Brycon

Lima, Flávio C. T., 2017, A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae), Zootaxa 4222 (1), pp. 1-189 : 15-17

Key to the species of cis-andean Brycon (excluding Brycon devillei )

The key provided below summarizes the main diagnostic features to diagnose the different cis-andean Brycon species. As is always the case with a dichotomous key, care should be exercised in its use, and the “Diagnosis” section of each species should be checked for additional diagnostic features and detailed comparisons. Juveniles (<100 mm SL) of snout-pointed Brycon species from eastern Brazil (steps 4 to 8) cannot be reliably distinguished among themselves. Brycon amazonicus populations from the Amazon basin at Peru possess a similar color pattern to B. hilarii , and the diagnosis of both species in the latter area is difficult (see under Brycon amazonicus ).

1. A dark vertical band at the distal portion of caudal fin or caudal fin finely dotted with small spots, in the latter case, with a black adipose fin; closed fontanels in specimens larger than 90 mm SL.................... Brycon pesu species-complex (Guyanese river systems, rio Orinoco basin, and Amazon basin)

- No dark vertical band at the distal portion of caudal fin or finely dotted caudal fin; adipose fin never black; fontanels open in specimens of all sizes..................................................................................2 2. Color pattern consisting only in a humeral dark blotch and a rounded dark caudal peduncle blotch ( Fig. 5 C); distal portion of maxillary expanded ( Fig. 6 B, C, E, G, J); fifth infraorbital bone as wide as high, or wider than high ( Fig. 6 B, C, E, G, J)....3

- Color pattern consisting in a humeral blotch and either a longitudinal stripe across caudal peduncle and middle caudal fin rays ( Fig. 5 E–F), or an variously-developed dark pigmentation over anal-fin basin and caudal-fin ( Fig. 5 G–L); several narrow longitudinal stripes, either straight or wavy, present across the body ( Fig. 5 E–L); width of maxillary approximately equal along its size, without a expanded distal portion ( Fig. 6 A, D, F, H, I); fifth infraorbital bone higher than wide ( Fig. 6 A, D, F, H; with the exception of Brycon polylepis )........................................................................ 14

3. Fifth infraorbital bone wider than high ( Fig. 6 B); head profile distinctly pointed....................................4

- Fifth infraorbital bone about as wide as high ( Fig. 6 C, E, G, J); head profile either obtuse or pointed....................7

4. Dentary teeth with poorly developed lateral cusps; fin hooks present in all rayed fins (including caudal fin) in mature males........................................................................................ Brycon coquenani (Río Kukenan, upper Río Caroni basin, Río Orinoco basin, Venezuela).

- Dentary teeth with relatively well-developed lateral cusps; fin hooks present only in anal- and pelvic-fins of mature males.. 5

5. Seven to 9 (modally 8) horizontal scale rows between the dorsal-fin origin and the lateral line; 3 to 5 (modally 4) horizontal scales rows between the lateral line and pelvic fin)...................................... Brycon howesi new species (Rio Jequitinhonha basin, eastern Brazil).

- Nine to 12 horizontal scale rows between the dorsal-fin origin and the lateral line; 4 to 7 horizontal scales rows between the lateral line and pelvic fin..................................................................................6

6. Caudal, dorsal, and anal fins carmine-red in life, light-colored in preserved specimens.................. Brycon vermelha (Rio Mucuri basin, eastern Brazil)

- Caudal, dorsal, and anal fins darkened in both living and preserved specimens......................... Bryconinsignis (Rio Paraíba do Sul basin and smaller adjacent coastal river systems, eastern Brazil).

7. Head profile distinctly pointed ( Fig. 6 C, G)................................................................8

- Head profile approximately obtuse ( Fig. 6 E, J).............................................................. 9

8. Mouth distinctly anisognathous, premaxillary pointed, extending beyond dentary, leaving outer, and often second, premaxillary teeth row exposed in ventral view............................................................ Brycon ferox (coastal river systems of southern Bahia and northern Espírito Santo, eastern Brazil).

9. Mouth approximately isognathous, premaxillary and dentary mostly overlapping, leaving only part of outer premaxillary series exposed in ventral view in some specimens....................................... Brycon dulcis new species (Rio Doce basin, eastern Brazil)

9. Opercle with a large dark patch of dark pigmentation........................................................10

- Opercle silvery or light-brown, never presenting a large dark patch of pigmentation................................ 11

10. Dark blotch on opercle lying at the center of the bone, very conspicuous............................................................................................... Brycon coxeyi (Upper Río Marañon basin, Ecuador and Peru)

- Patch of dark pigmentation on opercle diffuse, covering its upper half... Brycon stolzmanni (Upper Río Marañon basin, Peru)

11. Caudal peduncle dark blotch extending into the basis of the middle caudal-fin rays; lateral-line tubules presenting 2–5 branches............................................................................... .. Brycon nattereri (Upper rio Paraná, upper rio São Francisco, and upper rio Tocantins basins, Brazil)

- Caudal peduncle dark blotch never extending into the basis of the middle caudal-fin rays; lateral-line tubules generally simple, without secondary branches.........................................................................12

12. Snout obtuse, rounded in profile; upper jaw lenght 38.7–48.3 % of HL, mean 42.9..................... Brycon opalinus (Upper rio Paraíba do Sul and upper rio Doce basins, eastern Brazil)

- Snout acute, pointed in profile; upper jaw length 45.1–51.4 % of HL, mean 49.5................ Brycon vonoi new species (Rio Pardo basin, eastern Brazil)

13. A longitudinal broad dark midlateral stripe extending from supracleithrum ( Brycon whitei ) or mid-body/caudal peduncle into middle caudal-fin rays; no dark stripe at anal-fin basis ( Fig. 5 E–F)..............................................14

- No longitudinal broad midlateral stripe; a broad dark stripe present at anal-fin basis (with the exception of Brycon gouldingi ); dark pigmentation on caudal-fin either diffuse or forming a distinctly, variously shaped blotch which is not restricted to the middle caudal fin rays ( Figs. 5 G–L)......................................................................18

14. Inner pair of symphyseal teeth, situated immediately behind main series only slightly smaller than teeth on main series situated immediately in front; fifth infraorbital bone approximately as high as wide; body with series of discrete longitudinal straight stripes, formed by chromatophores situated in the center of the scales............................... Brycon polylepis (Lago de Maracaibo drainage and Río Orinoco basin, Venezuela and Colombia; rio Tocantins basin, Brazil; upper Amazon basin, Peru)

- Inner pair of symphyseal teeth, situated immediately behind main series, considerably smaller than teeth on main series situated immediately in front; fifth infraorbital bone higher than wide; body with series of wavy longitudinal stripes, formed by chromatophores concentrated on the upper and lower scales margins...........................................15

15. Longitudinal broad dark midlateral stripe extending from supracleithrum into middle caudal-fin rays ( Fig. 5 F); caudal, dorsal, pelvics, and anal fins pinkish in life........................................... .. Brycon whitei (Rio Orinoco basin)

- Longitudinal broad dark midlateral stripe extending from mid-body or caudal peduncle into middle caudal-fin rays ( Fig. 5 E) caudal, dorsal, pelvics and anal fins deep red or deep orange in life............................................ 16

16. Lateral line scales 67–82, modally 74; horizontal scale rows between dorsal fin and lateral line 11–17, modally 15.................................................................................................. .. Brycon hilarii (Rio Paraguai and middle rio Paraná basins; upper Amazon basin)

- Lateral line scales 49–63; horizontal scale rows between dorsal fin and lateral line 9–13.............................17 17. Head profile pointed; dentary teeth decreasing in size gradually, first four teeth not considerably larger than remaining teeth; second row of premaxillary teeth 5–8, modally 6.............................................. Brycon orbignyanus (Rio Paraná and rio Uruguai basins, Brazil, Uruguay, Paraguay, and Argentina)

- Head profile rounded, obtuse; dentary teeth decreasing in size abruptly, first four teeth considerably larger than remaining teeth; second row of premaxillary teeth 3–5, modally 5.............. Brycon orthotaenia (Rio São Francisco basin, Brazil)

18. Body with series of wavy longitudinal stripes, formed by pigmentation concentrated on the upper and lower scales margins ( Fig.5 G–H); pectoral and pelvic fins generally dark..........................................................19

- Body with series of dark, straight longitudinal stripes formed by pigmentation concentrated on the mid-distal portion of scales (Fig. I–L); pectoral and pelvic fins generally pale...........................................................20

19. Caudal fin and caudal peduncle with a well-defined V- or crescent-shaped blotch ( Fig. 5 H).............. Brycon gouldingi (Rio Tocantins basin, Brazil).

- Caudal fin and caudal peduncle with diffuse dark pigmentation, sometimes forming an oblique blurred bar on the upper caudal fin lobe but never V- or crescent-shaped blotch ( Fig. 5 G)....................................... Brycon amazonicus (western and central Amazon basin; Rio Orinoco basin)

20. An oblique, solid dark stripe extending from immediately behind pelvic-fin basis, through anal-fin basis, lower surface of caudal peduncle, middle area of caudal peduncle, to the upper caudal-fin lobe; no dark pigmentation on the lower caudal-fin lobe ( Fig. 5 I)............................................................................ Brycon melanopterus (Western and central Amazon basin lowlands)

- Dark stripe typically limited to anal-fin basis; typically a V- or crescent-shaped blotch on caudal fin; dark pigmentation on lower caudal-fin lobe less developed in some populations but almost always present ( Fig. 5 J–L).......... Brycon falcatus (Guyanese river systems, Rio Orinoco basin; Amazon basin, mostly shield-draining tributaries)

Figures

FIGURE 5. Diagrammatic representation of the patterns of dark colour markings found among cis-andean Brycon species, represented by selected species. A. Brycon stolzmanni. B. Brycon coxeyi. C. Brycon insignis. D. Brycon nattereri. E. Brycon hilarii. F. Brycon whitei. G. Brycon amazonicus. H. Brycon gouldingi. I. Brycon melanopterus. J-L. Brycon falcatus.

FIGURE 6. Diagrammatic representation of the head profile, maxillary and infraorbitals showing the distinct morphologies found among cis-andean Brycon species, represented by selected species. A. Brycon amazonicus, MZUSP 3815, 152.3 mm SL. B. Brycon insignis, MCZ 21112, 232.2 mm SL. C. Brycon dulcis, MZUSP 1531, 146.6 mm SL. D. Brycon falcatus, MZUSP 3845, 195.1 mm SL. E. Brycon opalinus, MCZ 21123, 210.5 mm SL. F. Brycon orbignyanus, MZUSP 3900, 108.9 mm HL. G. Brycon ferox, MCZ 60934, 310.3 mm SL. H. Brycon orthotaenia, MZUSP 2007, 188.7 mm SL. I. Brycon polylepis, MZUSP 70413, 203.9 mm SL. J. Brycon stolzmanni, UMMZ 185306, 120.0 mm SL.