Hemiodus jatuarana n. sp.

Fig. 1

Type material. Brazil, State of Pará, rio Trombetas: Oriximiná, Feb­Mar 1967, Expedição Permanente à Amazônia (EPA) leg.; MZUSP 54083, holotype, 192 mm SL; MZUSP 83358, 2, 193–195 mm SL, paratypes.

Diagnosis. Hemiodus jatuarana is readily distinguished from its congeners by the horizontally elongated dark spot on the caudal peduncle, and no other conspicuous dark pigmentation pattern, as those present in other Hemiodus species (e.g. round midlateral body spot in most Hemiodus species, vertical bars in H. quadrimaculatus species group, or longitudinal stripe of H. ternetzi Myers, 1927, H. thayeria Böhlke, 1955, and H. tocantinensis Langeani, 1999). Furthermore, it is separated from H. immaculatus, the most similar species, by having 25–27 epibranchial and 36–37 ceratobranchial gill rakers on first branchial arch (vs 14–16 and 21–25 in H. immaculatus), and caudal­fin lobes without longitudinal stripes (vs conspicuous longitudinal stripe on each caudal­fin lobe in H. immaculatus).

Character Holotype Paratype Paratype Description. Morphometric and meristic data are shown on Table 1. Medium size, 192 to 195 mm SL. Greatest body depth at dorsal­fin origin. Dorsal profile straight or slightly convex along head and predorsal portion, straight and descendent along dorsal­fin base, convex along post­dorsal portion and concave at caudal peduncle. Ventral profile convex from head to pelvic­fin base, straight or slightly convex along post­pelvic portion, convex at anal­fin base, and concave at caudal peduncle.

Head profile anteriorly pointed; interorbital region convex, equal to snout length, and greater than orbital diameter. Mouth slightly sub­terminal. Upper jaw not protractile with multicuspidate teeth with convex border. Lower jaw edentulous, rounded anteriorly. Adipose eyelid well developed, covering eye entirely, except for vertically elongate opening overlying pupil. Gill rakers triangular, posterior ones longer than the anterior, with small ctenii along adpharyngeal border; 25–27 epibranchial and 36–37 ceratobranchial gill rakers on first branchial arch.

Medium size (about three times in the eye diameter), thin, cycloid scales over entire body. Lateral­line scales from supracleithrum onto caudal­fin base 66 to 72 (68.3). Scales above lateral line in transverse series to dorsal­fin origin 12 or 13 (12.3); scales below lateral line in transverse series to pelvic­fin origin 6 or 7 (6.3). Cleithrum followed by 5 or 6 horizontally elongated scales forming small elevation above axillar depression, into which proximal end of first pectoral ray fits, in depressed fin. Axillary process of pelvic fin formed by three scales, last scale greatly elongated.

Dorsal fin ii + 9, last ray sometimes branched at base. Adipose fin about same size as orbital diameter. Pectoral fin i + 19 to 21 (i + 20), extending little beyond middle point between its base and pelvic­fin insertion. Pelvic­fin rays i + 11, extending beyond anal­fin origin. Anal fin ii + 8 to 10 (ii + 8.7), its posterior border slightly concave. Caudal fin 10 + 9; with lobes equal.

Color in alcohol. Relatively small, horizontally elongate spot of dark pigmentation present on caudal peduncle; no other conspicuous body markings (e.g. midlateral spot, vertical bands or horizontal stripe) present. Central portion of scales above lateral line peppered with small brown chromatophores. Dorsal, pectoral, pelvic, and anal fins hyaline; caudal­fin rays light brown.

Distribution. Known only from type­locality: Rio Trombetas, at Oriximiná, Pará, Brazil (fig. 2).

Etymology. The species name, jatuarana, is vernacular Portuguese word, derived from the Tupi­Guarani, applied to most of species of Hemiodus species in the Brazilian Amazon. A noun in apposition.

Comments. Hemiodus immaculatus and H. jatuarana have similar color pattern, body shape, and scale size, and occur in syntopy at the type locality of H. jatuarana (fig. 2).

It is interesting how rare specimens of H. jatuarana are in systematic collections. Frequently, large­size hemiodontids occur in river channels and are easy to capture, some being commercially exploited and relatively common in museum collections. Future efforts should be made around the type­locality in order to collect additional specimens of H. jatuarana.

Comparative material examined. Hemiodus immaculatus Kner, 1858. NMW 68641, Holotype, 179.2 mm SL, barra do Rio Negro [Brazil, State of Amazonas, City of Manaus]. Non types – Venezuela: Río Orinoco: ANSP 159602, 2/ 1, 185 mm SL, Río Sipapo; ANSP 165434, 1, 87.5 mm SL, Apure; USNM 233616, 16/5, 93.2–128.2 mm SL, beach on S side of river, just E of mouth of Río Caroni, 8°21’18’’N 62°42’36’’W, Bolivar; USNM 257529, 1, 134 mm SL, Guarico, Río Guariquito at government reserve, E­SE of Calabozo, 8°35’N 67°15’W. Brazil: Amazonas: Rio Canumã: MZUSP 7050, 36/6, 147.7– 176 mm SL. Rio Japurá: MZUSP 36055, 2/ 1, 175 mm SL, Lago Amanã, mouth of river; MZUSP 36056, 1, 115 mm SL, Igarapé Ubi, Lago Amanã, mouth of river; MZUSP 36057, 1, 149.3 mm SL, Igarapé Baré, Lago Amanã, mouth of river; MZUSP 36058, 1/0, Igarapé Urumatum, Lago Amanã, mouth of river. Rio Jutai: MZUSP 21305, 1, 218 mm SL, Riozinho, right margin. Rio Negro: MZUSP 6138, 2/ 1, 205 mm SL, upstream city of Manaus; MZUSP 6185, 11/ 3, 190–223 mm SL, Igarapé Jaraqui, left margin of the river upstream city of Manaus; MZUSP 6697, 9/1, 121.7 mm SL, around city of Manaus; MZUSP 9577, 1, 180 mm SL, Manaus fish market; MZUSP 32466, 2/ 1, 220 mm SL, Rio Arirará, near its mouth. Rio Preto da Eva; MZUSP 6073, 2/0, Manaus. Rio Puraquequara: MZUSP 6089, 4/ 1, 192 mm SL, Lago Puraquequara, mouth of the river. Pará: Rio Tapajós: MZUSP 9525, 1, 177 mm SL, Alter do Chão; MZUSP 32465, 5/ 1, 205 mm SL, between Itaituba and São Luis; MZUSP 32467, 1, 195 mm SL, São Luis, above Itaituba. Rio Trombetas: MZUSP 5409, 9/ 3, 180–200 mm SL, Oriximiná; MZUSP 15774 and 15775, 2/ 1, 247 mm SL, flooded forest of Lago Farias, Biological Reserve of rio Trombetas. Roraima: Rio Negro: MZUSP 32469, 3/0, rio Branco, between its mouth and Xeruini.