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A new species of Brycon (Characiformes: Characidae) from Nicaragua and Costa Rica, with a key to the lower Mesoamerican species of the genus

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A new species of Brycon is described from the Atlantic slope of Nicaragua and Costa Rica. Brycon costaricensis n. sp. differs from all other Central American Brycon species by the following combination of characters: 49 to 54 scales in the lateral line; 5 or 6 rows of scales between lateral line and pectoral fin base; 9 to 11 rows of scales between lateral line and dorsal fin base; 5 to 7 rows of scales between lateral line and anal fin base; anal fin notably longer than head, with 33 to 37 total rays; and a elongated and shallow caudal peduncle, whose length is 1.78 to 2.35 times its depth. A key to lower Mesoamerican species of the genus is also presented.
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Accepted by M. R. de Carvalho: 3 Oct. 2013; published: 30 Oct. 2013
ZOOTAXA
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ISSN 1175-5334 (online edition)
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http://dx.doi.org/10.11646/zootaxa.3731.2.6
http://zoobank.org/urn:lsid:zoobank.org:pub:E528CF92-A23A-4C1B-B6E4-308668EBF692
A new species of Brycon (Characiformes: Characidae) from Nicaragua and Costa
Rica, with a key to the lower Mesoamerican species of the genus
ARTURO ANGULO1, 3 & JATZIRY MARLENE GRACIAN-NEGRETE2
1Museo de Zoología, Escuela de Biología, Universidad de Costa Rica. 11501-2060. San Pedro de Montes de Oca, San José, Costa
Rica. E-mail: arturo.angulosibaja@ucr.ac.cr
2Instituto de Biología, Universidad Nacional Autónoma de México. Apdo. postal 70-153, CP 04510 Ciudad Universitaria, Tercer cto.
Exterior s/n México, D.F., México. E-mail: dolphinziry@hotmail.com
3Corresponding author
Abstract
A new species of Brycon is described from the Atlantic slope of Nicaragua and Costa Rica. Brycon costaricensis n. sp.
differs from all other Central American Brycon species by the following combination of characters: 49 to 54 scales in the
lateral line; 5 or 6 rows of scales between lateral line and pectoral fin base; 9 to 11 rows of scales between lateral line and
dorsal fin base; 5 to 7 rows of scales between lateral line and anal fin base; anal fin notably longer than head, with 33 to
37 total rays; and a elongated and shallow caudal peduncle, whose length is 1.78 to 2.35 times its depth. A key to lower
Mesoamerican species of the genus is also presented.
Key words: Central America, Atlantic slope, Primary freshwater fish, Teleostei, Bryconinae
Resumen
Se describe una nueva especie de Brycon para la vertiente Atlántica de Nicaragua y Costa Rica. Brycon
costaricensis n. sp. difiere de todos los demás miembros Centroamericanos del género por la siguiente
combinación de caracteres: 49 a 54 escamas en la línea lateral; 5 o 6 filas de escamas entre la línea lateral y la base
de la aleta pélvica; 9 a 11 filas de escamas entre la línea lateral y la base de la aleta dorsal; 5 a 7 filas de escamas
entre la línea lateral y la base de la aleta anal; aleta anal notablemente más larga que la cabeza, conformada por
entre 33 y 37 radios totales; y pedúnculo caudal alargado y poco profundo, cuya longitud oscila entre 1.78 y 2.35
veces su profundidad. Se incluye, además, una clave dicotómica para la identificación de las especies de Brycon de
Centroamérica.
Introduction
As presently recognized Brycon Müller and Troschel 1844 is one of the largest neotropical characiform genera,
containing at least 67 nominal species (Lima & Castro 2000) of which about 42 are valid (Lima 2003, 2004).
Species of the genus are widely distributed from Grijalva and Usumacinta basins in southern Mexico (Miller et al.
2006) to the La Plata basin in northern Argentina (Lima 2004). However, major diversity of Brycon species is
found in Panama and in the trans-Andean rivers of Colombia and Ecuador (Lima 2003).
Systematics of Brycon is still poorly understood (Lima 2004). Traditionally, species of the genus are diagnosed
from the remaining Characidae by the following combination of characters: three to four teeth rows in the
premaxillary, presence of an inner symphyseal tooth in the dentary, absence of an expanded coracoid bone and
presence of a relatively long anal fin with 18–38 branched rays (Howes 1982, Lima 2003, 2004).
Following Gery (1977) and Bussing (1976, 1985), on the basis of several meristic traits, and Reeves &
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256 · Zootaxa 3731 (2) © 2013 Magnolia Press
Bermingham (2006), on the basis of molecular data, two lower Mesoamerican Brycon species groups, the “Brycon
argenteus” and the “Brycon striatulus”, may be recognized. The Brycon argenteus group includes three species, B.
argenteus, B. obscurus and B. petrosus, with distributions that include both Pacific and Atlantic slopes (Reeves &
Bermingham 2006). The Brycon striatulus group includes four formally described species, B. behreae, B.
chagrensis, B. guatemalensis and B. striatulus, with a more extensive, but also more discontinuous, geographical
distribution than the Brycon argenteus group (Bussing 1976, 1985, 1998, Reeves & Bermingham 2006).
Traditionally, several authors (e.g. Bussing 1976, 1985, 1987, 1998) have included in B. guatemalensis four
allopatric populations occurring in: (1) Southeast of Mexico to northern Honduras, Atlantic slope, (2) Choluteca
river drainage, Pacific slope of Honduras, (3) North of Nicaragua to southeast of Costa Rica, Atlantic slope, and (4)
Guarumo river drainage, Atlantic slope of Panama. Even though Howes (1982), based on differences in
morphology and coloration, considered that the specimens identified as B. guatemalensis from western Panama, as
possibly representing a new species. Recent molecular evidence supports this hypothesis (Reeves & Bermingham
2006) and the formal description of this form is still pending.
On the other hand, Bussing (1998) noticed that the large hiatus between northern (Mexico, Belize, Guatemala
and Honduras) and southern (Nicaragua and Costa Rica) populations suggest a possible genetic isolation between
them and that very likely a comparative study using larger samples would prove that the Brycon from the Atlantic
versant of Nicaragua and Costa Rica to be an undescribed species. After examining several specimens cataloged as
B. guatemalensis from the Atlantic slope of Mexico, Belize, Honduras, Nicaragua and Costa Rica, we found
morphometric and meristic data that were discrepant between these northern and southern populations, according
to the Bussing’s (1998) observation. This paper is aimed at the formal description of this southern population
(Atlantic slope of Costa Rica and Nicaragua) as a distinct, new species. Additionally, a key to all described lower
Mesoamerican Brycon species is provided.
Material and methods
Counts and measurements (Table 1), this last given as proportions of standard length (SL) or head length (HL),
were taken on the left side of specimens and follow Fink & Weitzman (1974), Howes (1982), Menezes &
Weitzman (1990), Lima & Castro (2000) and Lima (2004). In the description, mean or mode for each measurement
or count, respectively, are given in parenthesis following the range. Vertebrae, supraneurals and some other
osteological characters were examined from two cleared and stained specimens (C&S), prepared according to the
method of Taylor & Van Dyke (1985). Comparative information on other collections and other valid species of
Brycon was obtained from Regan (1908), Fowler (1923), Hildebrand (1938), Howes (1982) and from specimens
listed in the Comparative Material. Institutional abbreviations are as follow: IBUNAM-CNPE = Colección
Nacional de Peces, Instituto de Biología, Universidad Nacional Autonoma de Mexico; LACM = Los Angeles
County Museum of Natural History; UCR = Museo de Zoología, Universidad de Costa Rica.
Aditionally, a geometric morphometric analysis was performed on 30 specimens of Brycon costaricensis
(UCR 0214-09 (n=2), UCR 0215-02 (n=3), UCR 0268-01 (n=3), UCR 0444-10 (n=4), UCR 0457-02 (n=7), UCR
0461-10 (n=3), UCR 0929-01 (n=2), UCR 1671-01 (n=3), UCR 1809-09 (n=3)), 30 specimens of B. guatemalensis
(IBUNAM-CNPE 5594 (n=1), IBUNAM-CNPE 5687 (n=6), IBUNAM-CNPE 8492 (n=2), LACM 32302-02
(n=3), LACM 32360-02 (n=3), LACM 32413-01 (n=3), LACM 32424-03 (n=3), LACM 32432-03 (n=3), UCR
0437-04 (n=6)) and 30 specimens of B. behreae (UCR 0101-06 (n=6), UCR 0311-01 (n=6), UCR 0393-01 (n=6),
UCR 0757-04 (n=6), UCR 2515-03 (n=6)) in order to quantify and compare body shape. A Cannon EOS Rebel T3
digital camera was used to photograph the left side of all specimens. TPSUtil version 1.53 (Rohlf 2012) was used
to append all files, creating a TPS combined data file including all specimens. Sixteen homologous landmarks (Fig.
1) were assigned and digitized for each specimen using the software TPSDig version 2.16 (Rohlf 2010).
Information unrelated to shape, including size, orientation and position, was removed by Generalized Least
Squared (GLS) Procrustes superimposition. A Canonical Variates Analysis (CVA), with the matrix of Procrustes
coordinates, was performed to show the axes on which groups are best discriminated by shape. Finally, to display
the shape features associated with CV axes, we used thin-plate spline algorithm (Bookstein 1991) to produce
transformation grids representing extreme positive and negative deviations along the axis. The superimposition and
CVA were completed in CoordGen (Sheets 2005a) and CVAGen (Sheets 2005b), respectively.
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NEW SPECIES OF BRYCON
TABLE 1 . Morphometric and meristic data of holotype (H) and paratypes (n=50) of Brycon costaricensis. (SD=standard
deviation).
Morphometrics H Mean SD Range
Standar length (mm) 128.1 116.52 55.80 47.8–325.1
Head length (mm) 30.7 27.39 12.57 12.1–75.0
Percentages of standard length
Head length 23.97 23.75 1.14 21.50–25.94
Greatest body depth 27.32 28.73 0.94 26.88–31.41
Snout to dorsal-fin origin length 49.18 51.02 1.33 48.00–53.74
Snout to pectoral-fin origin length 21.85 21.97 1.67 18.95–25.58
Snout to pelvic-fin origin length 39.34 42.12 1.65 39.06–45.27
Snout to anal-fin length 56.05 58.56 1.84 54.40–64.74
Dorsal-fin height 16.23 18.89 1.01 15.92–20.72
Pectoral-fin length 17.72 18.89 0.79 17.47–20.58
Pelvic-fin length 12.65 13.69 0.59 12.37–15.07
Pectoral-fin origin to pelvic-fin origin length 19.28 20.21 1.36 17.38–23.66
Pelvic-fin origin to dorsal-fin origin length 9.21 8.62 1.23 6.55–11.54
Dorsal-fin base length 11.63 11.53 0.43 10.45–12.40
Anal-fin base length 29.97 28.87 1.16 25.99–30.96
Posterior terminus of dorsal fin to adipose-fin length 22.40 22.50 0.96 20.16–25.03
Posterior terminus of dorsal fin to hypural joint length 36.14 35.76 1.48 33.27–39.19
Caudal peduncle length 15.37 15.17 0.71 13.52–17.48
Caudal peduncle depth 7.65 7.69 0.41 6.68–8.87
Percentages of head length
Head height 91.85 87.04 3.86 80.82–94.43
Snout length 22.15 26.29 1.75 22.07–29.38
Upper jaw length 32.58 36.19 2.16 32.42–41.39
Orbit diameter 30.94 33.36 3.01 25.00–37.19
Post-orbital head length 42.34 42.56 3.29 37.63–52.09
Least interorbital width 30.61 34.86 3.49 29.17–43.87
Meristics H Mean Mode Range
Lateral line scales 54 52.06 52 49–54
Scales from lateral line to dorsal-fin 10 9.80 10 9–11
Scales from lateral line to pelvic-fin 6 5.31 5 5–6
Scales from lateral line to anal-fin 7 6.24 6 5–7
Scales between posterior terminus of supraoccipital bone and
origin of dorsal-fin
19 19.39 19 17–22
Scales between posterior terminus of dorsal-fin and adipose fin 15 15.47 16 13–18
Circumpeduncular scales 14 14.42 14 13–17
Dorsal–fin rays ii9 ii9 ii9 ii9
Pectoral–fin rays i12 i11.60 i12 i11–i13
Pelvic–fin rays i7 i7.12 i7 i6–i8
Anal-fin rays i32 i31.68 iv32 iv29–iv33
Gill-rakers on first gill arch 28 28.44 29 26–30
Vertebrae - 45 45 45
Supraneural - 10 10 10
Premaxillary teeth 19 19.14 20 17–22
Maxillary teeth 12 11.57 11 9–15
Dentary teeh 20 18.37 18 15–22
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258 · Zootaxa 3731 (2) © 2013 Magnolia Press
FIGURE 1. Landmarks: (1) rostral tip of premaxilla, (2) posterior end of nuchal spine, (3) anterior insertion of dorsal fin, (4)
posterior insertion of dorsal fin, (5) anterior insertion of adipose fin, (6) dorsal insertion of caudal fin, (7) midpoint of caudal
border of hypural plate, (8) ventral insertion of caudal fin, (9) posterior insertion of anal fin, (10) anterior insertion of anal fin,
(11) dorsal base of pelvic fin, (12) dorsal base of pectoral fin, (13) dorsal end of opercle, (14) postero-ventral margin of
preopercle, (15) posterior end of maxilla, (16) center of eye.
Brycon costaricensis, new species
Table 1, Figure 2
Brycon guatemalensis (not Regan 1908): Meek, 1914: 108–109 (Costa Rica, Atlantic slope, Limón: Río Costa Rica, Quebrada
La Victoria, Río Zent and Río Parismina); Fowler, 1923: 23 (Nicaragua, Atlantic slope: Río Eden and Río Tunky);
Hildebrand, 1938: 275 (key), 281–282 (distribution, in part: “ranges on the Atlantic slope from Guatemala to Western
Panama”; Costa Rica and Nicaragua reference); Miller, 1966: 137 (distribution, in part: “Atlantic slope from the Río
Grijalva, Tabasco and Chiapas, Mexico southward to eastern Panamá”; Costa Rica and Nicaragua reference); Bussing,
1976: 158–161 (distribution, in part: Atlantic slope from Guatemala to Western Panama; Costa Rica and Nicaragua
reference); Bussing & López, 1977: 16, 20, 24, 27 (Costa Rica, Atlantic slope, Alajuela: Arenal Drainage); Géry, 1977:
339 (distribution, in part: “Central America”; Costa Rica and Nicaragua reference); Bussing, 1985: 457 (distribution, in
part: Atlantic slope from Guatemala to western Panama, with two discontinuities; Costa Rica and Nicaragua reference);
Bussing, 1987: 75–76 (distribution, in part: Atlantic slope from Grijalva, Mexico to western Panama, with two
discontinuities; Costa Rica and Nicaragua reference); Burcham, 1988: 277–283 (Costa Rica, Atlantic slope, Heredia: La
Selva Biological Station, Río Puerto Viejo: alimentation); Ulloa-Rojas et. al, 1989: 128–129 (Costa Rica, Atlantic slope,
Alajuela: Arenal Drainage); Bussing, 1993: 779 (Costa Rica, Atlantic slope, Heredia: La Selva Biological Station, Río
Puerto Viejo: ecology); Bussing, 1994: 196–198 (Costa Rica, Atlantic slope, Heredia: La Selva Biological Station, Río
Puerto Viejo: ecology); Horn, 1997: 259–263 (Costa Rica, Atlantic slope, Heredia: La Selva Biological Station, Río Puerto
Viejo: seed dispersion of Ficus glabatra); Bussing, 1998: 92–96 (distribution, in part: Atlantic slope from Grijalva,
Mexico to western Panama, with two discontinuities; Costa Rica and Nicaragua reference); Banack et al., 2002: 232, 237,
239–241 (Costa Rica, Atlantic slope, Heredia: La Selva Biological Station, Río Puerto Viejo: seed dispersion of Ficus
insipida); Drewe et al., 2004: 890–899 (Costa Rica, Atlantic slope, Heredia: La Selva Biological Station, Río Puerto Viejo:
gut morphology, alimentation, digestive enzyme activity); Smith & Bermingham, 2005: 1839 (distribution, in part: “San
Juan province”; Costa Rica and Nicaragua reference); Molina, 2006: 31–36 (Costa Rica: larval development); Reeves &
Bermingham, 2006: 88 (distribution, in part: from “Costa Rica to Mexico”; Costa Rica and Nicaragua reference); Herrera-
Vásquez et al., 2007: 168 (Costa Rica, Atlantic slope); Espinoza, 2008: 1975 (Costa Rica, Atlantic slope, Alajuela: Caño
Crucitas, Quebrada descubrimiento, Río Infiernillo, Quebrada Llano Verde and Quebrada Minas).
Holotype. UCR 2936-01: 128.1 mm SL, Costa Rica, Atlantic slope, Heredia, Sarapiquí drainage, La Virgen de
Sarapiquí, Río Sarapiquí, at the Tirimbina Biological Reserve, 149 m, 10°24'56.84"N, 84°07'18.70"W, C.A. Garita,
25 May 2013.
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NEW SPECIES OF BRYCON
FIGURE 2. (A) Holotype (128.1 mm SL) of Brycon costaricensis depicting live coloration (photo by Atsunobu Murase) and
(B) preserved paratype (UCR 0457, 98.5 mm SL).
Paratypes. 50 specimens (47.8–325.1 mm SL). Costa Rica: UCR 0214-09: 2, 105.0–132.9 mm SL, Limón,
Matina drainage, Quebrada Chocolate, 4.5 km SW of Moin, on road between Limón and Liverpool, 15 m,
9º59'04.99"N, 83º05'29.51"W, W.A. Bussing and S. Salas, 20 October 1967; UCR 0215-02: 3, 96.7–128.8 mm SL,
Limón, Parismina drainage, Río Siquirres 4–5 km W of Siquirres on road between Moravia and Siquirres, 240 m,
10º05'15.00"N, 83º32'44.27"W, H. Nanne, 15 October 1967; UCR 0263-08: 1, 234.0 mm SL, Alajuela, San Carlos
drainage, Quebrada Máquina, 4.2 km from Florencia de San Carlos on road between Ciudad Quesada and Muelle
de San Carlos, 90 m, 10º23'44.99"N, 84º28'39.33"W, W.A. Bussing, 1 September 1968; UCR 0444-10: 4, 144.8–
170.0 mm SL, Limón, Parismina drainage, Quebrada Salsipuedes, 1.5 km E. of Ventiocho Millas on provisional
road to Limón, 20 m, 10º05'19.99"N, 83º21'44.27"W, W.A. Bussing, M. Bussing and R. Nishimoto, 17 October
1970; UCR 0843-02: 5, 47.8–114.7 mm SL, Quebrada Santa Rita, from 1 km above to 1.5 km below bridge, 5 km
SW Florencia, San Carlos drainage, Alajuela, Costa Rica, 200 m, 10º19' 24.99"N, 84º31'0.01"W, J. Prendas, W.
González, W. López and M. Murillo, 22 February 1975; UCR 0929–01: 3, 130.6–265.1 mm SL, Alajuela, Lago de
Nicaragua drainage, Río Zapote 2.6 km S of Canalete, on Upala road, Lago de 85 m, 10º49'59.99"N,
85º02'09.83"W, W. Bussing, H. Camacho and W. Gonzáles, 17 December 1975; UCR 0948-03: 4, 64.2–99.8 mm
SL, Guanacaste, San Carlos drainage, Quebrada Pérez 2.6 km E of Arenal, 522 m, 10º28'19.99"N, 84º49'44.27"W,
W.A. Bussing, E. Bussing and W. González, 5 January 1976; UCR 1351-19: 1, 151.8 mm SL, Limón, Matina
drainage, Río Cuba, on road to Limón, Costa Rica, 15 m, 10º01'20.00"N, 83º13'14.75"W, W.A. Bussing, 25
September 1981; UCR 1570-02: 1, 230.0 mm SL, Alajuela, Lago de Nicaragua drainage, source of small stream, 2
km S of Bijagua, 440 m, 10º43'09.99"N, 85º03'59.99"W, W.A. Bussing, Ich. Course, 17 March 1984; UCR 1671-
01: 3, 84.0–153.2 mm SL, Guanacaste, San Juan drainage, Tributary of Río Bijagua, 10º44'25.00"N,
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260 · Zootaxa 3731 (2) © 2013 Magnolia Press
85º03'09.84"W, W.A. Bussing, Ich. Course, 4 May 1985; UCR 1809-09: 3, 96.2–148.1 mm SL, Limón, Tortuguero
drainage, Parque Nacional Tortuguero, Río Agua Fría, 10º27'49.99"N, 83º33'59.99"W, K. Winemiller, 18 June
1985; UCR 1827-05: 1 (C&S), 73.0 mm SL, Limón, Parismina drainage, Quebrada Herediana, 6 km NW of
Siquirres, on road to Guápiles, 10 m, 10º08'09.99"N, 83º33'29.51"W, W.A. Bussing, Ich. Course, 21 March 1986;
UCR 2147-02: 1, 140.4 mm SL, Alajuela, Lago de Nicaragua drainage, Río Caño Negro, Parque Nacional Volcán
Rincón de la Vieja, in the main stream, 310 m, 10º47'45.00"N, 84º57'19.68"W, S. Navarro, L. Villalba and J.
Fraizer, 11 March 1989; UCR 2852-01: 1 (C&S), 75.9 mm SL, Limón, Parismina drainage, Río Pacuare, J. Picado,
13 July 2004. Nicaragua: UCR 0268-01: 3, 72.5–105.5 mm SL, Zelaya, Escondido drainage, Río La Concha
(flowing into Río Mico), 18 km W of Ciudad Rama, 150 m, 12º10' 00.00"N, 84º28'39.33"W, J.D. Villa, 21 April
1968; UCR 0457-02: 7, 67.0–185.5 mm SL, Chontales, Prinzapolka drainage, Río Yoaya 13.6 km E of Siuna at
road, 300 m, 13º40'00.00"N, 84º21'44.27"W, W.A. Bussing and G. Campos, 14 April 1971; UCR 0461-10: 6, 55.9-
82.9 mm SL, Chontales, Escondido drainage, Río Muhán 17.4 km SE of Villa Somoza at Managua, Rama road,
100 m, 12º11'00.00", 86º15'05.04"W, W.A. Bussing, G. Campos and A. Zepeda, 17 April 1971; UCR 1086-01: 1,
325.1 mm SL, San Juan drainage, Quebrada Peor es Nada, R. Beatty, 27 April 1976.
Diagnosis. Brycon costaricensis differs from all other Central American Brycon species by possessing 49 to 54
scales in the lateral line (vs. 43 to 48 in B. argenteus, 55 to 61 in B. guatemalensis, and more than 64 in B. behreae,
B. chagrensis and B. striatulus) and a anal fin notably longer than head, with 33 to 37 total rays (vs. an anal fin
about equal to length of head, with 24 to 28 total rays in B. argenteus, B. obscurus, and B. petrosus, the last two
species with 48 to 55 and 53 to 58 scales in the lateral line, respectively). The following combination of characters
also can separate the species herein described from B. guatemalensis: 5 or 6 rows of scales between lateral line and
pectoral fin base (vs. 7 or 8); 9 to 11 (generally 10) rows of scales between lateral line and dorsal fin base (vs. 10 to
12, generally 11); 5 to 7 (generally 6) rows of scales between lateral line and anal fin base (vs. 7 to 9, generally 8);
and a elongated and shallow caudal peduncle, whose length is 1.78 to 2.35 times its depth (vs. a short and deep
caudal peduncle, whose length is 1.25 to 1.61 times its depth).
Description. Morphometric and meristic data are given in Table 1. Body moderately slender, robust and
moderately high in specimens above 300.0 mm of SL; largest body height at dorsal-fin level; sloped dorsal profile;
head large, slightly acute anteriorly and moderately deep posteriorly, head depth about 64.30 to 79.22% (71.73%)
of body deep; eye large and snout relatively short and conical, eye diameter about 0.86 to 1.65 (1.27) times snout
length; mouth terminal, heterognathous, premaxillary extending slightly ahead of dentary, leaving 2 rows of teeth
exposed in advance of it; maxillary almost reaching the middle of the eye, maxillary length about 28.38 to 37.33%
(32.22%) of head length; lower jaw shorter than upper, leaving 2 rows of teeth exposed in advance of it;
premaxillary teeth large, laterally in 2 series, anteriorly more or less definitely in 3 series (the outer series with 8–
10 (9) teeth, the second series with 7–10 (9) teeth and the inner series with 2 largest teeth); maxillary with 9–15
(11) medium sized teeth; dentary with 7–9 (8) large anterior teeth, 7–12 (9) small posterior teeth and 1 tooth at the
symphysis, forming the inner row; first gill arch with 13–15 (14) lower gill rakers, 13–15 (14) upper gill rakers and
1 at angle; scales cycloid; lateral line complete from supracleithrum to caudal-fin base and decurved anteriorly;
dorsal-fin origin equidistant from snout and base of caudal-fin or scarcely behind of the middle of SL; pectoral-fin
longer than pelvic-fin, its length about 1.22 to 1.51 (1.38) times the pelvic-fin length or 0.75 to 1.12 (0.94) times
the distance between the pectoral-fin origin and the pelvic-fin origin; anal-fin base almost equal in length that
maximum body depth, its length about 0.85 to 1.09 (1.00) times the body depth; caudal peduncle large and shallow,
its length about 1.78 to 2.35 (1.98) times its depth; caudal-fin broadly forked.
Color in life. See Figure 2A. Overall coloration silvery, some of the scales with blackish edges, forming
vertical streaks; olive dark back and pearl white belly; pinkish, yellowish, olive or bronze color opercular bones (in
adults); posterior edge of gill-opening blackish (in adults); paired fins transparent, light pink or reddish (in
juveniles), rosy gray or dark (in adults); dorsal and adipose fins light pink, yellowish, reddish (in juveniles), rosy
gray or dark (in adults); a more or less distinct blackish spot on the caudal peduncle; tail pale pink, yellowish,
reddish (mostly in juveniles) or dark (mostly in adults); anal and caudal fins usually dark-edged.
Color in alcohol. See Figure 2B. Dorso-lateral body surfaces silvery to coppery, dark olive to dark brown
dorsally, becoming gradually clear ventrally; posterior edge of gill-opening blackish (in adults); longitudinal stripes,
present in some specimens, extending all along the trunk; moderate to darkly pigmentation on paired fins; dorsal and
anal fins pale with some dark pigmentation on interradial membranes and distal margins; adipose-fin usually
pigmented at the basis; relatively faint, rounded dark area on caudal peduncle; caudal-fin usually dark-edged.
Zootaxa 3731 (2) © 2013 Magnolia Press · 261
NEW SPECIES OF BRYCON
Distribution. Brycon costaricensis is known from Wawa basin in northern Nicaragua to Matina basin in
southern Costa Rica, Atlantic slope (Figure 3). In addition, since no other Brycon species has been recorded
between Cangrejal, Aguán and Patuca basins in central Honduras and Coco and Ulám basins in northern Nicaragua
(Bussing 1998, Matamoros et al. 2009), B. guatemalensis (sensu stricto) should now be considered as restricted
from the Grijalva and Usumacinta basins in southern Mexico (Miller et al. 2006) to the Ulúa and Leán basins in
northwestern Honduras, in the Atlantic slope, and to the Choluteca basin at the Honduran Pacific slope (Matamoros
et al. 2009).
FIGURE 3. (A) Map of lower Central America, showing known distribution of Brycon costaricenses (light area); (B, C) type-
locality (D, E) indicated by the star, circles represent remaining localities.
Etymology. The specific name, costaricensis, refers to the country of the type locality: Costa Rica, Atlantic
slope, Heredia, Sarapiquí drainage, La Virgen de Sarapiquí, Río Sarapiquí.
Common names. Machaca, Sábalo, Sabalete, Machaca del Atlántico (Bussing 1998, Angulo in press).
Ecological notes. The literature mentioning Brycon guatemalensis should eventually be revised regarding the
origin of the material used (see Distribution). Brycon costaricensis inhabits some lakes in Nicaragua and Costa
Rica, but it is also abundant in fast-flowing rivers and streams since it is a very strong swimmer (Bussing & López
1977, Bussing 1998). It is found at elevations between 0 and 600 m in lakes, rivers and creeks (Bussing 1998). It
tolerates temperatures between 21 and 34 °C (Bussing 1998).
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FIGURE 4. A. Scatter plot of the first two axis of the CVA of the body shape for three Central American Brycon species
(circles=B. guatemalensis, squares=B. behreae, equis=B. costaricensis). Deformation grids indicate extreme shape along CV
axes (B=CV1-, C=CV1+, D=CV2-, E=CV2+).
Young specimens (less than 80 mm of total length) fed principally on insects while the largest ones (more than
80 mm of total length) consumed a large proportion of allochthonous vegetal matter, principally leaves (Burcham
1988). Horn (1997) and Banack et al. (2002) found that the largest individuals of this species can potentially
disperse Ficus spp. (Moraceae) seeds for long distances along watercourses. Drewe et al. (2004) found that largest
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NEW SPECIES OF BRYCON
individuals of B. costaricensis have relatively larger intestines than juveniles specimens, and an ontogenetical
change of main gut enzymes, associated with the ontogenetic change in diet (from carnivores to mainly
herbivores). In addition, as in the case of B. opalinus (Cuvier 1819), B. costaricensis possesses a large gall bladder,
suggesting the importance of the digestion of lipids in these species (Drewe et al. 2004, Gomiero et al. 2008).
Burcham (1988) also found that largest individuals of B. costaricensis are present in forest streams and usually
absent from deforested areas that indicates that the removal of fruit trees from the banks of small streams leads to
their local elimination or to a considerable decrease in their abundance.
Regarding the reproductive biology of B. costaricensis, little is known. Bussing (1998) mentions that pairs of
this species lay eggs in an excavated nest in the sand substratum of creeks. Additionally, Molina (2006) describes
their most relevant larval development characteristics after artificial fertilization of eggs of wild fish.
Brycon costaricensis is a delight for sport fisherman because of its fighting nature and the flesh is highly
regarded (Bussing 1998). The latter author reported for this species a maximun size of 500 mm and a maximun
weight of 4300 g.
Remarks. CVA recovered two distinct shape groups along both Canonical Variates (CV) (Figure 4). Brycon
guatemalensis and B. costaricensis specimens were evenly distributed among the two groups in CV1, meanwhile
B. costaricensis and B. behreae were likewise distributed among the two groups in CV2. Both canonical variate
axis are significant at the p <.001 level based on the Wilk’s lamda value (the sum of squares within groups divided
by the total sum of squares within and between groups). The CV1 explained 74.82% of the shape variance.
An assignment test performed in CVAgen based on CV1 determined that all specimens had been correctly
assigned to the respective group. Shape differences associated with the CV1 and CV2 are shown in Figure 4.
Brycon costaricensis, with positive scores on CV1 (Figure 4C) and negative scores on CV2 (Figure 4D), has
slender bodies and caudal peduncles larger and shallower than specimens with negative scores on CV1 (Figure 4B)
as well as deeper heads, eyes displaced dorsally, anterior fins insertion displaced anteriorly and the posterior end of
the supraocipital spine positioned anteriorly and dorsally than specimens with positive scores on CV2 (Figure 4E).
Key to species of Brycon from Middle America, adapted from Hildebrand (1938)
1. Scales in lateral line 42 to 61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
- Scales in lateral line 64 to 84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Anal fin about equal to length of head, with 24 to 28 total rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
- Anal fin notably longer than head, with 32 to 38 total rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scales in lateral line 43 to 48; 7 or 8 rows of scales between lateral line and origin of dorsal; 3 rows of scales between lateral
line and base of ventral; 11 to 14 scales series crossing back between dorsal and adipose; snout projecting very little, with
lower jaw reaching outer row of premaxillary teeth (Tuira and Bayano drainages on the Pacific slope and along the Atlantic
San Blas coast west to the Rio Cascajal, Panama) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. argenteus Meek & Hildebrand 1913
- Scales in lateral line 48 to 58; 7 to 10 rows of scales between lateral line and origin of dorsal; 3 or 4 rows of scales between lat-
eral line and base of ventral; 15 to 18 scales series crossing back between dorsal and adipose. . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. 48 to 55 scales in lateral line; pectoral fins short, failing to reach pelvic fins in small specimens by 2 or 3 rows of scales, about
1.4 in head; snout projecting less strongly, leaving only one row of premaxillary teeth exposed in advance of lower jaw; sides
plain silvery (rivers of central Panama: Rio Indio and Rio Cocle del Norte on the Atlantic slope and Rio Cocle del Sur on the
Pacific slope) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. obscurus Hildebrand 1938
- 53 to 58 scales in lateral line; pectoral fins long, reaching nearly or fully to base of pelvic fins in small specimens, proportion-
ately shorter in adult specimens, about 1.2 in head length; snout strongly projecting, 2 rows of teeth exposed in advance of
lower jaw; sides with more or less definite dark cross bars or reticulations formed by black margins on the scales (Chagres sys-
tem on the Atlantic slope and in the Rio Pacora and adjacent rivers on the Pacific slope, Panama) . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. petrosus Meek & Hildebrand 1913
5. Scales in lateral line 49 to 54; 5 or 6 rows of scales between lateral line and pectoral fin base; 9 to 11 rows of scales between
lateral line and dorsal fin base; 5 to 7 rows of scales between lateral line and anal fin base; caudal peduncle large and shallow,
its length is 1.78 to 2.35 times its depth (from Wawa basin in northern Nicaragua to Matina basin in southern Costa Rica,
Atlantic slope) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. costaricensis n. sp.
- Scales in lateral line 55 to 61; 7 or 8 rows of scales between lateral line and pectoral fin base; 10 to 12 rows of scales between
lateral line and dorsal fin base; 7 to 9 rows of scales between lateral line and anal fin base; caudal peduncle short and deep, its
length is 1.25 to 1.61 times its depth (from the Grijalva and Usumacinta basins in southern Mexico to the Ulúa and Leán basins
in northwestern Honduras, Atlantic slope, and in the Choluteca basin at the Honduran Pacific slope) . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. guatemalensis Regan 1908
6. Mandibula teeth large, usually 8 (rarely 7 or 9) in outer series; premaxillary teeth small, 12 to 14 in outer series (Pacific drain-
ages of Colombia to central Panama) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. striatulus (Kner 1863)
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264 · Zootaxa 3731 (2) © 2013 Magnolia Press
- Mandibular teeth small, usually more than 10 in outer series; premaxillary teeth larger, 15 or more in outer series . . . . . . . . 7
7. Pectoral short, generally failing to reach base of ventral by 3 to 6 scales, 5.2 to 5.8 in standard length; scales somewhat larger
and in more regular series, 66 to 79 between upper angle of gill opening and base of caudal; teeth somewhat larger, 10 to 14
(rarely 16) in outer series on mandible, 12 to 15 on maxillary, and 17 to 20 in outer series on premaxillaries; second suborbital
broad, its lower anterior angle less rounded (rivers west of the Panama’s Azuero Peninsula and continuing north until Costa
Rica’s Gulf of Nicoya, Pacific slope) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. behreae Hildebrand 1938
- Pectoral long, frequently reaching nearly or entirely to base of ventral, seldom falling short of this point by more than 2 rows of
scales, 4.1 to 5 in standard length; scales rather small and in more or less irregular series, 68 to 83 (usually more than 70)
between upper angle of gill opening and base of caudal; teeth rather small, 14 to 20 in outer series on mandible, 10 to 13 on
maxillary, and 15 to 18 in outer series on premaxillaries; second suborbital narrow, with rounded lower anterior angle (Rio
Chagres and adjacent drainages, Atlantic slope, Panama) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B. chagrensis (Kner 1863)
Discussion
Traditionally, several authors (e.g. Bussing 1976, 1985, 1987, 1998) included in B. guatemalensis four allopatric
populations distributed between Mexico and Panama. Howes (1982) based on differences in morphology and
coloration, considered that the specimens identified as B. guatemalensis from Río Guarumo, Atlantic versant of
western Panama, as possibly representing a new species. In this regard, Bussing (1998) noticed that some of the
morphometric characteristics mentioned by Howes (1982) as distinct for this population are quite variable and
possibly the length of the pectoral and anal fins will be of greatest importance in distinguishing this. Molecular data
provided by Reeves & Bermingham (2006) support the hypothesis of Howes (1982) and Bussing (1998) that
specimens of Brycon from the Atlantic slope of Panama are distinct from other B. guatemalensis populations. The
formal description of this form, requiring a detailed morphometric and meristic analysis, is still pending.
Bussing (1998) also noticed that the large hiatus between northern (Mexico, Belize, Guatemala and Honduras)
and southern (Nicaragua and Costa Rica) populations of B. guatemalensis suggest a possible genetic isolation
between them and that very probably a comparative study using larger samples would prove that the Brycon
populations from the Atlantic versant of Nicaragua and Costa Rica to be an undescribed species. This author,
however, does not refer to meristic or morphometric characters that could differentiate both populations. Reeves &
Bermingham (2006), according to Bussing´s (1998) observation, provided graphic evidence (see page 44, Figure 2)
which could suggest that specimens of Brycon from the Atlantic slope of Nicaragua (STRI 8991) and Costa Rica
(STRI 1216 and 2139) may be genetically distinct from B. guatemalensis from the Atlantic slope of Mexico (AP
1649), Guatemala (STRI 7808, 7810, 8182, 8238, 8244, 8265, 8267 and 8613) and Honduras (STRI 8467, 8469,
8610, 8611 and 8612), however, a more comprehensive study is necessary to corroborate this. Shape information
(see Remarks section) and morphometric and meristic data presented in this study confirm that both populations
present significative differences that merit their recognition of this southern population as a distinct, new species.
Comparative material examined
Brycon guatemalensis. 70 specimens (35.1–280.0 mm SL). Honduras: LACM 32302-02: 21, 34.0-148.0 mm SL,
Francisco Morazán, Rio Yequare, 5 mi. S of Escuela Panamericana, Zamorano, 13º55'59.99"N, 86º58'59.99"W, M.
Brame, 11 February 1969; LACM 32360-02: 4, 128.0–192.0 mm SL, Santa Bárbara, Rio Ulua at Gualtoquito on
Santa Bárbara, San Pedro Sula Highway, 15º00'00"N, 88º13'59.99"W, A. Valle, M. Martin, J. Beck, A. Brame, 19
March 1969; LACM 32413-01: 7, 35.1–45.2 mm SL, Comayagua, Rio Comayagua, at bridge, 16 km W on San
Pedro Sula, Tegucigalpa Highway, 14º22'00.00"N, 87º37'00.00"W, M. Martin, 27 January 1970; LACM 32424-03:
10, 31.9–46.1 mm SL, Comayagua, Rio Grande, 16.4 km S La Libertad on Comayagua, La Libertad,
14º34'59.99"N, 87º37'00.00"W, M. Martin, W. Plowden, 28 January 1970; LACM 32432-03: 3, 118.4–132.1 mm
SL, Quebrada San Nicholas, Santa Bárbara, 3.5 km SW Chinda on Chinda, Colinas Highway, 15º05'59.99"N,
88º10'00.00"W, M. Martin, 5 February 1970. Belize: UCR 0437-04, 8 (2 C&S), 55.5–84.9 mm SL, Toledo, Stream
tributary to Crique Huti (Jute), second bridge downstream from Colombia Forestry Station, H. Loftin, E.L. Tyson,
15 December 1969. Mexico: IBUNAM-CNPE 5594: 1, 280.0 mm SL, México, Chiapas, Santo Domingo,
Ocosingo, 17º01'17.04"N, 91º25'00.12"W, A. Hernández, 17 January 1987; IBUNAM-CNPE 5687: 8, 62.0–103.0
mm SL, México, Chiapas, Rio Lacantun, Ejido Pico de Oro, 16º21'06.00"N, 90º45'17.99W", A. Hernández, 15
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August 1987; IBUNAM-CNPE 5698: 3, 110.0–230.0 mm SL, México, Chiapas, Rio Lacanja, Ejido Pico de Oro,
16º24'03.96"N, 90º46'23.16"W, A. Hernández, 16 August 1987; IBUNAM-CNPE 8492: 2, 195.0–205.0 mm SL,
México, Chiapas, Rio Lacanja, Montes Azules, 16º24'04.00"N, 90º46'23.00"W, Huidobro, Burgos, Palma, Rosales,
29 April 1991; IBUNAM-CNPE 8514: 3, 55.0–105.1 mm SL, México, Chiapas, Ubilio Garcia, Rio Sto. Domingo,
Burgos, Becerril, Palma, Rosales, 19 February 1992.
Brycon behreae. 30 specimens (68.3–188.2 mm SL). Costa Rica: UCR 0101-06, 6, 72.1–188.2 mm SL,
Puntarenas, Coto drainage, Río Nuevo, 12 km E of the Río Claro village at Interamerican Highway, 8º38'54.99"N,
82º58'34.42"W, W.A. Bussing, O. Blanco, 2 January 1967; UCR 0311-01, 6, 105.2–225.6 mm SL, Puntarenas, Pirrís
drainage, Quebrada Bonita, S side of Damas, 9 km NW of Quepos, 9º29'20.00"N, 84º12'34.43"W, W.A. Bussing, R.
Nishimoto, J. Perry, C. Mata, 18 January 1969; UCR 393-01, 6, 77.4–97.4 mm SL, San José, Térraba drainage, Río
Pedregoso, 3 km SW of San Isidro del general on Dominical road, near coffee Beneficio San Jorge, 9º21'30.00"N,
83º43'14.75"W, C. Mata, 3 February 1970; UCR 0757-04, 6, 72.0–111.4 mm SL, Puntarenas, Térraba drainage,
Quebrada Angelina 0.5 km NO of Villa Briceño at Interamerican Highway, 8º43'29.99"N, 83º10'04.91"W, W.A.
Bussing, M. Bussing, E. Bussing, 1 March 1973; UCR 2515-03, 6, 68.3–95.5 mm SL, San José, Térraba drainage,
Rio Jilguero, San Isidro del General, 9º22'10.00"N, 83º41'59.98"W, C. Gamboa, 23 June 1998.
Acknowledgements
We are grateful to William A. Bussing Burhaus, Myrna I. López Sánchez, Ana Rosa Ramirez Coghi, Rita Vargas
Castillo, Monika Springer (UCR), Héctor Salvador Espinosa Pérez, Luis Fernando del Moral Flores, and Eduardo
Villalobos Segura (IBUNAM-CNPE) who provided us with material under their care and/or help in the laboratory.
We also thank Richard F. Feeney (LACM) for providing photographs of B. guatemalensis specimens, Carlos Garita
Alvarado for donating the specimen that was designated as the holotype of the species, and Atsunobu Murase for
providing a picture of it. Finally, we also thank Flávio C. T. Lima for valuable comments to the manuscript and
constructive suggestions.
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... Tales avances se han visto reflejados en diversas publicaciones científicas incrementando el número total de especies reconocidas para el país (e.g., Schmitter-Soto, 2017;Angulo et al., 2015;en prep., & Álvarez-Calderón et al., 2018; entre otros), ampliando los ámbitos de distribución vertical y/o geográfico conocido para varias especies (e.g. Angulo et al., 2015;2017;2018a, b;Arguedas, 2019;Rodríguez-Arias et al., 2019, & Angulo et al., 2020 e incluso añadiendo/describiendo nuevas especies para la ciencia, algunas de ellas con localidades tipo en Costa Rica (e.g., Matamoros et al., 2013;Angulo & Gracian-Negrete, 2013;Angulo et al., 2018a, & Ota et al., 2020, entre otros. Dado esto, el conocimiento sobre la composición taxonómica de la fauna íctica (de aguas continentales e insulares) costarricense ha cambiado, de forma sustancial, en los últimos años; no solo por la adición de múltiples especies y taxones supra-específicos sino también como consecuencia de diversos rearreglos y cambios taxonómicos en los diferentes niveles jerárquicos, principalmente géneros, pero también familias y órdenes Nelson et al., 2016;Angulo et al., 2017;2018;2020 en prep.), esto tomando como base la publicación de Bussing (1998). ...
... Los datos utilizados para generar la clave provienen de dos fuentes principales: (1) literatura científica, a lo que vale resaltar el aporte de referencias base, incluyendo los trabajos de Bussing (1998), Robertson & Allen (2015) y Robertson & Van Tassell (2019), y (2) revisión, caracterización y análisis de material museográfico de referencia parte del acervo de la colección ictiológica del museo de Zoología de la Universidad de Costa Rica (UCR), ver Angulo et al. (2016). En ese sentido, el material de la colección fue revisado y caracterizado siguiendo los protocolos y terminología provistos por Bussing (1998) y a como detallado en publicaciones específicas para determinados grupos taxonómicos (e.g., Angulo & Gracian-Negrete 2013;Angulo et al., 2018a, b); lo cual incluye conteos, mediciones y otras observaciones realizadas sobre el lado izquierdo de los ejemplares. Datos y observaciones, en la clave, referentes al patrón de coloración de los diferentes taxones en vida fueron tomados y realizadas en campo y comparadas con los datos publicados por Bussing (1998), Robertson & Allen (2015) y Robertson & Van Tassell (2019). ...
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Introducción: El conocimiento sobre la composición taxonómica de la fauna de peces de agua dulce de Costa Rica ha cambiado sustancialmente en las últimas dos décadas. No solamente por la adición de nuevas especies y táxones supra-específicos, sino también por reordenamientos y cambios taxonómicos en los diferentes niveles jerárquicos. Las claves taxonómicas disponibles se publicaron hace más de 20 años y están desactualizadas. Objetivo: Brindar información actualizada, en lenguaje sencillo, para la identificación de todas las familias costarricenses de peces continentales e insulares. Métodos: Utilizamos literatura especializada, colecciones de museos y especímenes recolectados recientemente para actualizar las claves disponibles tomando como referencia una lista de familias del 2013. Resultados: La clave dicotómica ilustrada, que cubre 53 familias, se basa en características externas relativamente fáciles de identificar. También incluimos información sobre la composición de especies, distribución general y uso del hábitat. Conclusión: Esta clave permite la identificación de 274 especies de peces costarricenses a nivel de familia, como base para su identificación a categorías más bajas.
... In this case, host association plays an important role, in addition to morphology in the distinction of the new species from its close relatives. To the best of our knowledge, no other species of Auriculostoma has been found in any of the other 42 species of Brycon Müller & Troschel, across its distributional range in the neotropics (Angulo & Gracián-Negrete 2013). The presence of the new species in B. guatemalensis can be hypothesized to be a result of a speciation event via host-switching since the banded tetra, Astyanax aeneus occurs sympatrically in the same river basin (Miller et al. 2005). ...
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This article describes the most relevant larval development characteristics of Brycon guatemalensis (Regan, 1908) after artifi cial fertilization of eggs of wild fi sh. The fi sh were captured in La Vieja river, San Carlos, Alajuela, Costa Rica, on November, 2005. Larvae hatched 52 hr after fertilization (TL 6,10 ± 0,12 mm); 28 hr after hatching the eyes were observed (TL 7,24 ± 0,28 mm); at 64 hr the mouth was evident for the fi rst time (TL 8,42 ± 0,15 mm); on day 4 the pectoral fi ns started to develop (TL 8,86 ± 0,55 mm); on day 6 the yolk sac disappeared and the larvae started to swim in a normal way (TL 10,22 ± 0,18 mm); on day 8 the rudiments of dorsal fi n started to form (T L 11,16 ± 0,09 mm); on day 12 the anal fi n started to develop (TL 11,80 ± 0,19 mm); on day 13 the caudal fi n started to bifurcate forming two lobes (TL 12,06 ± 0,33 mm); on day 28 the pelvic fi ns were observed for the fi rst time (TL 15,48 ± 0,71 mm). The sequence of fi n development is: caudal, pectorals, dorsal, anal and pelvic. (a) RESUMEN. Se describe las características más relevantes del desarrollo larval de Brycon guatemalensis (Regan, 1908) después de la fertilización artifi cial de huevos de peces silvestres en el río La Vieja, en San Carlos de Alajuela, Costa Rica en el mes de noviembre del 2005. Las larvas eclosionaron 52 hr después de la fertilización (LT 6,10 ± 0,12 mm); a las 28 hr (LT 7,24 ± 0,28 mm), se comienzan a apreciar los ojos; a las 64 hr se observa la formación de la boca (LT 8,42 ± 0,15 mm); a los 4 días se forman las aletas pectorales (LT 8,86 ± 0,55 mm); a los 6 días el saco vitelino desaparece y las larvas empiezan a nadar normalmente (LT 10,22 ± 0,18 mm); a los 8 días se observan los rudimentos de la aleta dorsal (LT 11,16 ± 0,09 mm); a los 12 días se comienza a formar la aleta anal (LT 11,80 ± 0,19 mm); a los 13 días se comienza a notar la forma bilobulada de la aleta caudal (LT 12,06 ± 0,33 mm); a los 28 días se da la aparición de las aletas pélvicas (LT 15,48 ± 0,71 mm). La secuencia del desarrollo de las aletas es: caudal, pectorales, dorsal, anal y pélvicas. KEY WORDS. Fish larvae, larvae development, Brycon guatemalensis, Characidae, Costa Rica Brycon guatemalensis (Regan, 1908) se distribuye geográfi camente en la vertiente atlántica entre el río Grijalva, México hasta Panamá occidental con dos discontinuidades y en la vertiente pacífi ca se ha registrado en la cuenca del río Choluteca, Honduras. Conocido localmente como machaca, es un recurso muy importante en la ictiofauna costarricense, alcanzando un tamaño máximo de 500 mm y peso de hasta 4,3 Kg. Morfológicamente los juveniles son plateados con el dorso oliváceo y el vientre blanco; las aletas son transparentes, la cola un poco amarilla o rosada y la dorsal anaranjada tenue. Los adultos se obscurecen; las aletas se tornan gris rosáceo y los opérculos también son rosados.
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