perforated scales in the lateral series, 25–30 branched anal-fin rays, and anal-fin origin located before a vertical through last dorsal-fin ray insertions. Key words: freshwater fishes, characids, Río de la Plata basin, Laguna Merín

Resumen Se redescribe Astyanax stenohalinus Messner, 1962, en base al material tipo y nuevos ejemplares colectados en varias localidades de Argentina y Uruguay. Esta especie se distingue por la combinación de los siguientes caracteres: presencia de ganchitos óseos en todas las aletas de los machos, dientes no expandidos en el extremo distal, 2 ó 3 dientes maxilares, 37–39 escamas perforadas en la línea lateral, 25–30 radios anales ramificados y el origen de la aleta anal está ubicado por delante de la vertical que pasa por la inserción del último radio dorsal.

Introduction Astyanax stenohalinus Messner, 1962, was described based on six specimens from Laguna Mazangano in República Oriental del Uruguay in a mimeographed paper that included a short diagnosis. At present, the combination of characters given by Messner in the original description is not enough to distinguish other congeners, such as A. latens Mirande, Aguilera & Azpelicueta, 2004; A. saguazu Casciotta, Almirón & Azpelicueta, 2003, and A. tupi Azpelicueta, Mirande, Almirón & Casciotta, 2003 from A. stenohalinus. Astyanax stenohalinus was cited in the Uruguayan literature only by Olazarri et al. (1970) and Nion et al. (2002). According to Malabarba et al. (2004), Messner (1962) was ignored by subsequent ichthyologists probably due to the limited distribution of the journal where it was published. Collecting trips in the rivers and streams in both margins of the Río de la Plata, río Uruguay and other areas of Uruguay allowed us to find specimens of A. stenohalinus that demonstrate its widespread geographical distribution. The aim of this paper is to provide a redescription of this species based on the revision of type material and specimens collected from several localities.

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Accepted by M.R. de Carvalho: 15 Mar. 2010; published: 23 Apr. 2010

Material and methods Specimens were cleared and counterstained (C&S) following Taylor & Van Dyke (1985). Measurements in mm were taken as straight line distances using digital calliper; all measurements (excluded standard length) are expressed as percentages of SL or head length. Standard length is taken from tip of snout to hypural joint; head length includes opercular flap; peduncle length is taken from insertion of last anal-fin ray to hypural joint. Vertebrae count includes four vertebrae of Weber apparatus. Scales below lateral line are counted from that line to pelvic-fin origin. Institutional abbreviations are as listed in Leviton et al. (1985), exepting AI (Asociación Ictiológica, La Plata, Argentina). Comparative material. The comparative material includes those species that share the distributional range of A. stenohalinus: Astyanax asuncionensis: MLP 8660, (5) 43.6–61.4 mm SL, Argentina, Santiago del Estero, Bañado de Añatuya. Astyanax chico: MACN-ict 8673, holotype, 69.0 mm SL Argentina, Jujuy, río San Francisco basin, río de Zora in rute 34. Astyanax leonidas: MLP 9580, holotype male, 45.6 mm SL, Argentina, Misiones, río Paraná basin, headwaters of arroyo Urugua-í. Astyanax ojiara: MLP 9470, holotype male, 50.5 mm SL, Argentina, Misiones, arroyo Benítez, headwaters of arroyo Yabotí-Miní, tributary of río Uruguay. Astyanax pynandi: MACN-ict 8543, holotype, 52.0 mm SL Argentina, Corrientes, Esteros del Iberá, Laguna Iberá, Lobo-Cua. Astyanax rutilus: MLP 8668, (4), 61.0–67.7 mm SL, Argentina, Santiago del Estero, Bañado de Figueroa. MLP 8798, (17) 28.8–39.6 mm SL, Argentina, Formosa, highway from Formosa to Clorinda. Astyanax stenohalinus: Uruguay: MHNM 582–2, holotype male, 65 mm SL, Departamento Cerro Largo, Laguna Mazangano (32º11’S–54º65’W); MHNM 582–1, paratype female, 68.7 mm SL, same collecting data as holotype (The other four specimens included in the original description were not found); ZVC P 1398, (20) 53.5–81.9 mm SL, Departamento Durazno, Río Negro, Arroyo de Los Perros; ZVC P 1400, (9) 68.7–99.1 mm SL, Departamento Cerro Largo, laguna Mazangano; ZVC P 1411, (15) 67.5–86.2 mm SL, Departamento Durazno, arroyo Rolón; ZVC P 1838, (3) 56.8–63.0 mm SL, Departamento Artigas, Estancia Pereyra Reverbel, Segunda Laguna; ZVC P 5655, (12) 51.0–87.2 mm SL, Departamento Tacuarembó, ciudad de Tacuarembó, Laguna de las Lavanderas; ZVC P 5854, (4) 36.2–40.8 mm SL, Departamento Rocha, arroyo Las Conchas; ZVC P 6538, (10) 30.8–93.1 mm SL, Departamento Cerro Largo, Río Tacuarí en Paso Ceniza; ZVC P 6580, (10) 28.9–80.2 mm SL, Departamento Treinta y Tres, río Tacuarí en Paso del Dragón; ZVC P 6612, (1) 48.9 mm SL, Departamento Cerro Largo, Arroyo Conventos en el Parque Rivera; ZVC P 6653, (13) 23.9–38.2 mm SL, Departamento Cerro Largo, Bañado Medina; ZVC P 6832, (1) 52.9, Departamento Rocha, arroyo sauce; ZVC P 6919, (6) 50.7–67.0 mm SL, Departamento Maldonado, Arroyo José Ignacio en Paso Correa; ZVC P 7111, (7) 51.2–95.2 mm SL, Departamento Lavalleja, río Cebollatí en Paso del Rey; ZVC P 7268, (11) 41.2–62.7 mm SL, Departamento Rocha, Potrerillo de Santa Teresa, Sangrador; ZVC P 7271, (11) 47.2–85.1 mm SL, Departamento Rocha, Potrerillo de Santa Teresa en la laguna. Argentina: AI 132, (2 C&S) 42.6-55.7 mm SL, Buenos Aires, Río de la Plata basin, Punta Indio, unmamed stream; AI 259, (6) 53.4–71.4 mm SL, Buenos Aires, Río de la Plata basin, Punta Indio, arroyo Casilda; AI 260, (5) 48.4–62.5 mm SL, Buenos Aires, Río de la Plata basin, Punta Indio, arroyo Villoldo; MACN-ict 9422, (3) 51.5–62.0 mm SL, Corrientes, río Uruguay basin, Río Timboy. Astyanax troya: MACN 8310, holotype, 73.8 mm SL, Argentina, Misiones, río Paraná basin, arroyo Cuñapirú Chico.

Astyanax stenohalinus Messner, 1962 (Figs. 1–5, Tab. 1) Emended diagnosis: Astyanax stenohalinus is distinguished from all other Astyanax species by the possession of hooks on all fins of males, teeth not expanded distally, two or three maxillary teeth, 37–39 perforated scales in lateral series, 25–30 branched anal fin rays, and anal-fin origin located before a vertical through last dorsal-fin ray insertions (Fig. 1). Description: Morphometrics of holotype and 14 specimens are presented in Table 1. Body relatively deep, especially in females (Fig. 2), with maximum body depth located immediately anterior to dorsal-fin origin. Dorsal profile of body curved from snout tip to dorsal-fin origin, with concavity over supraoccipital ASTYANAX STENOHALINUS, REDESCRIPTION

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area (Fig. 3); straight and slanted ventrally to caudal peduncle, straight along caudal peduncle to base of caudal-fin rays. Ventral profile of body similar to dorsal one. TABLE 1. Morphometric data of holotype and 14 specimens of Astyanax stenohalinus. holotype

males

68.3

42.1 – 62.5

Predorsal distance

55.6

53.0 – 56.1

(53.9)

54.3 – 55.9

(55.2)

Preventral distance

43.2

42.3 – 45.6

(43.7)

43.2 – 47.9

(45.8)

Preanal distance

63.3

58.2 – 62.7

(59.8)

60.6 – 65.3

(63.3)

Body depth

40.7

35.3 – 39.1

(37.3)

39.7 – 42.7

(41.1)

Dorsal-fin base

13.5

12.7 – 15.2

(13.7)

12.4 – 14.5

(13.8)

Anal-fin base

34.1

35.0 – 37.5

(36.2)

33.4 – 36.4

(35.0)

Pectoral-fin length

25.8

24.5 – 26.6

(25.9)

23.6 – 26.8

(25.2)

Pelvic-fin length

19.9

18.9 – 20.6

(19.8)

16.5 – 19.9

(18.6)

Distance between pectoral and pelvic-fin origins

22.5

17.7 – 20.2

(19.8)

20.6 – 22.5

(21.3)

Distance between pelvic and analfin origins

18.7

16.0 – 19.5

(17.4)

17.1 – 20.1

(18.3)

Head length

26.2

26.8 – 30.2

(27.8)

26.2 – 28.6

(27.2)

Peduncle depth

11.6

10.8 – 12.2

(11.5)

10.5 – 12.4

(11.4)

Peduncle length

40.2

33.9 – 40.0

(37.4)

34.4 – 40.4

(38.1)

Snout length

22.3

21.2 – 24.5

(22.3)

20.1 – 25.2

(23.1)

Eye diameter

39.1

33.3 – 41.4

(38.8)

37.7 – 40.6

(38.9)

Interorbital length

34.6

28.6 – 34.8

(31.6)

30.4 – 34.6

(32.6)

Postorbital length

43.0

40.2 – 46.8

(44.4)

42.4 – 45.5

(43.9)

Maxillary length

31.8

25.9 – 31.9

(29.3)

28.8 – 31.8

(31.1)

Standard length (mm)

mean

females

mean

46.1 – 71.4

Percents of standard length

Percents of head length

Dorsal-fin origin almost equidistant from tip of snout and base of caudal-fin rays. Anal-fin origin placed below posterior half of dorsal fin. Tip of pectoral fin surpassing pelvic-fin origin even in small specimens; in males, pectoral tip reaching half of pelvic fin. Tip of pelvic fin surpassing anal-fin origin in all males; in females, pelvic fin reaching or scarcely surpassing that point. Head with lower jaw as long as upper jaw. Premaxilla with short ascending process. Outer row of premaxillary teeth with 4–5, tricuspidate teeth, second or third tooth of outer row sometimes positioned out of line. Inner series with 5 teeth, symphysial tooth tetracuspidate, remaining teeth pentacuspidate to tricuspidate, with central cusp notably larger. Maxilla long and slender; anterodorsal maxillary process long; laminar process with 2–3 tricuspidate or unicuspidate teeth (Fig. 4). Dentary with 3–4 large pentacuspidate teeth followed by a median-sized tooth pentacuspidate or tricuspidate, and 7–9 smaller tricuspidate to unicuspidate teeth (Fig. 5). Eye larger than snout, interorbital distance about one third of head. Third infraorbital not contacting latero-sensory canal of preopercle. Dorsal fin with iii,9 rays; first dorsal-fin ray very small, easily visible in cleared and stained specimens. Distal margin of dorsal fin straight. Anal fin with v-vi, 25–30 (holotype: v,27) rays. Males with distal margin straight, and females with branched rays somewhat lengthened to form a small lobe. Caudal fin with i,17,i rays; upper lobe scarcely shorter and narrower than lower lobe. Pectoral-fin margin rounded; pectoral fin with i,12–14 (holotype: i,13). Pelvic-fin margin slightly rounded; pelvic fin with i,7 rays.

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Hooks on all fins of males. Few small hooks on distal region of dorsal-fin rays; one pair on each segment, on posterior branch of ray. Hooks extended on fifth and sixth unbranched and until 20th branched anal-fin rays; one pair of hooks on each segment, placed in both ray branches; hooks strong, curved dorsally. Caudal fin with very small hooks placed on distal portion of middle rays, one hook on each segment. Pectoral fin with few small hooks, placed on distal portion of ray, especially on internal branch, and one per segment. Pelvic fin with large hooks on last unbranched and both branches of all branched rays; hooks slightly curved dorsally and inward. Scales cycloid. Lateral series with 37–39 (holotype: 38) perforated scales. Scales between dorsal-fin origin and lateral line 6–7 (holotype: 7); scales between lateral line and pelvic-fin origin 6 (holotype: 7). Scales around caudal peduncle 15–16 (holotype: 16). Twelve to 16 scales forming an irregular row between tip of supraoccipital spine and dorsal-fin origin (holotype: 12). Fourteen to 18 scales (holotype: 14) situated along anal-fin base, covering base of all unbranched and first 15 to 20 branched anal-fin rays. First branchial arch with 27 or 28 gill rakers (2–3 on hypobranchial, 14 on ceratobranchial, 1 on cartilage, and 10 on epibranchial). Caudal fin with 10 dorsal and 9 ventral procurrent rays. Thirty six vertebrae including complex centrum+Weber apparatus. Dorsal-fin pterygiophores between neural spines of vertebrae 10–11 and 17–18; anal-fin pterygiophores between hemal spines of vertebrae 18 and 29. Eleven pairs of ribs. Five or 6 supraneurals with distal tips bifids (2 C&S specimens examined).

FIGURE 1. Astyanax stenohalinus. 1, holotype, MHNM 582-2 holotype, male, 65 mm SL, República Oriental del Uruguay, Departamento Cerro Largo, Laguna Mazangano (32º11’S–54º65’W). FIGURE 2. MHNM 582-1, paratype, female, 68.7 mm SL, collected with the holotype.

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FIGURE 3. Astyanax stenohalinus, AI 259, 68.3 mm SL, Argentina, Río de la Plata basin, Buenos Aires, Punta Indio, Arroyo Casilda.

FIGURE 4. Astyanax stenohalinus. AI 132, left upper jaw in lateral view. Scale bar= 1 mm.

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FIGURE 5. Astyanax stenohalinus. AI 132, right lower jaw in medial view. Scale bar= 1 mm.

FIGURE 6. Type locality, Departamento Cerro Largo, Laguna Mazangano (32º11’S-54º65’W)



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FIGURE 7. Geographical distribution of Astyanax stenohalinus. 1, río Timboy; 2, Segunda Laguna; 3, Arroyo Carpintería; 4, Laguna Mazangano (type locality); 5, Arroyo Conventos; 6, Bañado Medina; 7, Paso Ceniza; 8, Paso del Dragón; 9, Paso del Rey; 10, Arroyo de los Perros; 11, Arroyo Rolón; 12, Potrerillo de Santa Teresa; 13, Arroyo Las Conchas; 14, Arroyo Sauce; 15, Arroyo José Ignacio; and 16 arroyos Casilda and Villoldo.

Color in alcohol: Background light yellowish, dorsal region of body and head very slightly darker. A very narrow grey stripe extending along middorsal line. Narrow lateral band from humeral spot to dorsal-fin level, wider posteriorly, ending with large spot on caudal peduncle. Dark stripe continuing onto middle caudal-fin rays, especially dark at distal margin of rays. One vertically elongated humeral spot, posterior to vertical through pectoral-fin insertion, irregularly shaped. A second very faint humeral spot, positioned at vertical through middle pectoral fin. Most specimens with chromatophores concentrated along myosepta on lateral band. Dark chromatophores concentrated on scale margins of uppermost portion of body. Small chromatophores present on premaxilla, and around nares. Mouth surrounded by chromatophores. All fins, excluded caudal one, hyaline. Caudal fin with dark chromatophores concentrated on distal third of fin and uppermost and lowermost rays. Color upon capture: Background silver, a wide whitish lateral band, reddish caudal fin with middle portion faint yellowish and a light gray humeral spot. Distribution: Astyanax stenohalinus is known from Río Uruguay basin in Argentina and Uruguay; Río de la Plata basin in Argentina; Atlantic slope and Laguna Merín in Uruguay. The type locality is Laguna

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Mazangano, Río Negro basin, Uruguay (Fig. 6). See geographical distribution in the map (Fig. 7). Following Messner (1962), A. stenohalinus is also present in the río Vacacaí, Rio Grande do Sul, Brazil.

Discussion About thirty nominal species of Astyanax have been described from southernmost South America. A common character found in males of Astyanax is the presence of hooks on pelvic and anal fins; however, several of those species bear hooks on all fins of males. These species include: A. chico Casciotta & Almirón, 2004; A. hermosus (Miquelarena et al., 2005; A. ojiara Azpelicueta & García, 2000; A. rutilus Jenyns, 1842 (A. aramburui Protogino et al., 2006 is a probable junior synonym); A. stenohalinus Messner, 1962; A. troya Azpelicueta et al., 2002; and A. pynandi Casciotta et al., 2003. The high number of branched anal-fin rays of A. stenohalinus (25–30) separates it from A. chico (19–24), A. hermosus (17–22), A. ojiara (20–23), A. troya (18–21), and A. pynandi (21–26). Two or three maxillary teeth present in A. stenohalinus differentiate this species from A. rutilus, with only one. Two species have hooks on anal, pelvic, pectoral, and caudal fin of males: A. leonidas Azpelicueta et al., 2002 and A. tumbayaensis Miquelarena & Menni, 2005. The number of branched anal-fin rays distinguishes A. stenohalinus from A. leonidas and A. tumbayaensis (25–30 vs. 17–21 and 19–22 respectively) and the number of scales on lateral line differenciates A. stenohalinus (37–39) from both species (35–37 and 33–36 respectively). Astyanax stenohalinus shares the number of anal-fin rays, perforated scales of lateral line, transverse scales, and maxillary teeth with A. latens, A. saguazu, and A. tupi. However, the presence of hooks in all fins of males distinguishes A. stenohalinus from those three. Other Astyanax species living in sympatry with A. stenohalinus are A. abramis, A. asuncionensis, A. eigenmanniorum, A. jacuhiensis, A. laticeps, and A. rutilus. The number of branched anal-fin rays of A. stenohalinus (25–30) separates it from A. abramis (30–34), A. asuncionensis (30–32), A. eigenmanniorum (22–24), and A. laticeps (18–24). Finally, A. stenohalinus differs from A. jacuhiensis by the presence of 2–3 maxillary teeth vs. absence of teeth and the shape of the humeral spot.

Acknowledgments The authors thank C. Tremouilles (MLP) for help with the figures; S. D’Ambrosio, C. Bruno, P. Solimano, and the late P. García Tartalo for collecting some of the specimens; for financial support CIC, CONICET, and CSIC (partially funded ML). Finally, the authors thank M. Mirande (FML), one of the reviewers, for his valuable suggestions.

References Azpelicueta, M de las M., Mirande, J.M., Almirón, A.E. & Casciotta, J.R. (2003) A new species of Astyanax (Characiformes, Characidae) from Paraná river basin in Argentina. Revista del Museo de La Plata, Zoología, 15, 1– 12. Casciotta, J.R., Almirón, A.E. & Azpelicueta, M de las M. (2003) A new species of Astyanax from río Uruguay basin, Argentina (Characiformes, Characidae). Ichthyological explorations of Freshwaters, 14, 329–334. Leviton, A.E., Gibbs, R.H. Jr., Heal, E. & Dawson, C.E. (1985) Standards in herpetology and ichthyology: Part I. Standard symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia 1985, 802– 832. Malabarba, L.R., Weitzman, S.H. & Litz, T. (2004) Hyphessobrycon melanopleurus uruguayensis Messner, 1962, an available name and senior synonym of Cyanocharax macropinna Malabarba & Weitzman, 2003 (Ostariophysi: Characidae). Neotropical Ichthyology, 21, 99–102. Messner, E. (1962) Lista de los peces Tetragonopterinae (fam. Characidae) del Uruguay. Boletín de la Asociación



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Latinoamericana de Ictiólogos y Herpetólogos, 2, 4–5. Mirande, J.M., Aguilera, G. & Azpelicueta, M de las M. (2004) A new species of Astyanax (Characiformes, Characidae) from the upper río Bermejo basin, northwestern Argentina. Revue Suisse de Zoologie, 111, 213–223. Nión, H., Ríos, C. & Menesses, P. (2002) Peces del Uruguay. Lista sistemática y nombres comunes. DINARA, Infopesca, Montevideo, Uruguay, 105pp. Olazarri, J., Mones, A., Ximénez, A. & Philippi, M.E. (1970) Lista de los ejemplares-tipo depositados en el Museo Nacional de Historia Natural de Montevideo, Uruguay. I. Chordata. Comunicaciones Zoológicas del Museo de Historia Natural de Montevideo, 131, 1–12. Taylor, W.R. & Van Dyke, G.C. (1985) Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium, 9, 107–119.

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