Neotropical Ichthyology, 5(3):251-257, 2007 Copyright © 2007 Sociedade Brasileira de Ictiologia A new species of Hemibrycon (Teleostei: Characiformes: Characidae) from the río Ucayali drainage, Sierra del Divisor, Peru Vinicius A. Bertaco*, Luiz R. Malabarba*,**, Max Hidalgo*** and Hernán Ortega*** A new characid species, Hemibrycon divisorensis, is described from the río Ucayali drainage, Loreto, Peru. The new species is distinguished from all Hemibrycon species by the presence of a wide black asymmetrical spot covering base of caudal-fin rays and extending along entire length of caudal-fin rays 9 to 12-13 (except from H. surinamensis), and a black band in the lower half of the caudal peduncle extending from the region above the last anal-fin rays to the caudal-fin base. Furthermore, it is distinguished from most species of the genus by the number of scale rows below the lateral line (4-5 vs 5-9), except H. jabonero, H. microformaa, H. orcesi, and H. surinamensis. It differs from these species by scale and fin ray counts and color pattern. The lack of a supraorbital in Hemibrycon species is discussed and confirmed. Uma nova espécie de caracídeo, Hemibrycon divisorensis, é descrita para a bacia do río Ucayali, Loreto, Peru. A nova espécie distingue-se das demais espécies de Hemibrycon pela presença de uma ampla mancha preta assimétrica na base dos raios da nadadeira caudal estendida até a extremidade dos raios 9 a 12 ou 13 (exceto de H. surinamensis), e de uma faixa preta na metade inferior do pedúnculo caudal desde a região acima dos últimos raios da nadadeira anal até a base da nadadeira caudal. Ela distingue-se da maioria das espécies do gênero pelo número de escamas abaixo da linha lateral (4-5 vs 5-9), exceto de H. jabonero, H. microformaa, H. orcesi e H. surinamensis. Ela difere destas espécies pela contagem de escamas, raios das nadadeiras e colorido padrão. Discute-se e confirma-se a ausência do osso supraorbital em Hemibrycon. Key words: Neotropical, Amazon basin, Taxonomy, Supraorbital, Fin hooks, Carlastyanax. Introduction volves only description of new species occurring in restricted geographic areas of South America. Hemibrycon is a Neotropical genus of characid fishes Eigenmann (1917, 1927) further diagnosed Hemibrycon which comprises about 21 valid species, occurring in the based on the “caudal fin naked, premaxillary with two series coastal drainages of the Caribbean sea and East Pacific in of teeth, inner series with four teeth, infraorbital 2 in contact Colombia, río Tuira drainage in Panama, rivers drainages in with the lower limb of the preopercle, adipose fin present, anal Trinidad and Tobago, río Orinoco and lago Maracaibo in fin moderate or long, gill-rakers simple, teeth along the greater Venezuela, upper río Amazonas in Bolivia, Peru, and Ecuador, part or along the entire edge of the maxillary”. None of the and coastal drainages of French Guiana and Suriname (Lima characters are unique to the genus and most of them are et al., 2003; Román-Valencia & Ruiz-C., 2007). plesiomorphic within Characidae or treated as putative syna- The genus Hemibrycon was proposed by Günther (1864), pomorphies of more inclusive clades containing Hemibrycon as a subgenus of Tetragonopterus Cuvier, differing by “cleft (Malabarba & Weitzman, 2003). of the mouth of moderate width, and the entire edge of the Géry (1966) grouped Hemibrycon along with Boehlkea, maxillary denticulated”. Tetragonopterus polyodon Günther Bryconacidnus, Bryconamericus, Ceratobranchia, was designed as type-species. Hemibrycon was extensively Coptobrycon, Knodus, Microgenys, Nematobrycon, revised by Eigenmann (1927), whose accounts still constitute Piabarchus, Rhinobrycon, and Rhinopetitia, in a new subtribe, the single complete review of the genus. Publications on Hemibryconini, consisting of a group of Tetragonopterinae Hemibrycon subsequent to Eigenmann’s revision usually in- with four inner premaxillary teeth, frequently associated with *Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, 90619-900 Porto Alegre, RS, Brazil. [email protected] **Departamento de Zoologia, IB, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, 91501-970 Porto Alegre, RS, Brazil. [email protected] ***Departamento de Ictiologia, Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, PO Box 14-0434, Lima – 14, Peru. [email protected], [email protected] 251 252 New Hemibrycon from the río Ucayali drainage, Sierra del Divisor, Peru a great development of the third infraorbital, and, quite often, Universidade Católica do Rio Grande do Sul, Porto Alegre; the irregular implantation of the outer premaxillary row of MHNG, Muséum d’historie naturelle, Geneva; MNHN, teeth. Malabarba & Weitzman (2003) recognized Hemibrycon Muséum nationale d’historie naturelle, Paris; MUSM, Museo as belonging to a large monophyletic clade inside Characidae de Historia Natural de la Universidad Nacional Mayor de San (therein named Clade A), based on the putative derived pres- Marcos, Lima; NMW, Naturhistorisches Museum, Wien; ence of four teeth in the inner series of the premaxilla and USNM, National Museum of Natural History, Washington reduced number of dorsal-fin rays (ii,8). Additionally, they D.C.; ZMA, Universitat van Amsterdam Zoologisch Museum, considered Hemibrycon and Boehlkea as apparently the most Amsterdam; and ZMUC, Zoological Museum, University of basal genera in that clade, by lacking all specializations re- Copenhagen, Copenhagen. lated to insemination, development of caudal- and/or anal-fin glands or the jaw and teeth modifications related to the ven- Hemibrycon divisorensis, new species tral position of the mouth, as observed in the remaining gen- Figs. 1-3 era and species of Clade A. During a recent expedition to the Zona Reservada Sierra Holotype. MUSM 28860, 68.2 mm SL, male, Peru, Loreto, del Divisor, Peru, a new species of Hemibrycon was collected Requena, Zona Reservada Sierra del Divisor, upper río Tapiche, in the río Ucayali drainage and it is herein described. This is quebrada en la trocha 1, río Ucayali drainage, 07º12’02"S part of a systematic study of Hemibrycon conducted by the 73º53’00"W, 20 Aug 2005, M. Hidalgo & J. F. P. da Silva. senior author (doctoral thesis). Paratypes. MCP 41346, 4 (60.5-81.6 mm SL), 2 c&s (62.7-68.4 mm SL), MUSM 28040, 19, 35.0-73.0 mm SL, collected with holo- type. MCP 41347, 5, 48.9-65.0 mm SL, MUSM 28039, 11 (43.0- Materials and Methods 58.0 mm SL), 1 c&s (55.9 mm SL), Peru, Loreto, Zona Reservada Sierra del Divisor, Ojo de Contaya, quebrada en la trocha 4, río Counts were taken as described by Fink & Weitzman Ucayali drainage, 07º06’54"S 74º35’08"W, 6 Aug 2005, M. Hidalgo (1974), with the exception of number of scale rows below & J. F. P. da Silva. lateral line which were counted from the scale row ventral to lateral line to the scale row nearest the first pelvic-fin ray. Diagnosis. Hemibrycon divisorensis is distinguished from Vertebral counts, supraneurals, gill-rakers, teeth, and all other species of the genus by the presence of a wide black procurrent caudal-fin-ray counts were taken from cleared and asymmetrical spot covering the base of caudal-fin rays and stained specimens (c&s) prepared according to the method extending along entire length of caudal-fin rays 9 to 12-13 of Taylor & Van Dyke (1985). The gill raker at the junction of (except from H. surinamensis), and by the presence of a black the ceratobranchial and the epibranquial is included in the band in the lower half of the caudal peduncle from the region counting of gill rakers of lower limb. Maxillary tooth counts above the last anal-fin rays to the caudal-fin base (Figs. 1-2). were taken in type specimens included in Table 1. Counts for Furthermore, it is distinguished from most species of the ge- the holotype are indicated with an asterisk. Vertebral counts nus by the number of the scale rows below lateral line (4-5 vs include the four vertebrae integrated in the Weberian appara- 5-9), except from H. jabonero, H. microformaa, H. orcesi, and tus and the terminal centrum was counted as one vertebra. H. surinamensis. Hemibrycon divisorensis differs from H. Scanning electron micrographs (SEM) of teeth and jaws were orcesi and H. microformaa by the higher number of lateral taken from one cleared and stained dissected specimen. Tes- line scales (39-42 vs 34-35 and 33-37, respectively) and anal- tes were removed prior to clearing and staining, dehydrated fin rays (24-30 vs 18 and 14-16, respectively), and by color in an ethanol series until 99.5%, and critical point dried. The pattern; from H. jabonero and H. surinamensis by the higher dried testes were placed in stub with carbon tape and split number of scale sheath along anal-fin base (17-22 vs 8-14 and with a needle, coated with gold and carbon, and viewed with 15-16, respectively), and number of cusps in the inner row of SEM. the premaxilla teeth (5-7 vs 5, respectively). Measurements were taken point to point with an elec- tronic caliper from the left side of the specimens. All measure- Description. Morphometric data for Hemibrycon divisorensis ments other than SL are expressed as a percents of SL except summarized in Table 1. Largest male 68.4 mm SL, largest fe- subunits of the head, which are recorded as a percents of male 81.6 mm SL. Body compressed and moderately elon- head length (HL). gate; greatest body depth usually nearly to dorsal-fin origin. Specimens examined belong to the following institutions: Dorsal profile of head slightly convex to nearly straight. Dor- ANSP, Academy of Natural Sciences, Philadelphia; BMNH, sal body profile slightly convex from supraoccipital to dor- Natural History Museum, London; CAS, California Academy sal-fin origin; posteroventrally slanted from dorsal-fin origin of Sciences, San Francisco; FMNH, Field Museum of Natural to adipose fin.