Astyanax guianensis

description

Description. Morphometric data for Astyanax guianensis presented in Table 1. Small sized species (largest examined specimen 53.3 mm SL). Body compressed laterally, moderately elongate. Greatest body depth at dorsalfin origin. Dorsal profile of head convex from tip of snout to vertical through anterior border of anterior nostril and straight from that point to tip of supraoccipital spine. Dorsal profile of body straight to slightly convex at predorsal region, straight at dorsal-fin base, straight from end of dorsal-fin base to adipose-fin origin, and concave along caudal peduncle. Ventral profile of head and body slightly convex from anterior tip of lower lip to anal-fin origin, straight along anal-fin base, and slightly concave along caudal peduncle. Jaws aligned vertically, mouth terminal. Premaxillary teeth in two rows. Outer row with 2 (4), 3 (32), 4 (30) or 5 * (3) tricuspid teeth. Inner row with 5 * (66) or 6 (3) teeth, 4 of which pentacuspid, and lateralmost one tricuspid. Maxilla with 5 (17), 6 * (22), 7 (22), 8 (5), 9 (3) or 10 (1) uni- to tetracuspid teeth. Dentary with 4 (26) large pentacuspid teeth, followed by one or two smaller tricuspid and one series of 5 to 12 small

Redescription of Astyanax guianensis Eigenmann 1909 (Characiformes: Characidae), a poorly known and widespread fish from the Amazon, Orinoco and Guiana Shield drainages

diagnosis

Diagnosis. Astyanax guianensis can be distinguished from all congeners, except A. angustifrons (Regan), A. aurocaudatus Eigenmann, A. gisleni Dahl, A. goyanensis (Miranda Ribeiro), A. guaporensis, A. henseli Melo & Buckup, A. leopoldi Géry, Planquette & Le Bail, A. multidens, A. nasutus Meek, A. nicaraguensis Eigenmann, A. superbus Myers, and A. totae Haluch & Abilhoa by having five to 10 maxillary teeth (vs. none to four). Astyanax guianensis is distinguished from the aforementioned species, except A. angustifrons, A. goyanensis, A. guaporensis, A. leopoldi, A. multidens, A. nicaraguensis, and A. totae, by having 31 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. guaporensis by having five, rarely six (4 out of 59 examined specimens) horizontal scale row above lateral line (vs. six to seven) and the absence of a midlateral series of dark anteriorly-directed chevrons (vs. presence), and from A. totae by presenting 21 to 25 branched anal-fin rays (vs. 15 to 18).

Redescription of Astyanax guianensis Eigenmann 1909 (Characiformes: Characidae), a poorly known and widespread fish from the Amazon, Orinoco and Guiana Shield drainages

discussion

Remarks. Most features described by Eigenmann (1909) in the original description of Astyanax guianensis matches those observed by us. There are only two exceptions. Eigenmann (1909) mentioned four to seven maxillary teeth. In 70 examined specimens, five to 10 tiny teeth were counted in the maxilla, none had four. Eigenmann (1909) also mentioned the presence of 34 to 35 (rarely 36) scales on the lateral series. In 60 examined specimens, 31 to 35 scales were counted on the lateral series, none had 36. In the label corresponding to lot CAS 68733 (ex IU 12078), the word cotype, is written in reference to one specimen of Astyanax guianensis collected by Eigenmann at Rupununi, near Rockstone. A second label was found inside the jar, stating that this specimen was not cited in the original description of A. guianensis and should not be considered as cotype. We agree with this remark and thus will not consider this specimen as paratype. Pearson (1924) mentioned 12 specimens of Astyanax guaporensis from lagoons near Reyes [= pampa town 24 mi NE of Rurrenabaque], rio Beni, Bolivia, identified as Astyanax cf. guianensis by Marinho & Ohara (2013). Examination of this material (CAS 68730 [ex IU

Redescription of Astyanax guianensis Eigenmann 1909 (Characiformes: Characidae), a poorly known and widespread fish from the Amazon, Orinoco and Guiana Shield drainages