Hemigrammus kuroobi, Reia & Benine, 2019

Reia, Lais & Benine, Ricardo C., 2019, A new species of Hemigrammus Gill 1858 (Characiformes: Characidae) from the upper Rio Negro, Amazon basin, Brazil, Zootaxa 4555 (3), pp. 407-415 : 408-411

Hemigrammus kuroobi , new species

( Tab. 1, Figs. 1–4 )

Holotype: MZUSP 123957 , 45.0 mm SL, Brazil, Amazonas State , São Gabriel da Cachoeira , tributary of the Rio Miuá, Rio Negro basin, 00°06'12"S 66°53'8"W; C. Oliveira, M. Taylor, M. Alexandrou; 14 Aug 2008.

Paratypes: LBP 7074, 70, 12.2–48.0 mm SL, 3 C&S, 40.1–44.8 mm SL; MZUSP 123958 , 5 , 33.2 – 44.7 mm SL ; ZUEC 17026 , 5 , 35.5 – 40.9 mm SL ; MNRJ 51330 , 5 , 28.5 – 36.9 mm SL ; INPA 57937 , 5 , 31.1 –45.0 mm SL: same data as the holotype .

Diagnosis. Hemigrammus kuroobi differs from all congeners by having an unique color pattern characterized by a conspicuous humeral blotch clearly spaced from a conspicuous midlateral dark stripe, which extends from fifth or sixth anteriormost vertical scale row to the middle caudal-fin rays, running on the scale row just above the lateral line (vs. midlateral dark stripe, when present, extending from the posterior margin of the eye, humeral blotch, and/or from the vertical through dorsal-fin origin to the caudal-fin rays or to the caudal peduncle). See the discussion section for additional remarks on the diagnosis of the species.

Description. Morphometric data summarized in Table 1. Largest specimen examined 48.0 mm SL. Body compressed, moderately short, greatest body depth usually located anterior to dorsal-fin origin. Dorsal profile of head strongly convex from snout tip to vertical through anterior nostrils and slightly concave from that point to tip of supraoccipital spine. Dorsal body profile convex from tip of supraoccipital spine to end of dorsal-fin base, slightly inclined postero-ventrally from end of dorsal-fin to adipose-fin origin, and slightly concave along caudal peduncle. Ventral profile of body convex from anterior tip of dentary to anal-fin origin, straight along anal-fin base, and slightly concave along caudal peduncle.

Mouth terminal. Maxilla only reaching the vertical through third infraorbital. Premaxillary teeth in two rows. Inner row with 5*(29) or 6(3) pentacuspid teeth ( Fig. 2 ). Outer row with 3(9), 4*(22), or 5(1) tricuspid teeth, maxilla with 2(3), 3(24), or 4*(5) tricuspid teeth. Dentary with 4*(27), or 5(5) pentacuspid teeth followed by a series of 10–11 small conical or tricuspid teeth ( Fig. 2 ). Central cusp in all teeth more developed than lateral cusps.

Scales cycloid, with 5–10 parallel radii from focus to posterior border of scales. Lateral line incomplete, with 9(4), 10(10), 11*(11), 12(6), or 14(1) perforated scales. Total longitudinal lateral line scales 33(12), 34*(11), or 35(9). Scale rows between lateral line and dorsal-fin origin 5*(32). Scale rows between lateral line and midventral scale series 5(9) or 6*(23). Scales along supraoccipital process and origin dorsal fin 9(3), 10*(11), 11(15), or 12(3). Circumpeduncular scale rows 13(2), 14*(29), or 15(1). Single row of scales overlaying basal portion of anterior anal-fin rays. Caudal fin with small scales covering proximal two-third of both lobes.

Dorsal-fin rays ii(31), 9*(29), 10(1) or 12(1), or iii, 8(1). Pectoral-fin rays i, 9(2), 10*(10), 11(15), 12(5), their tips reaching beyond pelvic-fin origin, when adpressed. Pelvic-fin rays i, 7*(31), or 8(1), their tips not reaching anal-fin origin. Anal-fin rays v, 17(3), 18(4), 19(15), or 20*(10). Caudal-fin rays 9+8(3). Caudal fin forked, lobes of similar size, with 11(3) dorsal procurrent rays and 9(2), or 10(1) ventral procurrent rays. First gill arch with 10(6), 11*(18), or 12(7) gill rakers on lower limb and 6*(18), or 7(11) gill rakers on upper limb. Total vertebrae 33(3). Supraneurals 5(3).

Color in alcohol. Overall body coloration light to dark brown. Dorsal portion of head darker. Field of chromatophores covering both lips and dorsal portion of maxilla. Infraorbitals beige, with scattered chromatophores. Opercular area beige, with concentrated dark chromatophores. Dorsal portion of body dark brown. A single, vertically elongated, conspicuous dark humeral blotch. Background humeral area lighter, highlighting the humeral blotch ( Fig. 3 ). Conspicuous midlateral dark stripe, extending from fifth or sixth anteriormost vertical scale row to caudal peduncle, running on the scale row just above the lateral line. Midlateral stripe ontogenetically beginning restricted to caudal peduncle, then gradually developing forward, being fully developed in specimens over 30.0 mm SL ( Fig. 4 f–l). Adipose fin hyaline, with chromatophores randomly distributed; dorsal, pectoral, pelvic and anal fins hyaline, with chromatophores scattered on interradial membranes, more and densely concentrated on distal margins. Middle caudal-fin rays with moderate concentration of dark chromatophores. Small brownish colored scales covering proximal two-third of caudal-fin lobes.

Sexual dimorphism. Mature males (35.9–48.4 mm SL) bear one small bony hook per segment on the posterior branch of the first to fourth branched anal-fin rays.

Distribution. Hemigrammus kuroobi is only known from its type locality, a tributary of the Rio Miuá, upper Rio Negro, Amazon basin, Amazonas, Brazil ( Fig. 5 ).

Etymology. The specific epithet “ kuroobi ” is from Japanese Kuro (black) and Obi (band, belt), a martial arts terminology for the black-belt grade, in allusion to the gradual development of the conspicuous longitudinal black stripe of this species.

Figures

FIGURE 1. Hemigrammus kuroobi, new species: (a) holotype, MZUSP 123957, 45.0 mm SL; (b) paratype, MNRJ 51330, 36.0 mm SL, male; Brazil, Amazonas, tributary of Rio Miuá, upper Rio Negro.

FIGURE 2. Hemigrammus kuroobi LBP 7074, paratype, 44.8 mm SL: (a) left maxilla (medial view); (b) left premaxilla (medial view); (c) left dentary (medial view).

FIGURE 3. Hemigrammus kuroobi, paratype, LBP 7074, 46.3 mm SL, showing light area between humeral blotch and midlateral stripe (arrow).

FIGURE 4. Hemigrammus kuroobi, paratypes. (a) LBP 7074, 12.2 mm SL; (b) LBP 7074, 14.4 mm SL; (c) LBP 7074, 17.4 mm SL; (d) LBP 7074, 19.2 mm SL; (e) LBP 7074, 26.9 mm SL; (f) LBP 7074, 30.0 mm SL; (g) MNRJ 51330, 33.8 mm SL; (h) MNRJ 51330, 36.0 mm SL; (i) ZUEC 17026, 38.1 mm SL; (j) ZUEC 17026, 40.9 mm SL; (k) INPA 57937, 45.0 mm SL; (l) LBP 7074, 48.0 mm SL.

FIGURE 5. Map of upper rio Negro, showing the type-locality of Hemigrammus kuroobi (red star).