Bryconamericus ikaa, a new species from tributaries of the río Iguazú in Argentina (Characiformes, Characidae)

61 Ichthyol. Explor. Freshwaters, Vol. 15, No. 1, pp. 61-66, 6 figs., 1 tab., March 2004 2004 by Verlag Dr. Friedrich Pfeil, München, Germany ISSN 0936-9902 Bryconamericus ikaa, a new species from tributaries of the río Iguazú in Argentina (Characiformes, Characidae) Jorge R. Casciotta*, Adriana E. Almirón* and María de las Mercedes Azpelicueta* Bryconamericus ikaa, new species, from the río Iguazú basin in Misiones, Argentina, is distinguished from all congeneric species by the combination of: premaxilla with 4-6 teeth on the outer row, teeth aligned and tricuspidate or tetracuspidate, maxillary teeth 3-4 and usually pentacuspidate, 18-21 branched anal-fin rays, lateral line with 36-38 perforated scales, a short caudal peduncle (11.6-13.3 % SL), a ventrally elongate black humeral spot, a very faint second humeral spot, and a narrow black lateral band. Introduction After his expedition to the río Iguazú, Haseman (1911) stated that the fish fauna of that river system was poor in number of species. In actuality relatively few studies have been carried out on components of the fish fauna in the río Iguazú basin (Garavello, 1977; Almirón et al., 2002; Azpelicueta et al., 2003). Recent collecting trips to the río Iguazú basin yielded several new species, one of which, a new species of Bryconamericus is described herein. Additional collecting efforts in the Iguazú basin will probably demonstrate the presence of other new species. Material and methods Measurement and morphometric characters follow Azpelicueta et al. (2003). Specimens were cleared and stained (C&S) for cartilage and bone following Taylor & Van Dyke (1985). Abbreviations for collections: AI, Asociación Ictiológica, La Plata, Argentina; FML, Instituto Fundación Miguel Lillo, Tucumán; MACN, Museo Argentino de Ciencias Naturales, Buenos Aires; MHNG, Muséum d Histoire Naturelle, Genève; MLP, Museo de La Plata, La Plata. Bryconamericus ikaa, new species (Figs. 1-2) Holotype. MACN-ict 8648, 60.9 mm SL; Argentina: Misiones: Iguazú basin, arroyo Tateto (25 47' 12.8"S 53 58'12.9"W); J. Casciotta, A. Almirón & M. de las M. Azpelicueta; Feb 2002. Paratypes. Argentina: Misiones: río Iguazú basin: MHNG 2640.35, 4, 54.9-56.7 mm SL; AI 114, 4 (C&S), 46.8-49.7 mm SL; AI 108, 10, 49.5-55.7 mm SL; same data as holotype. AI 109, 5, 52.0- * División Zoología Vertebrados, Facultad de Ciencias Naturales y Museo de La Plata, Paseo del Bosque, 1900 La Plata, Argentina. E-mail: jrcas@museo.fcnym.unlp.edu.ar Ichthyol. Explor. Freshwaters, Vol. 15, No. 1

62 Fig. 1. Bryconamericus ikaa, holotype, MACN-ict 8648, 60.9 mm SL; Argentina: Misiones: arroyo Tateto, río Iguazú basin. Fig. 2. Bryconamericus ikaa, shortly upon capture, about 51.0 mm SL; Argentina: Misiones: arroyo Verde. 59.8 mm SL; arroyo Deseado on road 101 (25 47' 08.1"S 54 02'21.1"W); J. Casciotta, A. Almirón & M. de las M. Azpelicueta, Feb 2002. AI 113, 4, 41.2-52.8 mm SL; arroyo Verde in camp ground Salto Escondido (25 40'15.0"S 53 56'00.8"W); J. Casciotta, A. Almirón & M. Donato, Feb 2001. Diagnosis. Bryconamericus ikaa is distinguished from other species of the genus by the following combination of characters: 4-6 teeth in outer row of premaxilla, with teeth aligned, tricuspidate or tetracuspidate; 3-4 maxillary teeth, usually pentacuspidate teeth; 18-21 branched anal-fin rays; lateral line with 36-38 perforated scales; a short caudal peduncle (11.6-13.3 % SL); a ventrally elongate black humeral spot; a very faint second humeral spot; and a narrow black lateral band. Males with hooks on pelvic- and anal-fin rays. Description. Morphometrics of holotype and 14 paratypes in Table 1. Body relatively deep and laterally compressed (Fig. 1). Greatest body depth approximately at dorsal-fin origin. Dorsal profile of body markedly convex from upper lip to dorsal-fin origin, almost straight and slanted ventrally from rear of dorsal-fin base to caudal peduncle. Ventral profile of head and body sligthly convex from mouth to anal-fin origin. Ventral profile of body straight from anal-fin origin to caudal peduncle. Dorsal and ventral profiles of caudal peduncle straight. Dorsal-fin origin nearer base of caudal-fin Casciotta et al.: Bryconamericus ikaa

63 rays than to snout tip. Dorsal-fin origin located slightly behind vertical through last pelvic-fin ray insertion. Adipose fin present. Tip of pectoral fin not usually reaching pelvic-fin insertion. Tip of pelvic fin reaching anal-fin origin in males. Dorsal-fin rays ii,8; posterior margin of dorsal fin straight, second unbranched and first and second branched dorsal-fin rays of same length. Anal-fin rays: iii,18(3), iii,19(2), iii,20(2), iv,18(2), iv,19(4 including holotype), iv,20(1), iv,21(1). Males with hooks on last unbranched and first ten branched rays. Hooks slender, one pair per segment, located on posterior branch only. Males with distal margin of anal-fin straight or gently convex, females with distal margin rather concave. Pectoral-fin rays: i,10(2), i,11(7), i,12(6, including holotype), posterior pectoral-fin margin scarcely rounded. Pelvic-fin rays i,7, males with hooks on rays. Hooks sometimes on both branches of each ray. Caudal fin with 1 unbranched and 9 branched principal rays on upper lobe; 1 unbranched and 8 branched principal rays on lower lobe. Lower caudal-fin lobe slightly longer than upper lobe. Dorsal profile of head markedly convex on snout, straight over eye, and concave over supraoccipital spine. Snout rounded, upper jaw distinctly longer than lower jaw. Mouth located at level of lower orbital margin. Maxilla reaching first third of eye width. Maxilla with ascending process long, lateral process slender, long, and laminar, bearing 3-4 teeth with 3 or 5 cusps; 1 specimen with last tooth unicuspidate (Fig. 3a). Premaxilla with ascending process slender and acute, bearing 2 series of teeth, with larger median cusp. Outer series with 4-6 aligned tricuspidate or tetracuspidate teeth (Fig. 3a). Inner series of premaxillary teeth consisting of 4 teeth, with 3 to 5 cusps (Fig. 3b); symphysial tooth narrower. Dentary teeth 9-11, anterior three or four teeth larger than remaining ones, most teeth pentacuspidate, although small teeth with three or one cusps (Fig. 4). Dorsal margin of dentary straight, without notch between last tooth and posterior part of bone. Eye larger than snout. Posteroventral edge of third infraorbital in contact with sensory tube of preopercle. Scales cycloid. Lateral series with 36(4, including holotype), 37(7), 38(4) perforated scales. Scales between dorsal-fin origin and lateral line 5; 3.5-4.5 scales between lateral line and pelvic-fin insertion. Scales around caudal peduncle 14. Twelve to 14 scales forming a regular median series between supraoccipital process and dorsal-fin origin. Nine to 11 scales in single row along base of anal-fin rays. Gill-rakers on first branchial arch 6-7+1+9-10, in 4 cleared and stained specimens. Caudal fin with 11-12 dorsal and 10-11 ventral procurrent rays. Vertebra 35-36. Ten or 11 pairs of ribs. Colour upon capture. Flanks silvery, somewhat bluish or violet (Fig. 2). Broad lateral band silvery-whitish. Vertically elongate black humeral spot followed posteriorly by a faint second vertically elongate ovoid humeral spot. Tips of first dorsal and pelvic rays white; anal fin with anteriormost rays white, narrow white marginal band along fin. Basal portion of caudal fin yellowish and distal portion of caudal lobes white with intervening region hyaline. Caudal peduncle yellow. Upper portion of eye red. Colour in alcohol. Ground colour pale yellow, with upper area of lateral surface of body slightly darker. Most specimens with margin of scales Table 1. Bryconamericus ikaa, morphometric data of holotype (H) and 14 paratypes. H range mean SD Standard length [mm] 60.9 49.5-60.9 Percents of SL Body depth 34.2 33.7-36.4 34.8 0.79 Head length 25.6 25.6-28.4 27.0 0.84 Predorsal length 51.6 51.6-56.6 54.5 1.16 Prepelvic length 46.0 45.8-49.6 47.5 1.09 Preanal length 61.2 61.2-65.8 63.8 1.40 Dorsal-fin base 12.5 12.5-13.9 13.2 0.49 Anal-fin base 26.3 25.3-28.6 26.8 1.21 Pelvic-fin length 16.4 15,9-18.9 16.9 0.88 Pectoral-fin length 22.2 20.6-23.7 22.2 0.92 Caudal peduncle depth 11.7 11.1-11.9 11.6 0.26 Caudal peduncle length 11.7 11.6-13.3 12.3 0.50 Distance between pectoral and pelvic-fin origins 22.5 22.5-25.0 23.4 0.63 Distance between pelvic and anal-fin origins 17.9 16.5-19.9 18.3 1.06 Percents of head length Interorbital width 29.5 26.0-30.7 28.1 1.35 Head depth 86.5 78,9-90.0 84.0 3.33 Orbital diameter 36.5 32.3-36.7 35.1 1.40 Snout length 23.1 23.1-26.8 25.4 1.08 Upper jaw length 39.7 33.3-39.7 36.3 2.17 Maxillary length 27.6 25.2-28.5 27.2 0.91 Ichthyol. Explor. Freshwaters, Vol. 15, No. 1

64 b a Fig. 3. Bryconamericus ikaa, AI 114, 49.7 mm SL; a, right upper jaw, lateral view; b, second tooth of inner row. Scale bar 1 mm. dorsal of mid-lateral band with dark chromatophores forming reticulate pattern. Reticulate pattern apparent dark below midlateral stripe, albeit faint in some individuals. Dorsal portion of head and snout with black chromatophores. Few chromatophores on maxilla, lower jaw, and infraorbitals. Ventral region of head and vent unpigmented. Large vertically-elongate black humeral spot with rounded margins, and three scales wide, located behind third lateral line scale. Second humeral spot very faint. Narrow, grey mid-lateral band on body, formed by few superficial chromatophores and numerous deep-lying ones. Continuous posterior with wider spot on caudal peduncle. Lateral band extending to tip of medial caudal-fin rays, and also covering scales of caudal fin base. Posterior margin of eye with white blotch in some specimens. Dorsal fin with dark chromatophores, particularly concentrated on distal one half of membranes, except for tip of anterior rays. First unbranched dorsal-fin ray completely covered with dark chromatophores. Anal fin with dark chromatophores, particularly on distal half of fin on membranes and along anterior margins of ray. Females lacking chromatophores on most of rays. Males with many chromatophores concentrated on membranes and rays. Adipose fin completely covered by small scattered dark chromatophores. Caudal fin with chromatophores, concentrated Fig. 4. Bryconamericus ikaa, AI 114, 49.7 mm SL, right lower jaw, medial view. Scale bar 1 mm. on ray margins and close to distal edges. Pectoral fins with few dark chromatophores concentrated along ray margins. Pelvic fins with very few chromatophores especially on rays. Distribution and habitat. This species is known from arroyos Tateto, Deseado, and Verde, tributaries of the río Iguazú in Argentina (Fig. 5). The sampled localities have rapids with clear, flowing water, pools, and some areas of slow current (Fig. 6). Water depth was 0.40-2 m; bottom substrate was mud, sand, and mostly stones. Some areas have limited submerged vegetation. The temperature of the water near surface during summer was about 26 C. Etymology. The specific name ikaa is from the guaraní word I-kaá that means traveller of the river. A noun in apposition. Discussion Bryconamericus ikaa differs from many congeners reported from southeastern Brazil and the Río de la Plata basin in having 18-21 branched anal-fin rays (vs. B. eigenmanni 15-17, B. iheringii 15-17, B. rubropictus 13-17, B. thomasi 10-17, B. sylvicola 22-25). Other species of Bryconamericus with the same number of branched anal-fin rays as B. ikaa are B. agna, B. exodon, B. lambari, B. mennii, B. uporas, and B. pyahu. Bryconamericus ikaa differs from B. exodon in having a deeper body (33.7-36.3 % SL vs. 22.9-26.8). The narrow lateral band and the short cau- Casciotta et al.: Bryconamericus ikaa

65 Fig. 5. Distribution of Bryconamericus ikaa in province of Misiones, Argentina: 1, arroyo Verde; 2, arroyo Deseado, road 101; 3, arroyo Tateto (type locality). Fig. 6. Argentina: Misiones: arroyo Verde, habitat of Bryconamericus ikaa. dal peduncle (11.6-13.3 % SL) of B. ikaa distinguishes it from B. pyahu which has a wide lateral band and a longer caudal peduncle (14.7-18.3 % SL). It differs from B. agna in the presence of a narrow (vs. wide) lateral band and a longer predorsal distance (51.6-56.6 % SL vs. 47.3-50.3). It is distinguished from B. lambari by having a deeper body (33.7-36.3 % SL vs. 24.6-29.8) and fewer perforated scales on lateral line (36-38 vs. 38-40). It differs from B. uporas in having a narrow (vs. wide) lateral band, a deeper body (33.7-36.3 % SL vs. 28.9-32.2), and a longer preanal distance (61.2-65.8 % SL vs. 55.0-60.9). It differs from B. mennii in the longer preanal distance (61.2-65.8 % SL vs. 51.0-61.8), a shorter caudal peduncle (11.6-13.3 vs. 14.2-19.4 % SL), more branched anal-fin rays (18-21 vs. 16-19), and the external row of premaxillary teeth aligned (vs. not). Among examined congeners, B. ikaa looks most similar to B. iheringii. However, B. ikaa has more branched anal-fin rays (18-21 vs. 15-17), a greater head length (25.6-28.4 % SL vs. 23.1-25.4), a longer anal-fin base (25.3-28.6 % SL vs. 20.1-23.4), a shorter length of the caudal peduncle (11.6-13.3 % SL vs. 14.6-16.0), and a narrower interorbital width (26.0-30.7 % HL vs. 31.3-34.5). The dorsal tip of the ascending process of the premaxilla is slender and acute in B. ikaa whereas it is blunt, curved and stout in B. iheringii (compare Fig. 3 and Miquelarena, 1986: fig. 15a-b; pers. obs.). Recent collecting efforts in the rio Iguazú basin, Argentina, yielded about 26 species of fishes. Only two species of Bryconamericus were found in the basin, B. pyahu and B. ikaa described herein. Bryconamericus pyahu is restricted to one stream, tributary to the río San Antonio whereas B. ikaa was found in several creeks, tributary to the ríos San Antonio and Iguazú. Comparative material. Bryconamericus agna: FML 3700, holotype; MHNG 2611.46, 4; Argentina, Misiones: arroyo Tabay, Paraná basin. B. iheringii: AI 116, 3; Brazil, Rio Grande do Sul: São Lourenço do Sul, arroio Viúva Tereza and arroio Pinto. MLP 9073, 110; Argentina: Buenos Aires: Sierra de la Ventana. MLP 9103, 15; Argentina: Buenos Aires: Berisso, Los Talas (man-made ponds connected to Río de la Plata). B. exodon: MLP 18- Ichthyol. Explor. Freshwaters, Vol. 15, No. 1

66 IX-80-1, 2; Argentina: Buenos Aires: Río de la Plata in Punta Lara. B. mennii: AI 102, 3; Argentina: Misiones: arroyo Cuñapirú. B. thomasi: FML 1969, 94; Argentina: Salta: río Piedras. B. uporas: MLP 9568, holotype; Argentina: Misiones: Uruguay basin, arroyo Once Vueltas. B. pyahu: AI 101; Argentina: Misiones: Iguazú basin, arroyo Tateto. Acknowledgments We thank Carlos Tremouilles (MLP) for the drawings, Miguel Rinas for collecting permission (Ministerio de Ecología, Province of Misiones, Res. 166/98), and the Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC) for long term support to JRC. Literature cited Almirón, A. E., M. de las M. Azpelicueta & J. R. Casciotta. 2002. Astyanax ita sp. n. a new species from the Río Iguazú basin, in Argentina (Teleostei, Characiformes, Characidae). Zool. Abh., 52: 3-10. Azpelicueta, M. de las M., J. R. Casciotta & A. E. Almirón. 2003. Bryconamericus pyahu (Characiformes, Characidae), a new species from the río Iguazú basin, in Argentina. Rev. Suisse Zool. 110: 581-589. Garavello, J. C. 1977. Descrição de Apareiodon vittatus sp. n. do rio Iguaçu a comentários sobre as espéces do gênero Apareiodon Eigenmann, 1916 (Ostariophysi, Parodontidae). Rev. Bras. Biol. 37: 447-455. Haseman, J. D. 1911. Some new species of fishes from the rio Iguassú. Ann. Carnegie Mus., 7: 374-387. Miquelarena, A. M. 1986. Estudio de la dentición de peces caracoideos de la República Argentina. Biología Acuática, 8: 1-60. Taylor, W. R. & G. C. Van Dyke. 1985. Revised procedures for staining and clearing small fishes and other vertebrates for bone and cartilage study. Cybium, 9: 107-119. Received 3 June 2003 Revised 20 October 2003 Accepted 25 November 2003 Casciotta et al.: Bryconamericus ikaa