Charax hemigrammus

Charax hemigrammus (Eigenmann, 1912) Fig. 13

Asiphonichthys hemigrammus Eigenmann, 1912: 403 (original description, type locality: Guyana, Gluck Island). -Henn, 1928: 69 (listed in type catalog).

Charax hemigrammus, Lucena, 1987: 39 (diagnosis, description; distribution). -Lucena, 1989: 104; in key to species). -Lucena & Menezes, 2003: 201 (maximum length; distribution).

Diagnosis. Charax hemigrammus is distinguished from congeners except C. condei and C. stenopterus by having the lateral line incomplete and the dorsal part of body anterior to dorsal fin lacking scales (vs. lateral line complete and dorsal part of body anterior to dorsal fin scaled in Charax rupununi, C. tectifer, C. metae, C. delimai, C. caudimaculatus, C. notulatus, C. apurensis, C. macrolepis, C. michaeli, C. pauciradiatus, C. gibbosus, C. niger, and C. leticiae). Charax hemigrammus differs from C. condei in the scale rows from the pelvic-fin origin to the lateral line (11-12 vs. 6-9) and lateral series of scales (36-41 vs. 42-48), respectively and can be distinguished from C. stenopterus in having 9-22 ectopterygoid teeth (vs. ectopterygoid teeth absent).

Description. Morphometrics of examined specimens presented in Table 6. Body elongate, small compared to congeners (20-40.5 mm SL), compressed and comparatively low. Greatest body depth slightly in advance of dorsal-fin origin. Dorsal profile of head and body slightly convex from tip of snout to anterior region of fontanel, slightly concave from that point to base of supraoccipital spine, convex from that point to dorsal-fin origin, nearly straight along dorsal-fin base and from end of dorsal-fin base to caudal peduncle and slightly concave along caudal peduncle. Ventral profile of head and body convex from tip of lower jaw to anal-fin origin, nearly straight to slightly concave along anal-fin base and slightly concave from end of anal-fin base to beginning of procurrent rays. Snout pointed. Lower jaw included in upper jaw when mouth closed. Maxilla extending slightly beyond vertical through middle of orbit.

Dorsal-fin rays ii, 9 in all specimens, posteriormost ray unbranched. Adipose fin present. Unbranched anal-fin rays iv or v, usually iv; branched rays 41-48, 44.3. Pectoral-fin rays i, 13-15, 13.8. Posterior tips of longest pectoral-fin rays extending beyond pelvic-fin origin, but not reaching vertical crossing middle of pelvic-fin length. Pelvic-fin rays i, 7. Tips of longest pelvic-fin rays reaching vertical between bases of fifth and seventh branched anal-fin rays. Principal caudal-fin ray count 10/ 9 in all specimens.

Lateral line incomplete; perforated scales 7-10, 8.5. Lateral series scales 42-48, 45. Horizontal scale rows from pelvic-fin origin to lateral line 8-9, 8.7. Scale rows around caudal peduncle 15-16, 15.1. No scales anteriorly along anal-fin base.

Premaxillary with one anterior large conical tooth followed by set of smaller conical teeth, two large conical teeth and 1- 7 smaller conical teeth. Total number of premaxillary teeth 13- 20, 16.6. Maxillary teeth conical, 43-58, 50.6; larger specimens generally with higher counts. Dentary with anterior row including 4-8, 6.4 conical teeth and posterior row with 18-28, 22 conical teeth. Ectopterygoid teeth 9-22, 14.1.

Gill-rakers on lower limb of first gill-arch 8-9, 8.6. Branchiostegal rays 4; 3 rays originating from anterior cerathyal and 1 from posterior ceratohyal.

Color in alcohol (all examined specimens with original coloration barely preserved). Body pale, slightly darker dorsally due to presence of scattered dark chromatophores. Scattered dark chromatophores scattered over body. Roundish dark blotch at humeral region extending about two

scales horizontally and one scale vertically. Clear lateral stripe from behind dorsal portion of opercle to caudal base, probably dark in recently collected specimens. Concentration of dark chromatophores on caudal base forming oval-shaped blotch extending over bases of central caudal-fin rays. Dorsal portions of the head, snout and tip of lower jaw darker than remainder of head. Opercle with scattered dark chromatophores. All fins hyaline.

Distribution. Charax hemigrammus is known from the Essequibo River, Guyana; tributaries of the upper Amazon basin near municípios de Codajás and Tefé and tributaries of the rio Negro, Amazonas, Brazil (Fig. 7).

Specimens examined. Brazil. Amazonas: MZUSP 100354, 13, 20-33 mm SL, MZUSP 76217, 3, 26.5 - 34.5 and MZUSP 76248, 1, 26.5 mm SL, rio Jurupari, Tefé, approximately 3°19’S 64°43’W; MZUSP 62079, 15, SL 30-40.5 mm SL, Tapera, rio Negro.