Astyanax guaporensis Eigenmann, 1911

Marinho, Manoela M. F. & Ohara, Willian M., 2013, Redescription of Astyanax guaporensis Eigenmann, 1911 (Characiformes: Characidae), a small characid from the rio Madeira basin, Zootaxa 3652 (4), pp. 475-484 : 476-482

Astyanax guaporensis Eigenmann, 1911

Fig. 1

Astyanax guaporensis Eigenmann, 1911a: 176 , plate VII, fig. 4 [Type locality: Maciel, rio Guaporé].—Eigenmann, 1921: 274, plate 52, fig. 1 [identification key, literature compilation].—Eigenmann, 1927: 329, plate 52, fig. 1 [literature compilation].—Henn, 1928: 60 [type catalog].—Fowler, 1948: 49-50, fig. 42 [literature compilation].—Géry, 1977: 426 [identification key].—Ibarra & Stewart, 1987: 12 [type catalog].—Lima et al., 2003: 109 [literature compilation].—Lima et al., 2007: 45 [literature compilation].

Diagnosis. Astyanax guaporensis can be distinguished from all congeners, except A. leopoldi Géry, Planquette & Le Bail, A. orthodus Eigenmann, and A. superbus Myers by the presence of a series of transverse anteriorly directed V-shaped marks (vs. their absence). It can be distinguished from the aforementioned species by the absence of a black mark on the caudal peduncle (vs. its presence). Additionally, Astyanax guaporensis can be distinguished from all congeners, except A. angustifrons (Regan) , A. aurocaudatus Eigenmann, A. gisleni Dahl, A. goyanensis (Miranda Ribeiro) , A. guianensis Eigenmann, A. henseli Melo & Buckup, A. leopoldi Géry, Planquette & Le Bail, A. multidens Eigenmann, A. nasutus Meek, A. nicaraguensis Eigenmann, A. superbus Myers , and A. totae Haluch & Abilhoa by having five to nine maxillary teeth (vs. none to four). Astyanax guaporensis can be distinguished from the aforementioned species, except A. angustifrons , A. goyanensis , A. guianensis , A. leopoldi , A. nicaraguensis , and A. totae , by having 33 to 35 pored lateral-line scales (vs. more than 35). It can be distinguished from A. angustifrons , A. goyanensis , A. leopoldi , A. multidens , and A. nicaraguensis by having the middle caudal-fin rays hyaline (vs. middle caudal-fin rays dark), from A. guianensis by having six to seven horizontal scale row above lateral line (vs. five), and from A. totae by presenting 24 to 27 branched anal-fin rays (vs. 15 to 18).

Description. Morphometric data presented in Table 1 . Body somewhat compressed, moderately deep in larger specimens. Greatest body depth located at dorsal-fin origin. Dorsal profile convex from upper lip to vertical through anterior nostril, straight to slightly concave from latter point to base of supraoccipital spine, convex from that point to terminus of dorsal-fin base, straight from latter point to adipose fin, and concave along caudal peduncle. Ventral profile convex from lower lip to anal-fin origin, straight to slightly convex along anal-fin base, and slightly concave along caudal peduncle.

Mouth terminal. Posterior terminus of maxilla located approximately at vertical through anterior margin of orbit. Tooth cusps aligned in straight series, central cusp longer. Premaxillary teeth in two rows, outer series with one (1), three (16)*, four (5) or five (1) tricuspid teeth; inner series with five (22)* or six (1) tri- to pentacuspid teeth. Maxilla with five (6), six (12)*, seven (3), eight (1) or nine (1) uni- to pentacuspid teeth; anteriormost tooth usually larger ( Fig. 2 ). Dentary with four pentacuspid teeth (22)*, followed by a series of six to eight smaller teeth, uni- to tricuspid ( Fig. 3 ).

Scales cycloid. Lateral line slightly curved ventrally, with 33 (20), 34 (12) or 35* (4) perforated scales, continuous from supracleithrum to base of caudal fin. Longitudinal scale rows between dorsal-fin origin and lateral line 6 (35)* or 7 (2). Longitudinal scale rows between lateral line and pelvic-fin origin 5 (37)*. Median series of scales along dorsal line between tip of supraoccipital spine and dorsal-fin origin 8 (28) or 9 (5). Horizontal scale rows around caudal peduncle 14 (31)*. Single row of scales extending at first one-third of anal-fin base. Caudal fin with scales restricted to its base.

Dorsal-fin rays ii, 9 (37)*, distal profile of dorsal fin straight to slightly rounded. Dorsal-fin origin posterior to vertical through pelvic-fin origin; first dorsal-fin pterygiophore posterior to neural spine of fourth vertebra (5). Adipose fin present. Anal-fin rays iii or iv, 24 (5), 25 (10), 26 (10)* or 27 (10); first anal-fin pterygiophore posterior to hemal spine of 11th (5) vertebra. Pectoral-fin rays i, 12 (10)*, 13 (23) or 14 (3); tip of pectoral fin extending beyond pelvic-fin origin. Pelvic-fin rays i, 7 (37)*; tip of pelvic fin extending beyond anal-fin origin. Principal caudal-fin rays i, 9, 8, i; caudal fin forked, lobes somewhat pointed, of similar size. Dorsal procurrent caudal-fin rays 11 (2), 12 (2) or 13 (1); ventral procurrent caudal-fin rays 9 (1) or 10 (4). Gill-rakers on first gill arch: seven (4) on epibranchial, one (4) on cartilage between ceratobranchial and epibranchial, ten (4) on ceratobranchial, and three (4) on hypobranchial. Vertebrae 31 (1), 32 (2) or 33 (2). Supraneurals 3 (1) or 4 (4); distal portion slightly expanded.

Color in alcohol. Overall ground color yellowish. Anterior portion of maxilla and dentary, and top of head with small dark chromatophores. Few dark chromatophores on opercle. Scales of first two or three horizontal scale rows bordered by dark pigmentation, forming slight reticulated pattern. Some specimens with faint dark pigmentation bordering all scales, except on ventral portion of body. Humeral blotch conspicuous, vertically oriented, extending over one scale row ventral to, and three scale rows dorsal to lateral line, and over three scales horizontally. Portion of humeral blotch located dorsal to lateral line often interrupted by clear horizontal stripe. Humeral blotch followed posteriorly by clear area and then by pigmented area progressively fading posteriorly as a longitudinal stripe, from vertical through 7th or 8th lateral line, over fourth or fifth horizontal scale rows. Dark pigmentation along horizontal septum extending approximately from vertical through dorsal-fin origin to caudal peduncle, falling short of caudal-fin base. Series of 10-13 transverse anteriorly directed V-shaped marks of variable intensity over dark pigmentation along horizontal septum. First unbranched dorsal-fin ray with dark chromatophores, remaining dorsal-fin rays hyaline. Distal portion of interadial membranes of all dorsal-fin rays with scattered dark chromatophores. Pectoral, pelvic, caudal and adipose fins with scattered dark chromatophores. Anal fin with scattered dark chromatophores, frequently concentrated in proximal and distal portions of interadial membranes ( Fig. 1 c).

Color in life. Overall body coloration silver. Lateral and ventral surfaces of head, ventrolateral portions of body, and anteroventral portion of caudal peduncle covered with guanine. Head and body with iridescent hues of blue. Dorsal, anal and adipose fins and iris orange to yellow. Pectoral, pelvic and caudal fins hyaline. Dorsal portions of head and body yellow. Humeral blotch distinctly visible. Anteriorly directed V-shaped marks conspicuous ( Fig. 1 d).

Sexual dimorphism. Secondary sexual characters were not found in examined specimens.

Geographic distribution. Astyanax guaporensis is known from several localities in the rio Madeira, Amazon basin ( Fig. 4 ).

Ecological notes. In the rio Madeira basin, specimens of Astyanax guaporensis were found inhabiting clear water, usually in sandy beaches on small igarapés, such as Belmont, Karipunas and Caracol, but also in large rivers such as the Guaporé ( Fig. 5 ), Machado and Jaciparaná. Analysis of stomach contents of five specimens (UFRO-I 3666) revealed the presence of autochthonous Trichoptera, Diptera (Ceratopogonidae) , Ephemeroptera (Ephemeridae) , Hydracarina, and Hemiptera (Heteroptera).

Remarks. Astyanax guaporensis was described based on three specimens from the rio Guaporé, rio Madeira, under the original catalog numbers CM 3351, “ type ” ( Fig. 1 a), and CM 3352, two “cotypes” ( Fig. 1 b). Presently, the holotype and one of the paratypes are deposited at FMNH (54709 and 54710, respectively), but no further information about the other paratype is available. The CAS fish collection database indicates that CAS 68729 (IU 13268), represented by one specimen (approximately 28 mm SL), has the same data of the type series of A. guaporensis . Examination of its photograph allowed us to recognize it as conspecific with A. guaporensis and its original number is indeed CM 3352 (D. Catania, pers. comm.). Although not examined, specimen CAS 68729 is considered paratype of Astyanax guaporensis , along with FMNH 54710.

The type locality given by Eigenmann (1911a) in the original description of Astyanax guaporensis is “Maciel, rio Guaporé”. More detailed information is available in Eigenmann (1911b), where it is written “sixty miles above San Antônio de Guaporé”. On the map containing J. Haseman’s route in South America (Eigenmann, 1915), Maciel is pointed as a rubber farm at “São Antônio de Guaporé”, near the confluence of rivers São Miguel and Guaporé. The approximate coordinate for this locality is 12º31’S 63º30’W ( Fig. 4 ).

The redescription of Astyanax guaporensis is a contribution to the ichthyological survey of the rio Madeira basin intended to increase knowledge of the fish fauna of that area. During the development of the project “Monitoramento e Conservação da Ictiofauna do rio Madeira” (Assessment and conservation of the ichthyofauna of the Madeira River) from 2009 to 2011, eight species of Astyanax , two of which probably new, were recorded from that drainage: Astyanax cf. anterior , Astyanax aff. bimaculatus, A. guaporensis , Astyanax lineatus (Perugia) , A. maculisquamis Garutti & Britski , and Astyanax cf. maximus . Among these species, Astyanax guaporensis can be easily recognized by the presence of a series of anteriorly directed V-shaped dark marks along the medial portion of the body (vs. their absence), and by having five to nine maxillary teeth (vs. two or less).

In addition to the references of Astyanax guaporensis listed in fish catalogs, the citations of Pearson (1924, 1937) and Fowler (1940) correspond to misidentifications. In Pearson (1924), twelve specimens of A. guaporensis are mentioned from lagoons near Reyes [= pampa town 24 mi NE of Rurrenabaque], rio Beni, Bolivia. Photographs of nine specimens now under CAS 68730 (ex-IU17322), indicate they are not Astyanax guaporensis and are herein preliminary identified as Astyanax cf. guianensis . Pearson (1937) cited Astyanax guaporensis from the Beni - Mamoré basin, probably referring to the same specimens CAS 68730, and Fowler (1940) mentioned the same fishes collected by Pearson from Reyes, Bolívia.

Eigenmann (1911a, 1927) stated that Astyanax guaporensis and A. guianensis are closely allied species. Indeed, both species are very similar to each other externally (Eigenmann, 1912, plate LI, fig. 1), as well as to Astyanax multidens . These species are relatively small Astyanax species, with a somewhat diamond-shaped body, a vertically oriented humeral blotch, followed posteriorly by a clear area, and then by a more pigmented area that fades away posteriorly, no dark blotch on the caudal peduncle and five or more teeth on the maxilla. In spite of such similarities, no phylogenetic analyses including these species has been undertaken. The relationships of A. guaporensis with other characid species are unknown.

Material examined. Type specimens. Astyanax guaporensis . FMNH 54709 (holotype, 38.6 mm SL), rio Guaporé, Maciel (=rubber farm, near São Antônio de Guaporé, Rondônia, approximately 12º31’S 63º30’W), Brazil, J. D. Haseman, 23–26 Jul 1909. FMNH 54710 (1 paratype, 32.0 mm SL), same data of holotype. Non-type specimens. Astyanax guaporensis . Brazil, Rondônia. MZUSP 77888 (1, 30.7 mm SL), rio Guaporé, Forte Príncipe da Beira, Costa Marques, G. R. Kloss, 1987. UFRO-I 1542 (5, 29.2–34.9 mm SL), rio Jaciparaná, tributary of rio Madeira, Jaci Paraná district, Porto Velho, 9°17’1”S 64°23’57”W, C. Röpke, 12 Dec 2008. UFRO-I 1866 (2, 33.5– 34.9 mm SL), Madalena lake, rio Jaciparaná, about 13 km of mouth, Jaci Paraná district, Porto Velho, 9°17’0.9”S 64°23’57.1”W, C. Röpke, 10 Dec 2008. UFRO-I 3643 (5, 30.6–34.0 mm SL), Três Praias, rio Jaciparaná, about 13 km of mouth, Jaci Paraná district, Porto Velho, 9°28’20”S 64°24’27.4”W, A. Ribeiro, 18 Mar 2012. UFRO-I 3660 (21, 31.9–41.3 mm SL), downstream of Pimenteiras do Oeste, rio Guaporé, 13°31’23.2”S 61°8’3”W, G. Torrente- Villara, 21 May 2010. UFRO-I 3666 (541, 26.1-43.3 mm SL, 5 c&s), rio Guaporé, downstream of Pimenteiras do Oeste, 13° 31' 23.2" S 61°8'3" W, G. Torrente-Vilara, 21 May 2010. UFRO-I 3696 (11, 39.9–47.4 mm SL), rio Guaporé downstream of Pimenteiras do Oeste, 12°51’10”S 62°53’58.4”W, C. Zawadzki, 24 May 2010. UFRO-I 3698 (132, 32.1–45.4 mm SL), rio Guaporé, Pimenteiras do Oeste, 13°28’59.5”S 61°2’43.2” W, C. Zawadzki, 21 May 2010. UFRO-I 3713 (1, 34.6 mm SL), rio Cabixi, tributary of rio Guaporé, Cabixi, 13°30’14.1”S 60°30’41.8”W, W. M. Ohara, G. Torrente-Villara & T. Pires, 20 May 2010. UFRO-I 3714 (1, 32.7 mm SL), igarapé Caracol, about 9 km of Jaci Paraná district, Porto Velho, 9°14’34.6”S 64°19’20.2”W, W. M. Ohara, 21 Jul 2010. UFRO-I 3737 (2, 33.1–34.8 mm SL), Três Praias, rio Jaciparaná, about 13 km of mouth, Jaci Paraná district, Porto Velho, 9°27’11.1”S 64°24’46.6”W, C. Röpke, 7 Dec 2010. UFRO-I 3761 (1, 42.2 mm SL), rio Guaporé, near Pedras Negras community, São Francisco do Guaporé, 12°51’7.9”S 62°54’19.9”W, W. M. Ohara, 24 May 2010. UFRO-I 4119 (1, 31.5 mm SL), Madalena lake, rio Jaciparaná, about 13 km of mouth, Jaci Paraná district, Porto Velho, 9°17’13”S 64°24’0.7”W, L. C. R. Melo, 10 Jul 2009. UFRO-I 4870 (1, 36.47 mm SL), rio Cautário, tributary of rio Guaporé, RESEX do rio Cautário, Colocação Jatobá, Costa Marques, 12°35’S 60°55’W, G. Torrente-Vilara, 1 Jan 2004.

Comparative material. Brazil. Astyanax cf. anterior UFRO-I 15253 (13, 71.6–86.8 mm SL) rio Guaporé drainage, rio Madeira basin. Astyanax lineatus UFRO-I 15252 (1, 76.6 mm SL) rio Guaporé drainage, rio Madeira basin. Astyanax multidens MCZ 89559 (29 syntypes, 26.0–30.0 mm SL), rio Amazonas at Óbidos, Brazil; MZUSP (75, 27.3–45.3 mm SL), tributary of rio Teles Pires, rio Tapajós basin, Brazil. Astyanax cf. maximus UFRO-I 243 (1, 96.4 mm SL), rio Jaciparaná, rio Madeira basin; UFRO-I (1, 73.2 mm SL), rio Machado, rio Madeira basin. Astyanax aff. scabripinnis UFRO-I 15262 (5, 54.1–71.7 mm SL) rio Guaporé drainage, rio Madeira basin. Guiana. Astyanax guianensis BMNH 1911.10.31.314-8 (5 paratypes, 32.1–36.5 mm SL), BMNH 1911.10.31.319-20 (2 paratypes, 41.8 and 43.3 mm SL), Essequibo river at Warraputa.

Figures

FIGURE 1. Astyanax guaporensis: (a) holotype, FMNH 54709, 38.6 mm SL, photo by J. Birindelli, and (b) paratype, plate VII, fig. 4 of Eigenmann (1911 a), ex CM 3352, probably FMNH 54710, 32.0 mm SL, rio Guaporé at Maciel, Rondônia, Brazil; (c) UFRO-I 3698, 39.0 mm SL, and (d) UFRO-I 3698, live specimen, photo by T. Pires, rio Guaporé downstream of Pimenteiras do Oeste, Rondônia, Brazil.

FIGURE 2. Astyanax guaporensis, left side of upper jaw. UFRO-I 3666, rio Guaporé downstream of Pimenteiras do Oeste, Rondônia, Brazil. Scale bar 1 mm.

FIGURE 3. Astyanax guaporensis, medial view of left dentary. UFRO-I 3666, rio Guaporé downstream of Pimenteiras do Oeste, Rondônia, Brazil. Scale bar 1 mm.

FIGURE 4. Geographic distribution of Astyanax guaporensis in the rio Madeira basin, West Brazil. Type locality is represented by the blue triangle; blue circles are other localities. Cities are represented by gray squares.

FIGURE 5. Rio Guaporé downstream of Pimenteiras do Oeste, Rondônia, Brazil.

Tables

TABLE 1. Morphometrics of Astyanax guaporensis. SD = Standard Deviation.

	Holotype		Non types
		n	Range		Mean	SD
Standard length (mm) Percents of standard length	38.6	31	31.3 -	48.4	39.3	3.5
Depth at dorsal-fin origin	38.6	31	38.5 -	45.5	40.9	2.1
Snout to dorsal-fin origin	49.8	31	47.1 -	50.5	48.9	1.0
Snout to pectoral-fin origin	29.0	31	26.4 -	31.5	28.7	1.1
Snout to pelvic-fin origin	49.0	31	45.9 -	50.0	47.7	1.1
Snout to anal-fin origin	64.7	31	60.2 -	64.7	63.2	1.3
Caudal-peduncle depth	11.0	31	9.5 -	12.6	10.2	0.8
Caudal-peduncle length	9.6	31	9.6 -	13.9	10.8	1.1
Pectoral-fin length	18.6	31	18.6 -	25.0	23.6	1.5
Pelvic-fin length	15.8	31	15.8 -	24.9	19.2	1.5
Pelvic-fin origin to anal-fin origin	18.5	31	14.5 -	18.7	16.7	1.1
Dorsal-fin length	31.5	30	31.5 -	37.1	34.9	1.3
Dorsal-fin base length	16.1	31	15.1 -	19.0	16.3	0.9
Anal-fin length	20.8	28	20.2 -	24.2	22.5	1.1
Anal-fin base length	31.4	31	31.4 -	37.5	34.9	1.3
Eye to dorsal-fin origin	35.6	30	32.7 -	36.4	34.6	1.0
Dorsal-fin origin to caudal-fin base	55.4	31	52.8 -	60.7	57.4	1.7
Head depth	32.9	31	30.2 -	37.7	32.8	1.5
Head length	25.6	31	25.6 -	28.9	27.6	0.8
Percents of head length
Horizontal eye diameter	48.1	31	43.5 -	52.1	45.8	2.1
Snout length	22.5	31	22.5 -	27.4	25.8	1.2
Interorbital width	28.9	31	28.2 -	31.8	29.7	1.0
Upper jaw length	39.0	30	39.0 -	45.1	41.4	1.5