Hyphessobrycon klausanni sp. n. is described from small drainages of the upper Guaviare River (Orinoco River Basin) in Colombia. It differs from all congeners by having a wide, conspicuous, dark lateral stripe extending from the anterior margin of the eye across the body and continued through the middle caudal-fin rays, and that covers (vertically) three or four horizontal scale rows. It also differs by having an orange-yellow stripe extending from the anterosuperior margin of the eye to the caudal peduncle above the lateral line in life. It differs from all other species of Hyphessobrycon that have a similar dark lateral stripe: H. cyanotaenia, H. loretoensis, H. melanostichos, H. nigricinctus, H. herbertaxelrodi, H. eschwartzae, H. montogoi, H. psittacus, H. metae, H. margitae, H. vanzolinii, and H. peruvianus in having only three or four pored scales in the lateral line, 21 to 24 lateral scales and six teeth in the inner premaxillary row. Hyphessobrycon klausanni differs from H. loretoensis in having seven to eight maxillary teeth (vs. three to four) and in having a longer caudal peduncle (12.4–17.0% SL vs. 4.6–8.0% SL). Additionally Hyphessobrycon klausanni can be distinguished from the other species of Hyphessobrycon with a dark lateral stripe from the Orinoco River Basin (H. metae and H. acaciae) in having two teeth in the outer premaxillary row (vs. three to four) and 10 branched pectoral–fin rays (vs. 11 to 12). It further differs from H. metae by the length of the snout (17.6–22.8% HL vs. 9.9–15.2% HL) and by the length of the caudal peduncle (12.4–17.0% SL vs. 7.3–11.8% SL).

Hyphessobrycon klausanni sp. n. es descrita de pequeños drenajes del alto río Guaviare (cuenca del río Orinoco) en Colombia. Se diferencia de todos los congéneres por tener una amplia franja lateral oscura lateral que se extiende desde el margen anterior del ojo a través del cuerpo y se continúa hasta la base de la aleta caudal y que cubre (verticalmente) tres o cuatro escamas laterales, además difiere por tener una franja de color naranja-amarillo que se extiende desde el margen anterosuperior del ojo hasta el pedúnculo caudal por encima de la línea lateral en vida. Se diferencia de H. cyanotaenia, H. loretoensis, H. melanostichos, H. nigricinctus, H. herbertaxelrodi, H. eschwartzae, H. montogoi, H. psittacus, H. metae, H. margitae, H. vanzolinii, y H. peruvianus por tener solo 3 a 4 escamas con poros en la línea lateral, 21 a 24 escamas laterales y 6 dientes en la fila interna del premaxilar. Hyphessobrycon klausanni se diferencia de H. loretoensis por presentar 7 a 8 dientes maxilares (vs. 3 a 4) y la longitud del pedúnculo caudal (12.4–17.0% LE vs. 4.6–8.0% LE). Además se puede distinguir de las demás especies con banda lateral oscura presentes en la cuenca del rio Orinoco (H. metae y H. acaciae) por tener dos dientes en la fila externa del premaxilar (vs. 3 a 4) y 10 radios ramificados en la aleta pectoral (vs. 11 a 12), además se separa de H. metae por la longitud de hocico (17.6–22.8% LC vs. 9.9–15.2% LC) y por la longitud del pedúnculo caudal (12.4–17.0% LE vs. 7.3–11.8% LE).

New taxon, Neotropical Ichthyology, Guaviare River, diversity

Nuevo taxón, Ictiología Neotropical, río Guaviare, diversidad

Hyphessobrycon Durbin, 1908, with 147 valid species (Eschmeyer et al. 2016), is a member of the subfamily Tetragonopterinae in Characidae (Mirande 2010). In addition to being one of the largest characid genera, it is found in all major drainages of the Neotropics, from southern México to the La Plata River in Argentina (García-Alzate et al. 2013а). In morphological and molecular phylogenetic analyses Mirande (2010) and Oliveira et al. (2011) respectively, state that Hyphessobrycon is paraphyletic. The genus was proposed by Durbin in Eigenmann (1908) as a subgenus of Hemigrammus, the type species of which is Hemigrammus unilineatus (Gill, 1858) described from the Island of Trinidad. Hyphessobrycon is defined by the following combination of non-exclusive characters: lateral line incompletely pored, adipose fin present, few or no teeth present on the maxilla, third infraorbital bone not in contact with the preopercle, premaxilla with two rows of teeth, with five or more on each side of the inner row, and caudal fin not covered with scales (the character that supposedly differentiates it from Hemigrammus). Within Hyphessobrycon, species have been grouped primarily by similarities of colour pattern; some of which were proposed merely as artificial operational assemblages to aid species identification (Géry 1977), whereas others represent potential monophyletic groups, as is the case for the Rosy Tetra species group (Castro Paz et al. 2014).

Twenty-two species of Hyphessobrycon have been identified from the different hydrographic drainages in Colombia (García-Alzate et al. 2015) and thirteen species are found in streams of the Orinoco River Basin: H. acaciae, H. albolineatum, H. bentosi, H. diancistrus, H. epicharis, H. fernandezi, H. heterorhabdus, H. mavro, H. metae, H. niger, H. otrynus, H. sweglesi, and H. saizi. The objective of this paper is to describe a new species of Hyphessobrycon from the upper Guaviare River drainage, which is part of the Orinoco River Basin in Colombia.

Fishes were captured using seines and were preserved in situ in 10% formalin and later stored in 70% ethanol. Counts and measurements follow Fink and Weitzman (1974). Measurements were made with digital callipers to 0.1mm precision and are expressed as percentages of standard (SL) and head length (HL). In count ranges, values for the holotype are indicated with an asterisk (*) and number of individuals after the meristic counts in parentheses. Counts and measurements were taken on the left side of specimens when possible. Osteological observations were made on cleared and stained adult specimens (CS) prepared according to Taylor and Van Dyke (1985). Bone nomenclature follows Weitzman (1962) and Vari (1995). Type specimens are deposited in the University of Atlántico-Caribbean Region, Dept. Biology, Museum Collection, Barranquilla, Colombia (UARC-IC), Auburn University Natural History Museum Fish Collection, Auburn, Alabama (AUM), the Ichthyology Laboratory at the Universidad del Quindío, Armenia, Colombia (IUQ) and Museo Javeriano de Historia Natural “Lorenzo Uribe, S. J.”, Bogotá D. C. (MPUJ). In the list of paratypes, the number of individuals is given in parentheses immediately after the catalog number. Institutional abbreviations are as listed at http://www.asih.org/node/204, except UARC-IC. We performed a Principal Components Analysis (PCA) of morphometric characters of Hyphessobrycon metae, H. acaciae, H. mavro, H. niger, and H. klausanni and the Burnaby method was used to eliminate the influence of overall size, with the Past program, version 3.0 for Windows (Hammer et al. 2001). Species for which no specimens were available, such as Hyphessobrycon montogoi, H. margitae, H. vanzolinii, H. lucenorum, H. psittacus, and H. peruvianus were included in the comparisons using their original descriptions. The abbreviation masl means meters above sea level.

Although in our opinion the artificial groupings based on pigmentation patterns proposed by Géry (1977) lack a systematic basis upon which to evaluate relationships among species of Hyphessobrycon, some recent contributions use these criteria to segregate groups of species (Lima et al. 2014, García-Alzate et al. 2015, Ohara and Lima 2015, Zarske 2015) in an attempt to clarify the alpha taxonomy that forms the basis of our systematic study of this group. Among these species groups we find those defined by the presence of a dark longitudinal stripe (group e, Géry 1977: 470) which is further subdivided into the Hyphessobrycon agulha-group: including species with the lower half of the body all dark, especially above the anal fin, an usually horizontally elongate humeral spot that is more or less united with an asymmetrical, broad lateral stripe (Géry 1977: 470), the H. agulha-group was recently defined by Ohara and Lima (2015: 568) to include species that have a broad, relatively diffuse lateral stripe (typically more discernible ventrally, posterior to the midbody) and a humeral blotch that may or may not coalesce with the stripe, included the following species in this group: H. agulha, H. herbertaxelrodi, H. metae, H. peruvianus, H. mutabilis and H. loretoensis (in the latter two, the humeral blotch may or may not coalesce with the stripe), which also includes the following species: H. clavatus, H. lucenorum, H. vanzolinii, H. margaritae and Hyphessobrycon klausanni sp. n. Also, Lima et al. (2014) define the Hyphessobrycon heterorhabdus-group: to include species that share a well-defined, elongated humeral blotch, which is continuous with a midlateral, well-defined dark stripe that becomes blurred towards the caudal peduncle and also have a longitudinal red stripe, extending along the body above the midlateral line, as well as on the upper half of the eye red in living specimens that includes: H. heterorhabdus, H. amapaensis, H. eschwartzae and H. montagi. Hyphessobrycon klausanni is similar to H. metae, with which it shares a well-developed broad midlateral stripe and a well-developed humeral blotch. As mentioned by Ohara and Lima (2015), broad phylogenetic studies on the genus and related genera are necessary to evaluate its putative relationships, but these two species groups could be a starting point. As mentioned in the introduction, the genus Hyphessobrycon is paraphyletic and the new species described in this paper is not a member of the genus Hyphessobryconsensu stricto (García–Alzate et al. 2013 a, b) which includes the type species H. compressus and related species in Central America and some from the Colombian Chocó region: H. colombianus, H. sebastiani, H. condotensis, H. chocoensis and H. ecuadorensis. A phylogenetic reconstruction is needed that includes the type species and related Central American species to begin to unravel the phylogenetic relationships of the species of Hyphessobryconsensu lato.

Rapid taxonomic description of the many as yet unnamed fish species of the Neotropical ichthyological biodiversity is urgently needed given the accelerated rate of extirpation caused by human impacts in many aquatic ecosystems in the Orinoco River Basin. The loss of habitat for fish species is caused by many different human activities such as dam construction, urban water pollution, mining, poor agricultural and animal husbandry practices, the introduction of non-native species and overfishing (Barletta et al. 2012). The Guaviare River drainage in Colombia is an area of high priority for conservation (Machado-Allison et al. 2010), and even with greater recent efforts to sample this system, our knowledge of its fish fauna remains poor, categorized as medium (30–38%) by Portocarrero-Aya et al. (2014). In this contribution a new species, Hyphessobrycon klausanni, is described which shows that new taxa will continue to be discovered as more and better inventories are carried out in the upper Guaviare. This also confirms that the Guaviare River drainage remains a priority area for conservation and ichthyological exploration, with regards to species richness and endemism. However, the streams of the upper Guaviare are being impacted by water extraction, and conversion of riparian forests into cattle pastures and monoculture crops such as oil palms. These impacts will undoubtedly be reflected as changes in the composition, richness and ecosystem functions of the fish community and in some cases may eventually lead to the extinction of some species before they have even been discovered or described.

We are grateful for the support of the Biology Program, University of Atlántico (UA). We thank Javier Maldonado-Ocampo and Saúl Prada-Pedreros (MPUJ), Gustavo Casas Andreu and Hector Espinoza (IBUAM-P), Carlos Alberto Santos De Lucena (MCP), Francisco Provenzano (MBUCV-V), Hernan Ortega (MUSM), Janeth Muñoz Saba and Jaime Aguirre (ICMNH), Mark Sabaj Pérez (ANSP), David Werneke (AUM), Philip Willink (FMNH) and Carlos DoNascimiento (IAvH-P) for access to the fish collections in their care. John Fong (CAS) and James Maclain (BMNH) for kindly sending images of type species. We also wish to recognize the contributions of Vicente Pico and Nicole Botero, for financing and directing the “Reto-Este” project (SGI Ltda.-Ecopetrol) which led to the collection of Hyphessobrycon klausanni. Special thanks to Jhon Zamudio for the specimens he collected as part of the “Guarupayo” project as well as to the fisherman Juan de Dios Ocampo and Josué Ocampo. We thank Mr. Klaus-Peter Lang for financial assistance. Special thanks to Jonathan Armbruster for his helpful suggestions to improve the manuscript.