Diagnostic Description
provided by Fishbase
Distinguished from all other species of Hemigrammus, except Hemigrammus levis, by lacking a humeral spot and the presence of a conspicuous black spot, restricted to caudal fin, roughly triangular or rectangular, extending from base to tip of middle caudal-fin rays (its greatest depth at base of caudal-fin rays). Can be differentiated from Hemigrammus levis by the following characters: anal fin with 18-23 (mode 21) unbranched rays (vs. 16-18); largest tooth of the inner row of premaxilla and dentary with 5 cusps (vs. 7-9); anterior portion of longitudinal band as a broad uninterrupted pigmented area (vs. anterior portion of longitudinal band with a small round concentration of chromatophores at humeral region, surrounded by unpigmented areas anterior and posteriorly); distance of snout to anal-fin origin 58.6-65.9% SL, mean 62.0% (vs. 63.7-73.9% SL, mean 68.8%); anal base length 25.1-32.5% SL, mean 29.2% (19.3-24.7% SL, mean 22.0%), upper jaw length 39.6-48.3% HL (vs. 34.3-39.5% HL) (Ref. 74938).Description: Longitudinal scale series including pored scales 26-34. Dorsal fin ii9; Anal fin iii,18, 19, 20, 21, 22 or 23; Pectoral fin i9, 10, 11 or 12; Pelvic fin i6 or 7 (Ref. 74938).
Morphology
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Dorsal soft rays (total): 11; Analsoft rays: 21 - 23
Biology
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This fish is abundant in backwater margins from 0.3 to 1.3 m depth where it occurs in association with Poaceae and macrophytes (Ceratophyllum sp., Egeria densa, Eichornia spp., Ludwigia sedorde and Salvinia species. Stomach contents of two specimens consist of Spirogyra species, Cladocera, sediments (sand) and unidentifiable organic matter (Ref. 74938).
